Oil does drain down into the bottom cylinders. That’s why we run the engines up before shutdown to get as much oil as possible up into the tank.
Also, with radial engines, we need to pull the prop through before staring up to clear any oil that has run down and is sitting in the exhaust valves. Some Yaks have got a drain tap to do this more efficiently.
If it’s left it can cause hydraulic lock which can bend the con-rod and cause engine failure. The cans over the exhaust stubs help to catch any oil and stop it from making a mess on the ground or down your flying suit!
Re: the air system. It might seem archaic, but it is a very efficient and normally robust way of dealing with the very low temperatures in Russia. Air is used for starting the engine, brakes, flaps and undercarriage.
A normal battery starter system wouldn’t cope with the cold conditions, hydraulic fluid freezes – but air doesn’t!
A small battery is needed for the ‘shower of sparks’ starter, but the load is taken by the air starter.
The air system needs to be purged at the end of each sortie – via the ‘snot’ valve – this stops a mixture of air, oil and water creating an emulsion (very like margarine) and blocking the system.
The Yak I fly has been having compressor problems, but we have been flying it by topping up the air from an external bottle. It takes about two minutes. As the brakes operate off a lower pressure circuit, there is no problem taxying when the pressure is getting a bit low.
Also, having the aircraft clonking and hissing just adds to its character.
YR 😀
Sign In
