AD 89-11-07

89-11-07 McDONNELL DOUGLAS: Amendment 39-6222.

Applicability: McDonnell Douglas Model DC-6, -6A, -6B, R6D, C-118A (Military), and DC-7 series airplanes, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To detect stress corrosion cracks and to prevent failure of the wing center spar main landing gear fittings, accomplish the following:

A. Within one month after the effective date of this AD, unless already accomplished within the last five months, and thereafter at intervals not to exceed 500 hours time-in-service or one year, whichever occurs first, perform a dye penetrant inspection of the wing center spar main landing gear fittings around the bore and up to the wing lower skin, paying particular attention to the milled pocket in the outboard fitting, in accordance with Douglas Rework Drawing SR 06578001, "NC." After each inspection, apply LPS-3 corrosion inhibiting oil or equivalent to each fitting. After thefirst dye penetrant inspection, later inspections may be accomplished by using the following procedure:

1. Clean the LPS-3 using the best available cleanser,

2. Conduct a dye penetrant inspection, and, if unsuccessful,

3. Conduct a visual inspection.

B. If a crack is found as a result of the inspection required by paragraph A., above, prior to further flight, accomplish the following:

1. If a crack is found inside the recessed pocket areas, perform an eddy current inspection to determine if the crack extends above or below the recessed pocket areas.

2. If cracks are found inside the recessed pocket areas which are within the limits shown on McDonnell Douglas Rework Drawing SR 06578001, "NC," dated July 25, 1988, accomplish the trimout rework in accordance with that drawing. For a period of one year thereafter, conduct inspections in accordance with paragraph A. at intervals not to exceed three months. Thereafter, conduct inspections at intervals not to exceed 500 hours time-in-service or one year, whichever occurs first.

3. If cracks are found in the main landing gear cylinder bore or cracks are found which extend beyond the rework limits shown on McDonnell Douglas Rework Drawing SR 06578001,"NC," dated July 25, 1988, replace the fitting(s) with airworthy parts prior to further flight. If cracked fittings are replaced with new fittings made from 7075-T6 forging material, inspect the fittings in accordance with paragraph A., above, within 60 months after installation and thereafter at intervals not to exceed 12 months.

C. Installation of new fittings made of 7050-T7452 hand forging material constitutes terminating action for the inspections required by this AD.

D. 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, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain 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, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region.

E. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a base to comply with the repair requirement of this AD when approved by the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region.

All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to the McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Director of Publications, C1-LOO (54-60). These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or at the Los Angeles Aircraft CertificationOffice, 3229 East Spring Street, Long Beach, California.

This amendment (39-6222, AD 89-11-07) becomes effective on June 23, 1989.