The first step in tearing the Aerovee down was to get the engine off. This was actually not that bad, it took about 3h to remove and disconnect everything such that the engine case could be unbolted from the accessory mount. However, getting the prop off turned out to be a little bit more difficult than expected.

The prop is squeezed between the prop flange and the spinner with 6 long bolts and they did not want to come out. After generous applications of PB Blaster and leveraging a long 2×4 between the bolts and the engine case (I’m sure the thrust bearing liked that…) and finally hammering the most stubborn ones out the last bit it came off. Most of them were severely corroded.

The prop bolts. Most of them were severely corroded and had stuck themselves both into the prop flange and the holes in the prop itself.

The prop also does not look good. The side facing the engine is darkened and slightly crushed.

The prop hub is darkened and slightly crushed. I’m not sure whether the dark color indicates that the prop has moved and was heated by the friction or if it’s just the rust on the prop flange that has transfered into the urethane topcoat.

The instructions from Sensenich has a picture that looks burned like that and says this is what happens when the prop bolts have insufficient torque. The prop can then move against the prop flange every power stroke and this friction causes a lot of heat which burns the paint. Although the prop has clearly also been crushed, so that doesn’t seem consistent with undertorqued bolts.

The scary thing here is that since the bolts were so corroded that they wouldn’t move in their holes, the nuts might not actually have tightened the propeller against the flange but just tightened the bolt against its hole. If there’s so much friction between the bolt and the hole that the bolt doesn’t move when you tighten the nut, you’ll hit the specified torque just trying to move the bolt in the hole without actually getting compression all the way through the bolt to the spinner.

I don’t know if this means the prop is a goner, I’ll try to send some pictures to the manufacturer or to the Sonex tech support guys and see what they say. But this means more trouble, and we haven’t even opened the engine yet. At least there is another prop for the plane, a cruise prop (this is a climb one) so we aren’t grounded until it can be repaired, if that’s necessary.