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SOUTHWEST AIRSPORTS

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Metal Fatigue

After 100's of hours of flying, pilots should thoroughly check their Top 80's for fatigue cracks and breaks.

Breakage of the ABM sidebars, their attachment points to the frame, and the side bar pins (bolts) would be catastrophic.  These areas must be routinely and carefully checked, especially on motors with many hours.

Breakage of the fins on the cooling box can also be expected.  Cooling efficiency will be less but if a CHT (cylinder head temperature) gauge is used, pilots can easily monitor any increase in running temperatures.

Another common area of failure is the tubular frame near the lower cross member and the lower attachment points for the harness.  A body shop can TIG weld a break or crack.

Below is a photo of a throttle and kill switch failure caused by metal fatigue of the support bracket in a Top 80 paramotor.  If Miniplane used higher quality aluminum this would not occur.  When the bracket broke (white arrows), the ground circuit for the kill switch was also lost.  This is why pilots must always have a functioning choke to stop the engine if the kill switch circuit fails.  Also visible is an improved throttle return spring setup.  It is smoother and longer lasting than the OEM design.

throttle failure from metal fatigue in a Top 80 paramotor

The support bracket was easily repaired with a piece of aluminum and pop rivets.  Steel could also be used to make the repair but it weighs more but is less subject to fatigue.  The arrow shows the original point of failure.  The Top 80 engine generates severe vibration which is the cause of metal fatigue.  Modifying the throttle by adding a spring (prominent in the photo below) decreases stress on carburetor parts and the throttle shaft, in particular.  Check the link above for how to do this.

repair of the Miniplane Top 80 throttle support bracket

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