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Japanese Navy Aircraft Designations, Second World War

Japanese Navy Aircraft Designations, Second World War

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Japanese Navy Aircraft Designations, Second World War

Type Number System (from 1921)
Popular Names (from 1943)
Short Designation System (from late 1920s)
Experimental Shi numbers (from 1931)
Service Aeroplane Development Programme system (from 1939)
Allied Code Names
Manufacturer Codes
Short Designation Lists by Letter

The Japanese Navy used two main and two subsidiary aircraft designation systems during the Second World War, causing so much confusion on the Allied side that a fifth codename system was developed.

Type Number System (from 1921)

The earliest of the designation systems in use during the Second World War was the Type number system, which began in 1921. In this system each Naval aircraft was given a type number based on the year it entered service, followed by a short description of the aircraft’s purpose.

From 1921 to 1928 the year code was based on the regnal year of the current Japanese Emperor. In 1921-26 this was the Emperor Yoshihito, whose reign was known as the Taisho Era, and so aircraft from those years were Types Taisho 10 to Taisho 15. Emperor Hirohito took the throne in 1926, and aircraft accepted in 1927 and 1928 became Types Showa 2 and Showa 3.

After 1928 the Japanese Navy copied the Japanese Army in using the last digits of the calendar year. 1929 was 2589 in the Japanese calendar, and so aircraft from that year became Type 89s. Aircraft accepted in 1940 (2600) became the Type 0, and after that the last digit of the year was used.

Different models of the same aircraft were originally given a single digit model number, with dash numbers for subtypes (Model 1 for the first version, Model 1-1 for the first subtype).

This was changed in the last thirties to a system that used a two digit code. The first digit changed if the airframe was altered, the second digit if the engine was altered. The first version of an aircraft was thus the Model 11. If the engine changed it became the Model 12, if the airframe changed it became the Model 21 and if both changed it became the Model 22.

Finally sub-versions of a model were given a final letter, taken from a series of Japanese characters called the Ten Stems (or Celestial or Heavenly Stems), which makes up part of the Japanese Zodiac. The full sequence runs kou (or ko) otsu hei tei bo ki kou shin jin ki and was originally used during the Chinese Shang dynasty as part of a dating system. In English translations they are normally replaced by the abc (ko=a, otsu=b, hei=c)

Popular Names (from 1943)

The Type numbers were abandoned in 1943 in favour of popular names, apparently in an attempt to improve security. Names were allocated according to strict rules, which must have rather reduced their confusion value.


Named after/ names ending in

Carrier and seaplane fighters

Ending in wind (pu or fu)

Interceptor fighters

Ending in den (lightning)

Night fighters

Ending in light (ko)

Attack aircraft





Stars (sei) or constellations (zan)

Patrol aircraft

Seas and oceans




Trees, plants or flowers


Landscape effects

Short Designation System (from late 1920s)

The best known of the main systems is the Short Designation System, which resembled a more logical version of the system used by the US Navy. In the Japanese system each type of aircraft was given a basic three symbol code running Letter-Number-Letter. The first letter gives the type of aircraft (A for carrier fighter or B for carrier based torpedo bomber – see below for a fuller list).

The numbers were allocated in sequence to each aircraft of that type to enter service, regardless of manufacturer, so unlike in the US Navy system we can be certain that the Yokosuka B4Y was an earlier aircraft than the Nakajima B5N (the US Navy started the numerical sequence from 1 for each aircraft company, so one company’s F1 could be a much more modern aircraft than another’s F10).

The second letter is normally described as the manufacturers code (see list below), but is better though of as the designing company’s code. Unlike in the US Navy this code was not changed to reflect the company that had manufactured a particular aircraft, so all Zero fighters were A6Ms, regardless of where they were built (in the US Navy system identical aircraft could have different numbers and company codes – the F4U and FG were both versions of the Corsair fighter – the first produced by Chance Vought, the second by Goodyear).

On a limited number of occasions two aircraft from a batch of designs submitted to a particular specification were accepted, and so shared a number.

These first three symbols were followed by a second number, which specified the exact model of an aircraft – the A6M2 was thus the second major version of the Zero. This was sometimes followed by a third lower case letter, used to distinguish between minor versions of a particular model.

In this system the A6M2c would thus be the fourth sub-version of the second model of the Mitsubishi produced sixth generation Carrier based fighter.

Early in the development of most aircraft the model number used here and the first digit of model designation in the Type number system were the same, but there was no direct connection, as shown in the A6M7 Model 63 version of the Zero.

If an aircraft was given a new purpose, that letter was hyphenated at the end of the designation, as with the Nakajima A6M2-N, a float plane fighter (-N) version of the Zero.

Experimental Shi numbers (from 1931)

The main flaw with the type number and short designation systems was that they normally only applied to aircraft that reached a reasonably advanced stage of the design process. In 1931 they were supplemented by a system of experimental numbers based on the Imperial regnal year. 1931 was the sixth year of the reign of the Emperor Hirohito, or the sixth year of the Showa era. Projected that began in 1931 were thus known as Experimental 6-Shi, distinguished from each other by the manufacturers name and a short description of its main purpose. The Aichi B7A1 Ryusei, which entered service as the Navy Carrier Attack Bomber Ryusei in 1944, thus began life in 1941 as the Aichi Navy Experimental 16-Shi Carrier Attack Bomber.

Service Aeroplane Development Programme system (from 1939)

The Service Aeroplane Development Programme designations are the least well known of the Naval designation system because most details were destroyed just before the end of the war. The system was used early in the development of an aircraft, and consisted of the manufacturer code from the short designation system and a two digit number.

Allied Code Names

The famous Allied codenames were adopted during 1942 in an attempt to end the confusion caused by a tendency to describe all Japanese fighters as Zeros and bombers as Mitsubishis. Very little was known about the Japanese aircraft industry before the start of the fighting, and many of the aircraft types were unfamiliar. The code name system was developed by Captain Frank T. McCoy Jr, of Nashville Tennessee, who in the summer of 1942 was appointed head of the Materiel Section, Directorate of Intelligence, Allied Air Forces, Southwest Pacific Area, Melbourne (Australia). Existing aircraft were allocated code names during 1942, and new aircraft were added to the list when they were identified. A number of codes were allocated to obsolete or non-existence aircraft, and one was allocated to the Messerschmitt Bf 109, which was widely expected to appear in the Pacific.

The Allied codenames were allocated according to a simple pattern – male first names for fighters and reconnaissance seaplane, tree names for trainers, bird names for gliders and female first names for bombers, flying boats, reconnaissance aircraft and transports.

Manufacturer Codes


Aichi or North American








Hitachi or Grumman


Hiro or Hawker




Nihon or Junkers


Kawanishi or Kinner














Watanabe then Kyushu





Short Designation Lists by Letter

A – Carrier Fighter

Nakajima A1N
Nakajima A2N
Nakajima A3N
Nakajima A4N
Mitsubishi A5M ‘Claude’
Mitsubishi A6M Reisen (Zero) ‘Zeke’ or ‘Zero’
Mitsubishi A7M Reppu (Hurricane) ‘Sam’

B – Carrier Attack Bomber (Torpedo Bomber)

Mitsubishi B1M
Mitsubishi B2M
Yokosuka B3Y Navy Type 92 Carrier Attack Aircraft
Mitsubishi B4M1 Experimental 9-Shi Carrier Attack Aircraft
Nakajima B4N Experimental 9-Shi Carrier Attack Aircraft
Yokosuka B4Y Type 96 Carrier Attack Bomber Jean (or Kusho B4Y)
Nakajima B5N prototype 1936-37 accepted 1937 ('Kate')
Mitsubishi B5M1 ('Kate')
Nakajima B6N Tenzan (Heavenly Mountain) trials 1941
Aichi B7A Ryusei (Shooting Star) ‘Grace’ prototype 1942 produced 1944

C - Reconnaissance

Nakajima-Fokker C2N Reconnaissance Aircraft
Nakajima C3N Navy Type 97 Carrier Reconnaissance Aircraft
Mitsubishi C5M
Nakajima C6N Saiun (Painted Cloud) ('Myrt')

D – Carrier Dive Bomber

Aichi D1A
Nakajima D2N
Aichi D3A ‘Val’
Nakajima D3N Experimental 11-Shi Carrier Bomber
Yokosuka D3Y Myojo (Venus)
Yokosuka D4Y Suisei (Comet) ‘Judy’

E – Reconnaissance (Seaplane)

Yokosho E1Y Type 14 Reconnaissance Seaplane
Nakajima E2N Type 15 Reconnaissance Seaplane
Aichi E3A1 Navy Type 90-1 Reconnaissance Seaplane (HD 56)
Nakajima E4N Type 90-2 Reconnaissance Seaplane
Kawanishi E5K
Yokosho E5Y Navy Type 90-3 Reconnaissance Seaplane
Yokosho E6Y Type 91 Reconnaissance Seaplane
Kawanishi E7K 'Alf'
Kawanishi E8K1 Experimental 8-Shi Reconnaissance Seaplane
Nakajima E8N Navy Type 95 Reconnaissance Seaplane 'Dave'
Watanabe E9W1 Navy Type 96 Small Reconnaissance Seaplane
Kawanishi E10K1 Experimental 9-Shi Night Reconnaissance Seaplane
Aichi E11A1
Kawanishi E11K1
Aichi E12A (prototype only)
Nakajima E12N1 Experimental 12-Shi Two-seat Reconnaissance Seaplane
Aichi E13A ‘Jake’
Kawanishi E13K1 Experimental 12-Shi Three-seat Reconnaissance Seaplane
Yokosuka E14Y ‘Glen’
Kawanishi E15K Shiun (Violet Cloud)
Aichi E16A Zuiun (Auspicious Cloud) ‘Paul’

F – Catapult Launched Observation Seaplane

G – Land based Attack Bomber

Mitsubishi G1M
Hiro G2H
Mitsubishi G3M ‘Nell’
Mitsubishi G4M ‘Betty’
Nakajima G5N Shinzan (Mountain Recess)
Nakajima G8N Renzen (Mountain Range) ‘Rita’
Nakajima G10N1 Fugaku (Mount Fuji)

H – Flying Boats

Kawanishi H3K
Experimental Kusho 12-Shi Special Flying-boat H7Y1
Kawanishi H6K ‘Mavis’
Kawanishi H8K ‘Emily’
Aichi H9A Flying-boat trainer.
Yokosuka H5Y 'Cherry'

J – Land Based Fighter

Nakajima J1N Gekko (Moonlight) ‘Irving’
Mitsubishi J2M Raiden (Thunderbolt) ‘Jack’
Kawanishi J3K1
Mitsubishi J4M1 Senden (Flashing Lightning)
Nakajima J5N1 Tenrai (Heavenly Thunder)
Kawanishi J6K1 Jinpu (Squall)
Kyushu J7W Shinden (Magnificent Lightning)
Mitsubishi J8M Shusui (Swinging Sword)

K - Trainer

Yokosho K1Y Navy Type 13 Trainer
Yokosho K2Y Type 3 Land-based Primary Trainer
Mitsubishi K3M ‘Pine’
Yokosuka K4Y1 Type 90 Seaplane Trainer
Yokosuka K5Y ‘Willow’ Type 93 Intermediate Trainer
Kawanishi K6K1 Experimental 11-Shi Intermediate Seaplane Trainer
Watanabe K6W1 Experimental 11-Shi Intermediate Seaplane Trainer
Kawanishi K8K1 Navy Type 0 Primary Seaplane Trainer
Watanabe K8W1 Experimental 12-Shi Primary Seaplane Trainer
Kyushu K9W Momiji (Maple)
Kyushu K10W1
Kyushu K11W Shiragiku (White Chrysanthemum)

Aichi M6A1-K Nanzan (Southern Mountain)

L - Transport

Nakajima L1N1 Navy Type AT-2 Transport 'Thora'
Douglas L2D
Kusho L3Y
Mitsubishi L4M1

M – Special seaplane

N – Floatplane Fighter

Kawanishi N1K Kyofu (Mighty Wind) ‘Rex’

Nakajima A6M2-N

P – Bomber

Q – Anti-submarine Patrol Bomber

Kyushu Q1W Tokai (Eastern Sea) ‘Lorna’
Kyushu Q3W1 Nankai (South Sea) – never produced

R – Long range land-based reconnaissance

Yokosuka R1Y Seiun (Blue Cloud)
Yokosuka R2Y Keiun (Beautiful Cloud)

Nakajima J1N-R

S – Night Fighter

Nakajima J1N-S
Yokosuka P1Y-2 Kyokko (Aurora)

Special Designations

Yokosuka MXY7 Ohka (Cherry Blossom)
Nakajima Kikka
Kawanishi Baika (Plum Blossom)

The Akutan Zero: How a Captured Japanese Fighter Plane Helped Win World War II

Until the Japanese attack on Pearl Harbor, most American servicemen had never seen a plane like the “Zero,” so named not because of the prominent Rising Sun emblem painted on the side but for the manufacturer’s type designation: Mitsubishi 6M2 Type 0 Model 21. Those servicemen had heard of the Zero’s reputation, though. Fast and powerful, it was known as a nearly invincible fighter plane with a 12:1 kill ratio in dogfights with the Chinese as early as 1940. The Zero cemented its reputation in an April 1942 battle with well-trained English pilots over Ceylon (now Sri Lanka). In that sortie, 36 Zeroes took on 60 British aircraft𠅊nd shot down 27 of them, with the loss of just a single Zero. So formidable was the Zero that the official American strategy for pilots attacked by the Japanese fighter boiled down to this: run away.

It’s curious, then, that Japan allocated any of its mighty fighter planes to an attack on the Aleutian Islands in June 1942 instead of saving them all for the massive campaign it was poised to mount at Midway Island. In fact, no one knows exactly why Japan invaded the Aleutians. The inhospitable chain of 120 small islands sweeps westward some 1,000 miles from mainland Alaska into the Pacific Ocean. Uniformly barren and rocky, the islands offer no support for human settlement. Some historians believe the Aleutian attack was an attempt by Japan to lure American naval power away from Midway Island, which would make an Imperial victory there easier. Others think Japanese troops planned to island-hop through the Aleutians to Alaska Territory, and then invade the mainland United States through Canada.

Whatever the rationale, sending Zeroes to the Aleutians would prove to be a critical intelligence error for Japan. On June 4, with orders to bomb the Allied base Dutch Harbor on Unalaska Island, young pilot Tadayoshi Koga, thought to have been 19 years old, strapped himself into his plane and prepared to carry out the mission of the Imperial Army. Little is known about Koga. In an undated service photo, he looks directly into the camera, almost smiling, his left hand tucked into the pocket of his uniform. Confident? Definitely. Perhaps even showing a bit of swagger. But then, what Japanese pilot wouldn’t swagger with the indomitable Zero at his command?

When Koga took off for Dutch Harbor that June morning, he probably expected to complete his mission and return to base as usual. Things didn’t work out that way. Emerging from the ubiquitous fog that envelopes the entire Aleutian Islands chain five or six days a week, Koga acquired his target and strafed the enemy base. During the engagement, his plane took ground fire that severed its main oil line. Now, piloting a fighter trailing a stream of oil, Koga realized that the moment the last drop of lubricant spilled out, his plane’s engine would seize and his Zero would plummet to earth.

