Page 42 - Demo

38to be aware of your single engine safety speeds. The Varsity was powered by 2 Bristol Hercules engines as had been used on the Halifax during the war I believe. With a jet engine you just have one throttle leaver to accelerate the engine. This is the same for light piston engine aircraft but for piston engine aircraft with variable pitch propellors it is more complicated. The controls are with what we called crinkly chips and lollypops, these referred to the shape of the handle. The lollypops were throttles and opening the throttle would give more power up to a point. To get more power you also had to increase the RPM, and this was done with the crinkly chips. However, to increase the RPM, which was done by adjusting the pitch of the propeller, you first had to throttle back a bit. You then set whatever RPM was required and synchronised the propellers. If you did not synchronise them, you got a beating sound which was rather annoying. You then locked the RPM levers and used the throttles as required. Later, flying Shackletons we always cruised with the throttles fully open to get the best fuel consumption. Every half hour or so the engineer would tell you what RPM to set and that was it. You had to be careful because if you handled the aircraft roughly it would slow down and then be hard to accelerate without increasing RPM which was not supposed to happen. If during the cruise you had to do something, say attack a submarine you would first throttle back and then set 2400 RPM before using the throttles to give whatever speed you wanted. The other problem with these piston engines was starting them. You had to do various things to get them to go and the system at Oakington was that the aircraft was full of fuel at the start of the day. It would then fly an hour and a half sortie before coming back for an engine running crew change. After the fourth sortie of the day the last crew would shut it down. Theoretically it would have been possible to do the whole course without ever starting the engines and to avoid this you had to be especially programmed to have some sorties at the start and end of the day.