I went up for a little flight today – a final shakedown of some work on the fuel system
I’ve been to FL200 a number of times but never really bothered to note the aircraft pitch. What matters is the IAS and how close you are to the stall.
This time I watched it on the Sandel EHSI on which the pitch is clearly visible.
The pitch after levelling off is as shown above – 7.5 degrees up. The pitch at which it was apparent it would not climb any higher (this was ISA+10 and about 60 USG still in the tanks) reached 10 degrees.
I thought the max AOA of most GA wing aerofoils is about 15 degrees.
So what is the real limit here?
Presumably as the AOA goes up, the parasitic drag increases rapidly and the engine power is not enough.
The other interesting challenge is the mixture setting. Best power is about 130F ROP, but you can’t just lean to peak EGT, see what it is, and enrich by 130F. If you do that, you lose so much power in trying the peak EGT that you will be on the back of the curve in seconds.
The peak EGT figure itself varies with altitude, not surprisingly. 1530 (today) at 3000ft and 1430 at FL193.
At the ceiling of the plane, I assume you’d be at something like best lift/drag angle of attack, or less than critical angle of attack. Flying along to the left of the drag bucket would make you sink, given limited engine power at altitude.
