This extract covering the Vultee Vengeance was found in a book I received as a 78th birthday present this week. It is about the hazards and trials of test flying aircraft, from the early days through to long after WWII.
I thought it would be of interest here.
mike hallam.
'Tests of Character' by Donald Middleton. Pub.1995 Airlife
(from pages 58 & 59)
"The outbreak of war saw the RAF without a dive-bomber. The remarkable success of the Junkers 87 Stuka in the Spanish Civil War and the assault on France and the Low Countires persuaded the British Government that this was an error of omission which should be rapidly rectified. The British aircraft industry was too heavily involved with priority work building fighters and bombers to bother with what appeared to be a fringe design with limited applications at that time. So the British Purchasing Commission in the United States investigated the purchase of an American aircraft. Earlier requirements formulated by the French Government had led to fairly small Vultee Company to design a suitable dive-bomber, the V-72, for which orders were to be placed by the French. Their defeat in 1940 left these orders in limbo so the British Purchasing Commission showed interest. The V-72 was designed with twin rudders and was fully stressed for dive-bombing with slotted surface wing flaps and dive brakes. The Vengeance, as the British version was called, a name also used by the USAAF, reverted to a single fin and rudder and had a 1,700 h.p. Wright Cyclone 18 cylinder twin row radial engine. It became a tough, strong weapon, built like a tank as one pilot described it.
Unusually, the contract specified the test flying procedure by both the contractor's pilots and the RAF Resident Technical Officers. Two prototypes were available at Vultee Field, Downey, and the first one was evaluated by Gp Capt. 'George' Bulman, who was Head of the Test Branch of the Purchasing Commission. W/Cdr Mike Crossley RAF was also involved in the flight test programme. To increase the production facility for the Vengeance the Northropp Corporation was contracted to build the machine in addition to Vultee.
American responsibility for test flying rested with the famous Vance Breese who was responsible for the change from twin rudders to a single one after taxying trials had proved his earlier contention that two rudders would give inadequate control on the ground. In July 1941 Vance Breese made the first flight. He was not satisfied with the dive brakes and recommended that holes should be punched over the surfaces as was done with the Douglas Dauntless. This was rejected by the engineers, but the orientation of the slots was changed. An interesting aspect of the Vengeance programme was that it was almost certainly the first time that telemetry was used to record by instruments on the ground data obtained from the aircraft in the air. During the stalling check it was found that, although the stall was fairly innoccuous and aileron control held it laterally stable throughout, there was a degree of buffeting at high accelerations which caused concern for the integrity of the tail structure. Strain gauges were fitted and the information being transmitted to the ground receiver could be heard in the form of tones in the pilot's headphones. Frank Davis, on the departure of Breese, took over the responsibility for the tests and made one stall for each reading of the strain gauge; he would then manually switch to the next gauge ready for another stall. It required several hundred stalls from 1 G to 6 G to cover all the permutations. The tests proved the integrity of the structure without modification. A problem arose with the rudder control which was considered too heavy for a dive-bomber in which quick and easy directional changes must be made to achieve accurate aim. This was overcome by installing a spring tab at the trailing edge of the rudder. Recovery from a high speed dive was another contentious area. As speed built up the aircraft tended to tuck under and required excessive stick forces for recovery. On one occasion Frank Davis was diving to test an oil system valve for negative G when rudder flutter occurred and the surface tore away behind the hinge line. The balance area forward of the hinge line was still under pedal control but tended to be fully over to one side or the other including yaw. Davis was able to hold it on the stick and the fin gave sufficient directional stability to land safely.
This was another example ot the hazard of fabric-covered surfaces in high speed flight. The rudder was altered to have an all-metal skin. This also solved the problem of heavy pull-out forces from the dive as it was decided to modify the elevators similarly. By the end of 1941 most of the bugs had been eliminated from the new dive-bomber which the RAF was looking forward to operating. Unfortunately for their desires the Japanese attack on Pearl Harbour on 7 December 1941 completely altered the situation. The Americans realised that they would need many more aircraft so delivery schedules were completely altered, but that is another story. The 1,200 which were delivered to the RAF gave extremely good service. mainly in Burma, with Hurricanes giving top cover to their attacks."