AD 2003-11-19 Airworthiness Directives; Boeing Model 727-100 and 727-200 Series Airplanes

Exclude Certain Airplanes Two operators request that the applicability of the proposed AD be revised to exclude airplanes equipped with single-pitch channels that use radio altimeter-based glideslope gain programming. One commenter reports that most of the affected airplanes in its fleet have been modified to incorporate a dual-pitch computer configuration in accordance with Sperry Service Bulletin 21-1132-121, dated November 23, 1982 (for SP-50 autopilots); or 21-1132-122, dated February 7, 1983 (for SP-150 autopilots). (Those service bulletins were cited in the proposed AD as the appropriate source of service information for the one-time test of the modified autopilot.) This commenter adds that compliance with paragraphs (b) and (c) of the proposed AD would be impossible for those airplanes because the proposed AD and Boeing service bulletin are targeted for airplanes with single-channel autopilot systems. In addition, this commenter states that paragraph (a) of the proposed AD imposes an undesirable restriction on modified airplanes by preventing them from flying category II and category III approaches into airports with inoperative middle markers. This commenter asserts that this restriction is unnecessary for the modified airplanes because their autopilot configurations use radio altimeter glideslope gain programming (radio altitude-based desensitization), and are therefore not susceptible to the airworthiness concern associated with inoperative middle markers addressed by the proposed AD. The commenter recommends that the applicability of the proposed AD be revised to exclude those airplanes. The other commenter notes that affected airplanes with single-pitch channels on which the actions specified in Boeing Service Bulletin 727-22-0052 have been incorporated do not use the middle marker in gain programming. The commenter concludes that these airplanes should not be prohibited from category II approaches if no middle marker is available. The FAA agrees. In this case, where the autopilot has already been modified with an FAA-approved design that does not normally use time-based gain programming, the FAA agrees that excluding airplanes equipped with radio altimeter-based autopilots from the applicability of the AD will not compromise the safety of the fleet. The applicability of this AD has been revised accordingly. Request To Revise

Required as indicated, unless accomplished previously. To prevent undesirable and potentially dangerous pitch oscillations during coupled instrument landing system (ILS) approaches, accomplish the following: Revision of Airplane Flight Manual (AFM) (a) For any airplane on which autopilot coupled ILS approaches with time-based glideslope gain programming are used: Within 6 months after the effective date of this AD, revise the Limitations Section, under AUTOPILOT/FLIGHT DIRECTOR SYSTEM, of the FAA-approved AFM by adding the following (this may be accomplished by inserting a copy of this AD into the AFM): “Coupled ILS approaches are prohibited unless the autopilot has been modified in accordance with AD 2003-11-19, amendment 39-13178. CAT II autopilot coupled ILS approach shall not be performed if the Middle Marker (ground or airborne system) is inoperative or nonexistent. Disconnect the autopilot at, or prior to, 80 ft. (above the runway's touchdown-zone elevation) during coupled ILS CAT II approaches.” Modification and Testing of Autopilot (b) Except as provided by paragraph (d) of this AD: Within 18 months after the effective date of this AD, modify the existing SP-50 or SP-150 single-channel autopilot in accordance with Boeing Alert Service Bulletin 727-22A0093, dated December 20, 2000. (c) Except as provided by paragraphs (d) and (e) of this AD: After modification of the autopilot unit required by paragraph (b) of this AD, and before reinstallation of the modified autopilot and further flight, perform a one-time test procedure of the modified autopilot, in accordance with Sperry Service Bulletin 21-1132-121, dated November 23, 1982 (for SP-50 autopilots); or 21-1132-122, dated February 7, 1983 (for SP-150 autopilots); as applicable. Testing done before the effective date of this AD in accordance with Component Maintenance Manual (CMM) test procedures is also acceptable, provided that the procedures implement all the CMM changes and test steps described in the applicable Sperry service bulletin. For autopilot units manufactured with the actions of the applicable Sperry service bulletin already incorporated, testing is not required. Exempt Conditions (d) For airplanes with autopilots already modified prior to the effective date of this AD in accordance with Sperry Service Bulletin 21-1132-121 or 21-1132-122: Only the AFM limitation specified in paragraph (a) of this AD is required. (e) For any airplane on which coupled approaches are not used: Only the AFM limitation specified in paragraph (a) of this AD is required, provided a flight deck placard is installed that states, “Autopilot coupled ILS approach prohibited” or equivalent, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the Manager's approval letter must specifically reference this AD. However, for any airplane placed into service that uses autopilot coupled ILS approaches, the requirements of this AD must be accomplished before the first flight when a coupled approach is used. Part Installation (f) As of 6 months after the effective date of this AD, no person may install on any airplane an autopilot pitch control computer unless it has been modified in accordance with this AD. Alternative Methods of Compliance (g) 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, FAA. Operators shall submit their requests through an appropriate FAA Principal Operations or Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. Special Flight Permits (h) 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. Incorporation by Reference (i) Unless otherwise specified in this AD, the actions must be done in accordance with Boeing Alert Service Bulletin 727-22A0093, dated December 20, 2000; Sperry Service Bulletin 21-1132-121, dated November 23, 1982; and Sperry Service Bulletin 21-1132-122, dated February 7, 1983; as applicable. Only the first page of Sperry Service Bulletins 21-1132-121 and 21-1132-122 contain the document number; no other page of the documents contain this information. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, PO 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. Effective Date (j) This amendment becomes effective on July 16, 2003. Issued in Renton, Washington, on May 28, 2003. Vi L. Lipski, Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 03-13976 Filed 6-10-03; 8:45 am] BILLING CODE 4910-13-P