On Saturday, September 8, 2018 at 5:53:12 PM UTC-4, wrote:
On Saturday, September 8, 2018 at 2:42:00 PM UTC-5, wrote:
On Friday, September 7, 2018 at 11:10:08 PM UTC-4, wrote:
My experience bringing power back to idle after glider release in less than 30 seconds and then not adding power all the way to landing has not been a problem. Our previous engine was well over TBO when replaced, with no issues.
Having more sophisticated engine monitoring might help to run lean of peak to save gas.
Keeping your head outside the cockpit may save you more than gas.

What kind of airplane?
Your experience certainly differs from my 40 years of running towplanes..
UH

UH, do you think recording engine parameters and analyzing them post flight might be worth the effort?

I do wonder if our standard procedure is deficient, maybe analyzing engine parameters would reveal a bad procedure (or a tow pilot that doesn't follow a good procedure). And it would gather hard data that might show, as Dan suggests, that shock cooling is a myth....

Our procedure is to speed up to 100-110 mph put a notch of flaps down and throttle back to 2200 RPM immediately after release, descend/spiral down while reducing RPM by 100 every 10 seconds, until we get to 1500, then we are free to go to any speed/RPM. Sometimes we sideslip, but not always. Please critique!

Maybe we ought to start a new thread on cooldown techniques....

Cheers,
Jim

This has been studied and findings published in the past. I think it was in Soaring and was quite some time ago. It may also have been in Free Flight.
Our procedure, used in Super Cub and Pawnee, is to smoothly reduce throttle to 2300 rpm while accelerating to 110 mph. We carry this through the descent, including some of the downwind, followed by gradual reduction as speed is reduced to approach speed. We try to not be less than 2 minutes from release/throttle reduction to throttle closed. We discourage slips because this can make the flow through the cowl unbalanced which can lead to less even cooling.
I know Lycoming does not believe shock cooling is a myth. They have a recommended cooling rate, but I can't quote it from memory.
We have CHT on all 4 cylinders to watch for one getting unusually hot. This tends to be due to a damaged baffle though one time we did find signs of an intake leak that can make a cylinder go lean.
If you want to do the study, go for it and then compare with what your engine manufacturer recommends.
FWIW
UH