At 09:07 AM 23/09/2004 -0700, you wrote:
There's a video and a report of exactly that at;
http://www.gliderforum.com/printer-friendly.asp?threadid=167
Mandy
Thanks Mandy
I thought somebody would be able to come up with the cross-reference. Note that all reports of the anomalous spin mode were at rearward (but still within limits) CG, and report DELAYED recovery - so the lesson is to use FULL RECOVERY ACTION and hold on full forward stick if necessary. Moving the ailerons at this stage may also discover the configuration the leads to a faster recovery.
Practice and familiarity lead to confident execution of the exercise. Also, as Drew indicated, we ballast the Puchacz to a more forward CG for deliberate spinning.
A further thought - for a given aircraft configuration and CG position, the stall (and hence the spin) only occur once the elevator position reaches or exceeds a certain rearward position. This is well known amongst aerobatic aeroplane pilots, and knowing the required stick position to induce the stall/spin in the first place is useful knowledge. TO REPEAT, THE STALL IS INITIATED AT A STICK POSITION THAT DEPENDS ON CONFIGURATION AND CG POSITION, REGARDLESS OF AIRCRAFT ATTITUDE. Airspeed, however, depends on G loading - which is why incipient recovery occurs when the wing is unloaded.
Of course, in some configurations and CG positions, no stick position that is achievable (i.e. forward of the aft limit stop) will cause a spin.
Since almost all aircraft are designed to have a download caused by the tailplane to keep them in balance, a rearward CG will make the elevator more sensitive - hence Leigh (and others') comments on the different handling of the K-21 with the spin kit added.
I once had an "interesting" experience in cloud in a light aeroplane - as I climbed to try and break out above cloud, the elevator got progressively lighter until I decided it was time to divert back to clear air over lower ground where I could shed the ice that was accumulating on the wings (and presumably tail surfaces also). Discretion is definitely the better part of valour!
Wombat
There was discussion some 12 - 18 months ago regarding the possibility for the Puchacz to occasionally adopt a flatter mode of spinning at rearwards CG. This mode involved a flatter attitude and slower rate of descent, but also a delayed recovery (i.e. it took more than 1 full turn after the initiation of recovery before the recovery took effect) if the aircraft was held in a developed spin beyond the stage of established autorotation.
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