Thrust required during turn versus climb
Hi all,
Got a question,
Forgot the relevant formula’s a long time ago, but what requires more thrust? A level turn at 1.3g or a climb with 100fpm. Talking about B737 7 through 9 series
Reason I’m asking is we are getting a FMS software update that now displays a T or B behind the max altitude to indicate wether you are thrust limited or buffet limited at the max altitude.
Recently had a discussion with a check airman during a check when flying close to the max altitude. I briefed my college that when any turn where given by ATC we would select bank angle 10 first before executing the turn because we were flying close to the max altitude and were thrust limited to maintain airspeed during a turn.
The check airman pulled out a chart indicating max altitude and where it had a asterix behind an altitude to indicate when you were thrust limited. However the chart indicated thrust limited based on a 100fpm climb.
This says nothing imho about the ability to maintain airspeed in a bank!
Of course I would not execute a turn at 39 degrees at altitude(1.3g) but what would require more thrust, A bank angle of say 25 degrees at altitude or a 100fpm climb?
I’m afraid that the new software update is gonna lead to a false sense of security when executing a turn at max altitude.
Airplane concerned is B737(7,8,9). I have never flown the B737 where the upper and lower amber bands touch each other, in other words you can always turn theoretically with 39 degrees of bank before hitting high or low speed buffet, however when flying close to max altitude you don’t have the ability to maintain speed at that bank angle.
So, what requires more thrust? A climb with 100fpm residual climb or a bank angle of 39 degrees and what is indicated by the T behind max altitude in the FMS: the ability to maintain airspeed or the ability to sustain a 100fpm climb.
I’ve forwarded the question to our flight technical department but am curious as to opinions here?
Relevant documentation FCOM performance inflight long range cruise max operating altitude tables and FCTM max altitude.