Lowell,

Sure others have some thoughts, I'll share a few.

I do not ever recall seeing the term "Rotational torque" per se, occurring in any rotax documents, if we are talking about a 912ULS.

Contrary to notions that "rotational torque", whatever it is, increases with use/age, my experience with piston engines used in a number of machines (cars, trucks, planes, tractors, lawn mowers, just about everything else) is that they get easier to spin over with age due to wear & reduced compression (cylinder & ring wear & valves). Blowby is usually higher, not lower. In the short term during break in turn over effort increases maybe, but not in a high hour engine.

There are some things that my manual says to check on the 912uls, two of them torque values - neither are called "rotational torque" (is there such a thing as "linear torque??).

1) Slipper clutch torque - lock the crank and determine what the breakout force in inch pounds is for the slipper clutch. Since earlier engines do not have a slipper clutch, this is not done in those cases.

2) Overload clutch - Lock the crank, secure the engine - Torque required to break out the overload clutch - several hundred foot pounds to slip over the cogs.


Only other gearbox routine measurement, I am aware of, is gear lash.

If we are talking some other aircraft engine not a rotax - the appropriate manuals would be the place to go.

FYI - the only case I have seen increases in compression with senior engines is if they have combustion chambers loaded up with carbon one/or lead deposits. - usually evident from the clattering of preignition under load.

"Rotational torque" is something new to me.....possibly a colloquial moniker?