With mere minutes to get the plane down safely, Koga headed west for Akutan Island. Designated by the Japanese army as an emergency landing field, Akutan boasted a long, grassy strip that must have looked to Koga like a sure bet for a smooth landing. That turf concealed a trap, though: Boggy soil lurked just below what appeared to be a solid landing strip. The bog snared Koga’s landing wheels and flipped the Zero end over end. It came to rest upside-down.

All Japanese pilots had standing orders to destroy any disabled Zeroes lest they fall into enemy hands. Koga’s plane appeared so undamaged, however, that his wingmen couldn’t bring themselves to shoot it up, fearing they might kill their friend. They circled once or twice before returning to their aircraft carrier at the western end of the island chain. Koga hadn’t survived, however: His neck had broken when the plane flipped over. And he and his Zero lay in the mist on Akutan, just waiting to be discovered by the Allies.

On July 10, as the world’s attention focused on the pivotal Battle of Midway, a U.S. Navy pilot on routine patrol over the Aleutians spotted Koga’s wreckage through a break in the clouds. But Akutan Island would not give up its prize easily. After three recovery attempts, the Navy finally managed to capture the plane and send it to a base in San Diego, California, for restoration. At last, the Zero’s secrets would be revealed.

Salvaging what they could and fabricating the few new parts needed, Navy mechanics brought the plane back up to flying condition. On September 20, Lieutenant Commander Eddie Sanders became the first pilot to fly a Zero in American colors. The plane performed beautifully, and Sanders went on to fly 24 test flights in 25 days. In the process, he discovered the Zero possessed not one but two Achilles’ heels. First, it was nearly impossible to perform rolls at moderately high speeds. This meant that forcing the enemy into such a maneuver would confer a tactical advantage to Allied pilots. Second, a poorly designed carburetor caused the engine to sputter badly when the plane was placed into a dive at a high rate of speed. Thus, forcing the Zeroes to dive during a dogfight might make them easy targets for Allied gunners.

Now armed with the knowledge needed to best the Zero in combat, the Allies quickly formulated strategies to defeat the Japanese in the air and, just as importantly, demystified the plane’s aura of invincibility. As quoted in Jim Rearden’s book 𠇌racking the Zero Mystery,” Marine Captain Kenneth Walsh described how he used information from the Zero test flights to finish the war with 17 aerial victories over Zeroes: “With [a] Zero on my tail I did a split S, and with its nose down and full throttle my Corsair picked up speed fast. I wanted at least 240 knots, preferably 260. Then, as prescribed, I rolled hard right. As I did this and continued my dive, tracers from the Zero zinged past my plane’s belly. From information that came from Koga’s Zero, I knew the Zero rolled more slowly to the right than to the left. If I hadn’t known which way to turn or roll, I𠆝 have probably rolled to my left. If I had done that, the Zero would likely have turned with me, locked on, and had me. I used that maneuver a number of times to get away from Zeros.”

Using these new air tactics over the ensuing months, the Allies won battle after battle in the Pacific, and the Zero—once the pride of the Japanese air force—was reduced to a kamikaze vehicle. Masatake Okumiya, a Japanese officer who led many Zero squadrons and authored the book “Zero,” described the significance of the Allies’ capture of Koga’s plane as “no less serious than the Japanese defeat at Midway” and said it 𠇍id much to hasten our final defeat.”


On November 14, 1910, a 24‑year‑old civilian pilot, Eugene Burton Ely, took off in a 50 horsepower Curtiss plane from a wooden platform built over the bow of the cruiser Birmingham later, on January 18, 1911, Ely landed a Curtiss Model D on a platform aboard Pennsylvania. [2] The Naval Appropriations Act for Fiscal Year 1920 provided funds for the conversion of Jupiter into a ship designed for the launching and recovery of airplanes at sea—the United States Navy's first aircraft carrier. [2] Renamed Langley, she was commissioned in 1922. Commander Kenneth Whiting was placed in command. [2] In 1924, Langley reported for duty with the Battle Fleet, ending two years as an experimental ship. [2]

In 1922, Congress also authorized the conversion of the unfinished battlecruisers Lexington and the Saratoga as permitted under the terms of the Washington Naval Treaty, signed in February 1922. [2] The keel of Ranger, the first American ship designed and constructed as an aircraft carrier, was laid down in 1931, and the ship was commissioned in 1934. [2]

Following Ranger and before the entry of the United States into World War II, four more carriers were commissioned. Wasp was essentially an improved version of Ranger. The others were the three ships of the Yorktown class. [3]

Designation Class Ships Active Description Lead Ship
CV-1 [4] Langley [4] 1 [4] 1922 – 1936 [4] Converted from USS Jupiter. [2] Experimental ship, served 1925–36 as an aircraft carrier before being converted to a seaplane tender and given the new hull symbol AV-3. [2]
CV-2 [5] Lexington [5] 2 [5] 1927 – 1946 [5] The ships were laid down and partly built as part of a six-member battlecruiser class before being converted to carriers while under construction. [5]
CV-4 [6] Ranger [6] 1 [6] 1934 – 1946 [6] First purpose-built US Navy aircraft carrier. [6]
CV-5 [7] Yorktown [7] 3 [7] 1937 – 1947 [7] [8] Hornet was built after Wasp. [7] By the end of September 1942, both Yorktown and Hornet were on the bottom of the Pacific USS Enterprise, the orphaned sister of the class, became a symbol of the Pacific War. [7]
CV-7 [7] Wasp [7] 1 [7] 1940 – 1942 [7] Modified Yorktown class, built on 3,000 fewer tons to use up allotted tonnage under the Washington Naval Treaty. [7]

The Imperial Japanese Navy struck Pearl Harbor on December 7, 1941, but none of the Pacific Fleet's aircraft carriers were in the harbor. [9] Because a large fraction of the navy's battleship fleet was put out of commission by the attack, the undamaged aircraft carriers were forced to become the load-bearers of the early part of the war. [ citation needed ] The first aircraft carrier offensive of the U.S. Navy came on February 1, 1942, when the carriers Enterprise and Yorktown, attacked the Japanese bases in the Marshall and Gilbert Islands. [9] The Battle of the Coral Sea became the first sea battle in history in which neither opposing fleet saw the other. [ citation needed ] The Battle of Midway started as a Japanese offensive on Midway Atoll met by an outnumbered U.S. carrier force, and resulted in a U.S. victory. [9] The Battle of Midway was the turning point in the Pacific War. [9]

In 1943, new designations for carriers were established, limiting the CV designation to USS Saratoga, USS Enterprise, and the Essex class. [10] The new designations were CVB (Aircraft carrier, large) for the 45,000 long tons (46,000 t) carriers being built, and CVL (Aircraft carriers, small) for the 10,000 long tons (10,000 t) class built on light cruiser hulls. [10] The same directive reclassified escort carriers as combatant ships, and changed their symbol from ACV to CVE. [10] By the end of the war, the Navy had access to around 100 carriers of varying sizes.

On September 2, 1945, Japan signed the surrender agreement aboard USS Missouri, ending World War II. [11]

Designation Class Ships Active Description Lead Ship
CV-9 [12] Essex [12] 24 [12] 1942 – 1991 [12] This class constituted the 20th century's largest class of heavy warships, with 24 ships built. [13] 32 ships were originally ordered, but some were cancelled. [12] (Some sources consider the 13 ships of the Ticonderoga class a separate class or "long hull" variants of the Essex class, and Oriskany a one-ship class). [14]
CVL-22 Independence [15] 9 [15] 1943 – 1970 [15] [16] This class was a result of President Franklin Delano Roosevelt ' s interest in Navy shipbuilding plans. [15] In August 1941, with war looming, he noted that no new fleet aircraft carriers were expected before 1944 and proposed to quickly convert some of the many cruisers then building. [15]

Training ships Edit

During World War II, the United States Navy purchased two Great Lakes side-wheel paddle steamers and converted them into freshwater aircraft carrier training ships. Both vessels were designated with the hull classification symbol IX and lacked hangar decks, elevators or armaments. The role of these ships was for the training of pilots for carrier take-offs and landings. [17] Together Sable and Wolverine trained 17,820 pilots in 116,000 carrier landings. [18]

Designation Class Ships Active Description Lead Ship
IX-64 Wolverine 1 1942–1945 Former Great Lakes paddle steamer Seeandbee converted for aircraft takeoff and landing training
IX-81 Sable 1 1943–1945 Former Great Lakes paddle steamer Greater Buffalo converted for aircraft takeoff and landing training

Aircraft carrier technology underwent many changes during the Cold War. The first of the 45,000-ton carriers, USS Midway was commissioned eight days after the end of World War II, on September 10. [19] A larger ship was planned, and in 1948, President Harry Truman approved the construction of a "supercarrier", a 65,000-ton aircraft carrier to be named USS United States however, the project was canceled in April 1949 by the Secretary of Defense. [19] The Navy's first supercarriers came later, in 1955, with the Forrestal class. [20] 1953 saw the first test of an angled-deck carrier, USS Antietam. [21]

The "N" suffix was added to the designation system to represent nuclear powered carriers in 1956. [21] The first carrier to receive this suffix was USS Enterprise, commissioned in 1961. [22] The last conventionally powered carrier, USS John F. Kennedy, was commissioned in 1968 and was decommissioned in 2007. [23]

The Korean War began June 25, 1950, and the need for planes and troops was urgent. [21] Returning from Korea, USS Boxer made a record trip across the Pacific—7 days, 10 hours, and 36 minutes. [21] In 1952, all carriers with designations "CV" or "CVB" were reclassified as attack carriers and given the sign "CVA". [21]

As the Mercury-Redstone 3 mission ended, USS Lake Champlain recovered Commander Alan B. Shepard, the first American in space, on May 5, 1961. [24] Another aircraft carrier USS Hornet, recovered the Apollo 11 astronauts after their splashdown. [25] Apollo 11 was the first manned landing mission to the moon, and was composed of astronauts Neil Armstrong, Buzz Aldrin, and Michael Collins. [26]

In 1975, the first Nimitz-class aircraft carrier was commissioned the Nimitz class are the largest warships in the world and is the only aircraft carrier class in commission with the U.S. Navy (except for USS Enterprise, which, though still technically in commission as of August 2013, is currently being dismantled). [27] Construction and commissioning of the Nimitz class continued after the Cold War. [28]

Also, in 1975, the U.S. Navy simplified the carrier designations—CV, CVA, CVAN, CVB, CVL—into CV for conventionally powered carriers and CVN for nuclear-powered carriers. [29]

Designation Class Ships Active Description Lead Ship
CV-41 [30] Midway [30] 3 [30] 1945 – 1992 [30] This class was one of the longest lived carrier designs in history. First commissioned in late 1945, the lead ship of the class, USS Midway was not decommissioned until 1992, shortly after seeing service in the Gulf War. [30] Six were planned three were built including USS Coral Sea and USS Franklin D. Roosevelt. [30] The class was originally designated CVB. [30]
CVL-48 [31] Saipan [31] 2 [31] 1946 – 1970 [31] [32] Built on modified Baltimore-class cruiser hulls. [31] Both were converted to command-and-control ships in the mid-1950s: Saipan to USS Arlington (AGMR-2) , Wright to CC-2. [31]
CVA-58 [33] United States [33] 1 keel [33] None commissioned [33] This class was never commissioned (3 more were planned). [33] See Revolt of the Admirals for details. [33]
CV-59 [20] Forrestal [20] 4 [20] 1955 – 1998 [20] The Forrestal class was the first class of "supercarriers" of the Navy, so called because of their then-extraordinarily high tonnage (75,000 tons, 25% larger than the Midway class), and full integration of the angled deck. [20] [30]
CV-63 [34] Kitty Hawk [34] 3 [34] 1961 – 2009 [35] Sometimes called "Improved Forrestal class". [36] Sometimes mistaken as a four-ship class, with USS John F. Kennedy (see below) as a member. [37] The biggest differences from the Forrestals are greater length, and a different placement of starboard elevators two are forward of the island, with a third at the portside stern. [37] This class includes USS America.
CVN-65 [22] Enterprise [22] 1 [27] 1961 [38] – 2012 First nuclear-powered aircraft carrier, using eight A2W reactors. [39] Enlarged, modified, and nuclear-powered Kitty Hawk-class design. [39] Six ships of this class were planned, only the lead ship was constructed. Enterprise had been in active operational service for 51 years, longer than any combatant ship in American history.
CV-67 [40] John F. Kennedy [40] 1 [40] 1968 – 2007 [40] [41] Last conventionally powered aircraft carrier built (as of 2013). [23] Sometimes grouped as a Kitty Hawk-class ship. [23] Laid down as a nuclear ship to use four A3W reactors, converted to conventional propulsion early in construction. [42]
CVN-68 [27] Nimitz [27] 10 [27] [28] 1975 – Present [27] A line of nuclear-powered supercarriers in service with the US Navy using two A4W reactors, and the largest capital ships in the world. [27] [43] The Nimitz class are numbered with consecutive hull numbers starting with CVN-68. [27] Ten ships are in the class as of 2009 [update] . [27] [28]

When the Cold War ended in 1991, the U.S. Navy had conventionally powered carriers from the Midway, Forrestal, and Kitty Hawk classes active, along with USS John F. Kennedy and the nuclear Nimitz class and USS Enterprise however, all of the conventional carriers have been decommissioned. [20] [27] [30] [35] [38] [40] Construction of the Nimitz-class continued after the Cold War, and the last Nimitz-class carrier, USS George H.W. Bush, was commissioned in 2009. [28]

The next class of supercarriers—the Gerald R. Ford class—launched the first ship in 2017. [44] The new carriers will be stealthier, and feature A1B reactors, electromagnetic catapults, advanced arresting gear, reduced crew requirements, and a hull design based upon that of the Nimitz class. [44] [45] [46] Ten carriers are planned for the Gerald R. Ford class. [44]

Designation Class Ships Active Description Lead ship
CVN-78 [44] Gerald R. Ford [44] 1 (9 more planned) [47] 2017-present [48] The next generation supercarrier for the United States Navy. [44] Carriers of the Gerald R. Ford class will incorporate many new design features including a new nuclear reactor design, stealthier features to help reduce radar profile, electromagnetic catapults, advanced arresting gear, and reduced crewing requirements. [44] [45] [46] The Gerald R. Ford class uses the basic hull design of the preceding Nimitz class. [44] Ten ships are currently planned for the Gerald R. Ford class. [44]

During World War II, the U.S. Navy built escort carriers in large numbers for patrol work, and scouting and escorting convoys. [49] Escort carriers, based on merchant ship hulls, were smaller than aircraft carriers escort carrier crews referred to the ships as "Jeep carriers", the press called them "baby flat tops". [49] The escort carriers had lighter armor than aircraft carriers, were slower, had less defensive armament, and less aircraft capacity compared to aircraft carriers. [49] This smaller variant of carriers was designated "CVE" a common joke amongst crews was "CVE" meant "Combustible, Vulnerable and Expendable". [49]

Early in the war, German submarines and aircraft were interfering with shipping. [49] The worst losses occurred far at sea—out of the reach of land-based air forces—leading the Royal Navy to experiment with catapult-launching fighter aircraft from merchant ships, a somewhat successful approach. [49] However, the number of planes was still limited, so the United Kingdom appealed to the United States for help. [49]

Naval aviation [ edit | edit source ]

Planes from the Japanese aircraft carrier Shōkaku preparing the attack on Pearl Harbor.

