Feathering rod

[btrjillo]

Hi All,

Last April I purchased N70JZ #29 from Ron Hess, and am enjoying it immensely.

Recently, during gearbox removal, we found the actuator rod that pushes forward into the prop to feather, was worn.  As  the photo shows, it was worn about half way through it’s diameter on the bottom, at the forward end.

We replaced it with a spare from Jim’s well stocked…well…stockroom.   Thanks Jim.

Has anyone else has this issue?

cheers,

Bryan

 

[mikeschumann]

I had a very similar situation a couple of years ago.  I had a prop strike in my Phoenix.  We removed the gearbox and sent it to Lockwood for inspection.  No damage found.

When we reinstalled the gearbox, the pushrod was not properly centered in the prop's feathering bearing.  We should have realized this when we put everything back together, as we had to do a MAJOR adjustment on the feathering mechanism.

The next time we did an annual, we discovered the problem.  Not only was the push rod damaged (not nearly as much as is shown in your photo), but the prop feathering bearing also needed to be replaced.

About a year later, during an oil change, we discovered a lot of metal on the magnetic chip detector near the gearbox.  We never did figure out what that was from.  Subsequent oil changes did not have any metal on the chip detector.

I would take a VERY close look at the feathering mechanism on your prop.  The push rod damage that you have is either due to a misassembly, like what I had, or a frozen feathering bearing.

Good luck.

 

[Jim Lee]

Mike is correct, this type of damage has only been seen when the prop is reinstalled incorrectly, and the push rod misses the cup on the prop hub.  It pushes directly on the bearing, and rubs against the outside of the cup.  Sometimes there is minor wear on the pushrod even when it is in the correct position, but it would take 1000 hours to wear enough that it needs replacing.

When installing a prop, you can see that the prop push rod is hanging down where it doesn't belong.  It has to be propped up from the rear so that it is centered when the prop goes on.  Or the pushrod can be removed when the prop is installed, and then the pushrod can be placed into position by feel.

The pushrod adjustments should never be messed with.  They are for the initial installation at the factory.  If you think that it needs to be adjusted, something else is wrong with the prop hub, the pushrod, or the pushrod location.

Any metal in the oil is not from the pushrod.  There is no way for the incorrectly installed pushrod metal chips to enter the gearbox.  What you will see is metal dust on top of the engine at the location of the pushrod exit from the gearbox.

These images are from the Woodcomp factory.  There have been several design changes over the years and your pushrod/bearing/cup interface may look different.  You can see in the photos why the length of the pushrod would change if it is installed incorrectly, leaving one to believe that an adjustment needs to be made.

BTW, I hold certifications from Woodcomp from my two training classes at the factory to inspect, overhaul, and replace blades.  In the Phoenix Maintenance Manual there are photos of the old Panenka style hub (gold and black) which I won't touch.  The "newer" style hub which has a boxy silver appearance is a great design and easy to work on.

 

[btrjillo]

This is what the new rod looked like before being machined to proper length ( The worn rod had a step in it about 1” from the tip, and was worn about halfway through… see original post):  

 

[Ed Babovec]

I have a few of the new rods in stock.  If anyone needs one, please contact.