The fixxed pitch prop is a badly ignored part of an airplane. Overhaul??, but its fix pitched....wrong!!

I would first say, talk to your prop shop.

First on the lighter side: Hub corrosion happens, you might not think it looks bad, but a little corrosion can have disasterous effects on a prop. If you have not had the thing checked out in atleast 10 years (prop shop may recommend sooner) your taking a risk. Also think of metal fatigue, possibility of cracking that your mechanic can't possibly spot, I am a mechanic and try to do the best I can with these. Also as a mechanic, I can say that your propeller will come out of balance over time due to dressing out nicks.

Now, warp your brain around this...Your propeller is subject to many forces other than the pilot pulling on it. This is going back to my school days, here are the 5 forces taught to mechanics:

1. Centrifugal Force: pulls out on the blades. Taken from my old Jeppesen Powerplant Textbook, the centrifugal force can be greater than 7500 times the weight of the propeller. Lets see, 14 pounds times 7,500 = Stretch!!

2. Thrust bending force: bends the tips forward when producing thrust.

3. Torque bending force: bends the blade in the opposite direction of rotation.

4. Aerodynamic twisting moment: tries to twist the blade to a higher angle.

5. Centrifugal twisting moment: This twists the blades to a lower angle of attack, and is much stronger than #4.

Your propeller puts up with a lot of abuse, not to forget the gyroscopic forces brought on by our maneuvering and erosion and nicks. Why would anyone not consider taking the thing down to the propshop for a checkup? 3 Years ago, mine was done to the tune of $650, is that worth your safety?

If your fixxed pitch gets a higher static RPM than your POH or maintenance manual calls out, you are due.

My own recommendations as a mechanic: 10 years or at engine overhaul. Your prop shop would have the right answer.

Joe Ashment

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