This SB is a visual inspection of the front prop hub. Unfortunately, on the RV-12 there is a Front Spinner Plate blocking the view necessary to inspect the front prop hub. To remove the Front Spinner Plate all six bolts that hold the front prop hub must be removed. Blade pitch angle will need to be re-established when front prop hub is reassembled and re-torqued. This is a lot of work for a repetitive inspection every 50 hours of flight. I fly ~ 150 hours/year so I will have to do this inspection three times annually.
At some point Sensenisch redesigned the front hub to eliminate the pitch cylinder. Perhaps the large hole in the aluminum hub reduced strength and now cracks are developing along the thinnest edge at 90? to the axis? Maybe this becomes a problem because of the way the Rotax 912 stops so suddenly when you shut it down.
The new design front prop hub eliminates the large hole and instead has three smaller holes along the central axis of the hub. See drawing below. Special pins are inserted in the two outer holes to rough in the blade pitch angle. Once set, the pins are removed. No more large pitch cylinder and corresponding large hole in front prop hub.
So I?m wondering if Sensenich will offer the new front prop hub as a one-time fix for this service bulletin. Perhaps discount price, or free replacement, like they did for SB11-04-15 where 2A0R5 revision B Hubs were replaced free because a small percentage of hubs were prone to prop blade pitch loss.
It will be real nice if I don?t have to disassemble my prop three times/year?
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 633
LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H