The propellers plane of damage ?

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Marc Zeitlin

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Aesquire

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An early Ultralight pioneer, Paul Yarnell, was doing a foot launch with an Easy Riser when his heel clipped the prop. The tip landed about 300 yards away, and he stopped the engine ( teeth clench kill switch ) before any real damage was done to the airframe. This was a McCulloch MAC-101 direct drive spinning over 10,000 rpm, and a fiberglass prop. Took quite a search to find the tip, about 3 inches long, despite witnesses seeing it fall, seemingly from space.

Cut the heel off his boot and left a nasty bruise, but no other damage, iirc.
 

wktaylor

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Prop material is 'key' to understanding blade failure mode.

Aluminum blades will fail differently than steel blades and wood-blades and/or 100% composite blades and/or wood-composite blades.

Likewise fixed-pitch prop blade failures are 'simpler' than props with individual blades connected to a 'hub'... more ways to fail.

Vigilant1 [repeat?]. I was the O-2A/B [C337 FAC] lead engineer at SA-ALC in the early 1980s. I investigated a Class A mishap where the rear prop blade separated due to a defective [fatigue-cracked] hub. The first liberated blade severed a boom and the aircraft tumbled into the ground. The hub with the opposite blade simply tore-off the crankshaft flange and went sailing away. That mishap was sad... 2-crew killed due to a 'pencil-whipped' hub inspection. Grounding the O-2 fleet for 'urgent inspections' identified several other Acft with rear-engine cracked blade-hubs. Complacency kills!!! Eventually all rear engine prop-hubs were replaced with up-graded hubs and 'red-colored' hydraulic oil... 'last-chance' to see deep-red-stains leaking-thru cracks during pre/post flight inspections.
 
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