Name the Plane: May, 2006

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