AD 93-14-21

93-14-21 BOEING: Amendment 39-8646. Docket 93-NM-109-AD.

Applicability: All Model 747-400 series airplanes, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To reduce the effect on airplane systems should they enter ground operating mode while the airplane is in flight due to depressurization of hydraulic system number one or four, accomplish the following:

(a) Within 15 days after the effective date of this AD, revise the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) by accomplishing paragraphs (a)(1) and (a)(2) of this AD.

(1) Insert a copy of 747-400 Operations Manual Bulletin 93-5, dated July 26, 1993, into the AFM.

(2) Include the requirements of paragraphs (a)(2)(i), (a)(2)(ii), and (a)(2)(iii) of this AD in the AFM. This may be accomplished by inserting a copy of this AD in the AFM.

(i) Do not operate the airplane unless both the number 4 hydraulic engine drivenpump and the number 4 hydraulic demand pump are operative.

(ii) If hydraulic system number 1 or 4 becomes inoperative while the airplane is in flight, the flight crew shall accomplish the procedures contained in 747-400 Operations Manual Bulletin 93-5, dated July 26, 1993.

(iii) If hydraulic system number 4 becomes inoperative while the airplane is in flight, the flight crew shall consider the ramifications of changes in system operation should the airplane enter the "ground mode." Specifically, consideration shall be given to trip and reserve fuel requirements, and enroute and destination forecasts for potential icing conditions. If these or other conditions present a significant adverse effect on safety if the flight is continued, the crew shall consider, as an alternative, diverting to a suitable airport. It is the responsibility of the captain to assess the situation and execute sound judgement to determine a safe course of action. A landing shall be made at the most suitable airport.

(b) Within 60 days after the effective date of this AD, install a system that provides full pitot and total air temperature heat in the event an airplane enters "ground mode" while the airplane is in flight, in accordance with Boeing Alert Service Bulletin 747-30A2069, dated July 15, 1993.

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

(d) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane toa location where the requirements of this AD can be accomplished.

(e) The AFM revision shall be accomplished in accordance with 747-400 Operations Manual Bulletin 93-5, dated July 26, 1993. The installation shall be done in accordance with Boeing Alert Service Bulletin 747-30A2069, dated July 15, 1993. 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, 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.

(f) This amendment becomes effective on August 9, 1993.