AD 90-23-10

90-23-10 MCDONNELL DOUGLAS: Amendment 39-6798. Docket No. 89-NM-215-AD.

Applicability: Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes and Model MD-88 airplanes; equipped with Whittaker Controls power transfer unit shutoff (PTU S/O) valve, Part Number (P/N) 240695 or P/N 240695-1; certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent dual hydraulic system failure, accomplish the following:

A. For those airplanes with Whittaker Controls PTU S/O valve P/N 240695 installed,

1. Prior to the accumulation of 2,000 landings, or within 200 landings after October 23, 1989 (the effective date of Amendment 39-6356, AD 89-22-02), whichever occurs later, unless accomplished within the last 1,800 landings, replace the PTU S/O valve body attachment screws, P/N NAS 1101E-14, with new screws of the same part number, in accordance with the installation instructions of McDonnell Douglas Telex MD-80-COM-24/JCE, dated September 18, 1989. Thereafter, replace the attachment screws at intervals not to exceed 2,000 landings until replacement of the valves in accordance with paragraph A.2. of this AD is accomplished. Replacement of Whittaker Controls PTU S/O valve P/N 240695, with PTU S/O valve P/N 240695-2 constitutes terminating action for the requirements of this paragraph.

2. Within 90 days after the effective date of this amendment, replace all Whittaker Controls PTU S/O valves P/N 240695, with Whittaker Controls PTU S/O valves P/N 240695-2; or modify the valves P/N 240695 to the P/N 240695-2 configuration in accordance with Whittaker Controls Service Bulletin 240695-29-1, dated March 15, 1988, and Service Bulletin 240695-29-3, dated May 14, 1990. (Accomplishment of the procedures specified in both service bulletins is required.)

B. For those airplanes with the Whittaker Controls PTU S/O valve P/N 240695-1 installed, within 180 days after the effective date of this amendment, replace all Whittaker Controls PTU S/O valve P/N 240695-1, with PTU S/O valve P/N 240695-2; or modify the valve P/N 240695-1 to the P/N 240695-2 configuration in accordance with Whittaker Controls Service Bulletin 240695-29-3, dated May 14, 1990.

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, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

NOTE: The request should be submitted directly to the Manager, Los Angeles ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Los Angeles ACO.

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.

All persons affected by this directive who have not already receivedthe appropriate service documents from the manufacturer may obtain copies upon request to McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90801, ATTN: Business Unit Manager, Technical Publications, C1-HCW (54-60); or from Whittaker Controls, 12838 Saticoy Street, North Hollywood, California 91605. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington, or the Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California.

Airworthiness Directive 90-23-10 supersedes AD 89-22-02, Amendment 39-6356.

This amendment (39-6798, AD 90-23-10) becomes effective on December 10, 1990.