Vultee A-31 Vengeance - Design and Development

Design and Development

In 1940, Vultee Aircraft started the design of a single engined dive-bomber, the Vultee Model 72 (V-72) to meet the requirements of the French Armée de l'Air. The V-72 was built with private funds and was intended for sale to foreign markets. The V-72 was a low-wing, single-engine monoplane with a closed cockpit and a crew of two. An air-cooled radial Wright Twin Cyclone GR-2600-A5B-5 engine rated at 1,600 hp (1,200 kW) powered the V-72. It was armed with both fixed forward firing and flexible mounted .30 in (7.62 mm) machine guns in the rear cockpit. The aircraft also carried up to 1,500 lb (680 kg) of bombs in an interior bomb bay and on external wing racks.

The Vengeance was uniquely designed to dive vertically rather than at an angle. To this end the it had a 0° angle of incidence on the wing to better align the nose of the aircraft with the target during the dive. This resulted in the aircraft cruising in a nose-up attitude giving a poor forward view for the pilot, particularly during landing. It had an unusual, "W"-shaped wing planform. This resulted from an error in calculating its centre of gravity. Moving the wing back by "sweeping" the centre section was a simpler fix than re-designing the wing root. This gives impression of an inverted gull wing when seen from an angle, when in fact the wing has a more conventional dihedral on the outer wing panels.

France placed an order for 300 V-72s, with deliveries intended to start in October 1940. The fall of France in June 1940 stopped these plans, but at the same time the British Purchasing Commission, impressed by the performance of the German Junkers Ju 87, was shopping for a dive bomber for the Royal Air Force, and as it was the only aircraft available, placed an order for 200 V-72s (named Vengeance by Vultee) on 3 July 1940, with orders for a further 100 being placed in December. As Vultee's factory at Downey was already busy building BT-13 Valiant trainers, the aircraft were to be built at the Stinson factory at Nashville, and under license by Northrop at Hawthorne, California.

The first prototype V-72 flew from Vultee's factory at Downey, California on 30 March 1941. Additional aircraft were ordered for Britain in June 1941 under the Lend-Lease scheme, with these being given the US Army Air Corps designation A-31.

After the U.S. entered the war following the attack on Pearl Harbor, a number of V-72 and A-31 aircraft were re-possessed for use by the Army Air Corps. As the Army Air Corps became interested in dive bombing, it decided to order production of an improved version of the Vengeance, designated the A-35, for both its own use and for supply to its allies under Lend-Lease. It was fitted with a more powerful Wright Twin Cyclone R-2600-19 engine and improved armament. As US Army test pilots disliked the poor pilot view resulting from the zero-incidence wing, this was "corrected" in the A-35, giving a better attitude in cruise but losing its accuracy as a dive bomber.

When production of the Vengeance was completed in 1944, a total of 1,931 aircraft had been produced. The majority were produced at the Vultee plant in Nashville, Tennessee.

Indecision about which aircraft type should replace it in production at the Vultee plant led to several "make-work" contracts for Vengeance aircraft to prevent dispersion of the skilled workforce. This resulted in overproduction of what was considered an obsolete aircraft.