Japan began the war with a highly competent naval air force designed around some of the best airplanes in the world: the A6M Zero was considered the best carrier aircraft of the beginning of the war, the Mitsubishi G3M bomber was remarkable for its range and speed, and the Kawanishi H8K was the world's best flying boat. Ε] The Japanese pilot corps at the beginning of the war were of high caliber as compared to their contemporaries around the world due to intense training and frontline experience in the Sino-Japanese War. Ζ] The Navy also had a competent tactical bombing force based around the Mitsubishi G3M and G4M bombers, which astonished the world by being the first planes to sink enemy capital ships underway, claiming battleship Prince of Wales and the battlecruiser Repulse.

As the war progressed, the Allies found weaknesses in Japanese naval aviation. Though most Japanese aircraft were characterized by great operating ranges, they had very little in the way of defensive armament and armor. Η] As a result, the more numerous, heavily armed and armored American aircraft were able to develop techniques that nullified the advantages of the Japanese aircraft. Although there were delays in engine development, ⎖] several new competitive designs were developed during the war, but industrial weaknesses, lack of raw materials and disorganization due to Allied bombing raids hampered their mass-production. Furthermore, the IJN did not have an efficient process for rapid training of aviators, as two years of training were usually considered necessary for a carrier flyer. Therefore, they were not able to effectively replace seasoned pilots lost through combat attrition following their initial successes in the Pacific campaign. Η] The inexperience of IJN pilots who were trained in the later part of the war was especially evident during the Battle of the Philippine Sea, when their aircraft were shot down in droves by the American naval pilots in what the Americans later called the "Great Marianas Turkey Shoot". Following the Battle of Leyte Gulf, the Japanese Navy increasingly opted towards deploying aircraft in the kamikaze role.

Japan's first jet-powered aircraft, the Imperial Japanese Navy's Nakajima J9Y Kikka (1945).

Towards the end of the conflict, several competitive plane designs were developed, such as the 1943 Shiden, but such planes were produced too late and in insufficient numbers (415 units for the Shiden) to affect the outcome of the war. ⎗] Radical new plane designs were also developed, such as the canard design Shinden, and especially jet-powered aircraft such as the Nakajima Kikka and the rocket-propelled Mitsubishi J8M. These jet designs were partially based on technology received from Nazi Germany, usually in the form of a few drawings only, Kikka being based on the Messerschmitt Me 262 and the J8M on the Messerschmitt Me 163), so Japanese manufacturers had to play a key role in the final engineering. ⎘] These developments also happened too late in the conflict to have any influence on the outcome. The Kikka only flew twice before the end of the war. ⎙]


During the first year of the Pacific War beginning on 7 December 1941, Allied personnel often struggled to quickly, succinctly, and accurately identify Japanese aircraft encountered in combat. They found the Japanese designation system bewildering and awkward, as it allocated two names to each aircraft. One was the manufacturer's alphanumeric project code, and the other was the official military designation, which consisted of a description of the aircraft plus the year it entered service. For example, the military designation of the Mitsubishi A5M fighter was the "Navy Type 96 Carrier Fighter". Type 96 meant that the aircraft had entered service in Imperial year 2596, equivalent to Gregorian calendar year 1936. Other aircraft, however, which had entered service the same year carried the same type number aircraft such as the Type 96 Carrier Bomber and the Type 96 Land Attack Bomber. Ώ] Adding to the confusion, the US Army and US Navy each had their own different systems for identifying Japanese aircraft. ΐ]

In mid-1942, Captain Frank T. McCoy, a United States Army Air Forces military intelligence officer from the 38th Bombardment Group assigned to the Allied Technical Air Intelligence Unit in Australia, set out to devise a simpler method for identifying Japanese aircraft. Together with Technical Sergeant Francis M. Williams and Corporal Joseph Grattan, McCoy divided the Japanese aircraft into two categories fighters and everything else. He gave boys' names to the fighters, and the names of girls to the others. Later, training aircraft were named after trees, Α] Β] single engine reconnaissance aircraft were given men's names and multi-engine aircraft of the same type were given women's names. Transports were given girls' names that all began with the letter "T". Gliders were given the names of birds. ΐ]

McCoy's system quickly caught on and spread to other US and Allied units throughout the Pacific theater. By the end of 1942, all American forces in the Pacific and east Asia had begun using McCoy's system, and British Commonwealth nations adopted the system shortly thereafter. The list eventually included 122 names and was used until the end of World War II. To this day, many Western historical accounts of the Pacific War still use McCoy's system to identify Japanese aircraft. ΐ] Γ]

In an effort to make the names sound somewhat comical, McCoy gave many of the aircraft 'hillbilly' names, such as "Zeke" and "Rufe," that he had encountered while growing up in Tennessee. Δ] Others were given names of people the creators of the system knew personally the Mitsubishi G4M bomber, with its large gun blisters was named "Betty" in homage to a busty female friend of Williams. The Aichi D3A "Val" got its name from an Australian Army sergeant. Ε] Not all of McCoy's chosen names caught on. Many Allied personnel continued calling the Mitsubishi Navy Type 0 Carrier Fighter "Zero" instead of McCoy's name of "Zeke." Also, McCoy's name for an upgraded version of the Zero, "Hap," in tribute to US Army general Henry H. Arnold, had to be changed to "Hamp" when it was learned that Arnold disapproved. Α] Δ]

Nakajima B5N2 “Kate” Type 97-3 Carrier Attack Aircraft at Pearl Harbor

“Nakajima “Kates” were the world’s most advanced carrier attack bombers at the start of the Pacific War. They sank five battleships in the Pearl Harbor attack — four with torpedoes and one with a bomb that detonated the Arizona’s million-pound powder magazine. Kates were crucial in all carrier vs carrier battles during the war and in the Japanese amphibious landings early in the conflict. Although deficient in protection, they were kept in service until their loss rates became prohibitive in 1944.”

Header photo source: U.S. Navy photo 80-G-427153 from the U.S. Navy Naval History and Heritage Command. Captured Kate 1943.

Key Points

  • The Japanese called this type of aircraft a kanjo kōgeki-ki.
    • In English, this meant “carrier attack aircraft.”
    • Informally, a kankō.
    • Most navies would call it a torpedo bomber.
    • Manufacturing project designation: B5N2.
    • Allied code name: “Kate.”
    • Official operational designation: Type 97-3 Carrier Attack Aircraft.
    • 40 Kates attacked with aerial torpedoes, sinking four battleships (California, Oklahoma, West Virginia, Nevada).
    • 49 B5N2s attacked with high-level bombs, destroying the Arizona with a crucial hit.
    • Teisatsu was an observer, navigator, bombardier.
    • Often (but not always) the senior crew member if so, the aircraft commander.


    At Pearl Harbor, Japan’s most devastating aircraft was the Nakajima B5N2, also known as the “Kate” and the Type 97-3 Carrier Attack Aircraft.

    • In the opening minutes of the attack, 40 Kates savaged Battleship Row with torpedoes. When they finished, Oklahoma and West Virginia had sunk, and California and Nevada were sinking.
    • Immediately afterward, 49 more Type 97-3s appeared. They flew along the backbone of battleship row at almost 10,000 feet. Each dropped a massive 800-kg (almost 1,800-lb.) class bomb designed to penetrate a battleship’s armored deck and ignite a magazine. One of these bombs destroyed the Arizona in a blast heard for miles.
    • In the second wave, 54 more B5N2s arrived. This swarm ignored ships and attacked airfields. Each dropped two or more bombs, bringing heavy devastation and loss of life.

    Pearl Harbor was just the beginning. Kates quickly proved that they could sink maneuvering ships at sea as well as ships sitting in harbor. In the first year of the war alone, they sank or helped sink three U.S. carriers: Lexington, Yorktown, and Hornet [Aireview staff]. A postwar summary[46], concluded that, “The achievements of Kate were compatible with those of the Zero.”

    Although the Type 97-3’s level bombing attacks were ineffective against ships at sea, Type 97-3s used level bombing to support Japanese troops in Japan’s lightning advance through the South Pacific.

    Carrier Bombers and Attack Aircraft
    Japanese carriers embarked two kinds of bombers. First, they had dive bombers, which they designated kanjo bakugekki -ki (carrier bombers.) Diving steeply, they dropped their bombs at close range for accuracy. Of course, this put them deep into anti-aircraft fire. Dive bombers usually could only carry a single medium-size bomb.

    The other type of bomber on Japanese carriers was the kanjo kōgeki-ki. (Kan meant ship, jo meant embarked, kogeki meant attack, and ki meant machine — in this case an aircraft.) Therefore, it was a “carrier attack aircraft.” Informally, Japanese crews shortened this to kankō. Other navies called such planes torpedo bombers. However, neither torpedo (gyorai) nor bomb (bakudan) appeared in the Japanese designation. Like torpedo bombers in other navies, kankōs attacked with either torpedoes or bombs. “Attack aircraft” reflects this versatility. The kankō at Pearl Harbor had three times the bomb capacity of the dive bomber. It always dropped its bombs in level flight, increasing safety but limiting accuracy.

    What I Call the Kankō that Attacked Pearl Harbor in this Study Report
    Japan’s kankō when the war began was generically designated the B5N and the Type 97 Carrier Attack Aircraft. Its first version was called the B5N1 and the Type 97-1 Carrier Attack Aircraft. The second, which was used at Pearl Harbor, was called the B5N2 and the Type 97-3 Carrier Attack Aircraft. Like the Japanese, I use the term Type 97-3 rather than giving the whole name when context makes “Type 97-3” unambiguous. In the Allied code name designation system, both versions were called the Kate.

    Referring to Japanese aircraft is problematic because the Japanese designation systems in World War II were complex, changed frequently, and used inconsistently [Francillon 1995 46-59, Mikesh 170-181]. If you are familiar with Japanese aircraft designations, you probably want to skip the Appendix on Japanese Naval Aircraft Designations, although you might want to read why I call the kankō that attacked Pearl Harbor the Type 97-3 Carrier Attack Aircraft instead of the Type 97 Model 12.

    The Aircraft

    The Type 97 kankōs were single-engine, low-wing monoplanes with well-cowled engines and flush-riveted skin to minimize aerodynamic drag [Francillon 1969 61]. Both had a crew of three seated one behind the other. The cowling was an NACA (U.S. National Advisory Committee for Aeronautics, NASA’s predecessor) design that also minimized drag [ Aireview staff 45, Hawkins 4].

    The Kate’s fuselage had an oval cross-section and used semi-monocoque construction. In a pure monocoque construction, the outer skin supports the aircraft structure completely, like an egg shell. In semi-monocoque construction, the skin is strengthened by adding internal ribs. Even with these ribs, semi-monocoque construction is lighter than a tubular structure.

    Figure 1: Semi-Monocoque Fuselage Construction

    Source: [email protected], taken at Pearl Harbor Aviation Museum.

    Like torpedo bombers in other navies, the Type 97-3 had a crew of three. Figure 6 shows that the members of the Type-97 crew sat under a single glazed canopy. Each could open the canopy around his station independently [King 133]. Each had a bucket seat with a seat belt [King 133]. There was no need for shoulder harnesses because the Kate did not engage in violent maneuvering like the Zero [King 133]. The crew communicated via unpowered speaking “Gosport” tubes [Hawkins 6, King 152, Mori 1323].

    Source: San Diego Air and Space Museum Archive. Catalog Number 01_00086081.

    The B5N wings had a flush-riveted stressed metal skin with all-metal flaps and fabric-covered ailerons [Francillon 1969 61 1995 415]. The slotted flaps extended to the wing fold, the ailerons from the fold outward [Hawkins 9]. These big wings gave the B5N the lift capacity it needed to carry its big ordnance loads. In addition, their size gave ample room for the Kate’s wide-stance hydraulic inward-folding landing gear attached to the main spar. This was the first use of hydraulically folding landing gear on a Japanese single-engine aircraft [ Aireview staff 45]. Size also gave room for fuel tanks between the wing’s two strong spars [Hawkins 9].

    Source: U.S. Navy Photograph of a B5N2 descending after having been fatally damaged by a PB4Y patrol bomber.

    Figure 3: Underside of Type 97-3 Wings

    Source: [email protected], Taken at the Valor in the Pacific Memorial. The exhibit is a fiberglass model.

    For carrier deck and hangar storage, the Kate’s wings folded upward. Jury struts were attached to the fuselage to support the weight of the folded wings during storage [Hawkins 9]. To minimize folded height and width on hangar decks, the right wing folded partially under the left [Hawkins 5]. To develop this low-wing design, Nakajima used knowledge gained earlier by examining designs from Northrup, Douglas, and Clerk [ Aireview staff 45, Hawkins 10], but the wing design was not a mere copy of foreign aircraft wings. The tail had fabric-covered control surfaces [Hawkins 10].

    Figure 4: Overlapping Wings for Storage

    Source: National Archives Photograph in Francillon [1969].

    Ordnance Carriage
    Kates carried their ordnance externally, under the fuselage. They had different racks for different ordnance loads [Hawkins 6], which were typically a single torpedo, a single 800-kg class bomb, two or three 250-kg class bombs, or six 60-kg class bombs. In China, two 250-kg class bombs or six 60-kg class bombs dominated ordnance selection [Aireview staff 46]. For some bombs, there were front and back fuzes, which could be selected by the bombardier before the drop [Panko Fuzes]. One fuze detonated the bomb on contact, while the other delayed the explosion about 0.2 second. The former was best for outdoor targets, the latter for penetrating buildings before exploding. The variety of weapons racks could cause re-arming issues in the stress of combat, such as at Midway.

    Figure 5: Kate with Bomb Load. Probably with three 250-kg (550-lb.) bombs

    Source: Imperial Japanese Navy via U.S. Navy

    Engine and Performance
    The B5N2 used a Nakajima 14-cylinder, two-row, air-cooled radial engine, the Sakae 11 [Francillon 1995 414]. The Imperial Japanese Navy used two engine designation systems. Sakae 11 was the operational designation [Francillon, 1995 515]. The manufacturing project designation was the NK1B, where N meant Nakajima, K meant air cooled, 1 meant that it was the first air-cooled engine in the current numbering sequence, and B meant that it was the second version of the engine [Francillon, 1995 515]. As in aircraft designation, Japanese engine designations were complex and changed over time [Francillon, 1995 515].

    The Sakae 11 generated 1,000 hp at takeoff and 970 hp at 9,845 ft (3,000 m) [Francillon 1995 415]. It gave a top speed of 235 mph at 11,810 ft and a cruising speed of 161 mph at 9,845 ft [Francillon 1995 415]. Carrying a heavy bomb load reduced these numbers, but the Kate was still faster than America’s torpedo bomber at the start of war in the Pacific, the Douglas TBD Devastator, and the main British torpedo bomber in 1941, the Fairey Swordfish biplane [Francillon 1969 16]. America soon introduced the excellent TBF/TBM Avenger torpedo bomber, but America’s defective aerial torpedo meant that USN torpedo attacks still brought little profit until the torpedo was greatly modified in late 1943 [Panko Torpedo].

