MT-Prop Governor problem

[bhester]

Posted to the RV-List by Mark Phillips

I recently test flighted a new RV with an Aerosport IO-360, Hartzell BA prop and MT governor, and the prop would surge approximately 150-200 rpms about once per second under takeoff & climb power. Pretty darn interesting on a first flight. After calling Hartzell (they new about it and suggested calling Vans), Vans (the tech guy I talked to seemed a bit evasive, but gave me MTs phone#), then MT, I finally learned that any of their governors with a model # with anything earlier than an -F suffix has to be returned for modification to an -F series level. This particular governor was a -B series purchased from Vans about 16-18 months ago. Off to MT in DeLand Florida it went and was back in about 10 days- It now performs perfectly.

But- I recently visited a builder near me who had bought the same governor, but had not yet installed it. I asked to see it and it is a -C series unit. He had no idea that when he installed it on his plane and had the surging problem he would have to pull it for modification as well- quite a hassle on a flying airplane, much easier to do before initial installation of course.

I sent Vans a polite e-mail asking if they were aware of this situation, and if so, were they planning to notify those who had bought these governors. No response in over a week, so I thought I'd give y'all a little heads-up so you can avoid the same hassle I had. If you have one of these units, contact Juergen at: http://www.mt-propellerusa.com/home.htm

Mark Phillips, RV-6A "Mojo" Fiveonepw@aol.com
Columbia, TN
http://websites.expercraft.com/n51pw/

[sjhurlbut]

Vans knows about this already. I had the same problem in Aug 2006 and that was not the first one.

See archives for info,

Steve
RV7A

[Bryan Wood]

Mine did something similar and I found it wasn't the governor, but the mount had come loose. One the mounting bolts had backed out about 1/2 turn allowing the mount to flex just the slightest little bit. Tightened it and the problem corrected. By mount I mean the Van's weldment that holds the cable in place for the governor cable.

Bryan

[Andy Hill]

We have had correspndance with MT over this... and there are other threads on here about it.

MT upgraded our C (?) to an F (?) free of charge prior flying, but stated there was not necessarily a "problem" with the C, but for "peace of mind" etc... they offered to upgrade it.

We had no problems for the 1st 15+ hours, then on one takeoff and a subsequent touch and go I saw the surging. Bearing in mind advice from this site, I "cycled" the prop downwind and the next touch and go no problem.

It seems this governor can be sensitive to "cold oil", and a suggestion from here was 5 cycles prior takeoff solved the problem... We flew again today, still **** cold, and a good 3-4 cycles prior takeoff meant no surging... so assuming it is "winter" where you are, it might help?

Andy & Ellie Hill
RV-8 QB http://www.g-hilz.co.uk

[kiwipete]

Mark

I had exactly the same problem. Sent it back to MT and now all is well.
I also sent a email to Van's and got the following reply:

Peter,

thanks for your interest and comments. We have considered a "letter" but because of the rare occurrence and relative inconsistency of the occurrence and that combined with the fact that the majority of respondents actually have some other problem not associated with the governor we decided against it. If flight safety were a serious threat we would issue a letter. As it turns out the few governors returned to MT have mostly been OK and a very few have actually needed any modification. Peter, don't forget to follow the fine pitch adjustment directions for your "limit" screw on the Hartzell propeller. Symptoms very similar to your apparent MT surge result from attempting to use the governor to limit the rmp to 2700 on takeoff rather than the propeller "limit" screw. (this instruction is in the Hartzell manual that comes with the propeller) Also, be sure and check your tachometer. Mechanical ones can give similar symptoms, particularly when aircraft pitch attitudes change from climb to level flight. The magnetic coupling inside the cheaper tachs can allow the couplers to move and this results in an rpm change that appears on the tach as a surge but is not "real" at the engine.


Fly safe,

Tom at Van's

My email to Vans:


In the process of test flying my RV7 with a new MT governor and Hartzell blended airfoil prop both supplied by Van's I started to get prop surge's. I contacted MT in Germany and they said it was a known problem with the P-860-4 governor's that have a serial number not ending if F. Mine had a B. My fellow builders S. Boynett (72126)a D I looked on the Vansairforce site and found that there seems to be a number of people effected by this.
The surges are about 100 rpm but are very noticable at full power and could be very disconcerting to someone test flying a RV for the first time.
As it's a problem acknowledged by MT and as there could be a number of people with Firewall forward kits that have been supplied with these governors is it worth putting out a service letter, advising people to update the governor before installation if they intend to use it with a Hartzell Blended airfoil prop. MT suggested this was the only prop effected.


Yours Sincerely

Peter Reid

[Andy Hill]

Peter, don't forget to follow the fine pitch adjustment directions for your "limit" screw on the Hartzell propeller. Symptoms very similar to your apparent MT surge result from attempting to use the governor to limit the rmp to 2700 on takeoff rather than the propeller "limit" screw. (this instruction is in the Hartzell manual that comes with the propeller)

Oops - guilty as charged

We thought it was a bit "lazy" at governing the 2700RPM on takeoff with a slight (but well within limits) overspeed

Of course I had read the whole Hartzell book, but another section seems to have just caught my eye

Best do some adjusting before next flight

Andy Hill
RV-8