Dave Martin wrote:

Is anyone currently working on the b1900d FDM?

The reason I ask is that while the model is gorgeous, the FDM is relatively broken.

I've tried fixing the FDM before a couple of months ago but I didn't get anything acceptable.

The aircraft accelerates at a hell of a rate on the ground but wont unstick until about 160kts with flap and when it does, the torque effect requires full right aileron to counteract until the airspeed reaches 200kts. (which takes a matter of seconds).

Also, if you fight the aircraft level and then apply full-flap, cut the throttles and hold your altitude to the stall, you find that the stall occurs at 120kts and immediately causes a vicious spin.

For the Torque, don't the b1900d's have counter-rotating props?

As for the FDM's aerodynamics, I've yet to work out exactly what is wrong (the numbers look right but the result is rather like a dragster without wings).

My guess is the approach speed is too high ... you have to be careful because as the file is setup, approach speed is 105 at 13 deg aoa, but full stall is 14 deg aoa. This is saying the aircraft approaches at 105 kts just above the edge of a stall. Add some additional weight (which is often the case) and this could put you right up near 120 for a stall point.

I think that either the approach aoa should be dropped significantly, or the speed you can just barely fly without stalling needs to be decreased. Just a guess, but I bet you could fly it down into the range of 80-85 kts full flaps without stalling it (given a moderate load and reasonable temp conditions.)

I don't have a b1900 POH, but I wouldn't be surprised if I ended up with one by the end of the year ...

I'd agree that the propellors should probably be made counter rotating by negating the moment on one of the sides. The Beech99 is a similar airplane which actually flies pretty close to the POH numbers so you could probably yank data out of there and at least make the 1900 a bit more plausible.

Yes, the 3d model and 3d cockpit is gorgeous. :-)



Curtis Olson        http://www.flightgear.org/~curt
HumanFIRST Program  http://www.humanfirst.umn.edu/
FlightGear Project  http://www.flightgear.org
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