CONCERNING PLATFORM TOWING ONLY.
Accidental release of Nose Wire Hook (part number STL237.000.AD) on Discus, Stealth and Combat series gliders while platform towing.
This safety advisory concerns only the gliders used for platform towing. If you take off using other methods, you shouldn't worry about this.
We have become aware of the potential for an accidental release of the nose wire attachment while platform-towing with the Discus, Stealth and Combat series gliders that use Nose Wire Hook STL237.000.AD.
Platform-tow systems require a nose release system to hold the glider while the system accelerates for take-off at 25-30mph airspeed. Gliders are typically fitted with a nose release rope by attaching a rope around the keel close to the nose plate and then carefully passing the rope through the gap between the nose cone and the nose wire hook. The nose rope attaches to the tow system nose release catch, which is operated by the pilot at take-off. Recent designs of platform-tow systems require that the nose release system be in line with the keel to reduce stress on topless gliders.
The potential for an accidental release exists during platform tow when:
a) the nose release rope is close to horizontal and it presses against the nose cone which in turn presses against the safety spring on the nose wire hook allowing the front wires to release from the nose wire hook, or
b) the nose release rope presses on the nose cone and rotates it down,. The nose cone can open the safety spring on the nose wire hook allowing the front wires to release from the nose wire hook.
Aeros has developed a modification of the nose wires - hook junction that addresses the issue for pilots who intend to platform-tow their gliders. The approximate design of it is shown on the (attached) drawing.