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Date: Sat, 03 Jan 2009 06:58:10 -0500
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From: "Fred Moreno" <fredmoreno@optusnet.com.au>
Subject: FW: reversing MT
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Jeff wrote:

"...The composite MT prop (even with the nickel leading edge) takes=20
a beating and gets pitted easily.  Making this a reversing prop (that=20
is, going into Beta) invites heavy ingestion of rocks and debris=20
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.=20

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. =20

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.  =20

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.=20

Fred Moreno, ex-MT prop operator