KAWASAKI Ki 61 HIEN (SWALLOW) 'TONY' TIMELINE
November 1935: Ki 28 work began in anticipation of the 1936 Fighter Competition. With its
Ha-9-II Ko / 800 hp. engine it could reach 301.
1936 Competition: The Ki 28 demonstrated sparkling performance in speed, acceleration
and climb against the Mitsubishi Ki 33 and Nakajima Ki 27. "Although it had a wider turn
radius, the Ki 28's higher speed ensured that the aircraft could travel 360 degrees in the
same lapsed time as the other fighters." The Ki 27 was the most maneuverable of the three.
December 1940: The first of 12 Ki 61 prototypes was completed, S/N 6101.
2nd week of December 1940: 1st flight. Kawasaki Ha-40 (Licensed Daimler Benz DB 601A): 1,150 hp.
18 April 1942: Warrant Officer Ryozaburo Umekawa was relaxing on the ground smoking a cigarette
with Major Yoshitsugu Aramaki at Mito airfield when they were alerted to the Doolittle Raid on
Tokyo. With Binoculars they spotted a medium-size US aircraft flying at about 650 ft. They had
been flying gunnery trials. WO Umekawa attempted to intercept a b-25B heading south at 1000 ft.
with non-explosive ammunition. He managed to make three passes and hit near the wing root of
the bomber, noting oil or fuel streaming back. Lack of fuel forced WO Umekawa to turn back. This
was the 1st combat sortie of the Ki 61.
Note: Fore a more comprehensive report of this interception which included A6M2s and Ki 27s read
Aircraft of the Aces No.114, "Ki-61 and Ki-100 ACES" by Nicholas Millman.
August 1942: Twelve test aircraft had been completed. When test flown against the P-40E, Bf 109E,
Ki.43-II and Ki.44-I, the Ki.61 was deemed to have the best performance overall.
December 1942: The 68th Sentai began transitioning from Nakajima Ki 27s to Kawasaki Ki 61s at
the Akeno Rikugun Koku Gakko ( Army Aviation School ) in Japan. 34 Ki.61s had been produced.
Retractable tail wheel.
Armament: 2 x 12.7 mm. Ho-103 machine cannon in the cowl + 2 x 7.7 mm machine guns, wings.
Note: The Japanese Army designated any automatic weapon above 11 mm. as a machine cannon.
January 1943: Production Ki 61-la/Ko are delivered with.
Engine: Kawasaki Ha-40: 1,175 hp./2,500 rpm./T.O. 1,100 hp./2,400 rpm./13,780 ft. (4,201 m.).
Compression ratio: 6.9:1
Armament: 2 x 7.7 mm. type 89 + 2 x 12.7 mm. Ho-103/200 rpg.
April 1943: 68th and 78th Sentais are equipped with the Ki-61-la.
16 June 1943: Ki-61-la 1st combat. 68th Sentai stationed at Wewak, New Guinea.
18 July 1943: First air to air combat was against P-38Gs.
" The P-38 pilots all like the "Tony". It may have been a bit faster than the current Jap fighters
we were fighting, but we had plenty of speed to spare, and the "Tony" was a lot less maneuverable
than either the Zero-Sen or the "Oscar", so it was an easy victory when encountered. It also
appeared , to our delight, that the pilots who flew them were not of the highest skill."
Five-kill Lightning ace Charles King, 39th FS / 35th FG.
August 1943: 800 20 mm. MG 151 cannon with ammunition had been transshipped from a German
submarine to a Japanese Submarine in the Indian Ocean.
September 1943: Special Kawasaki modification teams were sent overseas bases to modify the wing
armament of a proportion of the operational aircraft. Simultaneously all remaining Ki 61-la/Ko airframes
on the Kagamigahara assembly line were modified to take the German MG 151 20 mm. cannon.
Production of the Ki.61-I Hei (Ki.61-Ic) began.
October 1943: 800 20 mm. MG 151 cannon with ammunition had been transshipped from a German
submarine to a Japanese Submarine in the Indian Ocean.
Mid-December 1943: The 78th Sentai received six Ki.61-I Hei (Ki.61-Ic) fighters with German MG 151
20 mm. cannon in the wings.
December 1943: Eight Ki.61-IIs were completed with a bigger wing.
Engine: Kawasaki Ha-140: 1,500 hp./2,750 rpm./T.O. 1,350 hp./2,650 rpm./2,000 m. 1,250 hp./
2,650 rpm./5,700 m. Compression ratio was 7.2:1.
Wing span remained the same but area increased 10% to 236.8 sq. ft.
Redesigned aft canopy for improved visibility.
Poor engine reliability, very weak crankshaft.
Revised airframe was weak and the wing would crack in flight.
Note: Reverting to the standard wing of the Ki.61-I corrected the cracking problem.
Performance of this Ki.61-II was now 394 mph./6,000 m. and 5,000m could be attained in 6 minutes.
January 1944: Ki 61-l-KAId/Tei production models begin to appear with the same armament as the Ki 61-lb.
The fuselage is extended 7.5 in. longer to 29 ft. 2.75 in. Replacing the 12.7 mm. cowl cannon with
the 20 mm. cannon required 200 mm lengthening of the fuselage.
Autumn 1944: Ki 61-l-KAId/Tei has constant problems with wing armament and is discontinued.
Wing armament is 2 x 30 mm. Ho-105 cannon.
Note: Ki 61 pilots adopted hit-&-run tactics to cope with the F6F Hellcat and were proven relatively effective.
April 1944: Ki 61-ll-KAIa / Ko 1st flight. Eight of the Ki.61-II airframes were flown. The ninth became
the Ki.61-II-Kai Ko.
*Armament: 2 x 12.7mm./200 rpg. + 2 x 20 mm./120 rpg.
*Fuselage was lengthened to 32 ft. 2/3 in.
August 1944: Production of the Ki.61-II-Kai began.
September 1944: Ki 61-ll-KAIa begin to appear operationally. 99 aircraft of this type are produced
in the spring
Date ?: Ki 61-ll-KAIb/Otso with an armament of 4 x 20 mm. cannon. Rudder area was enlarged.
January 1945: Production of the Ki.61-I Tei was terminated with 1,358 of this model being produced.
Note: Many of the Ki.61-I Tei had the wing armament and cockpit armor removed to improve high
Note: Frequent failures of the main bearings, the superchargers and the oil & coolant systems soon
rendered the Ha-140 an even more notoriously unreliable engine than the Ha-40. When it did
function smoothly, however, it was universally admitted that the Ki 61-ll-KAI was a quite outstanding
fighter capable of holding its own with the best Allied warplanes in its class.
Note: One authoritative source reports that only 99 Ki.61-II Kai were eventually delivered and an
unknown quantity of these had the teardrop canopy.
Air International August 1975 Vol.9 No.2.
P-38 Lightning vs. Ki 61 Tony, New Guinea 1943-44
Aircraft of the Aces 114: Ki-61 and Ki-100 Aces by Nicholas Millman
Edited by CORSNING, 02 April 2017 - 12:27 PM.