Jerry Hey wrote:

These  Ivo prop blades cracked.  Came of a Tailwind.  This story
gets
repeated so often.  How does this company stay in business?  I know
a
few rotary guys are interested in Ivo's.  The question is Why?
Jerry

    Jerry,

      What engine was being used by the Tailwind? How many hours on
the

    Ivo? Were the blades torqued to proper value?

    Kelly Troyer

This is a failure mode of the IVO I have not seen before. These are
either
ground adjustable twist blades or they are from a variable twist
configuration.
Usually IVO blades fail when used on large displacement certified
aircraft engines
due to high peak torque pulses. That is not what happened in this
case. These
blades failed from over torque ing the twist mechanism so the blades
failed in
torsion mode. In this case it had nothing to do with the type of
engine.

It is not clear whether it was a stock amount of variable twist or
somebody
manually twisted them beyond the design limits.

Paul Lamar

Paul, I forwarded  your questions to the Tailwind pilot and here is
his response:

Jerry it was nearly in the center of the adjustment range. I made very
little adustment after I installed it. They are kind of a pain if you
have a spinner. After installation you put some metal tape over the
cracks where the blades join. Then the fun begins. First you do a full
range rpm runup then you check the tapes to make sure they don't break.
Then you check the tapes after the first 15 min. 30 min. 1 hr. 2 hr. 4
hr. and then  every preflight inspection. If a tape breaks or cracks
you clean it and put a new tape on it and start the process over again.
Then your supposed to retorque the prop bolts to 65 ft/lbs every 10
hrs. I did the process by the book and it still broke. If I can get
them to give me some new blades, I'll make some of those guys a really
good deal on an Ivo Prop. The lack of hard power pulses on a rotary may
make a good match for one, but Bob don't want anymore
Ivo.................Bob 149

If it was in the center of the twist range it could be blade torsional flutter.
Strange failure mode. Perhaps Bob is not being entirely candid :)

Paul Lamar
 
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