    Defensive Limitations
    Given the Kate’s limited engine power, Nakajima could not add armor to the Kate because this would seriously degrade speed. The need to carry enough gasoline to meet range requirements, in turn, precluded self-sealing fuel tanks. Their thick rubber bladders reduced fuel volume too much. (When the Kate’s successor, the Tenzan , used self-sealing fuel tanks in a prototype, fuel capacity was reduced by 30 percent [Francillon 1995 431].) Although the Kate was rightly called the best torpedo bomber in the world at the start of the war in the Pacific, it was a slugger with a glass jaw.

    If fighter support was not present, a flight of Kates was easy prey for enemy fighters. Coming in from the front, a fighter could attack with impunity because B5Ns had no forward-firing machine guns. One Type 97 pilot who faced a head-on fighter attack reported that Wildcat fighters attacking from the front destroyed his nine-ship hikōtai completely, its pilots being unable to do anything but try to ram the attackers [Mori 3549]. Even attacks from the rear only faced a single 7.7 mm (.303-caliber) Type 92 machine gun. Even several Type 97 flying in close formation posed limited risk to attacking fighters.

    The Crew Roles

    The Japanese Navy used many terms based on English. The flight crew of an aircraft was called a peah (pair) regardless of its size [King 140]. The Kate peah consisted of a pilot, teisatsu (observer), and a radio operator/gunner. Each had important roles during an attack.

    Source: San Diego Air and Space Museum Archive. Catalog Number 01_00086081.

    The Pilot
    The pilot’s seat back attached to a pole, allowing the him to raise his seat for takeoff and landing. This improved visibility the over the long nose of the big tail-dragger. When the seat was at its highest elevation, the pilot’s head was just below the top of the windshield [Hawkins 6].

    Figure 7: Pilot’s Seat

    Source: Imperial Japanese Navy via Burin Do 1992.

    Japanese fighter pilots dismissed B5N pilots as “cart drivers” because the big kankō was slow and had little maneuverability [Mori 22 4041]. However, flying the Kate required extreme concentration and split-second decision making. The pilot had 16 instruments to monitor constantly, had to fly in close formation, and had to fly very smoothly because variation in engine power caused fuel burn to spike in a heavily loaded airplane [Mori 691]. In addition, during a torpedo or bomb drop, it was essential to fly absolutely level, with no pitch, yaw, or roll. Any small variation would throw the bomb off target. When Juzo Mori attacked the California , he had to make a series of split-second decisions about not attacking the Helena , aborting his first run at the California , and swinging around to attack the California again, this time successfully [1809-1840]. He then had to weave an escape route through heavy anti-aircraft fire seeking revenge [1845]. He had to do all this flying at very low level in an aircraft of limited maneuverability.

    Radio Operator / Machine Gunner
    In the rear sat the radio operator/machine gunner, who keyed messages in Morse code [Mori 1614]. The radio in a Kate was fairly good. This radio was much better than the miserable set in Zeroes, so to return to the striking force, Zeroes and Kates rendezvoused, and the B5N2s shepherded the fighters back to the carriers. When Mitsuo Fuchida had his radio operator break radio silence and send the message Tora, Tora, Tora to his carriers to advise that surprise had been achieved, the transmission was heard in Japan, although only because of odd atmospheric conditions [Fuchida 1952, King 149].

    The rear-seater had a rather cheap-looking folding chair that faced forward for radio operation [King 133]. During the Pearl Harbor attack, there was radio silence, so the radio operator/gunner focused entirely on gunnery [King 134]. To use the machine gun, the rear-seater folded his chair, clipped it to the side of the cockpit, unstowed the gun, and stood up to fire [King 134]. (On Val dive bombers, in contrast, the rear seat swiveled front to back [King 134]). He was normally tethered to the floor by his parachute cord, but crews did not use parachutes during the Pearl Harbor attack, so he had no attachment to the aircraft beyond his hands on the gun and his knees braced against the side of the fuselage [King 148].

    The weapon itself was a Type 92 7.7 mm (.303 in) machine gun with six 97-round drum magazines—one on the gun and five spares [Mori 1702]. Based on the British Lewis machine gun used on World War I aircraft, it fired 600 rounds per minute, and its muzzle velocity of 2,500 ft per second gave it an effective range of 600 m [Francillon 1995 431]. Its arc of aim was about forty degrees left, right, and down and about 80 degrees upward [King 134]. As already noted, this gun was puny compared to those in American fighters, most of which had six .50 caliber machine guns with larger bullets, greater range, and a much higher volume of fire.

    Figure 8: Type 92 Machine Gun (7.7 mm, .303 in)

    Source: Imperial Japanese Navy via Burin Do 1992.

    Figure 9: Side View of Captured Type 97-3 Carrier Attack Bomber Showing an Unstowed Machine Gun

    Source: National Archives Photograph in Francillon [1969].

    The middle-seater had the most complex job. He was the teisatsu, which is usually translated as observer [King 130]. On reconnaissance and maritime patrol missions, observation was, in fact, his main task. To improve his view, he could raise or lower his seat up to about 14 inches, and swivel his seat a bit over 35 degrees right or left [King 133]. He also had two small windows in the fuselage sides to illuminate his charts and manuals.

    However, observation was only one aspect of the teisatsu’s job. Most importantly, he was the aircraft’s navigator, which was a critical task for long-distance missions over water. Chief Petty Officer 1 st Class Haruo Yoshino, the teisatsu on a Kaga Kate in the Pearl Harbor attack, noted that he had been trained in many navigation tools, including the use of charts, maps, slide rules, sextants, and navigation by the stars [King 130]. On missions, he brought a large bag called a yōgubukurō, which stored his navigation gear this plus binoculars, flare gun, and possibly an aerial camera [King 130]. Access to a downward photo-reconnaissance camera was also available from this position.

    Dropping Bombs
    On level bombing missions, the teisatsu was the bombardier. To sight the target, he had two trap doors on the left side of the floor. He unstowed his Type 90 telescopic bomb sight and lowered it into one of the doors [King 132]. As the aircraft neared the target, the teisatsu directed the pilot to go slightly to the left or right. When the bombsight was lined up with the target, the teisatsu released the bombs [King 132]. The bombardier preceded the drop by a steady vocalization, which he changed to a shout at the moment of drop [King 132]. Because the doors were on the left side of the cockpit, the bombs (or torpedo) were offset to the right side of the fuselage. A five-plane formation arranged in a V was called a “buntai,” and the lead Kate’s bombardier dropped first, with the other four aircraft toggling simultaneously.

    Figure 10: Underside of Type 97-3 Wings

    Source: [email protected], Taken at the Valor in the Pacific Memorial. The exhibit is a fiberglass model.

    Torpedo Attacks
    In torpedo attacks, the teisatsu’s job was more passive. As the aircraft neared potential targets, the teisatsu, who had time to look around, selected a target and directed the pilot to it. Teisatsu Haruo Yoshino originally selected the West Virginia, but the ship was blanketed by water spray from other torpedoes. He directed the pilot to switch to the Oklahoma [King 150]. Either the pilot or the teisatsu could release the torpedo. At Pearl Harbor, Yoshino performed the release, freeing the pilot to concentrate on low-level flying [King 151]. After the torpedo release, the teisatsu told the pilot which way to turn to escape.

    Although the teisatsu’s role in torpedo attacks was important, the pilot was in control of the torpedo attack [Mori]. Only he could aim the aircraft at its target, using a sight on the top of the instrument panel [King 133]. Only he had the perspective to know when to drop the torpedo, especially at sea, where almost every torpedo release involved complex deflection shooting at a precise speed and altitude against a moving target. He had to make these calculations mentally while dodging flak and flying the airplane at low altitude [King 133].

    Carrier landings are always difficult, especially for heavy bombers that lack agility. To ease the pilot’s mental load, the teisatsu constantly called out instrument data during the landing [King 138].

    Who Was in Charge?
    The pilot and teisatsu were usually noncommissioned officers, while the radio operator/gunner was an enlisted sailor. When the teisatsu was the senior member of the crew, he was the aircraft commander or kichō [King 130]. In the Pearl Harbor Raid, Commander Mitsuo Fuchida led the entire attack from the teisatsu position of a Kate [Fuchida 2011]. On the way toward Oahu, he navigated for the entire first wave [Fuchida 2011].

    Kates in the Pearl Harbor Attack

    The objective of the Pearl Harbor attack was to keep American battleships from interfering with Japan’s main goal—its thrust south to the oil fields of Borneo and the Dutch East Indies [Fukudome]. Both sides envisioned an eventual climactic slug-out between battleship that would decide the course of the war. With fewer battleships, Admiral Husband E. Kimmel would be outnumbered and would not sortie his battleships at the start of war per the Rainbow 5 War Plan. Figure 11 shows where the battleships were moored on the west side of Ford Island. One battleship not on Battleship Row was Pennsylvania, which was in dry dock being overhauled. Pearl Harbor’s ninth battleship, Colorado, was in Bremerton Washington being overhauled [Yarnell].

    Figure 11: Battleship Row, Carrier Berths, and Seaplane Base with PBY Patrol Bombers

    Sources: Contemporary NASA Satellite Photo, [email protected]

    The Imperial Japanese Navy also knew the importance of carriers. Figure 11 shows the normal mooring spots of the three carriers stationed at Pearl Harbor. Note that Enterprise normally moored directly in front of California . The Lexington and Saratoga , in turn, usually berthed on the West Side of the island [Panko Enterprise]. There was a Battleship Row, but there was no carrier row. The Japanese knew that no carriers had been reported to be in harbor, but they still had these sixteen Kates attack from the west.

    Enterprise and Lexington were away on missions to deliver airplanes to Midway and Wake [NHHC], there being no escort carriers available yet. Enterprise had actually been scheduled to return to port the day before the attack, but it was delayed by heavy seas [Bureau of Ships 3]. Pearl Harbor’s third carrier, Saratoga, was entering the harbor at San Diego to pick up her airplanes after it had been refitted in Bellingham, Washington [NHHC].

    The Torpedo Attack at Pearl Harbor

    Torpedoes were the only reliable way to destroy battleships. The mine effect of the warhead’s explosion could break open a battleship’s side, especially if it hit below the armor belt. Japan’s Type 97 Modification 2 (not Model 2) aerial torpedo (koku gyorai) was certainly the best aerial torpedo in the world at the timer. It weighed 1,840 lb and had a 610 lb warhead with an explosive charge of 450 lb [NTMJ Aerial Torpedoes]. This was far more powerful than any bomb dropped on Pearl Harbor. Best of all, it was reliable, having been relentlessly tested and developed since 1931. Finally, it was delivered by superbly trained aircrews from Akagi, Kaga, Sōryū and Hiryū. The green aircrews of the newly worked up Shōkaku and Zuikaku would be in less vital parts of the attack.

    Due to their weight and speed, when the aerial torpedoes struck the water, they kept diving down. At shallow Pearl Harbor, this initial plunge would have driven the Type 91 Mod 2 into the mud. The Japanese worked furiously to modify the torpedo to pitch up immediately upon entering the water instead of waiting for it to right itself after water entry. (The torpedo was heavier on the bottom than the top, but this natural and automatic method for righting the torpedo took time that the plunging torpedo did not have.)

    The solution was a gyroscope that controlled two ailerons at the front to the tail cone. This anti-roll mechanism ensured that the torpedo would be upright when it struck the water, allowing the horizontal rudders to be pitched up upon water entry without the danger of throwing the torpedo left, right, or even down. The big stabilizing fins at the very back of the torpedo were there to reduce wobble, not to pitch the torpedo up or down as it dropped through the air [Panko Torpedo].

    Figure 12: Japanese Type 91 Modification 2 Torpedo with Anti-Roll Fins (Left) and Stabilizing Fins (Right) and

    Source: Photograph Taken at Pacific Aviation Museum, Pearl Harbor.

    Figure 13: Rear Horizontal Rudder Effect when Torpedo is Upright on Water Entry (Unrolled)

    Figure 14: Rear Horizontal Rudder Effect when Torpedo is Not Upright (Rolled) on Water Entry

    Torpedo attacks were extremely risky. The Kates had to approach flying steady at wave-top level and low speed. If the ships were alerted and fully armed, their guns could savage torpedo attackers. Consequently, torpedo attack at Pearl Harbor was slated to occur at the very start of the assault so they could strike before American guns were crewed and ready, but a mix-up in signals led to dive bombers attacking the PBYs on the southern tip of Ford Island two minutes before the first torpedo bombers arrived at 7:57 [Aiken].

    Despite this near-absence of warning, some of the guns on the battleships quickly got into action. In fact, several pilots and teisatsus marveled at the amount of fire they received [Aiken, Fuchida 1952, King 152-153]. Since April 1941, each battleship constantly manned two 5-inch dual-purpose guns and two .50-caliber machine guns [Gannon 545-546]. The 5-inch guns had a locked but quickly accessible, ready supply of 15 shells [Gannon 545-546, Wallin 106]. The machine gun had 300 to 400 rounds of locked, ready ammunition [Wallin 106, Zimm 268]. The machine guns got into action almost immediately, the 5-inch guns about four minutes later [Wallin 106-107]. Unfortunately, the 5-inchers were slow-firing guns, and their central director was not manned during the attack. In turn, the .50-caliber machine gun did not hit hard enough to take out aircraft dependably [Gannon 560-570].

    However, the torpedo attack was brief, and AA fire did not become effective until near to its close, when 12 Kaga Kates made the final torpedo drops against battleship row [King 153]. Five of these B5N2s were shot down by anti-aircraft fire, and all but the first were damaged [Allen, King 153-154]. The five Kates lost to this final dozen torpedo attackers were the only B5N2s lost from the 144 that took part in the attack. If the battleships had been given even a little more warning, the results of the raid might have been different.

    Figure 15: Kate with Torpedo

    Source: Imperial Japanese Navy via U.S. Navy.

    In total, 40 Kates attacked with torpedoes. Figure 16 shows that 24 attacked from the east. The first 12 were from the Akagi, the final 12 from the Kaga [King 150]. This stream of Kates approached in line, several hundred meters apart. This delay between successive torpedo attackers gave individual torpedo bombers at least a brief time to pick individual targets. To give their torpedoes long enough runs to arm before striking, most B5N2s attacking from the east approached through the Southeast Loch (see Figure 16). Consequently, a large majority of the torpedoes launched at battleships were dropped against the Oklahoma and West Virginia, which lay directly in front of the loch. Only three Japanese torpedoes hit other battleships.

    Figure 16: Type 97-3 Torpedo Attack at Pearl Harbor

    Sources: Contemporary NASA satellite photo, [email protected]

    Sixteen other Type 97-3s attacked from the west. These Kates were from the Hiryū and Sōryū, and their hoped-for targets were Lexington and Saratoga, which they had been told the night before were not in port [Mori 1669].

    Due to the mistaken identification of the Utah as a current battleship, six of the eight Kates from the Sōryū wasted their torpedoes on the former battleship and the ships around it [Fuchida 1952, Mori 1825ff, Panko Utah]. One more attacked Helena, which was a cruiser and therefore not a top-priority target [Mori 1809]. Only one swung around the island and attacked Battleship Row from the west. This Kate, piloted by Jūzō Mori, gave the California its second torpedo hit [Mori 1831ff], sealing its fate.

