During an instruction flight, in an aerodrome circuit, one of the tail rotor blades failed. The
resulting unbalance caused the separation of the tail rotor and second blade, followed by the loss
of control in flight of the helicopter, and its collision with the ground. The failure of the first blade
at one of its fastening points was caused by progressive fatigue damage. What caused this fatigue
damage and its propagation speed could not be determined. The modification to the design of the
root of the LH212 tail rotor blade with respect to that of the Dragonfly (used to substantiate the
design of the tail rotor) may have contributed to reducing the fatigue life of these parts.
On the failure of the blade followed by the separation of the tail rotor, the only manoeuvre likely
to limit the consequences of the accident was the immediate performance of an autorotation.
A similar scenario had occurred 17 months earlier on one of the tail rotor blades of another LH212
flown by the same operator. In this case, the consequences were only material and the damage
sequence leading up to the event was not identified by the operator.
The examinations conducted by the BEA showed that, due to the location of the incipient crack
zone, it was difficult to search for damage on a blade in service, before it had become extensive,
using conventional workshop methods.