ORIGINAL: mmattockx
ORIGINAL: gadix
well over heating is a possebility because the engine is not in a movment -like in the air- so due to the fact that this is a AIR COOLED engine, while on the ground it will get hoter than in the air.
I am curious why people think the airflow over the engine is any different when the aircraft is flying than when fixed on a stand. Either way, it is seeing whatever prop blast it sees. Just because the aircraft is moving a bit doesn''t mean the airflow around the inner part of the prop disk is any different at all.
The reason an engine will overheat on the stand is that the LOAD is greater. Pulling full throttle static thrust is the biggest load the engine will ever see. It is the same as extended hovering at full power. This is why people use lighter load break-in props on the bench to keep the engine from overheating. When the aircraft is flying, the load is less because we seldom fly at sustained full power and the prop unloads with the forward speed. This is why a flying break in is often easier on the engine than a test stand break in, not because cooling is better. If prop load is reduced, then a test stand break in is no different than a flying break in and it is easier to control and monitor everything on the stand.
To AirWizard, how do KNOW you don''''t have overheating problems? Just because the engine hasn''''t died yet doesn''''t mean it isn''''t overheating in flight.
Mark
Thanks for setting the record straight. No house fan is going to put more air across an engine than a prop does and using a smaller break in prop is the way to go always when breaking in an engine. The cowl should also be removed so any kind of ducting is not even an issue. 3W has a recomended test stand procedure that calls for running the engine at 2000-2500 rpm for four hours. I considered it but would just as well be flying for those four hours instead.