WHAT AIRPLANE IS THIS?

The “Messerschmitt Bf-109” of the Far East

Many of the Aces who won their victories against the Japanese have recorded their exploits in numerous books. In several of these books, and even in at least one “war movie” made during the conflict, the Allied pilots tell about shooting down a “Japanese” Me-109.

It was “common knowledge” back then that the Japanese were flying the famous German fighter since it was “better” than their own designs. Everyone thought that except for those pilots who had to oppose the Mitsubishi Zero. They knew that was a great fighter. But even they thought that the Japanese were getting airplanes and engines from the Germans and flying the Me-109 in combat.

Sorry, T’wasn’t so. The Japanese never operated the German airplane in combat. However, they did operate a fighter that looked like the famous German airplane in the air. And this airplane, the Kawasaki Ki-61 Hein, was powered by the Ha-40 engine that was a direct copy of the Daimler-Benz DB 601 that powered the German fighter.

Using the same engine meant that both aircraft’s front profile looked similar since each housed the same components. Put Japanese markings on the Bf-109 in diagram 1 and a pilot in combat would be hard put to distinguish it from the Japanese Ki-61 in diagram 2. While the mistake made by first-hand accounts is understandable, it is still incorrect. The Japanese Me-109 was always the Ki-61 Hein, also known by its allied code name, the Tony.

The Germans did give the Japanese a few DB 601A engines to back engineer. But the Japanese also designed an airplane around this engine. This was the Ki-60 and it was powered by one of the 1,175 hp German engines the Japanese had received. The Ki-60 had a different design philosophy from most other Japanese fighters. Instead of being designed for extreme maneuverability at any cost, the Ki-60 was optimized for high speed.

The Japanese thinking on this was that this engine would have a smaller frontal cross section since the liquid cooled DB engine was slim as opposed to the large radials powering their other fighters. Therefore, higher top speeds should be possible. In the end however, the Ki-60 proved just marginally faster than the radial engined Zero, 348 vs. 332 mph.

The Ki-60 also possessed some other “small” problems. It was nearly completely unstable laterally. Too much rudder input could cause uncontrolled skidding. Once into a spin, the pilot had to get out fast because it was usually a flat spin and not recoverable. While the Zero’s aileron control became very heavy at speeds over 350 mph, the Ki-60 controls, all of them not just the ailerons, could freeze solid at 375 mph. All these “little quirks” equated to an airplane that was definitely not combat-ready.

The Ki-60 airframe was trashed and a totally new one was designed. While resembling the Ki-60, the Ki-61 was a completely different airplane. Power was provided by the Kawasaki Ha-40, now built in Japan and producing the same 1.175 hp as the DB 601A. But the wings had a very high aspect ratio. The wingspan was nearly 40 ft. but the width, the wing chord, was very slim. Viewed from the top, the Tony’s wings resembled those of a clipped wing glider.

The new wings produced extra lift increasing the airplane’s maneuverability over the Ki-60. They also helped reduce some of the airplane’s snapping tendencies and lowered its stall speed, the Ki-60’s was over 100 mph, to a more reasonable 76 mph (the A6M2 Zero stalled at 58 mph with full flaps). The fuselage sported a larger vertical fin and a slimmer frontal cross section. The airplane was considerably lighter than the Ki-60 as well.

All these changes not only made the Ki-61 a combat flyable airplane but raised its top speed to 355 mph. The “glider-like” wings and light weight made it more maneuverable which the Japanese pilots, raised on Zeros and Oscars that could swap ends faster than a tree in a tornado, greatly appreciated.

The first Ki-61flew in December, 1941. After the initial twelve prototypes, the production version was called the “Type 3 Fighter Model 1-Ko” and was armed with one 12.7 mm (~50 cal.) machine gun in each wing and two 7.7 mm (30 cal.) ones in the cowling. Luckily the name was shortened to the Ki-61-I Otsu (the contest airplane).

Later models, the Ki-61-I-KAI Hei, replaced the wing machine guns with 20 mm cannon. About 388 of the original airplanes were also converted to cannon armament. The Ki-61-II received an improved engine, the Ha-140 producing 1,500 hp raising the top speed above 360 mph. But only 129 of these were built because the Ha-140 engines could not be produced in quantity since B-29s were by then bombing Japanese heavy industry into oblivion.

About 2,660 Ki-61s were produced. They served well on most fronts for the Japanese Air Force. The 7,650 lb. airplane could reach 16,405 ft. (5,000 meters) in seven minutes and could out-turn its look alike, the Bf-109 (all versions) by a whole lot. Its best combat feature was little understood at the time but came in handy when the airspeed dropped in a fight. The Ki-61 had a light power to weight ratio and it could accelerate quickly. Today, we say it was able to quickly recover energy, (sometimes called “unloading”). In a fight, the airplane that can retain energy in a tight turn (keep up its airspeed) and regain it faster will usually emerge the victor all else being equal. The Ki-61 performed that task better than even the famed A6M2 Zero.

The airplane in the contest photo takes us back to just one moment during those desperate days when the Far Eastern sky blazed all the way from India to the Hawaiian and Californian shores. The sky was overcast and dreary in December, 1944. Japan was fighting for its Imperial life and losing. But there was still some hope left as the 244th Sentai’s commander, Major Kobayashi, led his squadron of now obsolete Ki-61-Is on a mission. Taken by his Number 2 wingman (the Japanese used a 3-pilot wingman system) this photo is of the 244th’s CO on an actual mission. The number 1 wingman’s airplane can just be seen in front of the Major’s vertical fin.

We do not know what happened on this mission. By late 1944, the Ki-61 was outclassed by the Hellcats, Mustangs and Corsairs of the American’s. Whatever fate awaited the Major and his men, we can only marvel at their courage and dedication in the face of overwhelming and insurmountable odds. Knowing they would be both outnumbered and out equipped, they nevertheless headed into the fray.

As for the clues:

The Mitsubishi Ki-109 was a twin-engine heavy interceptor meant to counter American B-29 attacks. -- The contest photo airplane has just one engine.

The Japanese never operated Bf-109's despite rumors and legends to the contrary. Combat sightings of "Japanese 109s" were actually of Ki-61 Hiens. This is a strong clue that “D”, the Hein answer was correct.

The Ki-61-I Hien resembled the German Bf-109 and was powered by a Japanese-built version of the Daimler-Benz engine that powered the Messerschmitt – Taken together, this clue and the one above rule out the 109 as a possible answer.

Not all airplanes with a radiator mounted on the bottom of the fuselage were Apaches or Mustangs. The Japanese also discovered this trick. – Yes, the Japanese did discover that a radiator’s drag could be compensated for by confining the hot exhaust air and directing it to the rear and they did so sooner than did the Americans. The Mustang produced a net 300 lb. of extra thrust but the Japanese did not reduce the exhaust outlet area enough to obtain such a net power increase. The clue was meant to eliminate the Apache answer by illustrating that not all WW II fighters with rear mounted radiator scoops were built by North American Aviation.


Back to NTP Aviation History