[Federal Register Volume 63, Number 153 (Monday, August 10, 1998)]
[Proposed Rules]
[Pages 42596-42598]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-21262]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-150-AD]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 737-100, -
200, -300, -400, and -500 series airplanes. This proposal would 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. This proposal also would 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, would terminate the repetitive 
testing. This proposal is prompted by reports of engine power loss 
caused by unsatisfactory performance of the fuel boost pumps. The 
actions specified by the proposed AD are intended to prevent fuel 
suction feed operation on both engines without flight crew indication, 
and possible consequent multiple engine power loss.

DATES: Comments must be received by September 24, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-150-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Dorr M. Anderson, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2684; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by

[[Page 42597]]

interested persons. A report summarizing each FAA-public contact 
concerned with the substance of this proposal will be filed in the 
Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-NM-150-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 98-NM-150-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received several reports of engine power loss, 
including one total power loss event, on Boeing Model 737-300, -400, 
and -500 series airplanes. These events were the result of degraded 
performance of the fuel boost pumps located in the main tanks. In each 
case, the low pressure indication system did not indicate that the 
pumps were operating unsatisfactorily.
    Degradation of the fuel boost pumps involved in the reported engine 
power loss events was caused by corrosion of a braze connection in the 
rotor of the pump motor. This corrosion results in a decrease in the 
impeller rotation speed, which reduces the output pressure of the pump. 
Only boost pumps manufactured by the General Electric Company (GEC) of 
the United Kingdom are affected by this problem. Other FAA-approved 
main tank fuel boost pumps have not exhibited evidence of this 
corrosion problem.
    Further investigation revealed that the low pressure switches for 
the fuel boost pumps were set at a pressure threshold that is too low. 
These pressure switches will not always detect degraded pump 
performance and will not provide indication of the problem to flight 
and maintenance crews until the output fuel pressure drops to an 
extremely low level. Low pressure switches with the improper pressure 
threshold are installed downstream of all FAA-approved main tank fuel 
boost pumps.
    If not corrected, 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 power loss.
    The reported engine power loss events occurred on Model 737-300, -
400, and -500 series airplanes. However, the subject fuel boost pump 
system on the Model 737-100 and -200 series airplanes is similar to 
that on the affected Model 737-300, -400, and -500 series airplanes. 
Therefore, those Model 737-100 and -200 series airplanes may be subject 
to the same unsafe condition revealed on the Model 737-300, -400, and -
500 series airplanes.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
737-28A1114, Revision 1, dated April 2, 1998, which describes 
procedures for 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. The alert service 
bulletin also describes procedures for replacement of the existing low 
pressure switches for boost pumps located in the main fuel tanks with 
higher threshold low pressure switches, which eliminates the need for 
the repetitive testing. Accomplishment of the replacement of the low 
pressure switches specified in the alert service bulletin is intended 
to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require accomplishment of the actions specified in 
the alert service bulletin described previously, except as discussed 
below.

Differences Between Proposed Rule and Service Bulletin

    Operators should note that, although the alert service bulletin 
recommends accomplishing the pump output pressure testing within 180 
days, the FAA has determined that an interval of 180 days would not 
address the identified unsafe condition in a timely manner. In 
developing an appropriate compliance time for this proposed AD, the FAA 
considered not only the manufacturer's recommendation, but the degree 
of urgency associated with addressing the subject unsafe condition, the 
average utilization of the affected fleet, availability of spare fuel 
boost pumps, and the time necessary to perform the testing (two hours). 
In light of all of these factors, the FAA finds a 90-day compliance 
time for initiating the proposed actions to be warranted, in that it 
represents an appropriate interval of time allowable for affected 
airplanes to continue to operate without compromising safety.
    The alert service bulletin does not restrict dispatch with main 
tank fuel boost pumps inoperative, in accordance with the Minimum 
Equipment List. However, this proposed AD would not allow dispatch of 
any airplane with any main tank fuel boost pump inoperative until the 
initial test of the boost pumps is accomplished. This restriction will 
limit the exposure to fuel suction feed operation.
    The alert service bulletin also recommends that the low pressure 
switches should be replaced on airplanes equipped with one or more 
boost pumps manufactured by GEC or Argo-Tech. Further, the alert 
service bulletin does not recommend replacement of any low pressure 
switches for airplanes on which pumps manufactured by TRW are 
installed. However, this proposed AD would require, within 3 years, 
replacement of low pressure switches for all airplanes, regardless of 
the type of boost pump installed. The FAA has determined that the 
pressure threshold of the existing low pressure switches is set too low 
to allow timely identification of any fuel boost pump with degraded 
performance.

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 would be affected by this proposed AD.
    For airplanes equipped with one or more main tank fuel boost pumps 
manufactured by GEC, it would take between 2 and 8 work hours per 
airplane to accomplish the proposed testing, at an average labor rate 
of $60 per work hour. Based on these figures, the cost impact of the 
proposed testing on U.S. operators of these airplanes is estimated to 
be between $136,800 and $547,200, or between $120 and $480 per 
airplane, per testing cycle.
    For all airplanes, it would take between 4 and 6 work hours per 
airplane to accomplish the proposed modification, at an average labor 
rate of $60 per work hour. Required parts would be provided by the 
airplane manufacturer at no cost to the operator. Based on these 
figures, the cost impact of the proposed modification on U.S. operators 
is estimated to be between $273,600 and $410,400, or between $240 and 
$360 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no

[[Page 42598]]

operator has yet accomplished any of the proposed 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 proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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.


Sec. 39.13  [Amended]

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

Boeing: 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 (d) 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:
    (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 required by paragraph (a)(2) of this AD has been 
accomplished.
    (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 Boeing Alert Service Bulletin 737-28A1114, Revision 1, dated 
April 2, 1998.
    (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 paragraph (a) 
of this AD.
    (b) For airplanes equipped with one or more main tank fuel boost 
pumps manufactured by Argo-Tech: 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.
    (c) For airplanes equipped with all four main tank fuel boost 
pumps manufactured by Thompson Rand Wooldridge (TRW): Within 3 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.
    (d) 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.

    (e) 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.

    Issued in Renton, Washington, on August 3, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-21262 Filed 8-7-98; 8:45 am]
BILLING CODE 4910-13-U