Eurocopter is to issue a Service Bulletin that should solve a fleet-wide problem with the EC 145’s tail-rotor controls. In April, the FAA had issued an airworthiness directive (AD) calling for inspections and possible part replacement. The AD followed an in-flight incident that caused severe vibrations.
In the incident, the threaded portion of the tail-rotor control lever containing a dynamic weight broke off, leading to severe vibrations. Concerned that such vibrations could cause a loss of control, German and U.S. civil aviation authorities have required operators to perform inspections immediately.
The maintenance technician should look for score marks, notching and scratches. If a control lever is found to be out of the maintenance manual limits, or if a crack is detected, the part should be replaced with an airworthy one.
The problem apparently ensues from a 2006 alert Service Bulletin that was supposed to improve the aircraft’s controls. It was designed to reduce operational pedal control forces. These improvements involved two modifications: installing modified pedal control levers and an optimized tail-rotor control lever assembly “consisting of modified weights and modified control lever pre-assemblies.”
The AD affects helicopters from S/N 9004 to 9074, for which the Service Bulletin was made mandatory. It also affects all helicopters with S/N 9075 and higher, as the modifications were made production standard from that serial number.
According to a Eurocopter spokes-man, the company has already introduced a technical solution into new production helicopters. It is based on
a reinforced control lever on the tail rotor’s head assembly.
The FAA estimates that the AD affects 26 helicopters in the U.S. Each inspection is said to take one work hour and cost nearly $7,000 per helicopter. This assumes, according to the FAA, one tail-rotor control lever and one weight are replaced on each helicopter during the first year.