Flight Crew Private
Flight Crew Last 90 Days 11; Flight Crew Total 168.7; Flight Crew Type 9.3
Aircraft Equipment Problem Critical; Ground Event / Encounter Ground Strike - Aircraft
Aircraft Aircraft Damaged
Aircraft; Human Factors
Heavy vibrations were felt during the landing roll while slowing to 20 MPH or less. Thinking the source was the nose wheel; back pressure was applied to the elevator to try to stop vibrations. When doing so had no effect on the vibrations the back pressure was relieved which made the vibrations greater and back pressure was reapplied. At that moment the right main gear folded under the aircraft at a speed of 10 MPH or less.
The right main gear torque link bolt detached and the right main gear folded causing substantial damage to right engine; propeller and main fuel tank.FAA considered this to be a result of a hard landing.  I was providing multi-engine instruction to the owner of the aircraft. The landings made were well within the realm of normal landings with no side load on the gear. The aircraft had recently had an annual inspection and the landing gear had been worked on.
A private pilot undergoing multi-engine training in his C-310 with an instructor suffered the collapse of the right main gear on landing roll. The instructor believed all immediately prior training landings were well in the 'normal' range; but noted the landing gear had been subject to maintenance on a recent annual inspection.