enginehistory.org

[jschauer]

Many warbird operators are using reduced power on takeoff hoping to ease the stress on the engines, any thoughts on this?

[kmccutcheon]

I've always heard that at takeoff power the mixture was enriched to prevent detonation and that less than wide-open-throttle takeoffs with their high power at slow airspeeds could cause overheating.
Many operators now have both EGT and CHT on every cylinder, so as long as the temps stay reasonable, I can't see how the lower power settings can hurt. On the other hand, if the temps are higher then the operator is acutally increasing the stress on the engine by choosing the lower power setting.
The thing I don't know is whether the operators you are referring to are really monitoring their engines carefully enough to circumvent the "automatic" enrichment features without damage.
Do you have any more details?
_________________
Kimble D. McCutcheon

[jschauer]

I fly as flight engineer on FIFI and we are discusing the use of reduced power to save the cylinders, I don't know enough to debate this. What you said in your reply makes sense for a carburetor'd engine but we have direct fuel injection, so we don't get the cooling effect of the fuel in the induction system. The last version of the KC-97 had charts for using 100/130 vs 115/145 when it wasn't available and they just reduced manifold pressure about 5" and torque also. We don't have torquemeters on our engines, just CHT mounted on the #1 cylinder. We can't afford to instrument all the cylinders, that would surely help though. The cylinders for the -57 engines, (BA series) are getting very hard to find. We are looking into re-engining to a CA series engine, but that is going to be a major engineering feat, ie. total new exhaust, slower turning propeller, different engine mount, longer engine case. We would gain a much better engine, torquemeters, more power, cooler running, more parts availability.

[sbezman]

Pratt & Whitney's "The Aircraft Engine and Its Operation" has a discussion on this. As I recall, they advise against using reduced power for take-offs.