    In turn, four of the Hiryū’s eight B5N2s also went after the Helena and Oglala, all missing these targets. The other four swung into the line of attacking Akagi and Kaga Kates to go after battleships. In total, then, out of 16 torpedoes, six were wasted on the Utah and the nearby Raleigh, and five more were wasted on Helena [Fuchida 1952] A mitigating factor in this squandering of so many torpedoes is that pilots were attacking into the low, early morning sun, so they had a difficult time seeing and identifying targets.

    The High-Level Attack on Inboard Battleships in the First Wave at Pearl Harbor

    Figure 17 shows that some battleships were moored in pairs. One sat next to Ford Island, the other outboard. The inner ships — the Maryland, Tennessee, and Arizona — were safe from torpedoes.

    Figure 17: Battleship Moorings

    Source: National Archives Photo NH 50472, edited by [email protected]

    To attack the inner ships, a second swarm of 49 Kates flew over the backbone of Battleship Row, as Figure 18 shows. Each carried a single massive 800 kg (1,800 lb) bomb. They flew at almost 10,000 feet because dropping it from high altitude gave the bomb enough momentum to smash through the battleship’s armored deck. However, high-altitude bombing was not accurate. To compensate, the Type 97-3s flew in tight buntai chevrons of five, and all five dropped their bombs simultaneously. Even so, only eight of these bombs hit battleships [Zimm 232].

    Figure 18: Type 97-3 High-Level Bombing Attack at Pearl Harbor

    Sources: Contemporary NASA satellite photo, [email protected]

    In addition, some of the bombs that did hit failed to fully explode. Their explosive was Type 91 [NTMJ Bombs 35], which is trinitroanisole [NTMJ Explosives 35]. Trinitroanisole is one of the least-sensitive explosives [NOAA]. It needed to be insensitive so that it would not explode immediately after slamming into the battleship’s deck at high speed. However, insensitivity made it difficult to detonate. In the same vein, the bomb was given two rear fuzes that would only fire if they sensed that the bomb had crashed through the deck. Two fuzes increased the chance that the bomb would detonate given the shock tolerance required in the bomb [NTMJ Bombs 35]. Trinitroanisole is highly toxic when it burns [NOAA], so if the bomb only partially detonated, it could be mistaken for a poison gas bomb.

    The bombs that these Kates dropped in the first wave were Type 99 Number 80 Mark 5 special bombs [NMTJ Bombs p. 35]. The Type indicated that it was accepted in 1939. The Number was the bomb’s weight class in kilograms divided by 10, meaning the bomb was in the 800 kg class. (Its actual weight was 797 kg, or 1,757 lb.) Mark 5 indicates that it was a special armor-piercing bomb (not the fifth version of the bomb) [NMTJ Bombs p. 6]. The bomb was a special bomb only in the sense that it was not developed as part of the two main bomb programs — ordinary (anti-ship) bombs or land bombs. The bomb was fashioned from an obsolete 41 mm[1] shell from the battleship Nagato [Friedman 269]. For aerodynamics, the shell was tapered and fins were added.

    Figure 19: Type 99 Number 80 Mark 5 Special Bomb Used in the First Wave

    Source: U.S. Technical Mission to Japan [NTMJ Bombs p.35].

    The bomb was a nearly solid steel dart designed to pierce armored decks using sheer mass and speed. It had room only for 22 kg (49 lb) of explosive charge [NTMJ Bombs p. 35]. Unless the bomb exploded in a powder magazine, it did little damage. Only one did, the bomb that obliterated Arizona.

    The Second-Wave Attack on Airfields

    An hour after the first wave began, 54 more B5N2s appeared in the sky. In the second wave, their prey was airfields, not ships. These Kates flew in chutais (squadrons) of nine aircraft.

    [1] Some writers say that the bomb was based on a 40 mm cannon shell, while others list the diameter as 41 mm. The confusion is due to a specific Japanese subterfuge. The original shells were created for the Nagato. Its guns had a diameter of 41 mm (16.1 in), but the Japanese reported it as only 40 mm (15.7 in) [Freidman 269]. They made this change on March 29, 1922, because the Washington Naval Treaty of 1922 barred guns larger than 16 inches (40.6 mm). Underreporting the shell size by a single millimeter allowed it to be reported as having an acceptable diameter. When it was converted into a bomb before the war, this fiction was maintained [NTMJ Bombs].

    Second-Wave Kate Targets

    Combined Fleet Operations Order No. 2 [MHS 16] called for launching 54 Type 97-3s under the overall command of Lt. Cmdr. Shigekazu Shimazaki. These were divided into datais of 27 Kates each.

    • The Shōkaku B5N2s, led by Shimazaki, were to attack as a unit against Hickam Field. They did extensive damage there.
    • The Zuikaku Type 97-3s, commanded by Lt. Tatsuo Ichihara, were to hit three different targets: NAS Kaneohe, Ford Island in NAS Pearl Harbor, and Barbers Point.

    The Zuikaku Kates certainly hit Kaneohe. Patrol Wing 1’s official report [PatWing1] said that two groups of nine attacked, although it referred to them as two-seat bombers. The facts that each dropped multiple bombs and dropped them in level flight, however, suggests that they were B5N2s. Wenger, Cressman, and Di Virgilio [1663-1672] corroborated the number of aircraft. The Kates at Kaneohe attacked at low level [PatWing1]. They needed to attack from below the clouds to aim, and the cloud base was low over Kaneohe that morning [Wenger, Cressman, Di Virgilio 1663-1672]. Fortunately for the Americans, the cumbersome Kate bombsight was inaccurate at low altitudes, so bombs had to be dropped by rough estimation [Wenger, Cressman, Di Virgilio 1678-1687].

    If the remaining nine Kates in in Ichihara’s daitai had hit Ford Island, the loss of life probably would have been considerable. However, Ford Island did not receive noticeable bomb damage during the second wave, so it is not clear how the remaining nine Kates in Ichihara’s group actually proceeded.

    Figure 24: Kate Targets for the Second Wave

    Kate Bomb Loads

    Also according to Combined Fleet Operations Order No. 2 [MHS 16], each Kate was slated to carry one Type 98 #25 land bomb and six Type 97 #6 land bombs [MHS 16]. However, Figure 21 shows that some B5N2s, at least, carried two Type 98 250 kg bombs and no Type 97s. (This photograph was taken of B5N2s attacking Kaneohe.) Gunston [167] specifically said that 18 had two 250 kg bombs and that the remaining 36 had one 250 kg bomb and six 60 kg bombs. Unfortunately, Gunston did not give a source for his statement. It seems best to simply note the two bomb loadouts and say that both might have been used in the second-wave attack by Type 97-3s in Hawaii.

    Figure 21: Kates Carrying Two 250 kg Land Bombs Attacking NAS Kaneohe

    Source: Wenger, Cressman, Di Virgilio.

    Figure 21 and Figure 22 illustrate these two bombs. In Japanese terminology, land bombs were designed to be used against land targets. They were general purpose bombs, which primarily damaged through blast overpressure. However, they also produced shrapnel and heat damage, and were able to penetrate somewhat.

    Figure 22: Type 98 #25 Land Bomb

    Source: Naval Technical Mission to Japan [NTMJ Bombs p. 12].

    Figure 23: Type 97 #6 Land Bomb

    Source: Naval Technical Mission to Japan [NTMJ Bombs p. 8].

    Table 1 has information about the explosive charges and penetration abilities of these bombs. Note that neither would have had difficulty penetrating roofs on hangars and other buildings. (A tour guide at Hickam erroneously said that these were armor-piercing bombs because they smashed through the roof in several buildings.) Their fuzes would be set to delay their detonation until they hit the floor or at least penetrated the building considerably.

    Table 1: Bomb Characteristics for Kates in the Second Wave at Pearl Harbor

    Bomb Weight (lb) Fill Percentage Explosive Charge (lb) Penetration of Reinforced Concrete (in)
    Type 98 #25 534 40% 213 16
    Type 97 #6 133 39% 52 8

    Bomb Weight (kg) Fill Percentage Explosive Charge (kg) Penetration of Reinforced Concrete (cm)
    Type 98 #25 242 40% 97 40
    Type 97 #6 60 39% 24 20

    Source: Naval Technical Mission to Japan [NTMJ Bombs 8 12].

    Note that the Type 98 #25 land bomb had 213 lb of explosive charge. This was the largest explosive charge of any bomb the Japanese dropped on Pearl Harbor, including the big ship killer in the first wave. Whether a group of nine Kates carried one 250 kg land bomb and six 60 kg land bombs or two 250 kg land bombs, they would cause serious devastation.


    Arrested Development

    During the 1930s, the Imperial Japanese Navy issued several requirements for carrier attack aircraft. Across most of these procurement cycles, the IJN failed to find anything acceptable, although it did order a few marginal aircraft. The Type 96 kankō — the Type 97’s immediate predecessor — came closest, carrying as much ordnance as the Kate. However, it had a top speed 50 kt slower than the B5N [Mori 696]. The Type 96 would be mincemeat in combat.

    Nakajima and Mitsubishi Both Win

    Japan finally held a successful prototype competition beginning in 1935 [Francillon 1995 412]. Nakajima and Mitsubishi competed. The Nakajima prototype was more advanced. It had hydraulically folding wings and combat Fowler flaps that made it very maneuverable [Francillon 1969 16]. It also had a variable-pitch propeller [Hawkins 5].

    The IJN was concerned that these innovations might not be reliable in operational units, and tests did show problems with the power-folding wings [Francillon 1995 16, Hawkins 6], the Fowler flaps [Hawkins 6], and the variable-pitch propeller [Hawkins 6]. Most of these problems were fixed in the first prototype, but the IJN remained concerned about maintenance in operational use [Francillon 1995 413]. At the same time, the Nakajima prototype was clearly superior in performance to the Mitsubishi entry, which still had fixed landing gear [Francillon 1995 16]. The IJN decided to purchase the Nakajima machine.

    To hedge its bet, the Imperial Japanese Navy also ordered some of the Mitsubishi kankōs [Francillon 1995 16]. However, the attractiveness of this backup strategy waned when Nakajima removed the power folding wings, Fowler flaps, and variable-pitch propeller in the second prototype [Francillon 1995 413]. This ameliorated reliability concerns. In the end, the IJN ordered only 115 Mitsubishi carrier attack aircraft. It ordered 1,149 Nakajimas.

    Nakajima built 669 of the aircraft, while Aichi built 200 and Dai-Juichi Kaigun Kokusho built 280 [Francillon 1995 17]. This pattern of secondary production was common in World War II for both Japan and America. Nakajima production ended in 1941, allowing it to work on the attack aircraft’s successor [Francillon 1969 17].

    The Type 97-1 Kankō (B5N1)

    The initial production version was designated the Type 97-1 Carrier Attack Aircraft [Aireview staff 46, Burin Do, Eden 380, Francillon 1995, Hawkins 6, Mondey 215]. Its manufacturing project designation was B5N1. It was powered by a Hiraki 3 engine that produced 700 hp on takeoff and 970 hp at 3,000 m (9,485 ft) [Francillon 1995 413]. Its 9 cylinders were organized in a single row, making its diameter considerable. As Figure 24 shows, its cowling was wider than the fuselage.

    Figure 25: Engine Cowling on the Type 97-1 and Type 97-3 Carrier Attack Bombers

    Type 97-1 (B5N1) with Wider Cowling

    Type 97-3 (B5N2) with Narrower Cowling

    Sources: Imperial Japanese Navy via U.S. Navy (Left) and U.S. Navy photo 80-G-427153 (Right).

    In late 1938, the B5N1 entered combat in China [Hawkins 7]. At first, it was phenomenally successful. However, when Soviet pilots and aircraft began to intercept Japanese attack aircraft in China, losses began to mount [Eden 380, Francillon 1995 413]. When fighter protection was unavailable, Kates suffered heavy losses.

    The Type 97-3 Kankō (B5N2)

    To increase performance, the Japanese navy established the B5N2 manufacturing program to put a more powerful engine in the aircraft. Nakajima selected its own Sakae 11 two-row 14-cylinder air-cooled radial driving a three-blade constant-speed propeller [Francillon 1995 414]. This engine produced 1,000 hp at takeoff and 970 hp at 3,000 m (9,485 ft) [Francillon 1995 17]. Having two rows of cylinders, the Sakae engine had a smaller diameter than the one-row Hiraki 3 engine in the B5N1. This made the cowling smaller [Francillon 1995 414]. Cowling size is the easiest way to distinguish between the B5N1 and the B5N2 that followed, as Figure 24 shows.

    The new version achieved operational status in December, 1939 [Eden 380, Francillon 1995 414, Hawkins 6]. It became the Type 97-3 Carrier Attack Aircraft [Aireview staff 46, Hawkins 7]. (The Mitsubishi kankō had been designated the Type 97-2 [Aireview staff 46, Hawkins 6-7]). Americans also code named it the Kate.

    Disappointingly, the new engine produced no performance gain. The data in the Characteristics section of this paper explain why. Although the Sakae produced more than 40 percent more power at takeoff, it only produced 15 percent more at 3,000 m. In addition, it was 100 kg (221 lb) heavier. Cruising speed rose only from 138 kt (159 mph) to 140 kt (161).
    However, the newer engine was more reliable, so production shifted to the B5N2 model anyway [Francillon 1995 414]. By the Pearl Harbor attack, Type 97-3s had replaced all Type 91-1s in front-line squadrons [Francillon 1995 414]. Some Type 97-1s were converted to trainers under the B5N1-K production designation [Francillon 1995 414].

    The small performance gain for the Type 97-3 convinced the IJN that it needed a completely new attack aircraft with more speed and range. This need was answered in 1939 [Eden], when Nakajima proposed a new carrier attack aircraft that looked like a scaled-up B5N with a larger tail surface in proportion to its body [Aireview staff 47]. Thanks to its engine, which was almost twice as powerful as the one in the B5N2, it would be able to fly 50 mph faster than the Type 97-3. It would also have 50 percent greater range [Aireview staff 47]. For added protection, its rear gunner would sit in a retractable turret, and it would also have a ventral machine gun to provide fire from attackers coming in below the aircraft [Aireview staff 47]. However, it still lacked a forward-facing machine gun.

    The new aircraft was designated the Tenzan (Heavenly Mountain). It received a name instead of a type designation because the Japanese dropped the shiki designation system for operational aircraft in July 1943, replacing shiki designations with popular names [Francillon 1995, Mikesh 180-181]. Its manufacturing project code was B6N1.

    Figure 26: B6N Tenzan

    B6N Tenzan after the war. Tested at the Technical Air Intelligence Center. U.S. Navy photograph posted to Wikipedia. https://commons.wikimedia.org/wiki/File:B6N_Taic.jpg.

    The first Tenzan prototype flew in 1941 however, the Tenzan did not enter service until April 1944 [Aireview staff 47], a consequence of its long and difficult development process. A major problem initially was the use of Nakajima’s Mamori engine, which was powerful but heavy and vibrated severely [Aireview staff 47]. Replacing the Mamori with a Mitsubishi Kansei engine took considerable time, and engine problems proved to be only one of the Tenzan’s development issues [Aireview staff 47]. The B6N2 resulted from the replacement of the Mamori by the Mitsubishi Kasei engine. The B6N2 was the version that became operational. It was not until April 1944 that the B6N2 began to replace the 97-3 [Aireview staff 47]. As a result, the Type 97-3 continued to be used in front-line service, enduring severe losses.

