Airworthiness directives › 98-25-52
AD 98-25-52 Airworthiness Directives; Boeing Model 747 Series Airplanes
Models named: 747 series. Read the applicability below — it usually turns on serial or part numbers too.
Applicability*9
All Model 747 series airplanes, certificated in any category.
Compliance
Required as indicated, unless accomplished previously. To prevent contact between the rotating paddle wheel and the stationary end plates within the center wing tank override/jettison fuel pumps or horizontal stabilizer tank transfer pumps due to excessive wear of the pump shaft carbon thrust bearing, which can cause sparks and/or a hot surface condition and consequent ignition of fuel vapor in the center wing tank or horizontal stabilizer tank during dry pump operation (no fuel flowing), accomplish the following: (a) Within 7 days after the effective date of this AD, revise the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) to include the following procedures. This may be accomplished by inserting a copy of this AD into the AFM. ``For Model 747-400 series airplanes equipped with a horizontal stabilizer tank, operation of the horizontal stabilizer tank transfer pumps is prohibited in flight. A tripped circuit breaker of a center wing tank override/ jettison pump or a tripped circuit breaker of a horizontal stabilizer tank transfer pump must not be reset until the associated fuel pump has been inspected for damage and any damage has been repaired. The center wing tank override/jettison pumps must be operated in accordance with either option 1 or option 2 below. Option 1 If the center wing tank override/jettison pumps are required for flight, the center tank must contain a minimum of 17,000 pounds (7,700 kilograms) at engine start. The fuel quantity indicating system of the center wing tank must be operative to dispatch with center wing tank fuel intended for use in the flight. Select both center wing tank override/jettison pump switches off at or before the fuel quantity of the center wing tank reaches 7,000 pounds (3,200 kilograms). Note: On Model 747-400 series airplanes, the `FUEL OVRD CTR L' and `FUEL OVRD CTR R' engine indication and crew alerting system (EICAS) messages will be displayed with the switches off. The center wing tank override/jettison pumps may be operated with less than 7,000 pounds of fuel in the center wing tank if required to address an emergency (such as fuel jettison or low fuel quantity). OPTION 2 If the center wing tank override/jettison pumps are required for flight, the center tank must contain a minimum of 50,000 pounds (22,700 kilograms) at engine start. The fuel quantity indicating system of the center wing tank must be operative to dispatch with center wing tank fuel intended for use in the flight. Select both center wing tank override/jettison pump switches off at or before center wing tank fuel quantity reaches 3,000 pounds (1,400 kilograms). The center wing tank override/jettison pumps may be operated with less than 3,000 pounds of fuel in the center wing tank if required to address an emergency (such as fuel jettison or low fuel quantity).'' (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 Operations Inspector or 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. (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 to all persons except those persons to whom it was made immediately effective by telegraphic AD T98-25-52, issued on December 3, 1998, which contained the requirements of this amendment. Issued in Renton, Washington, on December 15, 1998. Ali Bahrami, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 98-33691 Filed 12-23-98; 8:45 am] BILLING CODE 4910-13-U
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