COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Eurocopter AS 355 (Twin Ecureuil) Series Helicopters
AD/AS 355/32 Servo Control Securing Screws 7/88
TX
Applicability: All AS355 helicopters fitted with Dunlop servo control assemblies.
Requirement: | A. | Remove one at a time all 5mm diameter set screws P/N BS 4168 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 4.5Nm (40 in lbs) torque proof load. |
| B. | Remove from service all servo block attaching screws marked "HK 129". |
| C. | Check torque all 5mm screws attaching both 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. |
Compliance: | A. | Check within 10 hrs CTIS after 12 May 1988. |
| B. | Within 25 hrs CTIS after inspection. |
| C. | Within 25 hrs CTIS after 12 May 1988. |
| D. | Before further flight. |
| E. | Within 48 hours of discovery. |
Background: While investigating the cause of a main rotor vibration in an AS350 screw P/N BS 4168 attaching the servo block to the body was found sheared in two of the main rotor servos.
Examination of the screw revealed failure was due to hydrogen embrittlement. As batch details are still unsure a fleet inspection is required.