Jonathan,
Any propeller contact is a shock to the engine and prop.
Hollow or foam filled composite props made from carbon fiber tend to crack and
tear inside and there is hidden damage. As a rule, I replace damaged carbon
fiber
blades.
Solid Carbon fiber is only a bit tougher. Even Warp Drive prefers to just throw
away the blades and replace them. Their ground adjustable hubs are prone to
cracking on sudden stoppage but the cracks only show on NDI testing. The low
power hubs cand bend slightly out of shape on "the minor prop strike". This
is standard for aluminum. Always have the hub mic checked and I prefer to let
the factory do that now as I have made mistakes and missed things that the
factory
would have caught.
Metal fixed pitch propellers, I recommend shipping back to the factory for redo
and static rebalance. The slight brrrt can twist the tip making for unusual
harmonics in the prop and eventual problems. Beware of the used aircraft with
a minor prop strike. It reeks of cheap owner, lax maintainer, and eventual
vibrational
issues.
Wood props are a mixed bag, but normally the glue joints fail and the prop is
toast.
Ultrasound and X rays don't work well with wood props.
Constant speed props are a mixed bag. Any prop strike should be sent to the
factory.
The bearing surface at the collar and down in the hub can be distorted
with any shock load. The bearings are designed for rotational loads not bending
loads. As stated above, only through de-painting and NDI inspection can a
hub be returned to service. Hence, I believe in sending the hub back and have
it rebuilt.
Engine damage is also a mixed bag. Slipper clutches, types of gearboxes, crank
shafts, depend on the engine. I personally take a day and pull the engine, run
it to the facility and have the inspection done. It takes about 3-4 hours
to do it by the book.
No matter what, the pilot owner needs to pay the "dumb tax" if he made the
mistake.
We all do and we also know that flying is not cheap. Bad maintenance will
degrade an aircraft into a flying heap. Pilot wise, if it was necessary to
ground loop to prevent destruction of the aircraft, insurance will pay for it.
One thing I know for sure is, aircraft damage is easy to repair. It will be
time
consuming, inconvenient, and destroy the pocket book and pride but we own our
mistakes. If done right, the plane is as good or better than new. Cut corners
and it will bite you eventually.
Prop rebuilds on an Airmaster average is about $3-4000. Gearbox
teardown/rebuild
and engine inspection is in $2-3000 range for a Rotax. Lycoming/Continental
I don't have as much experience with.
Treat any prop strike as serious. I have yet to find a simple one.
Regards,
Bud Yerly
-----Original Message-----
From: owner-europa-list-server@matronics.com
<owner-europa-list-server@matronics.com>
On Behalf Of JonathanMilbank
Sent: Friday, April 02, 2021 3:50 PM
Subject: Europa-List: Acceptable prop strike damage?
Getting straight to the point, is there a "rule of thumb" for how much damage a
propeller can sustain before a shock load engine strip-down is necessary? I
suspect
that the decision lies with the engineer making the assessment.
Today a friend was flying his tail wheel RV6 in a strong crosswind on a tarred
runway and while landing he was dumped by a gust while attempting to go around,
perhaps over-rotated when pushing the stick forward and heard a sound like
kerbing
a car's wheels, as he described it. He didn't really feel a vibration,
nor did he hear the engine note change. So it was a fleeting "brrrrt" on the tar
and following the go around pattern flown, a later inspection showing no
evidence
on the runway surface.
The engine is an IO320 (I think), the propeller is fixed pitch metal and last 3
to 4 inches of the tips are now curled forward through a full 90 degrees. My
instinct is that a shock load engine strip-down isn't necessary in the
circumstances,
but what do I know? Very little indeed, apart from a slight recollection
that damage like minor nicks in prop leading edges can be dressed out provided
that they're not along the 1/3 nearest the hub.
I look forward to your replies, thanks.
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