This incident recently happened to me while landing my 360.  This A/C had 325 hours, at the time, since new and was built (not by me) with the standard "donut" main gear suspension.

The event was as follows.  After normal touchdown, on a paved runway, I felt the aircraft settle slightly on the left side and began hearing a scraping noise.  While stopping straight ahead on the RW, and ignoring Tower's repeated requests to taxi clear of the RW, I tried to guess the source of the noise.  After shutting down completely and exiting to inspect, I found the donut stack folded over in the middle and about two vertical inches at the end of the left, outback, main gear door scraped away on the aft corner.  The thru bolt for the donut stack was bent over double, two donuts were missing and the end of the bolt was pressing tightly against the tire.  Luckily the bolt was laying tangent to the tire, not poking into it.

This was very disconcerting to says the least.  Af first I thought the thru bolt had broken near the nut, but in fact the nut had backed completely off and fell away.  I found one of the donuts on the runway near the touchdown point, the other was never recovered, presumably falling away when the gear extended.  Also, luckily, the gear did not hang up in the gear well.

Airport personnel helped place the crippled gear leg on a small dolly and we towed the A/C to Byron Eskeson's hangar for repair.  Thanks Byron for being there one more time for me.  Aren't Lancair people great!

Luckily for me I still have my partially built kit/spare parts box.  I retrieved the two already made up donut stacks and swapped the parts.  Careful inspection of the right side original stack showed the probable source of the failure.  That stack had a washer top and bottom.  The manual, of course, calls for NO WASHERS due to the length of the threads.  There were no exposed threads on this thru bolt.  The other curiosity was that the builder used an all metal stop nut.  Presumably the failed side had the all metal stop nut also, but that should have been fine if there had been not washers involved.  The top of the thru bolt on the failed side also had a washer and I presume the nut on that side had one too, but I am not certain since the nut had fallen free.

Now, on to what matters to the rest of you.

1.   Ensure you do not have any washers on the long thru bolt of the donut stack
2.   Consider whether you should periodically remove the horizontal thru bolt (connecting the lower donut stack casting to the gear leg) to visually check the stop nut for security.  I do nut believe that you can see this nut without disassembly.

All in all, I was very lucky not to have a jammed landing gear condition or a blown tire.  Damage was limited to glass work on one door and replacement of the donut stacks.

Tom Thibault
N4XB, "Eagle Dancer"