Tough mission to figure out

[docmirror]

Cowboy, I'm interested in your approach of not flying the plane to its limits. The underlying assumption, I'm guessing, is that the higher the average % power, the less time between the practical need to overhaul the engine. Is that right, or is it a different line of thinking.

Assuming that is right, do you have evidence that this is the case? I hear from countless mechanics that flight school airplanes which fly frequently often go well beyond TBO and they are being put through the ringer, spending more time in the high workload phase of flight (the initial climb out) than a typical owner/operator who flies a lot of XC flights.

I cruise at 75% power if it's available. I often fly too high for that to happen, so that doesn't always happen, but if I'm restricted to lower altitudes, I will fly it at 75% power, keeping a close eye on the CHT's (first) and EGT's (second).

I get that 100% power wouldn't be desirable, but is there evidence that 55% power is likely to allow significantly more hours in service than a 65-75% regime? If so, by how much, and ultimately, which allows for more miles traveled (the important part if it's a travelling airplane) between overhauls?

Gosh, I don't have any empirical evidence to show you. Mainly I work on the systems approach to service life for wear items. If the system is rated for 75% for 2000 with regular mx, my expectation is that it will live 2000(x) hours running at 55%, where x is some applied variable from 1.2-1.5. Of course, it has to be admitted that at 55% power one is going slower, so the time in transit will come up similar in the end. I'm hoping that the fuel saved during the lower running at LOP will compensate for the overhaul cost when the time comes, but again - no empirical evidence to prove it out. Just that when systems are operated at higher relative settings things will wear faster due to heat and increased pressures.