MANUFACTURER: Eurocopter Deutschland GmbH Model
EC135 Helicopters SUBJECT: Airworthiness Directive 2009-11-10
SUMMARY: We are adopting a new airworthiness
directive (AD) for Eurocopter Deutschland GmbH (Eurocopter) Model
EC135 helicopters. This AD results from a report of abnormal main
rotor blade vibrations on a Eurocopter Model EC135 helicopter. This
AD also results from mandatory continuing airworthiness information
(MCAI) issued by the European Aviation Safety Agency (EASA), which
is the Technical Agent for the Member States of the European
Community. The MCAI states that an operator reported unusual
vibrations during the start phase of the main rotor blade on one
helicopter. The vibrations stopped after the application of torque.
Subsequent maintenance personnel found that six of the eight
attachment screws of the lower hub-shaft bearing support were
loose. This condition was discovered in two additional helicopters.
Loose screws in the bearing support, if not detected and corrected,
could result in abnormal main rotor blade vibrations and subsequent
damage to the main transmission.