Eurocopter is planning to retrofit the worldwide AS350B3e fleet with a modification to solve a tail rotor issue by August.

The manufacturer, owned by EADS, says the retrofit, which involves the removal of chin weights fitted to the tail rotor assembly and the installation of a load compensator, will fix issues suffered by operators of the B3e variant of the Ecureuil single-engined light helicopter that was launched by the manufacturer at the 2011 Heli-Expo event.

According to the European Aviation Safety Agency (EASA), several operators of new AS350B3e helos reported that pilots made precautionary landings after feeling vibrations emanating from the helicopter’s tail rotor. Subsequent inspections of three aircraft found that laminated half-bearings in the tail rotor had failed prematurely.

EASA says the issue may have contributed to one fatal accident involving a Guatemalan-registered AS350B3e in which the pilot felt strong vibrations from the tail rotor before losing control of the aircraft. Investigators found that before the accident, the laminated half-bearings were twice replaced on the helicopter due to their deterioration.

As a result, EASA urged operators to increase checks on the components of the tail rotor and imposed airspeed limitations to reduce the dynamic loads on the tail rotor, because of concerns that the problem could lead to a loss of control.

On Feb. 8, EASA cleared the modification, which it says “restores the tail rotor dynamic load level ... thereby eliminating the modified loading conditions of laminated half-bearings which caused the intensified deterioration and reported failures.”

Eurocopter adds, “After implementation of this modification, the current VNE reduction will be removed and therefore, initial B3e flight performances will be fully restored.”

Eurocopter plans to retrofit all B3e variant helicopters by August 2013 and says it is “in line with the schedule defined.”

EDITOR's NOTE: This article was changed to correct the operator of the helicopter involved in a fatal accident.