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Prop Governor studs PSA...

On the T-Bolt 390, Lycoming will install their 31c-16 studs (2") and they should have a nominal height above pad of 1.25-1.31". Unfortunately mine were run into 1.19-1.21".


In any case, the Hartzell governor, gasket, washer, lock washer and nut add up to 1.346.


You will not have a full thread out of the nut.


The next stud size is a 31C-17 - .125 longer than the -16 and will need to be ordered and changed out.


Maybe ask and see if they would install the -17 studs during the build?


I have a feeling many previous builders just installed as is, changed to the thinner washer, or ?


Lycoming customer service has been very good, FYI
 
On the T-Bolt 390

I have a feeling many previous builders just installed as is, changed to the thinner washer, or ?

Perhaps, they have changed? I checked photos of my installation and there are at least 2 threads showing. I received my engine in 2017. Thanks anyway for the heads-up.:rolleyes:
 
On the T-Bolt 390, Lycoming will install their 31c-16 studs (2") and they should have a nominal height above pad of 1.25-1.31". Unfortunately mine were run into 1.19-1.21".


In any case, the Hartzell governor, gasket, washer, lock washer and nut add up to 1.346.


You will not have a full thread out of the nut.


The next stud size is a 31C-17 - .125 longer than the -16 and will need to be ordered and changed out.


Maybe ask and see if they would install the -17 studs during the build?


I have a feeling many previous builders just installed as is, changed to the thinner washer, or ?


Lycoming customer service has been very good, FYI

The one thread rule only applies to nylon lock nuts, to help resist loosening. Your post states the use of a std nut with separate lock washer. Not sure why you would need to have a full thread exposed past the nut. It doesn't help anything.
 
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LR172 - INCORRECT. According to Hartzell propeller service letter and installation manual, "The studs must be of sufficient length to permit AT LEAST ONE thread to be visible above each mounting nut after the governor is installed".


The reason would be to be 100% certain that all the torque on the nut is applied through the required number of threads in the nut. Anything less than a protruding stud would be insufficient.


As always, please follow the manufacturers instructions........
Mark
 
LR172 - INCORRECT. According to Hartzell propeller service letter and installation manual, "The studs must be of sufficient length to permit AT LEAST ONE thread to be visible above each mounting nut after the governor is installed".


The reason would be to be 100% certain that all the torque on the nut is applied through the required number of threads in the nut. Anything less than a protruding stud would be insufficient.


As always, please follow the manufacturers instructions........
Mark

Didn't realize there was a unique hartzell requirement. I thought you were referring to the general FAA AC guidance.
 
On the T-Bolt 390, Lycoming will install their 31c-16 studs (2") and they should have a nominal height above pad of 1.25-1.31". Unfortunately mine were run into 1.19-1.21".


In any case, the Hartzell governor, gasket, washer, lock washer and nut add up to 1.346.


You will not have a full thread out of the nut.


The next stud size is a 31C-17 - .125 longer than the -16 and will need to be ordered and changed out.


Maybe ask and see if they would install the -17 studs during the build?


I have a feeling many previous builders just installed as is, changed to the thinner washer, or ?


Lycoming customer service has been very good, FYI

We use 31C16 studs with all Lycoming governors and never have an issue. I know at one point, we were shipped short studs packaged as the long stud P/N. The long thread which goes into the engine is .944 long and the short thread which secures the governor should be .710. Please double check and follow the engine manufacturers guidelines. You may have a different engine with specific requirements. I don't want to go you bad info.
 
We use 31C16 studs with all Lycoming governors and never have an issue.

Is this what you use for your governor on the YIO-390? Just ordered my engine but haven't spec'ed it out yet. Will probably take advantage of your group buy.
 
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