Sunday, March 27, 2005

Radial Engines

When I mentioned that there was a type of airplane I want to fly before they are all gone, my readers instantly knew what type I was thinking of and where I'll have to go to fly one. The DC-3 was the original airliner. Read the memoirs of any golden age aviator and you'll find the DC-3. I'd rather fly a DC-3 than a triple seven, although the paycheque would be a lot bigger for the latter. Silly that, as there's more skill required to fly the old one than the automatic one. But that's economics.

I've spent some of the weekend trying to learn more about the care and feeding of radial engines, and I've ordered a book. I need to corner a Beaver pilot or two, because so far I'm not finding anything I didn't know. But I'll put down what I know, as I'll get a blog post out of it, and someone else might not know.

Radial engines are piston engines, with the cylinders arranged all in one plane, like the arms of a slightly spastic starfish. There are always an uneven number of cylinders, because the firing order goes around the circle skipping ever second cylinder, and an odd number ensures that works out. For example, if the engine has nine cylinders, like an old DHC2 Beaver, then the firing proceeds as 1-3-5-7-9-2-4-6-8. The crankshaft is a clever arrangement of articulating rods on a hub. I even managed to find a clever animation of how that works.

I know that a radial engine go through a lot of oil. We're talking a quart or two an hour. Although they don't exactly consume all of it. They use oil the way a small child uses food: flinging it everywhere. The joke is that a new pilot for a bush company can find all the camps just by following the trail of oil drips on the ground between them.

Some of that oil has a tendency to pool in the bottom cylinders when the engine is shut down. Oil doesn't compress the way air and fuel vapour do, so the result of starting the engine, or even turning it through by hand, could be a bent piston rod. It's called hydraulic lock and the only way to get rid of it is to remove the spark plugs of the lower cylinder(s) and let the oil run out. Sounds like a fun thing to do in the dark when it's forty below.

That's not all I know about radial engines, but it's all I have time to write.


Lost Av8r said...

Cool stuff. I like the animation

Mike said...

What stands between 5 nymphomaniacs and 2 alcoholics?

A cockpit door.