Quicksilver MX wing bolt failure, ultralight aircraft wing bolt failure, wire braced ultralight wing bolt failure.

Quicksilver MX, Rotec Rally, Birdman Atlas, Skyseeker, Condor, and most other wire braced ultralight aircraft.

Problem area:
Leading and trailing edge wing wire bolts

Incident report:
During routine preflight inspection, it was found that the grade 8 bolts connecting the flying wires had broken off at the top of the threads, flush with the inner leading or trailing edge tube. Further inspection also revealed that corrosion of a very serious nature had started inside the aluminum fittings used to attach the compression struts to the leading and trailing edge spars. In more than one instance, pilots have reported being able to remove the compression strut from the aircraft by simply pulling down on the strut.

Suggestions:
Replace the grade 8 coarse thread bolts with fine thread aircraft grade AN bolts and replace the aluminum compression strut insert with a steel, or stainless steel insert, thereby insuring compatible metals and added strength in the bolt since the thread is not cut in but rather die cast.

Also it is recommended that pilots on a regular basis check the bolts with a wrench to ensure bolt is still intact.