tabbed lock washer on FAB carb attach plate

[alpinelakespilot2000]

Van's calls out for the use of tabbed lock washers to attach the FAB top plate to the carb (using the 4 non-drilled bolts).

How are these correctly used?
Does the bent tab go up or down (bend toward carb or bend toward bolt head)?
Any other instructions?
Anyone know what the torque of these bolts should be?

Thanks.

[Kyle Boatright]

IIRC, there are mulitple tabs on the washers. Two of them are bent over the corners of the carb. This prevents the washer from moving relative to the carb. The remaining tabs are bent in the opposite direction and secure the bolt.

Many people drill and safety wire the bolts.

Personally, I've always used the lock washers, but may drill the bolts next time. The reason is that these washers are a one time use item, so if you have to disassemble anything, you'll need to get new washers, which are several dollars and several days away. I find this to be a PITA when I'm ready to put stuff back together and go fly.

[Bob Axsom]

This came up a while back and following the advice I drilled the heads and safety wired all four bolts together. I am currently in the process of replacing my 0.063" mounting plate which I found cracked during my annual condition inspection of our RV-6A (~600 hrs) with a new one that I will cut from 0.090" sheet from Aircraft Spruce. The safety wire did the job nicely.

Bob Axsom