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Coarse pitch to improve glide? depends on your governer

scsmith

Well Known Member
When I first built my RV-8, I had an MT governor. I was able to pull to coarse pitch even at idle. So it made sense to think about pulling the prop back with the onset of engine trouble, in the hope that the prop pitch would stay coarse to improve glide ratio.


After about 7 years, there happened to be an AD on some MT governors (not mine) that led me to find that they have a six-year overhaul cycle. For just a little more than the cost of the MT overhaul, I bought a new Hartzell governor. It does not have a calendar-based overhaul interval.

One characteristic of the Hartzell governor, however is that it won't control the prop below about 1600 RPM or so. This made me wonder - if you pulled to coarse pitch while above 1600 RPM, and then dropped the RPM to idle, would the prop stay coarse? Or does the loss of prop control also allow it to move back to fine pitch at low RPM?

The answer is, it goes back to fine pitch. So, those of you, like me, with a Hartzell governor, forget about the idea of getting to coarse pitch to improve glide in an emergency.
 
Same here. I bought a Hartzell governor instead of overhauling the MT and discovered it would not govern at low rpm. Decided to overhaul the MT and reinstalled it.
Anyone (in Australia) want to buy a hardly used Hartzell governor???
Fin
9A
 
Uhh Steve - the other thing about that Hartzell Governor? Mikey has had one since the engine was new (probably 28 years), and since we’re overhauling, I took the governor to the prop shop. Don’t let it go too long between checks - ours was so worn it was going to be $2200 to overhaul - $2400 if we bought a reconditioned one. I got in on the group buy off the latest PCU’s for $1250.....

Just because they don’t have a defined overhaul period doesn’t mean they don’t need to be checked! ;)
 
slight thread drift...

Had a 15 year old MT governor on my O-360-A3A 3 bladed powered ship. Last spring I decided, in order to avoid prolonged downtime, to order a new one. MT told me that the type I used had been replaced by a new model. They made me a very good trade-in offer, also sending me the new unit before I shipped the old one back.
Kudos MT :cool:
 
Uhh Steve - the other thing about that Hartzell Governor? Mikey has had one since the engine was new (probably 28 years), and since we’re overhauling, I took the governor to the prop shop. Don’t let it go too long between checks - ours was so worn it was going to be $2200 to overhaul - $2400 if we bought a reconditioned one. I got in on the group buy off the latest PCU’s for $1250.....

Just because they don’t have a defined overhaul period doesn’t mean they don’t need to be checked! ;)

Have the prices gone up that much? ! Mine was $1400 new, just 4 years ago.
 
slight thread drift...

Had a 15 year old MT governor on my O-360-A3A 3 bladed powered ship. Last spring I decided, in order to avoid prolonged downtime, to order a new one. MT told me that the type I used had been replaced by a new model. They made me a very good trade-in offer, also sending me the new unit before I shipped the old one back.
Kudos MT :cool:

I don't know.......
The old model was good, for awhile. Then they changed the design slightly to make it cheaper to manufacture, and a bunch of them flew apart, leading to overspeeds and worse. Now they have a new model? I don't know whether to trust them or not?!?
 
MT Prop governor

MT has models that need oil pressure to increase pitch, and models that need oil pressure to decrease pitch. The MT manual I have indicates that if you want use the governor that increases pitch (reducing drag) when oil pressure is lost you must also have an appropriate counterweighted propeller or a prop with some kind of return spring.
 
I have a RV-4 with IO360 and Hartzell CS prop, not sure what kind of governor. The prop changes from high rpm to low rpm at idle and low rpm increases my glide ratio considerably.
 
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