A common operation in motorglider flight is to turn the engine off and glide for long periods. This leads to the engine being cold soaked.
Furthermore, ideally the engine isn't turned on until it's needed. "Need" is typically around 500' AGL, but in order to ensure that everything is going well before reaching the need point, it's best to start the engine at least at 1500'AGL.
The problem, though, is that the engine is cold soaked and the plane is still flying. The upshot is that even with the cowl flaps closed it takes a long, long time to reach minimum operating temperature. With the engine idling at 1800rpm or so, it might take 10 minutes or longer. The upshot is that with a 500fpm descent rate with the engine idling, we'd have to turn the engine on anytime we go below 5000'AGL. That sort of defeats the whole purpose of gliding!
What are my options here? Is it safe to progressively push past idle until the engine reaches operating temp? I'm thinking once the engine is idling well without the choke, then every 10 seconds to increase speed by 100rpm until such time as the plane stabilizes. I'm not sure how much power that would be, but I feel like 25% power would be enough to hang in the air either indefinitely or for a very long time (long enough to reach operating temps).
I'm also thinking about installing an oil heater and insulating the oil tank. Insulation could keep the oil from getting quite so cold, and one or two hundred watts put into the oil would help an idling engine more quickly heat up. But is that basically cheating, where I get the oil temp to 50C long before the engine metal is warm?
