AD 92-04-05

92-04-05 BOEING: Amendment 39-8176. Docket 91-NM-193-AD.

Applicability: Model 747 series airplanes; line numbers 1 through 856 except line numbers 679 and 685; certificated in any category.

Compliance: Required within one year after the effective date of this AD, unless previously accomplished.

To prevent an Auxiliary Power Unit (APU) pneumatic duct from contacting the elevator control rod in the event of a duct rupture, which could damage the elevator control system and result in a reduced ability to control the pitch of the airplane, accomplish the following:

(a) Install an APU pneumatic duct restraint in accordance with Boeing Alert Service Bulletin 747-36A2087, dated June 6, 1991.

(b) An alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Seattle ACO.

(c) 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.

(d) The installation shall be done in accordance with Boeing Alert Service Bulletin 747-36A2087, dated June 6, 1991. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington; or at the Office of the Federal Register, 1100 L Street NW., Room 8401, Washington, DC.

(e) This amendment (39-8176, AD 92-04-05) becomes effective on March 26, 1992.