On Wednesday, October 9, 2013 8:44:52 AM UTC-6, wrote:
Time for pogo sticks.



The idea of launching a glider by having someone run the wing originated with wooden gliders and quite low speeds for stall and aileron effectiveness. Those speeds have gradually crept up through the years, to the point that really nobody can run the wing of a modern glider, with waterballast, and anything less than 10 mph straight down the runway, to the point of aileron effectiveness. Mostly we hope that the wing runner lets go, with the aircraft in balanced position, and it picks up speed faster than one wing drops.. That often isn't true.



For airtows the results are usually just some scraped gel coat; sometimes a collision with a runway light, and occasionally a ground loop. There have been accidents where wing down gliders hurt bystanders, the Tonopah 15 m nationals being the one I remember best.



Clearly, for winching, wing-down events are much more serious.



The answer: either retractable or disposable pogo sticks on the wingtips, or mid-wing. Something that keeps the wings level to 25 mph and then either drops off or retracts into the wing.



Reading the UK Nimbus 3 report, it would seem that a video link between winch driver and launch point would be a good idea, and quite cheap with current technology. It would cut a crucial second or so out of the abort-the-launch loop



John Cochrane

John, wing-down events are indeed more serious for winch launch simply because of the CG hook and the large amount of energy being delivered to the glider by the winch. The best solution is one where wing drops don't happen at all - or are least extremely unlikely.

It's true that modern, heavy gliders have minimum aileron control speeds much higher than a wing runner can reach. Just as with aero tow, slow acceleration leaves a glider vulnerable to a wing drop. As with aero tow, reaching minimum control speed quickly is a very good thing.

The time for a glider on winch launch to reach aileron control speed from a standstill (Anywhere except the UK) is a second or less so how can a wing drop in that interval? Even in a crosswind, a glider can be balanced laterally so if the wing tip is simply released it will take two or three seconds for it to drop. Something has to cause it to drop or it won't happen.

A rare problem is a pilot unintentionally holding aileron input at the start of the roll. Control authority comes on fast that a wing may go down before a pilot realizes his error and backs off the aileron input. The solution is being careful to neutralize the ailerons before the roll starts.

Also rare (Again, outside the UK) is mis-aligned staging which results in the rope pulling the glider slightly sideways. This can start a wing down before aileron control speed is reached. The solution is to be careful to stage the glider so it points at the winch.

Strong gusts can be problem but the longer a glider wobbles along with minimal control authority, the greater the vulnerability to them.

Wing runners should be re-trained from what they learned with aero tow. Any attempt to hold on will be disastrous so they need to do a very "clean" release. They must also learn the art of balancing the wing rather than just holding it sort of level. They won't so much "run" the wing as take a very quick step or two.

Video is under serious consideration. As you say, a CCTV link is very cheap as are all sorts of data-links. I think one of the best uses is a simple data-link to send a "STOP" message to the winch operator. That message could be displayed in .2 seconds from when an observer at the launch point first sees a launch starting to go wrong and the rope cut with the guillotine in another .2 seconds stopping the launch.