81-08-51 DEHAVILLAND AIRCRAFT OF CANADA: Amendment 39-4263. Applies to DeHavilland DHC-7 series airplanes, serial numbers 3 through 42 inclusive.
1. To prevent failure of the main landing gear to extend, unless already accomplished, accomplish the following within the next ten hours time-in-service:
A. Using a suitable sharp pointed tool, attempt to rotate the thickest washer under the head of each bolt attaching the main landing gear actuator brackets P/N's 75710543-003 and 75710542-003 to the wing skin on each inboard nacelle.
B. If rotation is observed, replace existing barrel nuts DSC 100-8, retainers and washers with Esna barrel nuts P/N 2452-080 and washers P/N's MS20002-C8 and MS20002- 8 in accordance with DeHavilland Engineering Order 72136 prior to further flight. Torque bolts to 850-900 inch-lbs. and wirelock.
2. To prevent possible malfunction of the flaps, unless already accomplished, accomplish the following within the next ten hours time-in-service:
A. Using a 9/16 inch, 12 point socket wrench with standard length handle, attempt to tighten all bolts attaching the number 4 flap track bracket to each wing. Ref. PSM 1-7- 4, Chapter 57-52-00, Fig. 15, Item 160, for bolt location.
B. If movement of the bolt head is observed, replace existing barrel nuts DSC 100-8 with Esna barrel nuts P/N 2452-080 using additional MS20002-C8 washers, as required, to ensure correct bolt engagement in accordance with Engineering Order 72139 prior to further flight. Torque bolts to 900-1000 inch-lbs.
3. For aircraft Serial Numbers 28 through 42 inclusive, repeat inspections specified in paragraphs 1 and 2 above daily until replacement of existing barrel nuts DSC 100-8 is accomplished, in accordance with subparagraphs 1B and 2B, above.
4. For aircraft Serial Numbers 28 through 42 inclusive, replacement of existing barrel nuts DSC 100-8 is required within 50 hours time-in-service following receipt of this AD.
5. Alternatemeans of compliance or other actions which provide an equivalent level of safety may be used when approved by the Chief, Seattle Area Aircraft Certification Office, FAA Northwest Mountain Region.
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). All persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to the addresses listed above. These documents may also be examined at FAA Northwest Mountain Region, 9010 East Marginal Way South, Seattle, Washington 98108.
This amendment becomes effective November 25, 1981 and was effective earlier to those recipients of Telegraphic AD T-81-08-51 dated April 10, 1981.