Yak-7M experimental fighter by A.S.Yakovlev

Yak-7M (Modified) with M-105PA engine and VISH-61P propeller was a cannon-armed fighter variant of the Yak-7UTI, the second transformation of trainer aircraft into a combat machine.

Conversion was performed at Saratov factory N°21 by group of Yakovlev OKB engineers, who assisted in the Yak-1 mass production. Series built Yak-7UTI N°05-11 (repaired at the factory after long service and crash-landing) was modified in the manner similar to earlier I-28 and I-30 prototypes:

• ShKAS machineguns and associated mounts removed
• equipment of the rear cockpit deleted
• two wing-mounted ShVAK guns added, 110 rounds per gun
• wing structure strengthened
• wing fuel tanks capacity decreased by 23l each to provide room for ammo
• 80l (60kg) fuel tank installed in the second cockpit
• pilot�s seat got armor back
• automatic leading edge slats installed
• wingtips made more angular
• wing span reduced
• landing flap area increased from 1.77 to 2.15m²
• hardpoints, wiring and cockpit equipment for 6 RS-82 launchers added
• landing light FS-155 installed

As a result of all those changes, Yak-7M became heavier than original Yak-7UTI by some 360kg. But its firepower was superior to all Soviet fighters of 1941 and their foes: 3.84kg/s. Three Yak-7M cannons could be fired from any flight regimes, from any maneuvers. They were tested at air temperatures down to -30°C. Shell scattering was acceptable, and Yak-7M could be used effectively against ground targets. Firing of long series was not recommended due to some aiming loss.

Overall performance was similar to other Yak-7 fighters (with some correction for increased weight and poor conditions of converted airframe). Leading edge automatic slats improved handling even more: Yak-7M was no-spin aircraft (it had to be forced into the spin). Stability improved, critical speed was on all regimes lowered by 30...40km/h.

State Trials of the Yak-7M took place in October 1941 at Chkalovsk and in October-December at Sverdlovsk (where NII VVS was evacuated). Pilot V.I.Khomiakov, engineer A.T.Stepanets and mechanic V.F.Sbitnev. 39 flights were performed, total duration 20h35min - including ferry flight from Moscow to Sverdlovsk by pilot A.G.Proshakov.

Yak-7M was recommended for series production as fulfilling all major demands and suitable for pilots of average skill level. But it never entered production. None of improvements except extra fuel in the rear cockpit were used on series aircraft.