Any hard numbers on the planes performance capabilities?
Source: Japanese Aircraft of the Pacific War by: Rene J. Francillon
Page 129-134
When in June 1944 the USAAF began daylight bombing operations against Japan, the Japanese Army found themselves without an adequate high-altitude interceptor capable of successfully
engaging the B-29's at their cruising altitude of 30,000 ft. This situation had been foreseen
but, even in their most confident estimates, the Koku Hombu could not hope to have the
specialized interceptor aircraft then under development in service much before the late summer of 1945. As a stopgap the Army had planned to use the Ki-61-II KAI which had begun flight trials two months before. However, teething troubles with the aircraft's Ha-140 engine frustrated this plan, and proven and reliable Ki-61-II KAI airframes were left unused at the Kagamigahara plant while the fighter Sentais had to defend the homeland with older aircraft.
Time was of the essence and a solution had to be found to provide an alternate powerplant for
the Ki-61-II KAI and for the rapid supply of a new type of interceptor fighter to the Army.
Consequently, in November 1944, the Ministry of Munitions instruced Kawasaki to install a different engine in the Ki-61-II KAI.By the end of 1944 the factories producting engines with sufficiently small diameter to be mounted in a fighter aircraft already had their production facilities overtaxed by the pressing demands resulting from the war situation, and Kawasaki engineers had to find a suitable type of engine among those then manufactured for bomber aircraft. It soon appeared that the only powerplant combining availability and reliability with a suitable output was the 1,500 hp Mitsubishi Ha-112-II fourteen-cylinder double low radial. As this engine has a diameter of 1.22m (4ft) it appeared at first difficult to install it in the Ki-61-II KAI
airframe with its fuselage width of only 0.84m (2ft 9 1/16 in). However, the Kawasaki engineers were able to study the engine mounting of an imported Focke-Wulf Fw-190A, an
aircraft in which a radial engine had been successfully fitted to a slim fuselage, and to call on the experience of the Imperial Japanese Navy which had fitted the same Mitsubishi Ha-112-II to the Aichi-built D4Y3, earlier versions of this aircraft also being powered by an inverted-vee liquid cooled engine. Work began immediately on the experimental modification of three Ki-61-II KAIs and the first aircraft, designated Ki-100, made its first flight on 1 February 1945.
Compared with it's forerunner the Ki-100 was lighter- empty and loaded weight being respectively reduced by 315 kg and 285 kg to 2,525 kg and 3,495 kg (694 lb and 628 lb to 5,567 lb and 7,705 lb)- and manoeuvrability and handling characteristics were markedly improved due to the lower wing and power loadings. Even though the engines of the Ki-61-II KAI reached
it's calcuated performance only now and then as its engine was tempermental, the Ki-100
benefited from the high reliability of it's engine. Accelerated flight tests taking place in February 1945 revealed that the airvcraft performed even better than anticipated and a fourth Ki-61-II KAI was modified the same month to full production standard as Army Type 5 Fighter Model 1A (Ki-100-1a). Two hundread and seventy-one Ki-61-II KAI airframes were similarly converted at the Kagamigahara plant between March and June 1945 and were immediately delivered to Service units in Japan. Under combat conditions the Ki-100-Ia proved itself to be an outstanding fighter, equally suited to intercepting high-flying B-29's and to engaging the Grumman F6F Hellcats of the US Navy which were now frequently operating in the Japanese sky. To the allies the aircraft was a complete and unpleasant surprise, and it's Nipponese pilots joined their ground crews in hailing the Ki-100 as the best and most reliable operational fighter of the Imperial Japanese Army. The aircraft was easy to handle and gave a fighting chance even to the youngest pilots who often had less than 100 hours of flight training prior to joining their operational units.
