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Dynamic Prop Balancing at Condition Inspection

Tacco

Well Known Member
How often are you balancing your prop?

I'm thinking that if you re-pitch your prop, you need to re-balance it. Given that at each annual, you remove the prop to check prop nut torque (at least on the two-blade version), requiring re-pitching, you would need to do it annually. I'm

I wrong or being too conservative?
 
I do a lot of prop balancing on many different GA planes including my own -12. The acceptable balance number is .06ips or lower. If the customer isn’t in a hurry I usually get down to .02ips. I have had spinners that have very slight movement in the holes that will cause a balance to change from .03 to .08. That being said removing the prop will change your balance.
 
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Is it necessary to remove the prop to check the torque? The MM says to just "check in the tightening direction".
 
Is it necessary to remove the prop to check the torque? The MM says to just "check in the tightening direction".

On the Sensenich 2 blade the bolt heads are inside the center hub. By opening the hub you loose the pitch setting.
 
Is it necessary to remove the prop to check the torque? The MM says to just "check in the tightening direction".

You don’t need to remove the prop to check the torque. Check the bolts at the front spinner plate and the nuts on the back of the prop flange. You just need to remove the spinner. I’ve never had the bolt spin when checking the nut torque on the back of the prop flange even though I’m not holding the head of the bolt.
 

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That's a similar arrangement to the Warp Drives on the AirCam. Warp Drive says no need to loosen the hardware and re-tighten. That could change the pitch, so just apply a torque wrench to check.
 
Ok, so here's what I'm hearing. If you do an annual condition inspection of the prop per the SENSENICH requirements, you're going to have to rebalance because you totally remove the prop from the engine flange, disturbing the pitch. If you only follow the R-12 MM, you check the "clamping bolt torque" (which is easy, they're accessible without having to disturb prop pitch). That said, the Van's MM does defer to the prop manufacture's manual for inspection requirements.

Guess it depends on how thorough a condition inspect you want to do.
 
That's a thorough inspection for sure. Interesting that Van's doesn't specify it in the RV-12 Maintenance Manual.

Van's doesn't document inspections and procedures for parts and equipment produced by others under a specific ASTM (there are separate ASTM's for engines, propellers, etc.). At least not any more, for the reasons mentioned below.
Those manufacturers are responsible (mandated by the ASTM that applies to their product) for their own maint. and inspection procedures, and the documentation for them.
Another reason Van's doesn't do it is because every time a manufacturer makes a revision change to their procedures or processes, Van's documentation would have to be updated as well. Keeping track of all of that would be very burdensome.

When the RV-12 was introduced and the Sensenich propeller was still very new on the market, the documentation was much lower in detail than it is now.
I could be remembering wrong, but I don't think it originally specified that the propeller be disassembled for inspection.
Interestingly... one of the marketed benefits of the 3 blade prop. is that it can be removed from the engine as a complete assembly, without disturbing the pitch setting of the blades. I don't know whether complete disassembly for inspection is prescribed for that version.
 
Thanks Scott. Your post got me looking. Apparently, the old-style hub on the two-blade version requires you remove each blade at the annual condition inspection. The new style hub version for the two-blade, as well as the three-blade version, do not require the blades be removed. They only require that camping torque be checked.
 
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