Originally Posted by
Genghis the Engineer
How did you calculate these values? Without that information, it's very hard to usefully offer a comment about them.
I confess BTW that in about 13 years of doing aeroplane performance analysis as part of my job, I've never seen any particularly good reasons to trust purely calculated values, not firmly checked against carefully obtained flight test data. I'd be equally certain that FAA would only have signed off the C172 flight manual when confirmed by flight test data.
G
This is not taken from only a few operating points in flight.
The POH does effectively contain "some" test data.
Of course any flight models have to be cross-checked with extensive flight data.
I mainly used the flight data in the POH cruise performance of velocity, and fuel flow vs altitude, power setting, and temperature. Wing area, density altitude, etc..... there is approximately 100 operating conditions.
I also used the slow-flight regime of stall speed, climb rate vs altitude, glide performance. Prop efficiency variability.
Using numerical methods from university I fit the lift, and drag equations to determine the coefficients: Cl, Cd, Cdo, K, etc..
I cross checked the resultant perf calculations with the known published cruise performance data and my experience flying; especially hot TO
Satisfied that the fit was adequate (e.g. stall speed, stall angle, Vmax cruise, horiz and vert velocities vs altitude during climbs, etc.... ) I then calculated the special conditions above.
As for the FAA, I'm sure they do have
all the data in their files. The problem is that some
basic perf data is not in the POH !!!!
