99-11-05 BOEING: Amendment 39-11175. Docket 98-NM-383-AD. Issued December 7, 1999.

Applicability: All Model 737 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 (e) 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 failure of the secondary servo valve slide in the rudder power control unit (PCU) due to cracking of the slide, and consequent rudder hardover and reduced controllability of the airplane, accomplish the following:

(a) Perform a displacement test of the secondary slide in the dual servo valve in the rudder PCU, in accordance with Boeing Alert Service Bulletin 737-27A1221, Revision 1, dated January 28, 1999 (for Model 737-100, -200, -300 -400, and -500 series airplanes); or 737-27A1222, Revision 1, dated January 28, 1999 (for Model 737-600, -700, and -800 series airplanes); at the applicable time specified by paragraph (a)(1), (a)(2), (a)(3), or (a)(4) of this AD. Repeat the displacement test on that PCU thereafter at intervals not to exceed 24,000 flight hours.

NOTE 2: Accomplishment of the initial displacement testing required by paragraph (a) of this AD in accordance with Boeing Alert Service Bulletin 737-27A1221, dated January 14, 1999 (for Model 737-100, -200, -300, -400, and -500 series airplanes); or 737-27A1222, dated January 14, 1999 (for Model 737-600, -700, and -800, series airplanes) is acceptable only for the initial compliance requirements of this AD.

(1) For Model 737-100, -200, -300, -400, and -500 series airplanes: Conduct the displacement test within 16 months after the effective date of this AD.

(2) For airplanes on which a PCU specified in paragraph (a)(2)(I) or (a)(2)(ii) of this AD is installed within 16 months after the effective date of this AD: Conduct the displacement test within 16 months after the effective date of this AD.

(b) If the results of the displacement test required by paragraph (a) of this AD are outside the limits specified by Boeing Alert Service Bulletin 737-27A1221, Revision 1, dated January 28, 1999 (for Model 737-100, -200, -300, -400, and -500 series airplanes), or 737-27A1222, Revision 1, dated January 28, 1999 (for Model 737-600, -700, and -800 series airplanes): Prior to further flight, accomplish the actions specified in paragraphs (b)(1) and (b)(2) of this AD.

NOTE 3: Boeing Alert Service Bulletin 737-27A1222, Revision 1, dated January 28, 1999, refers to Parker Service Bulletin 381500-27-01, dated December 22, 1998, as an additional source of service information for accomplishment of the displacement test for Model 737-600, -700, and -800 series airplanes.

(c) As of 16 months after the effective date of this AD, no person shall install a main rudder PCU specified in paragraph (c)(1) or (c)(2) of this AD unless that PCU’s nameplate has been vibro-engraved with the letter "C" following the serial number. (Subsequent serial numbers greater than those listed below are displacement tested as part of the certified production process, and do not require the letter "C" to be vibro-engraved.)

(1) For Boeing Model 737-100, -200, -300, -400, and -500 series airplanes: A PCU having P/N 65-44861-12 and a serial number (S/N) 3509A or lower; or any PCU having P/N 65C37053-(XX).

(2) For Boeing Model 737-600, -700, and -800 series airplanes: A PCU having P/N 251A301-(X) and a S/N 0299 or lower.

(d) (1) Within 30 days after accomplishing the initial displacement test required by paragraph (a) of this AD: Submit a report of the testing to the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; fax (425) 227-1181. The report must include the displacement testing results (both positive and negative findings), test data for any failed valve assemblies, a description of any discrepancies if found, the part number and serial number of each rudder PCU tested, and the airplane serial number.

(3) Within 30 days after accomplishing the initial displacement test required by paragraph (a) of this AD: Submit failed valve assemblies for analysis to Parker Hannifin Corporation, Chief Engineer, Customer Support Operations, 16666 Von Karman Avenue, Irvine, California 92606.

(4) Information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056.

(e) 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 ACO. 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.

(f) 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.

(g) The actions shall be done in accordance with Boeing Alert Service Bulletin 737-27A1221, Revision 1, dated January 28, 1999, or Boeing Alert Service Bulletin 737-27A1222, Revision 1, dated January 28, 1999. This incorporation by reference of those documents was previously approved by the Director of the Federal Register as of June 28, 1999 (64 FR 27905, May 24, 1999). Copies may be obtained from Boeing Commercial Airplane Group, P. O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(h) The effective date of this amendment remains June 28, 1999.

FOR FURTHER INFORMATION CONTACT:

R.C. Jones, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1118; fax (425) 227-1181.