Eight manufacturers submitted eleven proposals to meet specification CA-10504 issued on 2 Oct 1956, which included a Marine Corp requirement for STOL operations from unimproved airstrips. The requirement called for a 1,500 foot take off over a 50 foot obstacle. Lift off speed with nozzles deflected was 78 to 86 knots for a lightweight aircraft.
Test pilot Bob Smyth cites - The tail pipes normally bent down 7° with respect to the fuselage reference line, but to satisfy the Marine Corp STOL requirement a hydraulic actuator, controlled by a knurled knob on the outboard throttle, could deflect the nozzles down to 30° (23° of travel). There was no trim change, and they reduced the stall speed by five knots, or for a given approach speed they reduced the angle of attack by 3°. Only the first seven aircraft were so fitted, as they were found to be only marginally effective in meeting the Marine Corp requirement. Actually, the concept would have worked well on the heavyweight EA-6B.
"Intruder - The Operational History of Grumman's A-6", Mark & Rick Morgan