One of our most successful fighter-planes at the Douglas El Segundo plant was the F4D-1 Skyray, a modified delta-wing design. It held speed records, time-to-climb records, etc, but it was a “first-line” fighter at a time when we weren’t fighting anybody, so it never fired a shot in anger. My contribution was mainly lab-testing of hydraulic subsystems, actuators, control valves, etc, to demonstrate that they met military specifications. The successor to the F4D Skyray was to be the F5D Skylancer.
Although the wing planform was the same, the F5D had a thinner wing, and was a bit sleeker, addressing all the areas of improvement which had been identified on the F4D.
Sometime before the scheduled first flight of the Skylancer, engineer Charlie Delevan of the flight controls design group, stopped me in the hall to say “Norm, what are we going to do about this roll-rate problem?” This was the first I’d heard about it, so I got him to explain the problem.
The ailerons (actually “elevons” on this flying-wing design) weren’t moving as fast as the designers intended, so the desired airplane roll rate would not be achieved..
I asked Charlie to show me the installation in the prototype airplane. This involved removing a panel on the outer wing, When I could see the installation, I quickly saw what I thought to be the problem. A hydraulic actuator will move as fast as the combination of fluid pressure and fluid flow will push it. Out on an extremity such as a wing tip, the centrally located hydraulic pump may not be able to keep up. To augment the pump flow, an “accumulator” is installed at or near the point of demand. In this case, the accumulator was a cylinder with a sliding piston separating the liquid chamber from the gas chamber. When flow demand lowers the system pressure locally, the gas pressure in the accumulator forces fluid out to briefly augment the flow available from the pump.
I pointed out to Charlie that the accumulator was mounted to the wing spar with a block clamp, which would deform the circular cross section of the barrel, causing the piston to drag. He doubted me but had the accumulator disassembled on a workbench nearby. Sure enough, there were signs of friction on the piston and barrel. They redesigned the mounting, replaced the accumulators, and the elevons performed as intended.
The Navy was evaluating candidates for its’ next generation of fighter planes, and the Douglas F5D Skylancer was being compared to the Vought F8U Crusader. At that time (1956) up to 80% of the Navy’s carrier-based airplanes were Douglas El Segundo products, and there was political pressure to spread the procurement around. In fact, John F Kennedy had promised to do that in one of his campaign speeches. The Navy stacked the deck in favor of the Vought entry, including cancelling a planned effort to set a speed record by the Skylanceer. Top speeed may or may not have been a deciding factor in the selection, but Leland Smith, who was our man at Edwards Air Force Base
at the time, says, “That happened 55 years ago, and I’m still pissed at the Navy.”
The next competition for a Navy fighter was more complex. With the advent of new electronic weapons control systems, radar systems and such, they felt that a one-man crew would suffer from “information overload” and favored a two-man crew. The proposed twin-engine F4H Phantom II by MacDonnell Aircraft would have a higher thrust/weight ratio, and two engines gave it a survivability edge over Ed Heinemann’s single engine Skylancer. This left the F5D with no future except as research platforms and as chase planes for other new designs.
All the Navy fighters since that time have had twin engines – the F-14. The F-15, and the F-18. The Navy variant of the F-35 will have a single engine, perhaps reflecting the improved reliability of jet engines these days. Then again, maybe it’s the nature of the threat. The enemy doesn’t came after you with machine gun bullets anymore.
We built 4 or 5 Skylancers, which were mostly used for experimental work (Neal Armstrong flew one of them). MacDonnell built 5195 Phantom IIs, setting the stage for its eventual takeover of Douglas Aircraft Co.