Timeline for Is a glider on a winch directionally stable?
Current License: CC BY-SA 4.0
9 events
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| Jul 23, 2022 at 19:53 | comment | added | Robert DiGiovanni | @Sanchises well, working backwards (and with minimal vertical torque arm between CG and attachment point) it would seem that the glider will have adequate roll control and more directional stability because it is accelerating. A little like stepping on the gas in a turn can help in a car. Bottom line: the winch launch must be flown. It would seem the winch acts as rudder (directional stability, pulling ahead of CG), so it would be ailerons as needed. | |
| Jul 23, 2022 at 19:38 | comment | added | Sanchises | Acceleration is in fact very sharp precisely for this reason. Instead of a wheel, a human tip runner is employed. But I'm more interested what happens halfway the winch launch than the ground roll which, with a good winch operator, is very short anyway. | |
| Jul 23, 2022 at 19:07 | comment | added | Robert DiGiovanni | @Sanchises I accept that, other than the (dropping) wing wheel and expert instruction there is little more to say. But the first few feet of roll would be critical as counter-acting aerodynamic forces will be relatively small. Since it varies with speed, what to look for in the literature might be a control "threshold". I wouldn't feel so bad if the winch acceleration was sharp, as long as it got me away from the ground. | |
| Jul 23, 2022 at 19:02 | comment | added | Sanchises | Anyway I'm not interested in pitch stability but directional/roll stability. A winch needs a >1km long track, so you can't just change the "pull direction" if you don't happen to have a stretch of grass in that direction. | |
| Jul 23, 2022 at 18:58 | comment | added | Robert DiGiovanni | @Sanchises I think you're ignoring the pitch contribution of the lifting wing. This is why DLG gliders reduce trim on launch but winch launch must maintain tension. So trim would be critical. For cross-winds, a U-2 like wing wheel may be possible to support the downwind wing. It seems pretty dumb not to move the winch pull direction anyways. I might find a field that does, or ask Peter or John to tow me up! | |
| Jul 23, 2022 at 17:44 | comment | added | Sanchises | The attachment of the winch always is directly under the CoM. During acceleration, there can be a very nasty nose up pitch moment. There's definitely crosswind limitations in the POH since most fields don't have the luxury of turning the winch straight into the wind. | |
| Jul 23, 2022 at 13:21 | history | edited | Robert DiGiovanni | CC BY-SA 4.0 |
Better answer
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| Jul 23, 2022 at 13:01 | history | edited | Robert DiGiovanni | CC BY-SA 4.0 |
Better answer
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| Jul 23, 2022 at 12:55 | history | answered | Robert DiGiovanni | CC BY-SA 4.0 |