On a related topic, is there any reason not to use AN7H drilled bolts (in the head) in order to lockwire the engine mounts versus adding the unique lock tab washers that are more difficult to obtain? I can't see any reason not to use the drilled bolts beyond the $4 cost from Spruce. On other aircraft, I note we use a lock tab washer that fits into the hole on the isolator and those are an MS standard. But Lancair specs an additional washer between the isolator and bolt head hence the hybrid lock tab washer requirement. An AN7H bolt would seem to be a simple answer to avoid the lock tab washer. I'm betting someone has already been down this road?
Paul,
I used this method to secure the engine mount bolts on my IV-P (TSIO-550E Continental). One concern is that the safety wire needs to go from the bolt head (moves around a bit as the isolator yields to engine torque/vibration) to the engine mount (stationary). To keep the wire from cutting into the isolator and/or the engine mount, I ran it inside some small diameter tygon tubing where it contacts the engine mount and lays across the isolator, and I didn’t “twist it tight,” but left a bit of slack in the twisted section between the engine mount and the bolt head. My theory is that the bolt could loosen slightly, but not back out; and I inspect these at each oil change. It’s worked well for 750+ hours.
Bob