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Compare the following against an aluminum alloy prop.
Why Choose an MT prop for the Lancair
IV???
Less Weight. After all, why did we choose a
Carbon Fiber airplane? Lighter is faster, Right? Why violate that
principle, when it comes to the prop???
But
here are more facts that validate the “lighter is better “
Especially when it comes to props!
1.
Polar moment of
inertia is about ˝ of a metal blade. Translates- Less stress on
hub.
2.
Less gyroscopic
loads on crankshaft flange/ engine mounts/ firewall engine mounts in
turbulence.
Wood construction gives MANY advantages over
metal as a material choice.
1.
No resonate
frequencies. No finite life. Can be serviced unlimited
times
2.
No fatigue
characteristics.
3.
Field
repairable. New stainless
steel leading edge erosion strips can be installed after a stone strike
for minimal cost. Wood damage can be repaired, and returned to
service.
4.
Tip strike (Gear
collapse), would not normally break internal engine parts. Boy, can this
save a bundle of $$$$$$$$$$$$$$$.
5.
Balance easier. Uses
less weight.
6.
Smoother/ Quieter/
with less vibration.
7.
MT blades fared
better than metal blades in bird strike tests at the University of
Dayton.
8.
Lightning strikes
tests show perfect behavior.
9.
Icing resistant. No
engine heat translated to prop blade.
Additional reasons that MT is a Superior Company
to deal with.
1.
Spinner is provided
-- and fitted. Kevlar “chrome” no upkeep spinner available.
2.
Saves many hours
time and has no wobbles.
3.
German
Engineering
Charlie K.
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On Sat, 1/3/09, Fred Moreno
<fredmoreno@optusnet.com.au> wrote:
From:
Fred Moreno <fredmoreno@optusnet.com.au>
Subject: [LML] FW:
reversing MT
To: lml@lancaironline.net
Date: Saturday, January
3, 2009, 6:58 AM
Jeff wrote:
"...The composite MT prop (even with the nickel leading edge) takes
a beating and gets pitted easily. Making this a reversing prop (that
is, going into Beta) invites heavy ingestion of rocks and debris
sucked back up into the prop after it passes over them..."
I can not comment on the reversing prop, but can confirm that the MT props
have nearly zero tolerance for even small rocks and bits of small gravel
that may be picked up. The leading edge sheath is very thin, and backed up
with wood. Thus it does not take much to make a big dent, much bigger than
would occur with an all metal blade.
With the MT prop, if the dent in the leading edge is less than about a
quarter of an inch wide, AND a tap test completed around the ding with a
large coin AT EVERY PREFLIGHT shows no hollow areas, they you are good to
go. More than a quarter of an inch, or any area of hollow sound,
particularly one that grows over time, means the prop is not flight worthy,
and has to go to an MT dealer for an expensive and time consuming repair.
The quote for restoring three blades to new conditions was eight weeks and
nearly half the purchase price of the prop. Once repaired, the same damage
can occur on the next flight if the little stone with your name on it
happens to be in the right place.
I punted instead.
Consider the MT to be viable on clean (preferably swept) paved runways,
taxiways, hangar areas and run up areas. Or keep a spare prop if you can
not tolerate several weeks of shipping and repair time. MT is slow to ship
the sheaths and repair kits that include special epoxy and vacuum bagging
supplies to put the new sheath on the blade. After that a lot of
time-consuming hand finishing and painting are required to complete the
repair. Don't forget that you need a crate for the round trip as well.
If
you get that rock at a strip far from home, you will have to leave the
airplane and catch a kerosene burner.
I concur that if you want a reversing prop, you should stay on very clean
pavement with NO loose stones present. Also, avoid all winter-time ice that
might be flicked up to eat a leading edge sheath. But if you operate off
pristine, clean pavement, then more than likely, you do not need a reversing
prop.
Fred Moreno, ex-MT prop operator
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