- what OS (Windows Xp/Vista, Mac etc.) are you running? Ubuntu 16.10
- what FlightGear version do you use? The latest from the default APT repositories on Ubuntu
- what graphics card do you have? Intel HD Graphics, I believe. (Thinkpad X230)
- does the problem occur with any aircraft, at any airport? No. Just the C172P.
- where did you download your aircraft/scenery from? This plane came with FlightGear.
To elaborate, while flying the C172P, the plane keeps "swerving" up, on a really steep angle, then sinking down, again at a really steep angle, and repeating that process.
This happens regardless of throttle or flap settings (So yes, having the wind flaps completely up, down, or somewhere in the middle, causes this problem for me).
How do I fix this? Am I flying it wrong? I use Autostart, take off at full throttle, decrease throttle to around 80%, and (try to) cruise.
Fixed by using mouse for elevator (the thing that makes you pull up & push down, for newbies who've stumbled across this thread, having the same problem). Press tab until it says something along the lines of "mouse flight controls, press tab to change", then move the mouse up & down.