As soon as flight trials had shown that the development of the Ki-100-Ia was a success, Kawasaki began preparations to produce two new versions. Characterized by an all-round-vision
canopy similar to that planned for the Ki-61-III and tested on a Ki-61-II KAI, the Ki-100-Ib was no longer a conversion from existing airframes but was built to the new standard from the start. The first Ki-100-Ibs were built at the Kagamigahara and Ichinomiya factories in May 1945 but production was hampered by Allied bombings, the Ichinomiya plant being forced to cease production in July 1945 and the Kagamigahara production being considerably showed down. When Japan surrendered only 106 Ki-100-Ibs had been built at Kagamigahara and the Ichinomiya plant had delivered only twelve aircraft of this version. In an attempt to further improve the performance of the aircraft at altitude, in March 1945 Kawasaki began the development of the Ki-100-II powered by a 1,500 hp Mitsubishi Ha-112-II Ru with Ru-102 turbosupercharger and water-methanol injection. Due to the lack of internal space the turbosupersharger was fitted beneath the fuselage without provision for an intercooler and air was ducted directly from the compressor to the carburettor. The installation of the turbosupercharger necessitated the relocation of some of the fuel lines and the ventral air scoop was offset to starboard while an additional intake was mounted in the port wing root.
The first Ki-100-II flew in May 1945 and within a month was joined on the flight trials by two additional prototypes. Compared with the Ki-100-I, the Ki-100-II was slightyl heavier and consequently suffered a performance penalty below 8,000m (26,250 ft). Despite the lack of intercooler preventing full advantage being gained from the installation of a turbosupercharger, the Ki-100-II had better performance than the Ki-100-1 above 8,000m (26,250ft) and its maximum speed of 590 km/h (367mph) was reached at 10,000m (32,810 ft), the cruising altitude of the B-29's during daylight operations. It was planned to begin producton of the Ki-100-II in September 1945 but the war ended before implementation of this schedule.
It was fitting that the last operational fighter of the IJA made the last flight for that Service when two Ki-100-Ibs of the 111th Sentai were ferried between Komachi and Yokosuka where they were shipped to the USA for evaluation.
Units Allocated:
5th,17th,18th,59th,111th, and 244th Sentais
Description: Single-seat fighter and fighter-bomber. All metal construction with fabric-covered control surfaces.
Powerplant: One Army Type 4 fourteen cylinder air cooled radial (Mitsubishi Ha-33) 62 or Ha-112-II rated at 1,500hp for take off, 1350hp at 2,000m (6,560 ft) and 1250 hp at 5,800m (19,030 ft), driving a constant-speed three-blade metal propeller (Ki-100-I).
Armament: Two fuselage mounted 20mm Ho-5 cannon and two wing mounted 12.7mm Type I (Ho-103) machine guns.
External stores: two 200 litre (44 Imp gal.) drop tanks, or two 250kg (551 lb) bombs.
Weights:
Empty: 2,525 kg (5,567 lb)
Loaded: 3,495 kg (7,705 lb)
Wing Loading: 174.8 kg/sq meter (35.8 lb/sq ft)
Power Loading: 2.33kg/hp (5.1 lb/hp)
Performance: Maximum speed: 580km/h at 6,000m (360 mph at 19,685 ft)
535km/h at 10,000m (332 mph at 32,810 ft)
Cruising Speed: 400 km/h at 4,000m (249 mph at 13,125 ft)
Climb to 5,000m (16,405 ft) in 6 minutes
to 10,000m (32,810 ft) in 20 min
Service Ceiling: 11,000m (36,090 ft)
Range-normal: 1,400km (870 miles)
-maximum: 2,200km (1,367 miles)
Production: A total of 396 Ki-100's, including 275 Ki-61-II KAI conversions, were built by
Kawasaki Kokuki Kogyo K.K. as follows:
Kagamigahara plant:
3 Ki-100 prototypes (Feb 1945)
272 Ki-100-Ia production aircraft (Feb-June 1945)
106 Ki-100-Ib production aircraft (May-Aug 1945)
3 Ki-100-II prototypes (May-June 1945)
Total: 384
Ichinomiya plant: 12 Ki-100-Ib production aircraft (May-July 1945)
End of book quote-----------------------
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