wlbragg wrote in Wed Aug 09, 2017 12:53 am:"USA-35B" exhibits less tolerance for getting out of the flight envelope and thus my guess would be that might be more realistic.
I agree, all the more that USA-35B are known as being the J3Cub wings.
I don't believe that the Du-Y lift curve (as it is) can be realistic. The stall angle and max CL are far from reachable, unless we accept the elevator tightness (-1.8 ).
Still I'm perplex when watching the attitude at high speed with USA-35B lift curve. Nose down, orientation/pitch-deg = -6.4 deg at 100 kt horizontal. Due to high CL for alpha around zero. Is it to get a low pitch-deg at the best-glide airspeed?
....with the "-1.8/-1.9058" numbers. It allows for a more aggressive stall or at least the ability to cause the same.
Both. The elevator is more brutal, making it more difficult to accurately control the pitch angle, and you reach the max-lift (CL-Max) angle, after which the lift starts to decrease. This is a true stall.
I would like to know where the -1.2004 comes from. I assume the -1.8 is taken from multiple current FG aircraft implementations?
Not really. That was my guess by trial and possibly error (shame
) or rather an estimated adjustment, although not blindly.
I see -1.12 (C172P), -1.16 (Seneca II), -1.8 (DR400), -2 (Tecnam P92 echo). I'm wondering if the C172P would not have the same problem (Cmalpha = -1.8 while it is at -0.65 for Cessna 182 in Megginson's table).
1- I changed the amplitude of elevator deflection angle (which was too weak at -8 deg Up) for -0.51 to +0.34 rd (-29.2 to +19.5 deg). Notice that these limits should be different for the J3Cub -34 to +29 deg) and the PA18 (-25 to +15 deg).
These values are based on the configuration books.
J3Cub,
PA182 - As it was not enough, I raised the initial -1.2 up to -1.8 in order to reach the USA 35B stall AoA and to be able to do a 3-point touchdown.
But this gives an elevator tightness. I still think that,
if we admit the the stall angle should be reached and a 3-point touchdown can be done, this high elevator value is due to the high Cmalpha (pitch moment due to alpha, Cmalpha = -1.8 after Du Y at low speed, high alpha, to be compared with -0.61 to -0.65 from
Megginson's tables for Cessna 182).
Otherwise, if we take Du-Y thesis values as granted (but what about its lift curve ?), I currently don't see what to do here.