[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]
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