AD 91-21-07

91-21-07 MCDONNELL DOUGLAS: Amendment 39-8054. Docket No. 91-NM-104-AD. Supersedes AD 90-26-53 and AD 91-01-51.

Applicability: Model DC-9 and DC-9-80 series airplanes, Model MD-88 airplanes, and C-9 (Military) airplanes; equipped with Primary Longitudinal Trim Relays (up and down), Leech (P/N) 9207-8333, -8333-1, -8968, -10101, -10296, and -10166; certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To eliminate overheating of primary longitudinal trim relays and the possibility of fire in the forward cargo compartment, accomplish the following:

(a) For Model DC-9 series airplanes (other than Model DC-9-80 series airplanes), and C-9 (military) airplanes: Within 17 days after February 27, 1991 (the effective date of Amendment 39-6894, AD 90-26-53; and Amendment 39-6894, AD 91-01-51), or prior to the accumulation of 8,000 flight hours on the subject relays, whichever occurs later, remove the relay cover and inspect theprimary longitudinal trim relays for evidence of contact degradation, arcing, carbon build-up, or other evidence of abnormal wear on the contacts; and perform a functional check of the system in accordance with McDonnell Douglas Alert Service Bulletin A27-316, dated December 22, 1990, or January 4, 1991.

(b) For Model DC-9-80 series airplanes and Model MD-88 airplanes: Within 30 days after February 27, 1991, or prior to the accumulation of 16,000 flight hours on the subject relays, whichever occurs later, remove the relay cover and inspect the primary longitudinal trim relays for evidence of contact degradation, arcing, carbon build-up, or other evidence of abnormal wear on the contacts; and perform a functional check of the system in accordance with McDonnell Douglas Alert Service Bulletin A27-316, dated December 22, 1990, or January 4, 1991.

(c) If damage is found during the inspections or functional tests required by paragraphs (a) and (b) of this AD, prior to further flight, remove and replace the relays in accordance with McDonnell Douglas Alert Service Bulletin A27-316, dated December 22, 1990, or January 4, 1991.

(d) For Model DC-9 series airplanes (other than Model DC-9-80 series airplanes) and C-9 (Military) airplanes: Within 90 days after the effective date of this AD or prior to the accumulation of 8,000 flight hours on the subject relays, whichever occurs later; and thereafter at intervals not to exceed 8,000 flight hours; remove and replace the primary longitudinal trim relays with new approved parts in accordance with McDonnell Douglas DC-9 Maintenance Manual, Chapter 27-40-4. This replacement constitutes terminating action for the inspection and functional test required by paragraph (a) of this AD.

(e) For Model DC-9-80 series airplanes and Model MD-88 airplanes: Within 90 days after the effective date of this AD, or prior to the accumulation of 16,000 flight hours on the subject relays, whichever occurs later; and thereafterat intervals not to exceed 16,000 flight hours; remove and replace the primary longitudinal trim relays with new approved parts in accordance with McDonnell Douglas MD-80 Maintenance Manual, Chapter 27-40-4. This replacement constitutes terminating action for the inspection and functional test required by paragraph (b) of this AD.

(f) 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, Los Angeles 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, Los Angeles ACO.

(g) 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.

(h) The inspection and replacement requirements shall be done inaccordance with McDonnell Douglas Alert Service Bulletin A27-316, dated December 22, 1990, or January 4, 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 McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846. Copies may be inspected at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington; or at the Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California; or at the Office of the Federal Register, 1100 L Street N.W., Room 8401, Washington, D.C.

Airworthiness Directive 91-21-07 supersedes AD 90-26-53, Amendment 39-6894; and AD 91-01-51, Amendment 39-6893.

This amendment (39-8054, AD 91-21-07) becomes effective on November 19, 1991.