Rear Admiral John P. Whitney requested Shepard's services as an aide de camp, but Shepard wanted to fly. Therefore, at Shepard's request, Ramage spoke to the admiral on his behalf, and Shepard was instead sent back to Patuxent. He flight tested the McDonnell F3H Demon, Vought F-8 Crusader, Douglas F4D Skyray and Grumman F-11 Tiger. The Vought F7U Cutlass tended to go into an inverted spin during a snap roll. This was not unusual; many aircraft did this, but normally if the pilot let go of the stick the aircraft would correct itself. When he attempted this in the F7U, Shepard found this was not the case. He was unable to break out of the spin and was forced to eject. In 1957, he was project test pilot on the Douglas F5D Skylancer. Shepard did not like the plane, and gave it an unfavorable report. The Navy canceled orders for it, buying the F8U instead. He also filed an unfavorable report on the F11F after a harrowing incident in which the engine failed on him during a high-speed dive. Fortunately, he managed to restart the engine.