00-3886. Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

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.

DATES:

Effective March 29, 2000.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of March 29, 2000.

ADDRESSES:

The service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT:

Dorr Anderson, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes was published as a supplemental notice of proposed rulemaking (NPRM) in the Federal Register on June 2, 1999 (64 FR 29602). That action proposed to require 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. That action also proposed to require 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.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Requests To Extend Compliance Time

Two commenters request that the proposed compliance time for replacement of the low pressure switches with higher low pressure switches be extended.

One commenter, the manufacturer, requests that the compliance time for installation of higher threshold switches on Model 737-200 series airplanes be extended from 2 to 3 years. The commenter states the vendor for the low pressure switches for Model 737-200 series airplanes had not committed to providing the required parts within the proposed 2-year compliance time. The commenter states that the pressure switch, unlike the one used on Model 737-300, -400, and -500 series airplanes, was previously used only on auxiliary fuel tank installations, and that production was in very low quantities. There are approximately 1,000 Model 737-200 series airplanes that would require the subject switch. The commenter also states that the vendor for the low pressure switches for Model 737-300, -400, and -500 is able to provide the needed hardware within the proposed compliance time.

Another commenter requests that airplanes with Argo-Tech/TRW boost pumps installed in the main tanks be allowed up to 4 years to install the higher threshold low pressure switches to accommodate parts replacement at heavy maintenance visits.

The FAA does not concur with the commenters' requests. In developing an appropriate compliance time for this action, the FAA considered not only the degree of urgency associated with addressing the subject unsafe condition, but the availability of required parts and the practical aspect of accomplishing the required replacement within an interval of time that parallels normal scheduled maintenance for the majority of affected operators. Subsequent to closure of the comment period of the proposed AD, the FAA has confirmed with the manufacturer that an ample number of required parts will be available for accomplishment of the replacement within the proposed 2-year compliance time. However, under the provisions of paragraph (c) of the final rule, the FAA may approve requests for adjustments to the compliance time if data are submitted to substantiate that such an adjustment would provide an acceptable level of safety.

Request To Follow Service Bulletin Threshold Time

One commenter, an operator, recommends that the compliance time for accomplishing the pump output pressure test follow the 180-day threshold recommended in Boeing Alert Service Bulletin 737-28A1114, Revision 1, dated April 2, 1998. The commenter states that the 180-day compliance time will not compromise safe operation of the airplane fuel feed system based upon results of their testing and the redundancy associated with the fuel system on Model 737 series airplanes.

The FAA does not concur with the commenter's request. As discussed in the preamble of the original NPRM (63 FR 42596, August 10, 1998), the FAA has determined that an interval of 180 days would not address the identified unsafe condition in a timely manner, as degraded fuel boost pump performance may go undetected. Degraded fuel boost pump performance that is not detected by the low pressure switch and annunciated on the flight deck could result in multi-engine suction feed operation without flight crew indication, and possible consequent multiple engine failure. Redundancy in the fuel system has not prevented a number of in-service engine failures associated with pumps operating in a degraded manner. Therefore, no change to the final rule is necessary.

Request To Limit the Applicability to Certain Fuel Pumps

One commenter requests that the applicability of the proposed AD be revised to only affect airplanes which are fitted with General Electric Company (GEC) boost pumps. The commenter points out that the Boeing Alert Service Bulletin 737-28A1114, Revision 1, dated April 2, 1998, reveals that the unsafe condition or flameout occurred on Model 737-300, -400, and -500 series airplanes equipped with GEC pumps. No case of flameout was reported on Model 737-100, or -200 series airplanes equipped with Pratt and Whitney Model JT8D engines. The commenter states that its request will in no way affect the safety of the airplane.

The FAA does not concur with the commenter's request. As discussed in the supplemental NPRM, the FAA has determined that all pump configurations on affected Boeing Model 737 series airplanes may be subject to the identified unsafe condition.

Explanation of Changes to Proposal

The FAA has revised paragraph (a)(4) of the final rule to clarify that accomplishment of the required replacement constitutes terminating action for paragraphs (a)(1), (a)(2), and (a)(3) of this AD.

Conclusion

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact

There are approximately 2,772 airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,140 airplanes of U.S. registry will be affected by this AD.

It will take approximately 2-8 work hours per airplane to accomplish the required testing for airplanes equipped with GEC pumps, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the testing required by this AD on U.S. operators is estimated to be $120-$480 per airplane, per testing cycle.

It will take approximately 4-6 work hours per airplane to accomplish the required modification, at an average labor rate of $60 per work hour. Required parts will cost $1,900 [for airplanes equipped with part number (P/N) 60B92400-3 low pressure switches] or $2,700 (for airplanes equipped with P/N 10-3067-3 low pressure switches). Based on these figures, the cost impact of the modification required by this AD on U.S. operators is estimated to be $273,600-$410,400, or $2,140-$3,060 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

Regulatory Impact

The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

§ 39.13

[Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

2000-04-02 Boeing: Amendment 39-11584. Docket 98-NM-150-AD.

Applicability: 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.

Compliance: Required as indicated, unless accomplished previously.

To prevent fuel suction feed operation on both engines without flight crew indication, and possible consequent multiple engine power loss, accomplish the following:

Requirements for Airplanes Equipped With GEC Boost Pumps:

(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.

Requirements for Airplanes Equipped With Non-GEC boost pumps:

(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.

Alternative Methods of Compliance

(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 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

(d) Special flight permits may be issued in accordance with §§ 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

(e) The tests and replacements shall be done in accordance with Boeing Alert Service Bulletin 737-28A1114, Revision 1, dated April 2, 1998. 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 March 29, 2000.

Issued in Renton, Washington, on February 14, 2000.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.