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During preflight I felt something while running my fingers over
the prop and prop-hub. Upon closer inspection I realized it was a
crack in the prop-hub, small enough to easily be missed. (Using
touch during pre-flight can save your buns.) So, unfortunately, I
had to scratch this flight.
I believe the crack was caused by me over torquing the hub by
about 10-15%. More isn't necessarily better! The manufacturer,
Warp Drive, had a few other customers with cracked hubs and felt
their original design arguably had a weak point, so they sent me a
replacement under the life-time warranty. Warp reported that the
other cracked hubs had many more hours on them then mine did. I
was up front with them about my over torquing, but they covered it
anyway. Nice.
I was disappointed to have to pack up and go home that day. Two
months later I would come to think of a cracked hub as a
relatively small problem.
SERVICE ALERT
2001-01
It has come to the attention of our
technical service staff that a small number of customers
operating the Kitfox™ aircraft with the Continental IO-240 have
experienced difficulties with the Warp Drive propeller commonly
used with this engine. Reports have been received stating that
cracks have been observed on the aluminum collar located at the
hub end of the propeller blade. These cracks have been located
close to the hub area.
Warp Drive has been informed of
these reports and is investigating the issues involved. It is
thought that the combination of a low inertia propeller coupled
to a high compression engine may result in abnormally high
propeller blade “shock” being experienced at low idle RPM’s.
SkyStar aircraft recommends that all
Kitfox™ owners operating the Continental IO-240 with a Warp
Drive propeller carefully inspect the propeller hub and collar
area prior to each flight for evidence of cracks. It is also
recommended that ground idle RPM be maintained at a speed of not
less that 1100 RPM.
We ask that individuals finding evidence of
cracks contact SkyStar's Technical Support staff at (208)
454-1665 or e-mail Technical support at
support@skystar.com.
Warp Drive will be offering more information as it becomes
available.
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