Prop position at shutdown after change from 3blade to 2blade hartzel

[mikejr718]

Just removed a 3 blade Hartzel top prop  and replaced it with a 2 blade hartzel  HC-C2YK-1BF and now when shutting down engine prop comes to a stop vertically, 12 and 6 oclock. After reading it appears i may need to remove the prop and move the bushing that orient it. I have read the 3 Blade install instructions and they dont mention moving bushings. Just seems odd that prop would end up vertical at shutdown. Prop functions fine and balances down to .03 ips .

1975 M20C  O-360-A1D

Edited January 28, 2020 by mikejr718

[G spot]

prop position has to do with the power impulses from the engine.  I am not a Mooney expert on this issue just a guy that knows enough to be dangerous

[N201MKTurbo]

You should fix that. Your engine is set up to get the minimum torsional stress on the crankshaft. the clocking of the prop is critical to minimizing these stresses. It should be 2 o clock 8 o clock with cylinder #1 at TDC.

let me see if I can find some guidance on that.

[Mooneymite]

Clocking of the prop is a mysterious subject.  I had a plane with the prop mounted with respect to TDC, but upon shut down, it always stopped at the 2 and 7 o'clock positions (facing the prop) instead of the normal 10/4 resting position.  We actually tried re-clocking the prop, but then realized that it had to do with a low compression cylinder as to how the prop stopped.

There's a neighbor that re-clocked the Jacobs engine on his Stearman trying to make the shaky Jake run smoother.  He had a catastrophic engine failure on the very next flight.  We don't know if it was just coincidence, or if the clocking is that critical.

I really can't find much definitive science  on the Internet, but obviously the engine manufacturers are very aware of the the science.

[N201MKTurbo]

I found it:

https://www.lycoming.com/sites/default/files/SI1098P Propeller Flange Bushing Location.pdf

It looks like an O-360-A1A would have the bushings in the top and bottom holes with the #1 cyl at TDC.

I suspect the STC for the 3 blade prop required the prop to be re-clocked. You should put it back to the original configuration.

 

[Jakes Simmons]

Appreciate you bringing this up. Next month I will be doing the same swap, down to the scimitar two blade. Have you had a chance to fly with the new prop yet? Crossing my fingers you gain an improvement, it was a hard check for me to write.

 

[chriscalandro]

What are you guys doing with the 3 blade props?

[tigers2007]

Wow it seems 50/50 when I shut down my 3-blade Hartzell on my A1D. Sometimes its a "Y" and sometimes its a " ⅄ ". H have to make it a  ⅄ in order to push it back into the hangar. I suppose that if Y and  ⅄  are opposites that it doesn't matter? I've never really thought about this. The prop was installed by Hartzell at the factory so...

[mikejr718]

The 3bladed prop had a vibration that we never could balance out.  Had it below .04ips and still shook in flight, worse at higher power settings. 
2 bladed much smoother. Balanced to .03 ips its a night and day difference. 
Performance wise the take off roll is noticeably longer and climb rate noticeable less. The big gain is in cruise speed. Plane is a 75  M20C At 75 percent power at 5500 ft I am seeing 149kts true. A couple of weeks ago saw 152 kts true at 24in/2400rpm but have not been able to duplicate it since.  With the 3 blade I would be lucky to see 140 kts. I can run higher power settings without the plane feeling like it’s shaking itself apart. It’s almost turbine smooth full throttle and prop all the way forward in climb. Also autopilot works much better with less vibration. 

[carusoam]

To know if your prop is clocked properly...

Go to a Mooney fly in...

All the tails are lined up in the back....

All the props are on the same angle... except for the one that isn’t clocked properly anymore...

Nine out of ten times the prop always stops in the same place based on the compression stroke of the cylinders...

 

Not sure what would cause the prop to land 50/50 in some other location... take notes the next time compressions are checked...?

What we have learned about yellow ranges on the tach...this is all about avoiding certain harmonic vibrations that occur in that range...  the type of vibrations that aren’t felt by the human body... or can’t be discerned during flight anyway...

To have the ranges of the instruments work, requires the equipment to be set up the same way as it was tested for AW...

So... if the prop is no longer clocked properly, it is a good idea to appease the vibration gods by getting the prop sorted out...

Doing a dynamic balance on a three blade prop seems to show vibrations that are a function of the three blade prop being driven by four cylinders... a known issue... but really hard to tell by the seat of the pants....

Nice to see GUS is here! 

PP thoughts only, not a mechanic...

Best regards,

-a-

[Jakes Simmons]

Thanks for the PIREP. My ‘76 Ranger was dynamically balanced with its current three blade. Came out well within specs, the vibrations weren’t too bad but then I got a ride in an older M20C up at Wilmar after dropping mine off for tank work. So smooth, I thought it was a turbine with its two blade. That set the bug in my head although I am sure I would have been fine keeping what I’ve got. With the ‘76 “dirty” wing, I’d also like all the cruise help I can get. 
    To answer Calandro, mine, like I am sure everyone else’s prop will be for sale once removed. It’s in fantastic shape, I will say the climb rate and acceleration on take off will be missed. I hope my new cruise experience will be similar to ‘718’s...

[Hank]

I've never tried to tell if my prop stops with the same blade up, but it's almost always in a ⅄ configuration, with one blade or another pointing roughly "up." It was dynamically balanced at install by the PO in 2003?, and I rechecked the balance during annual in 2018--still 0.01 ips. Nice, smooth Hartzell 3-blade airbrake, that limits my 1970 C model to 145-148 KTAS. 

Edited January 29, 2020 by Hank