Loading...

pdf Gfa ad 371 Issue 3 2017.07.27 Popular

By Tagged in G109, G109B 1204 downloads

Download (pdf, 213 KB)

gfa ad 371 Issue 3 27.07.2017.pdf

Gfa ad 371 Issue 3 2017.07.27

ULTRASONIC INSPECTION OF MAIN SPAR ROOT END STUB SPIGOTS 

Grob Twin Astir gliders worldwide have been subjected to inspection and replacement of their wing root, spar end stub fittings (Ref. AD 346). In Australia that process uncovered 5 out of 18 gliders with cracked pins, the last one found having less than 120 hours total flight time. The cracks are considered to be the result of poor welding and manufacturing technique. The British C.A.A issued AD 006-10-88 which asks for Grob 109 and 109B powered sailplanes to be visually inspected using 10x magnification for cracking of the spar stub pins at the toe of the fillet welds within 50 hours and then every 300 hours. GFA Issued AD371 Issue 1 which required ultrasonic inspection of the stub fittings within 50 hours and then every 500 hours. To date no cracks in the stub fittings have been reported. The pin loads on the G109 / G109 B are less than that of the Twin Astir and the fatigue environment more benign as the G109 / G109 B are non-aerobatic. Issue 2 of AD371 extends the reinspection interval to 1,000 hrs since the previous inspection. Issue 3 of AD371 clarifies that the spar stub pins require replacement at 3,000 hrs and that the inspections are not required after the pins have been replaced.