AD 89-14-52

89-14-52 BOEING OF CANADA, LTD., DE HAVILLAND DIVISION: Amendment 39- 6291. Final copy of telegraphic AD issued July 7, 1989.

Applicability: De Havilland Model DHC-8 series airplanes, Serial Numbers 3 and subsequent, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent asymmetric flap deployment, accomplish the following:

A. Within the next 25 hours time-in-service after the effective date of this AD:

1. Visually inspect the flap drive primary torque tubes in the vicinity of station YW 170 of the left and right wing where it enters the outboard side of each nacelle for signs of damage/wear due to chafing. Torque tubes must be replaced prior to further flight if wear exceeds either 0.010 inch in depth or 180 degrees of the circumference of the shafts.

2. Inspect cooling ducts (Part Number DSC 287-12-70/60) in the vicinity of station YW 170 of the left and right wing where it enters the outboardside of each nacelle for possible interference with the primary flap drive torque tube. Reposition cooling duct as necessary to provide a minimum clearance of 0.3 inch with the primary flap drive torque tube. If reinforcement wires of the cooling duct are broken due to chafing, the cooling duct must be repaired prior to further flight and replaced within 30 days.

3. Perform an operational check of the torque sensor, and take any indicated corrective actions, in accordance with Maintenance Program Task 2750/11. Refer to "Maintenance Program, Supplementary Information, PSM 1-8-7/1-83-7, Volume 2, Procedures - 27, Page 15, dated 15 July 1988."

B. Within 7 days after the completion of the inspections required by paragraph A., above, submit a report of findings, positive or negative, to the Manager, New York Aircraft Certification Office, ANE-170, FAA, New England Region, 181 South Franklin Avenue, Room 202, Valley Stream, New York, 11581. Reports must include the airplane serial number.

C. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, New York Aircraft Certification Office, FAA, New England Region.

NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who will either concur or comment and then send it to the Manager, New York Aircraft Certification Office.

D. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD.

These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or the New England Region, New York Aircraft Certification Office, 181 South Franklin Avenue, Room 202, Valley Stream, New York.

This amendment (39-6291, AD 89-14-52) becomes effective on August 21, 1989, as to allpersons except those persons to whom it was made immediately effective by telegraphic AD T89- 14-52, issued on July 7, 1989, which contained this amendment.