The second prototype, the Yak-30D, which joined the flight test programme early in 1949, had a 38 cm (15 in) section inserted in the aft fuselage, revised mainwheel doors forming a large section of the fuselage skinning, Fowler-type flaps in place of split flaps, increased fuel and ammunition capacity, and changes to the oxygen system and radio equipment. The Yak-30D was also fitted with air brakes on the aft fuselage. Normal loaded weight (without external fuel) was increased by 110 kg (243 lb).