by dany93 » Mon Dec 30, 2013 6:35 pm
Hi Stuart,
I've added the code lines for "spin and stall" in the C172P's last FDM (downloaded from the official site, 20130826 version).
In fact, the values needed to be fitted for the present FDM.
The spinning effect is obtained, but (as could be expected) with some imperfections.
Results:
1) With throttle at 0 (engine at idle):
- in a straight trajectory (wings levelled), the aircraft tends to "parachute" (baloon?) at constant AoA instead of diving. It can be true, I do not know this aircrfaft IRL.
Buffeting appears, the slip skid ball (unfortunately not very visible) is to be kept well centered before stall, do not let the aircraft yaw (control with rudder) to avoid spinning. That seems normal. Spin can be severe if we insist on holding the yoke back.
- in a turn, the spin did not easily occur for the same "parachuting" reason, even with the stick full backward. The stall AoA was hardly attained. Now, it can be obtained after increasing elevator efficiency, which seems sensible, not excessive after my tests.
2) With enough throttle, steep turns (stick pulled) can give severe spins when large AoA's are attained. Obviously worst with too much rudder (slip skid ball outwards). Correct (at least qualitatively.
3) In forward slip (throttle at 0), the upper (downwind) wing falls down when stall occurs, which is correct. However, from my point of view, the bank angle is too weak in forward slipping. Rudder efficiency seems slightly low (for decrabbing with crosswind at landing). After more testing, I've slightly increased rudder efficiency, not only for crosswind decrabbing but also because it's an important control for spin recovery. Even after this, I think it's still a bit weak.
I did not want to change noticeably (at risk of degradation) the general handling of the FDM in normal operation. I've only modified two or three minor parameters in order to obtain stall spinning. Let me know if you feel I've degraded something (I don't think so).
Future tests will probably bring some ideas for refinements, but I think the best is to have a first version. Would it be only to decide if it can be considered as an improvement, with no drawbacks.
The FDM is ready to be sent, what do you prefer ? Personal mail? A link? The file is a bit long to be inserted into the forum, unless someone else is interested. I don't want to pollute.
Dany
Last edited by
dany93 on Wed Jan 22, 2014 12:44 pm, edited 1 time in total.