Airworthiness Directive · Amendment 39-11584 · Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes
Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes
Model 737-100, -200, -300, -400, and -500 series airplanes; line numbers 1 through 3002 inclusive; 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 (c) 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.
This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, that requires repetitive testing of certain main tank fuel boost pumps to identify those with degraded performance, and replacement of degraded pumps with new or serviceable pumps. This AD also requires eventual replacement of the existing low pressure switches for boost pumps located in the main fuel tanks with higher threshold low pressure switches, which, when accomplished, terminates the repetitive testing. This amendment is prompted by reports of engine power loss caused by unsatisfactory performance of the fuel boost pumps. The actions specified by this AD are intended to prevent fuel suction feed operation on both engines without flight crew indication, and possible consequent multiple engine power loss.
To prevent fuel suction feed operation on both engines without flight crew indication, and possible consequent multiple engine power loss, accomplish the following:
(a) For airplanes equipped with one or more main tank fuel boost pumps manufactured by the General Electric Company (GEC), of the United Kingdom: Accomplish paragraphs (a)(1), (a)(2), (a)(3), and (a)(4) of this AD.
(1) As of the effective date of this AD, no airplane shall be dispatched with any main tank fuel boost pump inoperative unless the initial testing and any follow-on corrective actions required by paragraph (a)(2) of this AD have been accomplished on the operative pump in that main tank.
(2) Test each GEC-manufactured main tank fuel boost pump to determine the output pressure, in accordance with Boeing Alert Service Bulletin 737-28A1114, Revision 1, dated April 2, 1998; at the later of the times specified in paragraphs (a)(2)(i) and (a)(2)(ii) of this AD. If the fuel boost pump output pressure measured during the testing required by this paragraph is less than 23 pounds per square inch gauge (psig), as measured at the input to the engine fuel pump; or less than 36 psig, as measured at the fuel boost pump low pressure switch; prior to further flight, replace the fuel boost pump with a new or serviceable fuel pump, in accordance with the alert service bulletin.
(i) Prior to the accumulation of 3,000 total flight hours, or within 1 year since date of manufacture of the airplane, whichever occurs first; or
(ii) Within 90 days after the effective date of this AD.
(3) Repeat the testing required by paragraph (a)(2) of this AD thereafter at intervals not to exceed 6 months, until accomplishment of the requirements of paragraph (a)(4) of this AD.
(4) Within 2 years after the effective date of this AD, replace all four low pressure switches installed downstream of the main tank fuel boost pumps with higher threshold low pressure switches, in accordance with Boeing Alert Service Bulletin 737-28A1114, Revision 1, dated April 2, 1998. Accomplishment of this replacement constitutes terminating action for the requirements of paragraphs (a)(1), (a)(2), and (a)(3) of this AD.
(b) For airplanes other than those identified in paragraph (a) of this AD: Within 2 years after the effective date of this AD, replace all four low pressure switches installed downstream of the main tank fuel boost pumps with higher threshold low pressure switches, in accordance with Boeing Alert Service Bulletin 737-28A1114, Revision 1, dated April 2, 1998.
