AD 91-09-15

91-09-15 BOEING: Amendment 39-6974. Docket No. 90-NM-250-AD.

Applicability: Model 767 series airplanes, as listed in Boeing Service Bulletin 767-79- 0008, dated August 11, 1988, equipped with engine oil filter differential pressure switches on JT9D-7R4 engines and all Model 767 series airplanes equipped with engine oil filter differential pressure switches on PW4000 engines, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent false oil filter bypass indication or loss of oil quantity from failed pressure switches, accomplish the following:

A. Within the next 60 days after the effective date of this AD, or prior to the accumulation of 10,000 total service hours, whichever occurs later, and thereafter at intervals not to exceed 10,000 total service hours, replace the engine oil filter differential pressure switch, as follows:

1. For Pratt & Whitney PW4000 engines: replace part number (P/N) S332T004-23 with a new -23 switch.

2. For Pratt & Whitney JT9D-7R4 engines: replace P/N's S332T004-2, - 25, or -29, with a new -29 switch. If a -2 or -25 switch is currently installed, modification in accordance with Boeing Service Bulletin 767-79-0008, dated August 11, 1988, is required in order to install a -29 switch configuration.

NOTE: Reworking, modifying, or overhauling a used switch does not zero time the switch.

B. Pressure switches removed following the accumulation of 10,000 total service hours shall not be re-installed on any airplane.

C. 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.

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 received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington.

This amendment (39-6974, AD 91-09-15) becomes effective on May 28, 1991.