Robinson R22 Beta, G-DERB
Following a flight during which an unusual vibration developed, the helicopter landed safely but then experienced intense vibration whilst subsequently hover taxiing to a maintenance organisation. Inspection showed that one of the main rotor blades had cracked from the trailing edge, through approximately 75% of its chord, as far as the spar at about the 1/3 span position. The teeter hinge was found to be extremely stiff, and this had been assembled about 20 hours beforehand without the necessary shims. The cracking was attributed to higher than normal stresses caused by the stiff teeter hinge.
Published 10 December 2014