    Although no longer viable for bombing and torpedo missions, the good range of the Type 97-3 made it acceptable for rear-area sea lane patrols to escort convoys [Francillon 1995]. To detect submarines, some Kates received a magnetic airborne detector (MAD)[1] capable of detecting submerged submarines by their magnetism [NTMJ MAD]. The MAD device used in the war was the Type 3 Model 1, indicating that it was accepted in 1943 [NTMJ MAD 1]. The MAD gear used a horizontal spool of wire wound 600 times [NTMJ MAD 12]. The magnetic field in this detector spool changed as the aircraft passed over a submarine, generating a tiny electrical flow in the wire loop. An oscilloscope-like display showed the changed flow.

    Changes in aircraft pitch, roll, and yaw also induced a change in the magnetic field relative to the aircraft, so the loop was stabilized by a gyroscope to keep it dead level [NTMJ MAD 8-9].

    [1] The MAD abbreviation today stands for “magnetic anomaly detection.”

    In addition, the airplane’s electronics also induced small eddy currents in the aircraft fuselage, so these were measured by another wire loop and subtracted from the detector loop’s electrical readings [NTMJ MAD 10].

    Despite intensive development efforts, the system could detect only a large submarine 120 m to 150 m (390 ft to 490 ft) below the aircraft and within 100 m (165 ft) laterally [NTMJ MAD 11]. Given the fact that the submarines being hunted were submerged, the vertical detection range was particularly disappointing. The Japanese navy concluded that this performance was inadequate, but having no other option, it implemented the MAD system [NTMJ MAD 7].

    Given the very short range of MAD equipment, convoy protection required a group of six aircraft equipped with the MAD equipment to fly in a line abreast back and forth ahead of the convoy [USSBS 13]. Three thousand were ordered, but only 465 were delivered [NTMJ MAD 12], and only 90 to 100 were working at any time [NTMJ MAD 13]. Use was further limited by fuel shortages. Convoys often sailed without protection [NTMJ MAD 13]. Although our concern is the Kate, several aircraft types were used. In fact, only 50 of the sets were assigned to Kates [NTMJ MAD 15]. Overall, MAD-equipped aircraft were responsible for 11 submarine kills from August 1944 to July 1945. [NTMJ MAD 15]

    Some Kates also carried a Type 3 Mark 6 Model 4 radar [FEAF 29]. These radars operated at a wavelength of 150 MHz (corresponding to a wavelength of 2 m.) This radar had a nominal range of 110 km (68 mi) for large ships. The range was much smaller for submarines. On convoy protection flights, radar-equipped aircraft would sweep behind the convoy, flying perpendicular to the convoy’s path. Given the radar’s long range, only a single aircraft needed to crisscross behind the convoy, and it could scan a considerable distance behind the convoy [USSBS 13]. The following figures illustrate the placement of these Yagi radar antennas on B5N2s.

    Figure 27: Locations of Type 97-3 Radar Antennas

    Figure 28: Radar Antennas in Wing of Captured Type 97-3

    Source: National Archives Photograph in Francillon [1969].

    Figure 29: Location of Radar Antennas in Rear Fuselage of Captured Type 97-3

    Source: National Archives Photograph in Francillon [1969].

    By the end of the war, few Kates were left, thanks to combat losses, wear and tear, and their use in kamikaze attacks. Fearing rogue kamikaze attacks after the surrender, the United States destroyed nearly all remaining Japanese combat aircraft, including Kates. A few were taken for study, but no attempt was made to preserve them afterward.

    Historiography Notes

    The main historiography issue in this study is the question of the official designation for the version of the Kate that attacked Pearl Harbor — Type 97-3 or Type 97 Model 12. As discussed in the Appendix, Francillon [1995 52] said that the change from the one-digit model designation to the two-digit model designation occurred “in the late 1930s.” Mikesh [171] placed it later, “in late 1942 to 1943.” Neither cited a source. The staff of Aireview [46], a Japanese magazine, created a book on Japanese aircraft it specifically stated in 1953 that the second version of the B5N was the Type 97-3. Although the preponderance of limited available evidence indicates that Type 97-3 was the correct shiki designation, agreement on the evidence is not unanimous. If future research clarifies this issue, I will update this study report.

    Another frustrating issue was identifying which targets Lt. Ishihara’s 27 B5N2s hit in the second wave. The operational order for the fleet tasked his Kates to hit NAS Kaneohe, Ford Island, and Barbers Point. As discussed in the text, 18 did hit Kaneohe. However, bomb damage was not evident in the second wave at Ford Island, so nine of the Kates are unaccounted for. We have found no accounts written by crew members of second-wave Kates to cast light on this question. Again, if future research clarifies this issue, I will update this report.

    A related question is the bomb load carried by B5N2s in the second wave. The operational order called for all to be loaded with a single 250 kg bomb and six 60 kg bombs. However, photographic evidence for NAS Kaneohe indicates that at least some carried two 250 kg bombs. Gunston [167] stated that 18 had two 250 kg bombs and the rest had one 250 kg bomb and six 60 kg bombs. Unfortunately, Gunston did not list a source for this statement. This is another area where I hope future research will bring clarification.

    I have used primary or close-to-primary sources as much as I could. In particular, I have used several interview studies of Japanese technical specialists and senior officers. These interviews were conducted just after the war by U.S. forces. The Japanese officials proved to be surprisingly willing to give information despite likely resentment over the horrific destruction done to Japanese cities. In some cases, the cooperation appeared to reflect their desire to talk about achievements (and complain about problems). However, Wilkinson noted that there was often a more fundamental reason for cooperation. When he asked his Japanese contacts why they had given information so freely, he usually received the same answer: “Our emperor directed us to tell you everything.”

    For the information on how Type 97-3s were used in the Pearl Harbor attack, we took information primarily from Japanese Monograph No. 97 [MHS]. This is a collection of operational orders and other official Japanese documents about the attack. Of special importance is Combined Fleet Operations Order No. 2, which details Japanese planning for the Pearl Harbor attacks, including targets, types and numbers of aircraft assigned to different parts of the attack, the weapons they carried, and the leaders of various groups in the attack. Information presented by authors who were present in the attack make it appear that the operational orders were followed generally during the attack, [Fuchida 2011, King, Mori]. However, several issues remained. As just noted, the most vexing were the Kate bomb loads on the second wave and what the nine aircraft that were slated to hit Ford Island actually did.

    For general information about the Kate’s history, construction, and other matters, Francillon’s [1969 1995] books provide considerably more information than any other source. In fact, most other Western sources I have seen appear to take much of their information from his books, including directly copying text, usually without attribution. Several Japanese sources were particularly valuable because they looked at the Type 97 from Japan’s point of view.

    My overall historiographical goal has been to present a comprehensive review of available information on the Nakajima Type 97 Carrier Attack Aircraft, resolving conflicts between statements in different sources where possible, and where impossible, pointing them out.

    I have also added some analysis based on my background as a physicist, social scientist, information technology researcher, and business professor.

    I would be grateful for any information that will help me correct any errors in this paper. I hope to offer revised versions of this paper in the future.


    Category Type 97-1 Kankō B5N1 Kate Type 97-3 Kankō B5N2 Kate Tenzan Model 12 B6N2 Jill
    Span 15.5 m (50’ 10”) Same 14.9 m (48 ft 10 in)
    Length 10.3 m (33’ 10”) Same 10.9 m (35 ft 8 in)
    Wing Area 37.7 m 2 (406 ft 2 ) Same 37.2 m 2 (400.4 ft 2 )
    Empty Weight 2,106 kg (4,634 lb) 2,279 kg (5,024 lb) 3,010 kg (6,636 lb)
    Loaded Weight 3,700 kg (8,157 lb) 3,800 kg (8,378 lb) 5,200 kg (11,464 lb)
    Maximum Weight 4,015 kg (8,852 lb) 4,100 kg (9,039 lb) 5,650 kg (12,456 lb)
    Wing Loading 98.1 kg/m 2 (20.1 lb/ft 2 ) 100.8 kg/m 2 (20.6 lb/ft 2 ) 139.8 kg/m 2 (28.6 lb/ft 2 )
    Power and Performance
    Engine 1 x Nakajima Hiraki 3 nine cylinder, one-row air-cooled radial driving a 3-blade constant-speed propeller. 1 x Nakajima Sakae 11 two-row, 14-cylinder air cooled radial driving a 3-blade constant-speed propeller. Mitsubishi Kasei 25 two row,14-cylinder air cooled radial driving a 4-blade constant-speed propeller.
    Takeoff Engine Power 700 hp 1,000 hp 1,850 lb
    Critical Altitude Engine Power 840 hp at 3,000 m (9,485 ft) 970 hp at 3,000 m (9,485 ft) 1,680 hp at 5,500 m (18,040 ft).
    Power Loading 4.8 kg/hp (11.5 lb/hp) 3.8 kg/hp (8.4 lb/hp) 2.8 kg/hp (6.2 lb/hp)
    Maximum Speed 199 kt at 2,000 m (229 mph at 6,500 ft) 204 kt at 3,600 m (235 mph at 11,810 ft) 260 kt at 4,900 m (289 mph at 16,075 ft)
    Cruising Speed 138 kt at 2,000 m (159 mph at 6,500 ft) 140 kt at 3,000 m (161 mph at 9,845 ft) 180 kt at 4,000 m (207 mph at 13,125 ft)
    Climb to 3,000 m: 7 min, 50 s 3,000 m: 7 min, 40 s 5,000 m (10 m 24 s)
    Service Ceiling 7,400 m (24,280 ft) 8,260 m (27,100 ft) 9,040 m (29,660 ft)
    Normal Range 679 mi 608 mi 1,085 mi
    Armament One flexible rear-facing 7.7 mm Type 92 machine gun. No forward-firing machine gun. Same One rear-facing 7.7 mm Type 92 machine gun in retractable turret, plus one ventral rearward facing Type 92 machine gun. No forward-firing machine gun.
    Maximum Bomb Load 800 kg (1,764 lb) Same Same

    Source: Francillon 1995, pp. 415-416 for the B5N and pp. 43-44 for the B6N2. B6N1 data is not listed in the table because the B6N2 was the version introduced.

    Appendix on Japanese Naval Aircraft Designations

    Manufacturing Project Designation

    Many American writers call the aircraft that attacked Pearl Harbor the B5N2. This designation is short, easy to remember, and similar to the U.S. Navy’s official operational designations at the time (F4F-3, etc.). However, “B5N2” was not used by pilots, air crews, or maintenance personnel because it was not an operational designation. It was a manufacturing project designation used by manufacturers and the ministries that financed these projects [Francillon 1995 51-52, Mikesh 175-179]. However, we will use it because of its widespread familiarity today and because of the fact that B5N2 is widely used in Japanese publications and models.

    Breaking this designation down, B was the type of aircraft, in this case, a carrier attack aircraft. Other initial letters included A for fighters, D for dive bombers, and G for land-based carrier attack aircraft. The 5 meant that this was the fifth carrier attack bomber in the current series.[1] Finally, N indicated that it was created by Nakajima, and 2 meant that it was the second model of the aircraft.

    Allied Code Name System

    In turn, “Kate” came from the code name system used by the Allies, at least in the Pacific [Mikesh 10-24]. It was instigated by Captain Frank T. McCoy, aided by Technical Sergeant Francis M. “Fran” Williams [Mikesh 11-12]. McCoy was the “material officer” for the Allied Air Force, Southwest Pacific Area Headquarters. [Mikesh 11-12]. He and Williams developed their code name system because existing designations for Japanese aircraft were unworkable [Mikesh 12]. Their system was much simpler because it used easy-to-pronounce names—American boys’ names for fighters and girls’ names for bombers. Their system spread rapidly and was used extensively by U.S. and Allied operational forces during the war. However, the code name was not an official system when it began because it was not accepted at higher levels in the U.S. Army Air Forces [Avistar]. Fortunately, this unofficial status did not deter its use.

    More pertinently, the Allied code name system did not appear until almost a year after Pearl Harbor. McCoy and Williams did not even arrive in Australia until 1942, and they did not develop the code name system immediately [Mikesh 12]. It was first promulgated in September, 1942 as Intelligence Information Memorandum No. 12: Japanese Air Services and Japanese Aircraft [Avistar]. Code names were not seen in combat reports until late that year and then only a few times [Avistar]. Therefore, the name “Kate” would not have been used by Allied forces at the time of the Pearl Harbor attack. However, I use it extensively because it was so widely used by operational forces on the Allied side during most the war and, more importantly, is so familiar today. The term Kate is also attractive for this document because it refers to both version of the aircraft.

    Shiki Designation for Operational Use

    The aircraft’s official IJN operational designation was the Type 97-3 Carrier Attack Aircraft (kyū-nana-shiki kanjō kōgeki-ki). The shiki (type) designation for this aircraft was Kyū-nana-shiki, which translates as Type (shiki) 97 (kyū-nana). Ninety-seven indicated that the Kate was accepted in Imperial Year 2597 (1937 in the Western Calendar) [Francillon 1995 413]. The shiki system was used operationally by the Imperial Japanese Navy [Francillon 1995 52-54], so we will use it extensively. Its major problem is that it is long. When the context was clear, therefore, the Japanese simply called the aircraft the Type 97 or the Type 97 kankō. I do the same.

    Shiki Model Extensions

    Aircraft are usually produced in several versions. In the 1930s, the IJA and IJN used the gata (model) system, in which the year designation was followed by a dash and a one-digit model number. The first version of the Kate was the Type 97-1 Carrier Attack Aircraft (The -1 meant Model 1) [Aireview staff 46, Burin Do, Eden 380, Francillon 1995, Hawkins 6, Mondey 215]. The version that attacked Pearl Harbor and was used through the rest of the war was the Type 97-3 [Aireview staff 46, Burin Do, Hawkins 7]. This was the only version in operational use at the beginning of the War in the Pacific [Francillon 1969 17]. Why was the second version not labeled the Type 97-2? As noted earlier, the IJN also accepted a Mitsubishi attack aircraft in 1997. This was labeled the Type 97-2 Carrier Attack Aircraft [Hawkins 6-7]. When the second version of the Nakajima kankō was created later, the B5N2, it was designated the Type 97-3 [Aireview staff 46, Hawkins 7].

    This model system was changed over time. Instead of adding a single model number, the Type year was followed a two-digit model number, such as “Model 12” [Francillon 1995 53] This was pronounced “Model one two,” not “Model twelve.” It meant that this model used the 1st fuselage design but the 2nd engine. The revised model system was useful because fuselage designs and engines often changed at different times. In the revised model system, the initial aircraft would have been the Type 97 Model 11 Carrier Attack Aircraft. The version used at Pearl Harbor had a different engine, so it would have been the Type 97 Model 12 Carrier Attack Aircraft.

