Dave Bowie has asked me to post a note on the forum as he is not on line at
the moment. He has an NSI variable pitch prop fitted to his Europa which
has done approx. 750 hrs - 500 on a Rotax 912 and 250 on a 912s. One blade
has developed a serious crack where the thrust bearing flange joins the
shaft. The crack runs about 270 degrees around the circumference and goes
right through the wall of the cuff. If the crack had gone a full 360
Degrees, it looks like the blade would have been thrown. Dave said the first
indication of a problem was when a vibration developed in flight which he
thought was a miss fire at first, so he tried changing plugs etc. to no
avail. The prop was only suspected after he realised that the engine was
over speeding with the prop fully coarse. On checking each blade he found he
had considerably more movement in one blade than in the other two so he
dismantled the hub and after close inspection found the cracks. Several
flights were made in the coarse of trying to detect the fault but the total
flight time from the first indication of a problem was only about 30 mins.
Francis Donaldson (PFA) said he had not received any other similar incidents
but is obviously seriously concerned and will be investigating the matter
further, in the meantime I think it would be prudent for all NSI users to
check their props for any sign of movement in the blades.
Jim Naylor
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