Flight tests results Available to Purchase

INITIAL LIFT OFF ATTEMPTS were conducted with debris guards mounted to the engine intakes, the main engine debris guards carrying 24 temperature probes, the lift engine debris guards carrying 12 temperature probes each. Various methods of thrust management were looked at in order to investigate recirculation during vertical take‐off. All these tests indicated that vertical take‐off is not effected by intake temperature rises due to recirculation. It was found that because of the engine arrangement, jet separation from the surface takes place sufficiently far away from the fuselage to prevent reingestion of hot gases into the intakes. When increasing forward speed the aircraft catches up with the upgoing engine exhaust gases which separate from the ground at a point in front of the aircraft. During rolling take‐offs in the speed range between 30 KIAS and 40 KIAS these exhaust gases can be reingested by the cruise engine intakes, if the nozzles are rotated to angles more than 70dcg from the fuselage horizontal datum. Temporary recirculation has also been experienced during lift engine light‐up when low energy exhaust gases are reingested into the cruise engine intakes. This phenomenon disappears, as soon as lift engine speed exceeds 20 per cent.