AD 81-03-51

81-03-51 DEHAVILLAND: Amendment 39-4513. Applies to model DHC-7 airplanes serial numbers 3 through 36 certificated in all categories that have flap screw jacks 2 and 3, left and right hand, part numbers 24020-11, -111, -or -115; or 24040-11, -111, or -115 and are fitted with lock nuts, part number MS9952-08. To prevent possible damage to the flap system due to the disengagement of the lock nut, accomplish the following within the next 25 hours time in service after the effective date of this AD, unless already accomplished.

1. Inspect the flap screw jack tracks 2 and 3, Menasco part numbers 24020-11, -111 or -115 and 24040-11, -111 or -115 for correct locking feature of lock washer against the dome nut. To ensure the nuts are correctly installed, ensure that the cup lock washer P/N MS9952-08 has been tapped into groove of the lock nut P/N 24156-1 (Typical 6 places).

2. Lubricate the aft end bearing (P/N AD50991) lightly with grease P/N MIL-G- 23877 or equivalent.

3.Alternate means of compliance which provide an equivalent level of safety may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA Northwest Mountain Region.

4. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of inspections and/or modifications required by this AD.

The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1).

This amendment becomes effective December 21, 1982, and was effective earlier to those recipients of telegraphic AD T81-03-51, dated January 23, 1981.