Static RPM Test

Henning said:
:confused: Why wouldn't the governor prevent that?
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I don't know. I'm not a propeller engineer. I do know that I squawked my Cessna 185 for only developing 2750 statically, on an optical tach.

My IA, who owns 20 207's with the same engine and prop assured me it was normal and recommended by McCauley, which if you follow my earlier link is true.

It must be that the prop governing system is designed for air loads to work in the normal full RPM range, and static doesn't do that. I do know that my Cessna 185 and 207 developed 2850RPM, but only in flight.
 
Henning said:
:confused: Why wouldn't the governor prevent that?
Click to expand...

Because the prop control knob is all the way out and the prop pitch is flat, when doing a ground run for static readings.
 
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kgruber said:
I don't know. I'm not a propeller engineer. I do know that I squawked my Cessna 185 for only developing 2750 statically, on an optical tach.

My IA, who owns 20 207's with the same engine and prop assured me it was normal and recommended by McCauley, which if you follow my earlier link is true.

It must be that the prop governing system is designed for air loads to work in the normal full RPM range, and static doesn't do that. I do know that my Cessna 185 and 207 developed 2850RPM, but only in flight.
Click to expand...

If the governor is set at the limited RPM it will over shoot, the targeted number All hydromatic propellers will do that, simply because the mechanical governors are not that quick to act.
 
Tom-D said:
Because the prop control knob is all the way out and the prop pitch is flat, when doing a ground run for static readings.
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:confused: That didn't make sense to me. If the prop knob is all the way out/handle all the way back how will it ever develop max static RPM? The prop will only stay flat pitch for a short while until the the RPM range of the governor is reached and then will steepen the pitch to maintain that until it hits the coarse stop on the prop. So why would the static RPM test be testing the bottom end of the governor range?
 
Henning said:
:confused: That didn't make sense to me. If the prop knob is all the way out/handle all the way back how will it ever develop max static RPM? The prop will only stay flat pitch for a short while until the the RPM range of the governor is reached and then will steepen the pitch to maintain that until it hits the coarse stop on the prop. So why would the static RPM test be testing the bottom end of the governor range?
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When the prop knob is all the way out the governor allows the engine to go to the highest RPM allowed with minimum power applied. The high RPM stop is adjusted to the RPM set by the manufacturer when that RPM is reached the governor will allow the prop to increase blade angle and load the engine to prevent any higher RPM.
 
Tom-D said:
When the prop knob is all the way out the governor allows the engine to go to the highest RPM allowed with minimum power applied. The high RPM stop is adjusted to the RPM set by the manufacturer when that RPM is reached the governor will allow the prop to increase blade angle and load the engine to prevent any higher RPM.
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When the prop knob is all the way in, you mean. Balls to the wall.

Dan
 
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