On Monday, August 20, 2012 7:42:38 PM UTC-6, Darryl Ramm wrote:
On Monday, August 20, 2012 7:18:48 AM UTC-7, Bill D wrote:

For the first time in my life I heard a 1st person story of a release failure.



The story follows:







The glider, an ASK-21, was jerked forward by the tug so the front wheel rolled over the rope at the start of an aero tow. The slack was then taken out and the tow was launched without inspecting the hook and release. The working theory is that this somehow cocked the ring set in the hook so it failed to release even with pilot and passenger pulling on the release knobs. The pilot eventually got a successful release by yawing the glider strongly.







AFAIK, the hook in question had not reached it's 2000 tow life limit nor is there any history of repair or maintenance in the hook area. There had been cases where a commercial operator had insisted on providing tows using a chain link instead of a Tost ring set. We think it possible this had damaged the hook in some way.





BTW I'm also aware of a Tost release failing to release due to corrosion within the release, I believe likely a combination of pee-tube spray and lack of proper care and maintenance. Pee tube spray may not be a factor in typicality ASK-21s but I suspect quite a few tow releases get only a cursory look over pre-flight and during the annual inspection.



And on chain-links just say no. Tim's web site is a great resource for Tost stuff.



Darryl

The particular ASK-21 is fairly new (2000)and in excellent condition. It has always been stored in it's trailer when not being flown by highly qualified pilots. There is no evidence of corrosion anywhere. Records are being checked but indications are the release life limit has not been exceeded.

I participated in the last annual and while the release was checked, it was not subjected to special scrutiny. (It will be this time.) The ring pair was not checked for authenticity but it will be.