[flyenforfun]

Been reading around on prop clocking. I have a sensenich FP metal prop and lycoming o-360. Sensenich says position #1 prop blade at 11 o'clock position which TC marks on starter ring gear aligned. Read some people here say 3-9 position, some say horizontal? What is right?

 

[Kahuna]

Been reading around on prop clocking. I have a sensenich FP metal prop and lycoming o-360. Sensenich says position #1 prop blade at 11 o'clock position which TC marks on starter ring gear aligned. Read some people here say 3-9 position, some say horizontal? What is right?

Im not an expert, but I have worked with several.
Been around the prop clocking issue a few times.
The general consensus is this.
1. Clocking recommendations for these applications are generally done for hand proping.
2. The engine does not care where the prop is.
3. There are documentated cases where a change in clocking had a measured change to the airframe in vibration levels.
4. There have also been certified applications where a change in prop clocking was done for the same reason as #3.
5. Care must be taken to ensure proper bushing to counter bore fit depending on the prop and flange type.


Your results and installation may vary.

 

[flyenforfun]

I guess you are talking about the bushings on the flange on the engine and the counterbores in the prop spacer? Wouldnt the prop bolts align everything?

I guess I will just follow Sensenich's recommendation on clocking.

 

[Kahuna]

I guess you are talking about the bushings on the flange on the engine and the counterbores in the prop spacer? Wouldnt the prop bolts align everything?

I guess I will just follow Sensenich's recommendation on clocking.

Alignment and fit is done through the counter bores in the spacer or prop in conjunction with the bushings pressed into the flange. Depending on your engine model and or who has putzed with it, the bushings are of different lengths AND DIAMETERS.

 

[az_gila]

Alignment and fit is done through the counter bores in the spacer or prop in conjunction with the bushings pressed into the flange. Depending on your engine model and or who has putzed with it, the bushings are of different lengths AND DIAMETERS.

You can use this to see if your bushings are per Lycomings spec....

http://www.lycoming.textron.com/support/publications/service-instructions/pdfs/SI1098G.pdf

However note that the bushings may be stepped, so a larger diameter (dimension A on Page 5) may not be reflected to the bushing size of the portion that goes into the prop or prop spacer.

The "odd" sized bushing is needed to locate the flywheel in only one possible orientation (for the timing marks) but the prop may still be installed in 6 different ways...

IIRC the Sensenich prop spacer has all of it's 6 holes equally sized.

 

[Remyswing]

Usually, we put cylinder #4 at ignition position, and install propeller as close as possible to vertical position, momentum of propeller will help for start, in direction of rotation