COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Eurocopter AS 350 (Ecureuil) Series Helicopters
AD/ECUREUIL/42
Amdt 1
Servo Control Securing Screw 7/88 TX
Applicability: All AS350 helicopters fitted with Dunlop servo control assemblies.
Requirement: A. Unless already accomplished in accordance with this Directive, remove one at a time all 5 mm diameter set screws P/N BS4168 attaching the servo block to the body of the actuator. Before refitting used screws check screw strength using a threaded test block or nut and appropriate spacer and applying 4.5 Nm (40 in lbs) torque proof load.
B. Unless already accomplished in accordance with this Directive, remove from service all subject screws marked “HK 129".
C. Check torque all 5 mm screws attaching end fittings.
D. If any screw is found failed all screws fitted to that end fitting or servo block must be replaced.
E. Quarantine all screws not refitted. Report details including location in servo block of broken screw, servo S/N, TTIS, date and place of servo last O/H to nearest Airworthiness office by telephone for on-forwarding to CO Canberra Attn FWRM.
Note: Ensure all screws do not bottom out in the servo body.
Compliance: A. Before further flight after 6 May 1988.
B. Within 25 hrs CTIS after inspection.
C. Within 25 hrs CTIS after 16 May 1988.
D. Before further flight.
E. Within 48 hours of discovery.
Background: While investigating the cause of a main rotor vibration, screw P/N BS 4168 attaching the servo block to the body was found sheared in two of the main rotor assemblies.
Examination of the screws revealed failure was caused by hydrogen embrittlement. As batch details of these screws cannot be confirmed a fleet inspection was required. To urgently advise all operators of this problem a telex AD was issued. This amendment is raised to ensure servo end fitting screws which are of the same type are correctly torqued.