Message-ID: <000b01c1a89b$bddf2680$b60eb43f@f3g6s4>
Reply-To: "Dan Schaefer" <dfs155@earthlink.net>
Reply-To: lancair.list@olsusa.com
From: "Dan Schaefer" <dfs155@earthlink.net>
To: "Lancair list" <lancair.list@olsusa.com>
Subject: RE: constant-speed props
Date: Tue, 29 Jan 2002 00:05:38 -0800
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>>no need to worry about overspeeding prop

Well, allow me to let you all in on a little secret about the electrically
driven MT CS prop (as opposed to a hydraulically operated one).

The electric MT utilizes a very small DC motor and a gear train with enough
gear ratio to allow the small motor to muscle the blades though the required
pitch range while under load. My guess is that MT chose this small motor to
keep the weight down plus the ability to fit the whole thing inside the
spinner. Nothing wrong with this approach, with one important caveat: The
prop pitch just doesn't change very quickly when compared to the oil driven
props.

The operational result of this fact is that one must be careful to go a bit
slow when pushing in the throttle or you will get ahead of the prop and it
will overspeed, at least momentarily. This will happen at the beginning of a
take-off run and is particularly true doing a touch and go or a go-around.
Although the overspeed lasts only seconds, while the prop is trying to get
back to the proper setting, it will happen every time and eventually may
bring on problems.

On my first couple of takeoffs (and later, during a tower directed
go-around) after installing my MT electric, I was surprised to see over 3000
RPM for a short time. I have since learned that the solution to this is to
bring the throttle in over about 4 - 5 seconds. (Quite difficult to remember
in a hurried go-around, let me tell you!).

Even with this small problem (actually, just an operator work-load problem)
the MT CS unit is still a great prop for the Lancair!

Dan Schaefer


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