What causes "twitchy" trim in Caribou?

[barryward12345 0]

I have been trying to fly Mike Stones' DHC4 Caribou - and have found it to have very "twitchy" trim . To the point where it is very difficult to fly as it is almost impossible to attain straight and level flight. One click of the trim button in either direction either sends the aircraft into a 1000 fpm dive or rise. I don't know anything about the real aircraft except that they can fly very slow and are not known to be "widow makers" - so I can't believe that this Sim flight characteristic is accurate.I have tried reducing the trim efficiency factor in the aircraft.cfg file but this seems to achieve nothing.Also, selecting 1 notch of flaps sends this aircraft into an immediate 2000 fpm dive.This is a nice looking aircraft and I have found a "passable" panel and set of sounds for it -- it should be a very nice STOL Sim aircraft -- but I think that maybe Mikes' talent lies more in the modelling department than in the FDE department . ( Sorry Mike - but at least you do have some talent which is more than I can say for myself).But it would be nice if some FDE guru could have a look at the aircraft and see what can be done with it.Thanks for any assistanceBarry

[Guest jlwoodward]

Hi Barry,I don't know anything about this particular airplane, but in general there are some things you can try. Use FSedit, or if you are not comfortable with that, use Notepad and open the aircraft.cfg file. There is a slider for elevator trim effectiveness. You would probably want to reduce it to .75 or .50, or whatever helps. Other things are (1) a slider for pitch stability, which will dampen out oscillations, and (2) the value for pitch moment of inertia (MOI) which will slow down the response to the elevator if you increase it (it usually takes big changes).For the flaps, there is an adjustment for the pitch down. You would probably decrease it.These things don't always work. As a last resort, you can take the air and cfg files from a similar airplane that flies correctly, and just change a few things like contact points and the aircraft description.John Woodward