Sometimes Plato (427 BC – 347 BCE) hit the nail on the head; when he said ‘necessity (who) is the mother of invention’, he was obviously predicting what would happen to certain WW2 fighter aircraft and their engines! After the prototype Grumman F6F Hellcat flew, someone thought it would be a good idea to replace the Wright R-2600 Cyclone with the magnificent Pratt & Whitney R-2800 Double Wasp.
The Hawker Tornado programme was dumped because the Rolls-Royce Vulture engine it shared with the Avro Manchester was failing (engine fires in the Avro Manchester – although it could have been sorted for a fighter application, maybe), so the Napier Sabre engine won out and the RAF got it’s sister aircraft, the Typhoon.
It was 1945, and the Japanese were losing the war – badly. Boeing B-29s were razing their cities to the ground, and they need a high-flying interceptor, fast. Using the Kawasaki Ki-61 Hein as a basis, the IJAAF try to build a manouverable fighter with genuine high-altitude performance, the Ki-61-II-KAI. Unfortunately, the temperamental inline of the new fighter – the Kawasaki Ha-140 - was unreliable, and when the factory where most were being built was flattened by a B-29 raid, the IJAAF was left with several hundred engineless airframes laying around. In desperation, the slim fuselage of three of these useless airframes were modified to take the only high-performance engine available, the 1,500 hp Mitsubishi Ha-112-II Kinsei …..the result wa the Ki-100-1b Goshikisentoki (or ‘Type 5 Fighter’). This was an absolute winner of a fighter ‘plane – the first examples of which reached Homeland Defence units in July, 1945 - and despite having a maximum speed of only 360 mph, they were manouverable, hard-hitting (2 x 20 mm Ho-5 cannon in the nose, 2 x 12.7 mm Ho-103 machineguns in the wings) and a danger not just to B-29s but even Mustangs, Hellcats and Corsairs. Fortunately for the Allies, the number of conversions and new-built aircraft were only enough to equip a handful of IJAAF Sentai because of the general disruption and destruction of the war industries.
The example you can see here was on display in the ‘Milestones of Flight’ Gallery at the RAF Museum, London, during my visit earlier this year (it is now on its way to RAF Museum,Cosford, as part of a general movement of airframes between the two sites). It was one of only four captured Japanese aircraft brought back to the U.K. after the end of the war for further study, out of over 60 selected by Air Intelligence Units - shipping space was given over to returning PoWs, of course. Two of the others ended up in museums – a superb Mitsubishi Ki-46 “Dinah” at the RAF Museum, Cosford, and the cockpit section of a Mitsubishi A6M5 “Zeke” in the Imperial War Museum, London. I have a distant link to the fourth airframe, in that the Kokusai Ki-86a Army Type 4 biplane trainer, a licence-built version of the Bücker Bü 131 Jungmann (and which would now be the only survivor) was burnt by RAF authorities at the then-RAF Wroughton in the 1950s - long before I got there as part of the Science Museum staff.
This Ki-100-1b is now the sole survivor of its type in the world, and its current state of preservation is a credit to the staff of the RAF Museum. If you are visiting the U.K. track it down, and view a marvellous example of aeronautical improvisation.