    The key issue is when did the IJA and IJN convert from the one-digit model system to the two-digit model system? There are two major U. S. sources on the Japanese designation systems, and they disagree. Mikesh [171] says that the change occurred “Over a period from 1942 to 1943,” while Francillon [1995 52] says that the change took place “in the late thirties.” Both call the first model, the B5N1, the Type 97-1, with Mikesh [173] specifically calling it the Type 97-1, while Francillon [1995 413] expresses this as Type 97 Model 1. The disagreement comes with the B5N2. Mikesh [173] calls the second version of the Nakajima kankō (the B5N2) the Type 97-3 [173]. Francillon [1969 414] calls it the Type 97 Model 12. In the United Kingdom, Hawkins [6-7] also uses the Type 97-1 and -3 designations. He says that the -3 designation was “later” changed to Model 12 [7] but does not say when.

    Terminology appears to vary by country.

    • U.S. sources tend to be follow Francillon [1995]. Although few list sources, expressions that Francillon uses, such as “in the late ‘30s,” appear frequently.
    • In the UK, terminology was consistent for the B5N1 in sources I located [Eden 380, Hawkins 5, Mondey 215]. All three call it the Model 1. For the B5N2, Hawkins [7] uses the Model 3 designation, while Eden and Mondey do not list model designations for the B5N2.
    • The two main Japanese language sources on the Kate that I have found were Aireviewstaff and Burin Do. Aireviewstaff call the B5N2 the Type 97 Number 3. Burin Do calls it the Type 97-3.
    • I was able to locate four Japanese-sourced plastic model kits for the B5N2. Table 2 shows that all four list the B5N2 as the Model 3, although they express it differently.

    Table 2: Designations Used in Japanese Airplane Models of the B5N2

    Manufacturer Manufacturing Project Designation Allied Code Name Operational Shiki Designation
    Avioni-X B5N2 None Listed Model 3
    Hasegawa B5N2 Kate Type 97-3
    Marushin B5N Kate Type 97-3
    Nichima B5N2 Kate Type 97-3

    Given that only Francillon [1995] uses Model 12 for the B5N2, I chose to use Type 97-3 to refer to the second version of the Nakajima 1937 kankō.

    [1] In the U.S. Navy designation system, in F4F-3, the 4F meant that it was the fourth fighter accepted from Grumman (F), not the fourth fighter in the current numbering series.


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    Figure 1: Semi-Monocoque Fuselage Construction
    Figure 2: Crew Seating
    Figure 3: Underside of Type 97-3 Wings
    Figure 4: Overlapping Wings for Storage
    Figure 5: Kate with Bomb Load. Probably with three 250-kg (550-lb.) bombs
    Figure 6: Crew Seating
    Figure 7: Pilot’s Seat
    Figure 8: Type 92 Machine Gun (7.7 mm, .303 in)
    Figure 9: Side View of Captured Type 97-3 Carrier Attack Bomber Showing an Unstowed Machine Gun
    Figure 10: Kate Underside
    Figure 11: Battleship Row, Carrier Berths, and Seaplane Base with PBY Patrol Bombers
    Figure 12: Japanese Type 91 Modification 2 Torpedo with Anti-Roll Fins (Left) and Stabilizing Fins (Right) and
    Figure 13: Rear Horizontal Rudder Effect when Torpedo is Upright on Water Entry (Unrolled)
    Figure 14: Rear Horizontal Rudder Effect when Torpedo is Not Upright (Rolled) on Water Entry
    Figure 15: Kate with Torpedo
    Figure 16: Type 97-3 Torpedo Attack at Pearl Harbor
    Figure 17: Battleship Moorings
    Figure 18: Type 97-3 High-Level Bombing Attack at Pearl Harbor
    Figure 19: Type 99 Number 80 Mark 5 Special Bomb Used in the First Wave
    Figure 24: Kate Targets for the Second Wave
    Figure 21: Kates Carrying Two 250 kg Land Bombs Attacking NAS Kaneohe
    Figure 22: Type 98 #25 Land Bomb
    Figure 23: Type 97 #6 Land Bomb
    Figure 25: Engine Cowling on the Type 97-1 and Type 97-3 Carrier Attack Bombers
    Figure 26: B6N Tenzan
    Figure 27: Locations of Type 97-3 Radar Antennas
    Figure 28: Radar Antennas in Wing of Captured Type 97-3
    Figure 29: Location of Radar Antennas in Rear Fuselage of Captured Type 97-3


    Origins [ edit | edit source ]

    Japanese seaplane carrier Wakamiya.

    In 1912, the Royal Navy had informally established its own flying branch, the Royal Naval Air Service. The Japanese admirals, whose own Navy had been modeled on the Royal Navy and whom they admired, themselves proposed their own Naval Air Service. The Japanese Navy had also observed technical developments in other countries and saw that the airplane had potential. The following year, in 1913 a Navy transport ship, the Wakamiya was converted into a seaplane tender, a number of aircraft were also purchased.

    Siege of Tsingtao [ edit | edit source ]

    On 23 August 1914, as a result of its treaty with Great Britain, Japan declared war on Germany. The Japanese, together with a token British force, then laid siege to the German held territory of Kiaochow and its administrative capital Tsingtao on the Shandong peninsula. During the siege, starting from September, Maurice Farman seaplanes onboard (two active and two reserve) the Wakamiya conducted reconnaissance and aerial bombardments on German positions and ships. On 30 September the Wakamiya was later damaged by a mine, but the seaplanes (by transferring to land) continued to used against the German defenders until their surrender on 7 November 1914. The Wakamiya conducted the world's first naval-launched aerial raids in history [N 1] and was in effect the first aircraft carrier of the Imperial Japanese Navy. [N 2] By the end of the siege the aircraft had conducted 50 sorties and dropped 200 bombs, although damages to German defenses were light. ΐ]

    Interwar Years [ edit | edit source ]

    The Japanese navy had closely monitored the progress of aviation of the three Allied naval powers during World War I and concluded that Britain had made the greatest advances in naval aviation Α]

    The Sempill Mission was a British aeronaval technical mission led by Captain Sempill and sent to Japan in September 1921, with the objective of helping the Imperial Japanese Navy develop its aeronaval forces. The mission consisted in a group of 29 British instructors, headed by Captain William Sempill, and stayed in Japan for 18 months. Β] The British government hoped it would lead to lucrative an arms deal. The Japanese, were trained on several British aircraft, such as the Gloster Sparrowhawk, in various techniques such as torpedo bombing, flight control and carrier landing and take-offs. Skills that would later be employed in the shallow waters of Pearl Harbour in December 1941. Γ] The mission also brought the plans of the most recent British aircraft carriers, such as the HMS Argus and the HMS Hermes, which influenced the final stages of the development of the carrier Hōshō. The Hōshō became the first designed aircraft carrier from the keel up to be built. The military in Japan were also aided in their quest to build up their naval forces by Sempill who had become a Japanese spy. Over the next 20 years, the British Peer provided the Japanese with secret information on the latest British aviation technology. His espionage work helped the Japanese rapidly develop its military aircraft and its technologies before the Second World War. Δ]

    Under the Washington Naval Treaty two incomplete battlecruisers were allowed to be rebuilt as carriers, for the Japanese the Akagi and the Amagi. However the Amagi was damaged during an earthquake in 1923 and the Kaga became a replacement. With these two carriers much of Imperial Japanese Navy's doctrines and operating procedures were established.

    IJNAS vs US first encounter (1932) [ edit | edit source ]

    • During the Shanghai Incident on February 22, 1932 Lt Robert Short (US Army Reserve) while piloting a Boeing 218 with Chinese markings damaged one IJN Type 13 carrier attack aircraft, killing the pilot, Lt. Kotani and wounding the observer, before he was killed in action. [citation needed] Reportedly three days previously Short had shot down IJN Lt. Kidokoro. [citation needed]

    Sino-Japanese War [ edit | edit source ]

    From the onset of hostilities in 1937 until forces were diverted to combat the Americans in 1941, the Imperial Japanese Navy Air Service played a key role in military operations on the Chinese mainland. Despite the fierce rivalry between military branches, in the fall of 1937 General Matsui Iwane, the Army general in command of the theater, admitted the superiority of the Naval Air Services. His combat troops relied on the Navy for air support. Ε]

    Aircraft attacked Chinese positions in Shanghai and surrounding areas, naval bombers such as the G3M and G4M were used to bomb Chinese cities. Japanese fighter planes, notably the Mitsubishi Zero, gained tactical air superiority control of the skies over China belonged to the Japanese. Unlike other naval airforces, the IJNAS was responsible strategic bombing and operated long ranged bombers.

    The Japanese strategic bombing were mostly done against Chinese big cities, such as Shanghai, Wuhan and Chonging, with around 5,000 raids from February 1938 to August 1943.

    The bombing of Nanjing and Guangzhou, which began on 22 and 23 September 1937, called forth widespread protests culminating in a resolution by the Far Eastern Advisory Committee of the League of Nations. Lord Cranborne, the British Under-Secretary of State For Foreign Affairs, expressed his indignation in his own declaration.

    Words cannot express the feelings of profound horror with which the news of these raids had been received by the whole civilized world. They are often directed against places far from the actual area of hostilities. The military objective, where it exists, seems to take a completely second place. The main object seems to be to inspire terror by the indiscriminate slaughter of civilians. » Ζ]

    World War II [ edit | edit source ]

    Identification chart for Japanese military planes during WWII

    IJNAS planes taking off for Pearl Harbor

    1st Air Fleet Aichi dive bombers preparing to bomb American naval base in Pearl Harbor, Hawaii

    At the beginning of the Pacific war the Navy Air Service consisted of five naval air fleets Η] In April, 1941 the First Air Fleet was created, concentrating the Navy's carriers into a single powerful striking unit ⎖] The Japanese had a total of ten aircraft carriers: six fleet carriers, three smaller carriers, and one training carrier. The 11th Air Fleet contained most of the Navy's land based strike aircraft.

    On December 7, 1941, the Imperial Japanese Navy attacked Pearl Harbor crippling the U.S Pacific Fleet and destroying over 188 aircraft for a loss of 29 aircraft. On December 10, land based bombers of the 11th Airfleet were also able to sink HMS Prince of Wales and HMS Repulse.

    There were also air raids on the Philippines and attacks on Darwin in northern Australia.

    From 16 December 1941 to 20 March 1945 IJN aviation casualites killed were 14,242 aircrew and 1,579 officers.

    Aircraft strength 1941 [ edit | edit source ]

    The IJNAS had over 3,089 aircraft in 1941 and 370 trainers. [ citation needed ]

    • 1,830 first line aircraft including:
      • 660 fighters, 350 Mitsubishi Zeros⎗]
      • 330 Carrier based strike aircraft
      • 240 land based twin engined bombers
      • 520 seaplanes (includes fighters and reconnaissance) and flying boats.

      World War II Aircraft [ edit | edit source ]

        (Type 96 carrier-based fighter) Claude (Navy Type 0 Carrier Fighter) Zeke (Navy Land based Interceptor Fighter 'Shiden'/'Shiden Kai') George (Land based fighter) Jack (Navy Night Fighter 'Gekko') Irving
        (Navy bomber Model 11 'Ginga') Frances (Type 1 land-based attack aircraft) Betty (Type 96 Land-based Attack Aircraft 'Rikko') Nell

      Torpedo & Dive Bombers:

        (Navy Type 94 Carrier Bomber) Susie (Navy Type 99 Carrier Bomber) Val (Navy Type 33 Carrier Bomber 'Suisei') Judy (Navy Type 97 Carrier Attack Bomber) Kate (Navy Type 11 Carrier Attack Aircraft 'Tenzan') Jill (Navy Type 96 Carrier Attack Aircraft) Jean

      Float planes & Flying Boats

        (Navy Type 0 Reconnaissance Seaplane) Jake (Type 0 Small Reconnaissance Seaplane) Glen (Navy Type 16 Reconnaissance Seaplane 'Zuiun') Paul (Type 0 Observation Seaplane) Pete (Navy Type 95 Reconnaissance Seaplane) Dave (Navy Type 94 Reconnaissance Seaplane) Alf (Type 2 Large Flying Boat) Emily (Type 97 Large Flying Boat) Mavis (Navy Fighter Seaplane 'Kyōfū') Rex (Navy Type 2 Interceptor/Fighter-Bomber) Rufe

      Reconnaissance Planes:

        (Type 100 Transport Model 2 Topsy (Navy Type AT-2 Transport) Thora (Experimental 13-Shi Attack Bomber) Liz (used as transports)

      Japan’s Fatally Flawed Air Forces in World War II

      Japanese fighters and bombers lay abandoned at Atsugi Naval air base at the end of the war.

      World War II in the Pacific was a fight to seize and defend airfields. The Japanese made gaining and maintaining control of the air as much a requirement in their basic war strategy as they did the destruction of the U.S. Pacific Fleet. But as Commander Masatake Okumiya charged, “The Pacific War was started by men who did not understand the sea, and fought by men who did not understand the air.” He might well have added that the war was planned by men who did not understand industry, manpower and logistics.

      To say that the Japanese army and navy did not cooperate on aerial matters would be a serious understatement. “They hated each other,” Lt. Cmdr. Masataka Chihaya recalled, “[they] almost fought. Exchange of secrets and experiences, the common use of airplanes and other instruments, could not even be thought of.”

      Japan, although seemingly advanced in aerial tactics, entered the war with a narrow aerial doctrine, insufficient numbers of aircraft and those of generally poor design (excluding the Mitsubishi A6M2 Zero, of course), too few aircrews and inadequate logistics for a war of attrition. Neither its army nor its naval air arm was prepared for the duration, violence or sophistication of the war to come. Even its short-lived lead in aerial tactics collapsed once the Guadalcanal campaign began.

      Completely aside from having an industrial base able to produce enough aircraft, a nation’s air force needs to be balanced between aircraft, combat and maintenance crews, and air bases. If Japan was to seize an empire, its airfield builders would have to accompany the fighting forces every step of the way. Absent such construction units, the air force would have to use captured bases.

      Army air forces were doctrinally anachronistic. Air units were subordinate to ground force commanders, not independent entities on a footing equal to ground and naval commanders. Japan’s army had developed its air forces for continental warfare with the Soviets. Naval air, on the other hand, was tied to operations of the Combined Fleet, with naval officers, rather than air officers, making major air decisions.

      Admiral Isoroku Yamamoto had given some thought to a land-based air war, stating in 1936 that naval operations in the next war would consist of capturing an island, building an airfield and using that base to gain control over the surrounding waters. His ideas, however, did not take hold. The Japanese studied and trained hard at aerial tactics, but they failed to develop the airfield construction techniques and equipment, as well as the units, necessary to build air bases, maintenance, supply and dispersal facilities.

      Japan launched its December 1941 attacks from well-developed bases. During the southern advance, the navy’s 22nd Air Flotilla supported the attack into Malaya from three airfields in and around Saigon. Units were at full strength in aircraft and crews. Plentiful quantities of fuel and spare parts were available. The aircraft received excellent maintenance. Zeroes, for example, underwent a thorough overhaul every 150 hours of flight. As Japanese forces moved south, air units occupied, repaired and exploited captured enemy bases. Real problems developed, however, when those units reached undeveloped territories. Getting fuel, food and materiel to those bases determined whether the aircraft flew. Whether a base had been captured or built, however, it was nearly useless if seaborne supplies could not reach it.

      Mechanical complexity, battle damage and environmental stresses meant that maintenance was key to an aircraft’s availability, its performance and whether the crew survived. Considering Japan’s stressed economy, it should have been intolerable in terms of production and transportation to accept the loss of equipment that could have been repaired. Amazingly, the Japanese tolerated those losses.

