Paramotor forum.NL

Paul Haxby of UK paramotor training company AXB Sports, has passed on to us some safety information regarding a bolt on a Clemente Snap 145 paramotor that sheared during its removal as part of routine inspection and servicing of the motor. It would have inevitably sheared during flight had the inspectionnot been carried out.

The paramotor was 3 to 4 years old with only 40 hours airtime, and had not been used in acro or other high-stress activities or suffered any major impact.

The bolt held one of the swinging arms to the frame, and if it had snapped in flight a safety backup strap would have meant the harness would have dropped an estimated 150 mm on that side, but could have resulted in limited control and danger if during take off, landing or when flying close to the ground.

On inspection, engineer Keith Colder concluded that the bolt, an A2-70 stainless steel M10, was not defective, but that it was not strong enough for the intended application. He also suggested that modifications to the design of the swinging arm to frame attachment could make the joint stronger. Failure wasdue to the steady propagation of a fatigue crack under normal use.

The engineer recommends that

(1) All users immediately strip and examine the bolts attaching the swinging arms to the frame on any paramotor frame that is of the same or similar configuration as the Clemente (where the swinging arm rotates about the bolt, with no rigid support between the head of the bolt and the swinging arm, or where the bolt does not act by compressing a bush or tube onto which the arm is located).

(2) Even if no cracking is evident, replacement of all bolts is advisable. Only the designer/manufacturer can legitimately advise as to suitable replacement products, and take responsibility for their recommendations.

(3) All manufacturers review their design and material selection with respect to this critical joint, where possible carrying out a quantitative analysis of the loads and a FMEA (Failure Mode Effect Analysis)