Coming back to the (default) JSBSim Cessna 172p after spending a couple of months flying the YASim pa28-161, I find the 172 extremely slippery, far too much for a trainer. While the Cherokee tends to feel more stable in flight than a 172 (i.e. it has more roll, pitch, and yaw damping), the 172 still shouldn't be nearly so light in roll, pitch, or especially yaw as it currently is.

I've made a patched-up file that allows the 172p to handle much more realistically, but I'm not willing to upload it to CVS yet, because I'm not sure that I've done the right thing. To keep the 172 from wallowing, I increased the roll damping coefficient (Clp) from -0.484 to -1.2, the pitch damping coefficient (Cmq) from -12.4 to -15, and the yaw damping coefficient from -0.0937 to -0.2. The patched file ($FG_ROOT/Aircraft/c172p/c172p.xml) is available at

I don't want to commit this file to CVS yet for a couple of reasons:

1. Increasing the damping may simply mask a different problem, such as a unit mismatch or mistaken value for another coefficient (the biggest problem comes around yaw/roll coupling) -- someone who understands aerodynamics better needs to look at the actual moments generated by each coefficient at runtime to see if they are out of whack.

2. I have over 200 hours in a Piper since I last sat in a Cessna 172, so I don't know how accurate my memory is of its handling -- I remember that it felt a bit less stable than a Cherokee, but as a trainer, it still had a *lot* of damping compared to a high-performance aircraft.

My revised file seems to fly much better to me, but I'd like to hear opinions from other people with real experience in 172's, as well as the aerodynamic engineering types. I'd also be interested in feedback from non-pilots about the handling difference.

Thanks, and all the best,


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