During the winter of 1941–1942, Lavochkin worked unofficially to improve the LaGG-3. Design work was conducted in a small hut beside an airfield. In early 1942, Gorbunov replaced a LaGG-3's inline engine with the stronger Shvetsov ASh-82 radial engine. The nose was replaced with the nose of the ASh-82-powered Sukhoi Su-2. The new engine required work to maintain the aircraft's balance. The prototype first flew in March, and demonstrated surprisingly acceptable performance; air force test pilots considered it to be superior to the Yak-7, and intensive flight tests began in April. The aircraft was named LaG-5; the change from LaGG was because Mikhail Gudkov, one of the original LaGG designers, was no longer with the programme. By July, it was called La-5, although Gorbunov was still involved.