Norman was flying and testing a prototype when the accident happened. All the lines broke and Norman free fell without opening his rescue.
Following the reports of witnesses, it seems that Norman was in a heavy spiral dive when the lines broke.
Other people speak about a front collapse after the spiral dive. No one can confirm this. We do not know exactly what happened in flight, no one saw the complete process of the accident.
But we do know exactly why the lines broke.
The prototype was equiped with standard sheathed 1.6 mm Aramid (Technora) lines. These lines have a strength of about 200 kg after sewing.
Norman made 3 knots on every main line to trim the wing. These 3 single knots reduce the line strength by more than 70%. The lines broke exactly above one of the knots.
The advice from Housi Bollinger in the morning was to reduce the line lengths by making a knot in the stitched area and by making an extra loop at the maillons, this would have been the normal, safe way Norman and other GIN test pilots use for this kind of modification.
We have made some breaking strength tests to find the effect of knots on the strength of the line material used on the prototype flown by Norman.
1)- Line sewn as used in production; strength 195 kg; rupture at the end of the stitches; very high strength
2)- Line with 1 knot in the double part where it is stitched (as proposed by Housi); strength 119 kg; rupture at the knot; strength still sufficient
3)- Line with 1 knot in the main part of the line ; strength 64 kg; rupture at the knot; strength not sufficient
4)- Line with 3 knots in the main part of the line ( as flown by Norman ) ; strength 62 kg; rupture in the knot; strength not sufficient
We know that Norman as a professional test pilot was aware that knots reduce the strength of lines significantly.
Moreover Norman was responsible at GIN Gliders for testing the line breaking strength and stretching. With the R&D department, he was also in charge of safety matters, to find the optimum way to sew a line depending on the diameter to obtain maximum strength, to test the aging of products and materials, to communicate with the test laboratories for the certification testing, especially load and shock test, etc…
Norman took care of a lot of the safety aspects of our products for the pilot : it was the main objective of his job. As a test pilot, he was probably not aware so much for himself, believing that the lines would be strong enough for this flight and anyway, that he would be able to manage the worst case situation.
Norman’s high experience, serious attitude and his high level of professionalism make this incident even more difficult to understand and accept this tragic loss.
The lines broke 150 m above the ground, it means 3 to 4 seconds before the impact. This time is too short to deploy and open the rescue. In this type of accident it is also very hard to find the rescue handle to deploy the reserve.
Norman worked hard and with great passion to help produce high quality and safe gliders for all pilots.
We are missing our friend.
GIN staff.
