On Friday, May 10, 2013 10:25:24 AM UTC-6, Waveguru wrote:
Please describe to us a winch accident that would be the fault of the winch and not the pilot.



Boggs

First, Gary, let me say again I agree with your position on pilot responsibility and I would be perfectly willing to take a tow behind your payout winch. However, here's a couple of scenarios where a powerful winch can be safer than auto tow.

On a calm but strongly thermic day, a tailwind gust is encountered just as the glider begins rotation into the climb. If the winch has substantial reserve power, and is controlling rope tension, it will instantly add power to help the glider maintain a safe margin over stall in the critical rotation phase. In this case, the pilot has less control over his fate than the winch. If the winch or tow car power is marginal, the glider may stall in this situation.

This is why the DAeC Technical Committee guidelines set minimum power and rope speed requirements.

Another scenario is a winch which balks just after the glider is airborne leaving the glider momentarily gliding at minimum controllable airspeed. The winch then "catches" and applies full power. Without the runway surface supporting the tail wheel, and if the glider's CG is well above its hook, the inertial couple effect may cause a dangerous uncommanded pitch-up.

This is why the DAeC Technical Committee, in another paragraph, requires absolute smoothness in winch power without any tension oscillations or spikes in rope tension.