The US-made Brewster performed excellently in the offensive phase of the Continuation War in 1941. Due to political reasons, more Brewsters (or any other Allied-made aircraft) could not be bought anymore, and since Nazi Germany was reluctant to supply modern aircraft, it was decided to create a Brewster clone to supplement the VL Myrsky. The task was given to Torsti Verkkola, Arvo Ylinen and Martti Vainio.
The original Wright Cyclone engines were unobtainable, so the captured Soviet Shvetsov M-63 engine was chosen for the Humu. M-63s and two indigenous wing designs intended for the Humu, both a wooden and a metallic one, were tested on Brewsters, but with disappointing results. Nevertheless, the Finnish Air Force ordered a Humu prototype in October 1942. Unlike the Brewster, the Humu was mainly made out of wood to save expensive metal.
By fall 1943 the Brewster itself was becoming obsolescent, and the Humu was turning out to be inferior to it, so the Humu's intended role switched from a fighter into a reconnaissance aircraft. The FAF ordered 90 Humus in November 1943. A test run of five was to be finished by October 1944, and 85 examples for normal operational service were to be finished by the end of August 1945.
Serial production was halted in June 1944 as the tide of the war turned, but work on the prototype, coded HM-671, continued, although at a slow pace. It eventually made its maiden flight on 8 August 1944. As the Continuation War ended in September 1944, the Humu project was cancelled.
HM-671 flew for only 19 hours and 50 minutes.
Today HM-671 is at the Finnish Air Force Museum in Tikkakoski, but not currently on display. It was restored in 1972-1974.
- Crew: One
- Length: 8.03 m (26 ft 4 in)
- Wingspan: 10.67 m (35 ft 0 in)
- Height: 3.66 m (12 ft 0 in)
- Wing area: 19.40 m2 (208.8 ft2)
- Max. takeoff weight: 2,895 kg (6,380 lbs)
- Powerplant: 1 × Shvetsov M-63 9-cyl., 746 kW (1,000 hp)
- Maximum speed: 430 km/h (267 mph)
- Service ceiling: 8,000 m (26,250 ft)
- Rate of climb: 13.3 m/s (43.6 ft/s)
- Armament: 3 × 12.7 mm LKK/42 machine guns in the nose, 260 rounds for the outer guns and 450 for the centerline gun.