      Although a nucleus of well-trained army and navy maintenance men and armorers followed their aircraft south, maintenance units lagged behind during the early advances and were too few even when they caught up with the flying units. The army responded by sending forward individual maintenance units to plug gaps in maintenance coverage. The navy reduced support of homeland air bases to a minimum, so as to reinforce forward bases. Because service personnel arrived late or were too few, maintenance — and even the building of quarters and other facilities — fell to the aircrews themselves. Those tasks sapped the energy of men whose principal duty was flying.

      The more mobile a maintenance unit is, the less it can do without heavy equipment. The better a unit is at fixing things, however, the harder it may be to get where it needs to go. The Japanese were chronically short of shipping. Moving heavy maintenance units forward was always a problem. Unloading heavy equipment in locations where there were no piers, docks and roadways made air base maintenance all that much more difficult.

      The army’s piecemeal commitment of aviation maintenance units was due to the original absence of any strategic plans to put large army forces into the Southwest Pacific. Rising air losses in the Solomons, however, led the navy to request that the army bring in aircraft. But without a clear long-range plan or doctrine of what to do, no one could arrange the necessary logistical support.

      Depots where engines could be changed and major repairs made were few and scattered. The Fourth Air Army’s heavy equipment for engine changes and major structural repair on New Guinea, for instance, was poor. Periodic inspections, repairs, overhauls and even routine servicing fell off because of maintenance shortfalls. The Japanese had to abandon many aircraft during advances or retreats that easily could have been repaired at rear areas. Poor repair also denied them the opportunity to use worn-out aircraft in a training role.

      Aviation fuel in New Guinea was of poor quality and resulted in engine problems. The army’s main aircraft repair base at Halmahera, 1,000 miles from the front lines, never functioned adequately because it lacked equipment and mechanics. High humidity and rains corroded metal parts and wires. Electrical equipment grew fungus. Lubricating oils evaporated or ran off equipment. Allied bombings killed skilled mechanics and delayed aircraft maintenance. Ground crews suffered attrition from out-of-control aircraft, spinning propellers and from working around heavy objects.

      Because the army and navy did not cooperate, army aircraft on New Guinea had to fly 1,500 miles to Manila for engine changes even though the navy had major maintenance assets as close as Rabaul. Even at Rabaul, aircraft maintenance was so limited that of 60 fighters and 40 bombers that might be on hand, only a mix of 30 typically could fly on a given date.

      During the advance southward, Japanese pilots fought from unimproved airstrips, most of them small and unpaved. Although Japanese aircraft generally were lighter than Western counterparts and not so much in need of paved strips, occupying enemy airfields was never easy. Gasoline trucks were scarce and could be found at only a few of the large fields. Ground crews ordinarily had to refuel aircraft with hand pumps and barrels — a tedious process that slowed aircraft turnaround and consumed manpower. Even Rabaul’s aircraft were refueled from 200-liter drums rather than from gasoline trucks.

      When the Japanese navy flew its first nine fighters into the Philippine airport of Legaspi in December 1941, two of them were totally wrecked upon landing. The army flew two squadrons of Nakajima Ki-27s onto recently captured Singora Field in Malaya, and wrecked nine aircraft on the poor ground. When 27 Zeroes of the Tainan Kokutai (air group) flew into Tarakan Field — one of the worst in the East Indies — on Borneo in January 1942, two aircraft overshot the runway and were demolished. Slippery mud at that field made simple takeoffs and landings dangerous.

      Half the aircraft of the 23rd Air Flotilla lost in the first three months of the war were casualties of crackups on bad runways — partially due to weak landing gear and poor brakes, but mainly from bad terrain. Another 30 percent of the flotilla’s aircraft wore out and had to be scrapped. Only 18 of the 88 aircraft it wrote off went down in combat.

      Japanese naval aircraft flew into Lae on New Guinea in early April 1942. Zero ace Saburo Sakai described the strip, built by the Australians before the war to airlift supplies into, and gold out of, the Kokoda mine, as a “forsaken mudhole.” Although Japanese authorities considered it an improved airfield, it was so small that Japanese pilots compared it to landing on an aircraft carrier. Three decrepit trucks provided support there.

      Japanese navy tables of organization and equipment specified that each air unit was to have extra aircraft in its organization equal to one-third the operational complement. Yet by early April 1942, naval air units had no extras and were below their authorized operating strength. The navy general staff refused urgent requests from the shore-based 11th Air Fleet for replacement aircraft because not even the higher-priority carriers were up to strength.

      The navy general staff had been equally shortsighted in planning for mutually supporting air bases. Japanese officers who could see the big picture had no solution. “Nothing is more urgently needed than new ideas and devices,” Rear Adm. Matome Ugaki, chief of staff of the Combined Fleet, wrote in July 1942. “Something must be done by all means.”

      No one on either side of the Pacific had foreseen serious campaigns in the Solomons and on New Guinea. In the first 10 months of war, the Japanese navy managed to complete only one new air base, at Buin on Bougainville, and it had only one runway. Important though that base was, it was a rough field, and seven of 15 Zeroes were badly damaged when they landed there on October 8, 1942. Heavy rains delayed construction, and even significant additions to the construction troops did not help much. The runway continued to be soft and slippery during rains. When flying unit ground crews arrived and reported that Buin was unfit for operations, Admiral Ugaki, rather than arranging for construction assets to properly complete the field, groused to his diary: “How weak-minded they are! This is the time when every difficulty should be overcome. Don’t grumble, but try to use it by all means!” Fliers did try — and damaged about 10 aircraft a day when the runway was wet.

      The airfield at Guadalcanal bore bitter fruit when the Americans seized it just before the Japanese brought in their own aircraft. The Japanese failed to construct ferry sites and auxiliary airfields between Rabaul and Guadalcanal, 675 miles away, when they had the time. Lack of shipping to carry men and equipment for that task was the main problem, but their near total disregard of an aircraft’s combat radius was also at fault. For example, 18 Aichi D3A1 dive bombers were ditched into the sea in the first two days of the campaign when they ran out of gas.

      Japan had not developed a robust civil engineering infrastructure. It did have power rock crushers, concrete mixers, mobile power saws and mobile well-drilling equipment, but bulldozers, power shovels and other earthmoving machinery were in short supply. Picks, shovels, manpower and horsepower provided the backbone of Japanese engineering activities.

      Japan’s prewar military budgets had gone to warships, infantry divisions and aircraft, not to construction equipment. When war came, the hitherto-ignored lack of construction assets affected tactics. For instance, without mechanized equipment to cut dispersal areas, frontline aircraft were vulnerable to attack on the ground.

      Japanese planners did have one good reason for skimping on airfield construction units. The normal bearing capacity of most soil was good enough to handle lightweight Japanese aircraft. But Japan lacked sufficient steel to turn out large quantities of steel planking while it concentrated on aircraft, warships and merchantmen, and it was short of shipping to transport it. This meant that Japan depended on manpower to construct airfields. The military used native laborers wherever it could, paid them poorly and fed them little or nothing. They worked more than 2,500 Javanese to death while building a field on Noemfoor Island.

      The Japanese army had to use infantrymen to help build airfields. In December 1942, for example, the engineer regiment and three rifle battalions of the 5th Division were detailed to build airfields in the Solomons. “When we compare [our] clumsy result with what our enemy accomplished,” recalled Commander Chihaya, “building huge airfields in good numbers with inconceivable speed, we ceased to wonder why we were utterly beaten. Our enemy was superior in every respect.”

      Food at Japanese airfields was bad. Barracks were jungle slums. There were no laundry facilities, and men washed themselves in rivers, or under water-filled cans. Disease felled pilots and left serviceable aircraft grounded. Physical exhaustion lowered pilot performance, so that lesser-skilled opponents sometimes shot down veteran but feverish Japanese pilots.

      Manpower became critical with no tractors, and ground crews wore themselves out pushing aircraft around fields. They worked at night to avoid Allied air attacks, only to fall victim to the malaria mosquito, which was most active at night. Men worked seven days a week in wretched weather at exhausting and mind-numbing tasks. Ground crews became nervous and irritable from lack of sleep. It took longer and longer to accomplish a given assignment. Minor as well as major accidents increased.

      Raw human muscle wrestled bombs, cannon shells and machine gun rounds onto aircraft. Mechanics pulled maintenance on baking hot fields in direct tropical sunlight, for there were no hangars. When flooded airstrips dried after rains, dust billowed up in the wake of each aircraft, choking cockpit interiors and eroding engines.

      “The maintenance crews are exhausted, but they drag their weary bodies about the field, heaving and tugging to move the planes back into the jungle,” a navy pilot at Buin wrote in July 1943. “They pray for tractors such as the Americans have in abundance, but they know their dream of such “luxuries’ will not be fulfilled.”

      Commanders and planners lacked any understanding of the vast numbers of technicians required to support a modern army. Although there had always been shortages of trained mechanics, commanders showed little interest in sending their men to the ordnance school in Japan. The service schools themselves paid little attention to logistics and engineering support of combat forces. Nor did commanders establish schools or training programs at tactical units or in geographic army areas.

      Japan’s absence of standardization in weapons and equipment ranged from aircraft types to different engines, down to instruments and the smallest accessories. The army used a 24-volt electrical system, whereas the navy used a different voltage. Mounts to hold guns, cannons and rocket launchers varied between the two services. By the end of the war, Japan produced at least 90 basic aircraft types (53 navy and 37 army) and 164 variations on basic types (112 navy and 52 army), making the logisticians’ jobs that much harder.

      Japanese technicians and repairmen, already too few in number to handle even a well-managed maintenance system, were scattered in weak groups so as to cover the wide variety of equipment. Identifying, segregating and issuing the multitude of parts on a timely basis to the correct user was beyond their ability. The Japanese were hard-pressed to manage normal maintenance, let alone spare men and equipment for unauthorized field expedient modifications.

      Mechanics at forward airfields were not trained well enough to correct many of the factory faults that were discovered when new aircraft arrived on station. The Japanese military also failed to master the supply, maintenance and medical problems that arose once their aerial units reached tropical zones far from their main depots.

      Communications were a problem as well. The navy had great difficulty in controlling its combat air patrols because of bad radios. “It seemed to us,” recalled Rear Adm. Raizo Tanaka, “…that every time a battle situation became critical our radio communications would hit a snag, causing delay in important dispatches…but it seemed to hold no lesson for us since communication failures continued to plague us throughout the war.” Maintenance of aircraft radios was so difficult, spare parts so few and reliability so bad that many frustrated pilots actually removed them from their planes to save weight.

      Another limitation was that Home Island flight instructors were faced with too many students to train them effectively. The urgency of training pilots overwhelmed the curriculum. “We couldn’t watch for individual errors and take the long hours necessary to weed the faults out of a trainee,” Sakai recalled in 1943. “Hardly a day passed when fire engines and ambulances did not race down the runways, sirens shrieking, to dig one or more pilots out of the plane they had wrecked on a clumsy takeoff or landing.” The decision to press for quantity over quality meant that poorly trained fliers graduated to combat units. “We were told to rush men through,” Sakai said, “to forget the fine points, just teach them how to fly and shoot.”

      By the end of 1943, the army and navy had lost about 10,000 pilots. As American Lt. Gen. George C. Kenney reported to Washington, “Japan’s originally highly trained crews were superb but they are dead.” When matched to pilot production of 5,400 army and 5,000 navy in the same period, and when one considers the expansion in units, missions, tempo and geographical separation, it is clear that Japan’s pilot strength had not increased at all. Worse, the vast majority of prewar and even 1942-43 veterans were dead or wounded, and their replacements had none of the veterans’ experience.

      As the Japanese empire shrank, its air forces fell back on the logistics base. The aircraft repair system became less extended. Even so, by 1944 a growing shortage of spare parts for the older aircraft began to ground fighters and bombers. Minor battle damage to structurally weak aircraft, although repairable under better conditions, often meant that the plane never flew again.

      Aviation fuel existed in sufficient quantities throughout the Japanese military into mid-1944. As early as late 1943, however, commanders began teaching pilots how to conserve fuel. When the fuel shortage finally hit, it generally had no immediate or widespread effect on combat operations, but it had an adverse effect on training programs. When aviation gasoline became scarce, army trainees flew gliders during the first month of training to save fuel. Fuel shortages started affecting combat operations in mid-1944, just when American air activity was reaching its peak.

      Veteran instructors, including others on permanent limited duty and those recovering from wounds, began to leave their training duties to rejoin combat units. Many frontline pilots hated teaching anyway, especially as the number of training hours dropped and the quality of students declined. Men who had been rejected for pilot training over the previous two years were now accepted.

      By 1945 Japanese planes at Clark Field on Luzon were scattered far and wide in a dispersal effort. The field’s maintenance effort had collapsed. Hundreds of aircraft sat grounded with only minor problems. For example, one aircraft might be missing a carburetor, but since no one had arranged for the salvage of a good carburetor from an aircraft missing its landing gear, both aircraft were as good as shot down.

      An American intelligence officer who examined Clark after its capture reported, “It is impossible to describe the situation as a whole beyond saying that everywhere is evidence of disorganization and general shambles.” The Americans found 200 new aircraft engines at a village near Clark, most still in shipping crates. Ground crews had dispersed them far and wide in little dumps of three and four. They were hidden underneath houses, rice mills, shacks and public buildings. Huge numbers of parts such as carburetors, fuel pumps, generators and propellers were likewise scattered in fields and under houses, and also buried. Mechanics buried tools in no discernable pattern. Initial counts of aircraft in and around Clark topped 500, many of them obviously burned out, but many seemingly ready to fly.

      The Japanese had not experienced the logistical challenges that the Western powers had addressed during World War I and later relearned. Japan’s politicians, generals and admirals completely misjudged the character and the duration of the war they launched in 1941. Poor aerial logistics planning, lack of foresight, a racist contempt for their enemies, a weak, shallow, narrow industrial base and an inability to appreciate supply requirements or to learn from their failures characterized their aviation effort throughout the entire war.

      John W. Whitman, a retired infantry lieutenant colonel, is the author of Bataan: Our Last Ditch, The Bataan Campaign 1942. For further reading, he recommends: The Army Air Forces in World War II, Vol. 7: Services Around the World, edited by Wesley F. Craven and James E. Cate and Samurai! by Saburo Sakai.

      This feature was originally published in the September 2006 issue of Aviation History. For more great articles subscribe to Aviation History magazine today!

      The Japanese Air Army Force had one technical section, the First Tachikawa Air Army Arsenal, which was in charge of aviation research and development. The Arsenal included a testing section for captured Allied aircraft, the Air Technical Research Laboratory (Koku Gijutsu Kenkyujo). The Army Air Arsenal was also connected with Tachikawa Hikoki K.K. and Rikugun Kokukosho K.K., the Army-owned and operationed aircraft manufacturing companies.

      Due to the poor relations between the Imperial Japanese Army and Imperial Japanese Navy, the Army found it necessary to procure and operate their own aircraft carriers for the purposes of providing escort and protection for Army transport shipping convoys. These escort/transport carriers, were converted from small passenger liners or merchant ships. These escort carriers possessed the capacity to operate from eight to 38 aircraft, depending on type and size, and were also used to transport personnel and tanks.

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