Engine maintenance of a motor glider
It was recently made clear to me that the maintenance of an engine of a motor glider was not intuitive and could require special procedures to extend life. There are 2 types of engines - the 4 stroke type that most touring motor gliders have such as the Rotax 912 and then there is the 2 stroke engine and the Wankel engine for the self launch high performance gliders. Because there is no oil sump with these engines short starts and runs are fine without the buildup of acids in the oil. On the other hand 5 to 10 minute starts and runs on a Rotax 912 is courting trouble since the oil never gets hot enough to boil off acids etc. Therefore it is essential that several times a year that you run a four stroke to its operating temperature and keep it there for a reasonable period of time.
How come I know this? A couple of 912s recently were recondition after 12 years of use and a few hours of run time. They showed corrosion problems. Its one of those situations use it or lose it.