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Date: Fri, 02 Apr 2010 08:35:36 -0400
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From: "Dan Schaefer" <dfs155@roadrunner.com>
Subject: MT prop info FWIW
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While reading thru the list this morning, I noticed someone looking for an 
MT prop (no, I don't have what you're looking for) and thought I'd pass on 
some info that I came to grips with last summer regarding mine. It's an 
electrically controlled MTV-1-F/155-07 used on my Lyc O-235-L2C, so this may 
not apply to larger units.

On takeoff, just as I broke ground, the prop stopped increasing pitch and 
maintain the set RPM. I quickly pulled the throttle to get the RPM under 
2800 (Max continuous for this engine) which required a MP of about 13 
inches, and found I had enough power to turn 90 degrees to land on the 
crossing runway. After I caught my breath, I noticed that the prop CB had 
popped. Further checking showed that any time I tried to reduce RPM (run the 
prop to coarse pitch), with either operating mode (Auto or Manual) the 
breaker would blow. Interestingly, it would only happen when the engine was 
running - with the dengine stopped, I could run the pitch from stop to stop 
with the Manual control - no problem.

Long story short, after changing out the controller, brush-block/speed 
sensor, wiring harness and checking the slip-rings for a short to no avail, 
and since the prop was just past the recommended MT TBO (for 
time-in -service though not operating hours,which was about 700 hrs), I sent 
it to Florida for an overhaul. Like any normal person, I figured that after 
eliminating everything else, it had to be the prop itself. When it finally 
came back, with a clean bill of health, according to MT, the problem 
remained! (Incidentally, I have several new words for your vocabulary due to 
this if you're interested)! What was throwing me - and the MT service 
center - was that it only happened when the engine was running.

I took the prop back to my work-shop and examined it again (for the 
umpteenth time) and finally noticed that, though newly overhauled, it still 
had the original electric motor installed - and the motor was the only thing 
that I couldn't isolate and test with the engine running. Checking with MT, 
I was informed that their approved O/H instructions (at least for my prop) 
did not include installation of a new motor/gearbox. Since the prop was 
originally built in 1996 or so, they agreed with me that it was the only 
thing left that could cause the problem and they would have the factory send 
me a new one (since I didn't want to send the newly overhauled prop back 
across the country for them to do it). Of course, it had to come from 
Germany because, since my prop was built, MT has changed the motor to a 
larger unit requiring replacement of the front hub cover-plate as well.

This whole thing took all summer - from mid May until I got airborne again 
in late September! Too cold to fly in the winter up here in Northern Idaho 
(Coeur d'Alene) so just had a new Chadwick balance done a couple of weeks 
ago and all is well again.

The reason for this long rant is to let the community know that, when you 
get an O/H on your MT electric prop, you might want to determine whether 
you'll be getting your old motor back. I think I'd insist on a new one or at 
least, an overhauled one, particularly if your prop has a fairly early 
original build date.

Cheers,

Dan Schaefer
Early 235, N235SP 


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