What followed was a flurry of phone calls to determine the cause and how to avoid the re-occurance......There were also questions raised as to whether the prop was suitable for the 100hp motor.....I see that there is a service bulletin out for all IVO props.... http://ivoprop.com/servicebul2.htm
A Rotax supplier got in touch with the IVO manufacturer and the following was their response... (In the interrests of safety, I decided to post the content as the manufacturer requires motion detector tape and regular re-torqing and I hear that a second plane had the same problem up Country this week.....)
[/b]Dear XXXXXX (Name removed),
http://ivoprop.com/ultralightmodel.htm
IVOPROP "Ultralight Model For engines up to 100 hp"
If the prop blade bolt torque is not maintained and there is movement of the blades in the hub in the direction of rotation that is not detected because the motion detector tape is not used correctly there will be damage beyond repair by the time a problem is noticed.
With the meDium prop on the 912(S) drive lugs are used but only to hold the adapter to the flange.
The prop blade bolt torque still must be maintained and it is mandatory to use the motion detector tape correctly otherwise there will be movement in the hub causing damage as above.
The bolts can break, but more often there can be broken cams, elongated bolt holes, and cracking around the bolt holes.
912S and late model 912 80 hp 75 mm flange pattern for Ultrailght model propeller bolt holes are not threaded
so we use the stronger AN5 BOLTS,
EARLY MODEL 912 80 HP 75 MM PATTERN IS THREADED SO WE HAVE TO USE 8 MM BOLTS.
I suspect the bolts that broke were the 8 mm and not the AN5 because the bolts broke before there was damage to the cams or blade bolt holes. Was this the case?
Since early model 912 80 hp 75 MM pattern has threaded holes it might be better to use the meDium prop that would have
12 mm drive lugs around the 8 mm bolts.
Early model 912 80 hp
(change was around 1995)
75 mm BC, 8 mm threaded holes
100 mm BC, 8 mm ID, 12 mm OD drive lugs
Late model
75 mm BC, 8 mm (5/16") non threaded holes
4 inch BC (101.6 mm), 8 mm ID, 13 mm OD drive lugs
Recommendations:
912 80 hp
Ultralight 3 blade 68-72 or down to 64 +High pitch
meDium 2 blade 70-74
meDium 3 blade up to 68
912S 100 hp
Ultralight 3 blade +High pitch
meDium 2 blade 72-74
meDium 3 blade up to 70
914 115 hp
Ultralight Right turn 3 blade 72 +High pitch Electric adjust
(Yes, 4 UL model on 914 in data base since 1997)
meDium 2 blade 74
meDium 3 blade up to 72
With Ultralight model prop on 912S or 914 be aware of prop stall
where you will need to get some forward speed before adding
all the power.
The use of the service bulletin Motion Detector Tape is required
for all above combinations.
Regards, Ron
