Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml@lancaironline.net
Date: Mon, 29 Mar 2004 01:05:43 -0500
Message-ID: <redirect-3132533@logan.com>
From: "Dan Schaefer" <dfs155@adelphia.net>
Subject: MT Electric Prop
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In answer to Pete Cavitt's question about MT vs fixed pitch prop.

Pete, I ran an Amar DeMuth prop with about the same dia. and pitch on my 235
very early on and later switched to the MT electric C/S unit and there are
at least two things to say about it.

First, A-DM props scare the heebies out of me as I've had two fail, one on
the trip home from Redmond to LA that developed about an 8 in. crack 2/3 of
the way to the tip and a second (the replacement) that failed
catastrophically on take-off just at rotation. This one spontaneously lost
most of it's rear lamination on one side. Fortunately, I had enough runway
to stop with nothing worse than something only my laundry-man knows about
but a few seconds later, I'd have been a statistic. From the shaking and the
fact that the engine stopped immediately, it felt like I'd put a piston
through the side of the engine.

Second, with the Lancair's wide speed range, when I ordered my wood prop, I
opted for a cruise-pitch (similar to yours, if I remember, 62 x 72) and
could only make about 2350 RPM on the start of a take off run (at sea
level). As you can imagine, this led to some "interesting" take-offs when
the airplane was full and conditions weren't standard SL. I changed to the
two-blade MT elec. C/S and see 2750 RPM in the same conditions (rated for
2800 continuous) and then set the cruise RPM to around 2530. Takeoffs
immediately became a whole lot less exciting! Can't say that I saw a
significant speed increases in cruise though there was some - maybe 5 Kts.
During cruise conditions, the RPM stays where set quite well.

There is one small caveat however but it's easy to get used to. To keep
things as small as possible (and light too, I guess), the motor in the hub
that controls the prop uses quite a large gear ratio so the pitch doesn't
change as quickly as with a hydro unit. One learns quickly to go easy on the
throttle on takeoffs and particularly during a touch and go or a go around
or you will get ahead of the prop and get a momentary overspeed. During
these events, one needs to ease the throttle in and pay attention to RPM.
With my engine/prop combination, I take about 3 - 4 seconds to cob the
throttle - other combinations may be different but I'll bet not by much.

Dan Schaefer
N235SP