One of the most extraordinary fighters built and flown during World War II was the Humu - literally "Reckless" - produced by Valtion Lentokonetehdas. It was not that the Humu was unconventional in any respect. It was a copy of a seven-year-old American design adapted to make use of locally-available materials and captured equipment, and built without benefit of licence or assistance from the parent manufacturer. The Finnish air arm, Ilmavoimat, had acquired 43 Brewster B-239 shipboard fighters that had been declared surplus to US Navy requirements. These had proved singularly successful in Ilmavoimien service, and, in 1942, it was proposed that an attempt be made by the VL to remedy a shortfall of fighters of this type by producing a copy. Because of shortages of metal, this was to make as much use as possible of wood and to embody so-called "war booty" instrumentation and power plant - equipment captured from the Soviet forces by the Finns themselves and similar equipment captured by the Wehrmacht and sold to the Finns. The task of designing an entirely new wooden wing was assigned to M T Vainio, who was also responsible for the overall project, and, in October 1942, an order was placed with the VL for four prototypes, the intention at that time being to build a series of 90 aircraft. The chosen engine was the 930hp Shvetsov M-63, which was flown on 5 June 1943 in a B-239. Static testing of the wooden wing was not entirely satisfactory. Nevertheless, in September 1943, orders were confirmed for five prototypes of the Humu and 55 production aircraft. The wooden wing was found to add 250kg to air-frame weight, however, and the transfer of the fuel tanks from the wing to the fuselage shifted the CG aft, adversely affecting manoeuvrability. Initiation of series production was, therefore, delayed pending results of prototype tests, and in the summer of 1944 the programme was terminated as it was concluded that the Humu would have inadequate combat capability by the time it achieved service. Only one prototype Humu was completed, and this, having an armament of three 12.7mm guns and a mix of Finnish and Soviet instrumentation, flew on 8 August 1944. The M-63 engine failed to give its full power during subsequent flight testing, but 19 hrs 50 min were flown before, in 1945, the sole example of this remarkable aircraft was placed in storage.