about R = g / V * tan(roll)

[wadiprawita]

Dear All,

I found this formulation (for fixed wing) :

R = g / V * tan(roll)

where

R is turn rate (can be approximated by yaw rate)
g is gravity constant

my question is : Is V airspeed or inertial/ground speed ?

One more thing, can we approximate AoA or pitch from climb rate / vertical speed data ?

Regards

-doni-

[dmgoedde]

One more thing, can we approximate AoA or pitch from climb rate / vertical speed data ?Yes, I do with AttoPilot. Pitch approx = ArcTan(barometric climb rate / GPS vertical speed). It is not usable for fast closed-loop control for small plane pitch, but is useful for long-term bias correction in a data filter. I think for sluggish large planes (8' or 12' Telemaster) you should be able to get away with this approach for pitch control.

[wadiprawita]

Dear dmgoedde,

Do you mean

atan(climbrate/airspeed) or just atan(climbrate) ?

How about for roll ? V is airspeed or GPS speed ? Do You have experience with this ?

Regards

-doni-

[dmgoedde]

Dear dmgoedde,

Do you mean

atan(climbrate/airspeed) or just atan(climbrate) ?

How about for roll ? V is airspeed or GPS speed ? Do You have experience with this ?

Regards

-doni-Pitch = approx Atan(climbrate/GPS ground speed).... I say "approx" because GPS ground speed not = airspeed. Up until now Atto did not have airpseed sensor. The important thing is the equation yields zero angle when climbrate = 0 no matter WHAT the error is in forward speed... so in the end this is still very useful if you use it like I do: to bias-correct thermopile pitch over longer timeframes (not super long... 5 second average work well).

The V question... it is neither purely. There is built in assumption in that equation that plane is holding altitude by pulling through the turn... otherwise you have a non-zero roll angle but zero turn rate (imagine a knife edge manuever). You have aerodynamic forces that are influenced by wind speed and then airspeed plays into that... but plane has momentum that is not completely seperate from the ground speed frame of reference. If you can make the assumption that wind speed << plane airspeed, then in this case GPS ground speed is a close approximation, and you can use this for the V in the equation. This is my opinion, but you should consult a higher power.