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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