Rick Koch:
Is it okay (wise/safe for the engine, or anything else for that matter) to cruise for 2 or 2-1/2 hours at 11,500′ knowing that is right at the plane’s ceiling?
Editor:
You can cruise as high as you can get, at full throttle/full RPM (and properly leaned to 100 ROP for max power) as max power output is so low up there. Assuming everything is perfect, you can get about 75% at full RPM/full throttle, at about 8,000 feet Density Altitude (not just Pressure Altitude). Anything higher has to be a lower power level. Unlike some other planes, our unsupercharged planes can’t generally produce enough power up high to create cooling problems associated with the thin air. It is usually our bodies (and the regs) that are the limiting factor for cruising between 10,000 and 14,000 feet. If you decide to go up as high as you can, take a moment to read the Practical Density Altitude article in BAC Downloads.
We have spent many hours at those altitudes out West in our Sierra. When 9-11 occurred, we were grounded in Cedar City, Utah. When they finally released us IFR after several days (in VMC conditions), the only clearance we could get was to 14,000 East-bound over the mountains. If you look at a map you’ll see that they aren’t very far from the airport. We cleared them without circling, but it was close enough that if it had been IMC I would have had to request a 360 or two to play it safe.