Nose Wheel SB - how many washers is too many?

[Jesse]

I had an RV-10 come in today for the nose wheel SB. We had to compress the rubber donuts a little to remove the bolt, then realized there were 5 washers under the "hat". The SB says that if it needs more than 3 washers, the donuts need to be replaced. I know that the SB plate adds the thickness of 1 washer, but that would leave 4 washers. We decided to replace the donuts, but I wonder the reasoning for this limit. I have seen Mooneys with the donuts much more compressed than these were, and they didn't appear to be cracked or hardened.

Notes: the plane was new in 2007 and it has 1,030 hours on it. The engine mount did not have cracks.

Any comments?

 

[Walt]

Isolators have a minimum thickness spec (compression set), therefore I think we can conclude that one or more of the isolators is less than the min thickness if more than 3 washers are required.