Since you asked about the P38, the ailerons were partially hydraulically boosted and partially powered by the pilot. If there was a hydraulic failure the pilot could still fly the aircraft, albeit with a lot more force involved. Systems back then were a lot lower pressure than they are in today's aircraft. Back then the pressures were around 1100-1600 Psi vs today on most aircraft the systems are at 3000 Psi. But it was a triple redundant system on the P38, a normal system, a auxiliary system, and an emergency system. Normal used the engine driven hydraulic pumps, if they went dead you had a hand pump in the cockpit that you could manipulate a valve to then power the entire system with the hand pump, and in a really bad situation you switched to the emergency system that had a different reservoir and lines but was pressurized by the hand pump. The weird part about the system is the brakes are actually only pressurized with the hand pump so pilots had to constantly be pumping away on the hand pump while taxiing to have brake pressure.