Applicability: All Model 737-100, -200, -300, -400, and -500 series airplanes; certificated in any category.

Effective date: February 25, 1999

Compliance: Required as indicated in FAA AD 97-09-15 R1.

97-09-15 R1 BOEING: Amendment 39-10912. Docket 97-NM-157-AD. Revises AD 97-09-15, Amendment 39-10011.

Applicability: All Model 737-100, -200, -300, -400, and -500 series airplanes; certificated in any category.
NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (b) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent sudden uncommanded yawing of the airplane due to potential failures within the yaw damper system, and consequent injury to passengers and crewmembers, accomplish the following:

(a) Perform a one-time inspection of the engage solenoid valve of the yaw damper on the rudder power control unit (PCU) to determine the part number (P/N) of the valve. If any valve having Parker P/N 59600-5011 (Boeing P/N 10-60811-9), Parker P/N 59600-5007 (Boeing P/N 10-60811-3), or Parker P/N 59600-5003 (Boeing P/N 10-60811-1) is installed, prior to further flight, replace it with a valve having Parker P/N 881600-1001 (Boeing P/N 10-60811-13), Sterer P/N 45080-1 (Boeing P/N 10-60811-8), or Sterer P/N 45080 (Boeing P/N 10-60811-3). Accomplish the actions in accordance with procedures specified in Chapters 22-11-61 or 22-12-21 (for Model 737-100 and -200 series airplanes), as applicable; or Chapter 22-12-21 (for Model 737-300, -400, and -500 series airplanes) of the Boeing Maintenance Manual, as applicable. Accomplish the inspection at the earlier of the times specified in paragraphs (a)(1) and (a)(2) of this AD.

(1) Within 5 years or 15,000 flight hours after June 9, 1997 (the effective date of AD 97-09-15, amendment 39-10011), whichever occurs first.

(2) At the next time the PCU is sent to a repair facility.

NOTE 2: Boeing In-Service Activities Report 95-03-2725-10, dated February 16, 1995 (for Model 737-100 and -200 series airplanes), or 95-04-2725-10, dated February 24, 1995 (for Model 737-300, -400, and -500 series airplanes), provides additional information concerning interchangeability of solenoid valve part numbers.

NOTE 3: Operators should note that, as specified in paragraph (a) of this AD, both the Parker and Sterer P/N’s have the same Boeing P/N (10-60811-3). If, upon inspection, Boeing P/N 10-60811-3 is found to be installed, operators must ascertain the vendor P/N. Parts having Boeing P/N 10-60811-3 and Parker P/N 59600-5007 must be replaced and are not considered to be acceptable replacement parts. In addition, some engage solenoid valves may be labeled with only the name ”Bertea,” rather than ”Parker” or ”Parker-Bertea.”

(b) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle, ACO.

NOTE 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

(c) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

(d) This amendment becomes effective on December 29, 1998.

FOR FURTHER INFORMATION CONTACT:
Tin Truong, Aerospace Engineer, ANM-130S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2764; fax (425) 227-1181.