[Federal Register Volume 63, Number 247 (Thursday, December 24, 1998)]
[Rules and Regulations]
[Pages 71214-71216]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-33691]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-360-AD; Amendment 39-10957; AD 98-25-52]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This document publishes in the Federal Register an amendment 
adopting Airworthiness Directive (AD) T98-25-52 that was sent 
previously to all known U. S. owners and operators of all Boeing Model 
747 series airplanes by individual telegrams. This AD requires revising 
the Airplane Flight Manual to include procedures to prevent dry 
operation of the center wing fuel tank override/jettison pumps and, for 
certain airplanes, to prohibit operation of the horizontal stabilizer 
tank transfer pumps in flight. This action is prompted by a report 
indicating that several override/jettison fuel pumps from the center 
wing tanks and main tanks had been removed because circuit breakers for 
the override/jettison fuel pumps were tripped, or low pump output 
pressure was indicated. The actions specified by this AD are intended 
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 could 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).

DATES: Effective 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.
    Comments for inclusion in the Rules Docket must be received on or 
before February 22, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-360-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.

[[Page 71215]]

    Information pertaining to this amendment may be examined at the 
FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Sulmo Mariano, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2686; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: On December 3, 1998, the FAA issued 
telegraphic AD T98-25-52, which is applicable to all Boeing Model 747 
series airplanes. That action was prompted by a report indicating that 
an operator of Boeing Model 747 series airplanes removed seven 
override/jettison fuel pumps from center wing tanks on several 
airplanes because the circuit breakers for the override/jettison fuel 
pumps were tripped, or low pump output pressure was indicated. Seven 
more pumps of the same design had been removed from the main tank 
override/jettison positions for the same reason on several airplanes. 
The pumps were found to have severe wear of the pump shaft carbon 
thrust bearing after only 200 hours of pump operation.
    A priming stage paddle wheel is mounted on the pump shaft, and this 
steel paddle wheel is positioned between two steel end plates. Severe 
wear of the carbon thrust bearing allows the pump shaft to shift 
axially, which causes contact of the rotating steel paddle wheel and 
the stationary steel end plates. Boeing reported that, on one pump, 
0.10 inch of the steel paddle wheel had worn away during 200 hours of 
pump operation. The cause of such severe wear is still under 
investigation. (Such wear conditions were not found on the center wing 
fuel tank override/jettison pumps that were recovered from a Model 747-
100 series airplane involved in an accident, in which the airplane 
broke up shortly after takeoff from John F. Kennedy International 
Airport in Jamaica, New York, on July 17, 1996. In addition, those 
pumps are not believed to have been operating on the accident airplane 
during that flight because mission fuel had not been loaded into the 
center tank.)
    Contact between the rotating paddle wheel and the stationary end 
plates within a center wing tank override/jettison fuel pump due to 
excessive wear of the pump shaft carbon thrust bearing can cause sparks 
and/or a hot surface condition. This condition, if not corrected, could 
ignite fuel vapor in the center wing tank during dry pump operation (no 
fuel flowing).
    The pumps of the center wing fuel tank on Model 747 series 
airplanes are normally operated until the fuel in the tank is exhausted 
and the pump inlet is uncovered, exposing the fuel pump to dry or 
partially dry operation for a period of time during each flight when 
the center wing tank is used. The horizontal stabilizer tank on Model 
747-400 series airplanes uses the same pumps and also is run dry each 
time it is used.

Explanation of the Requirements of the Rule

    Since the unsafe condition described is likely to exist or develop 
on other airplanes of the same type design, the FAA issued telegraphic 
AD T98-25-52 to require revising the Limitations Section of the FAA-
approved Airplane Flight Manual (AFM) to include procedures to prevent 
dry operation of the center wing fuel tank override/jettison pumps and, 
for Model 747-400 series airplanes, to prohibit operation of the 
horizontal stabilizer tank transfer pumps in flight.
    The AFM revision provides for two options for accomplishment:
     Option 1 minimizes the effects of the limitations on 
available airplane payload due to maximum zero fuel weight limitations. 
This option ensures that the forward (right) and aft (left) center wing 
tank override/jettison pumps remain covered during rapid acceleration 
and high nose attitudes during takeoff and departure.
     Option 2 minimizes the unusable fuel retained on some 
Boeing Model 747-400 series airplanes, or airplanes with inoperative 
scavenge systems of the center wing tank. This option also ensures that 
the forward (right) and aft (left) center wing tank override/jettison 
pumps remain covered during rapid acceleration and high nose attitudes 
during takeoff and departure, and ensures that the shutoff of the 
center wing tank override/jettison pumps will not normally be required 
until the cruise phase of flight.
    This AD is considered to be interim action until final action is 
identified, at which time the FAA may consider further rulemaking.
    It should be noted that this AD does not require any interim action 
related to the main tank override/jettison pumps because those pumps 
are selected off well before the inlets are uncovered (no dry 
operation).
    Since it was found that immediate corrective action was required, 
notice and opportunity for prior public comment thereon were 
impracticable and contrary to the public interest, and good cause 
existed to make the AD effective immediately by individual telegrams 
issued on December 3, 1998, to all known U.S. owners and operators of 
all Boeing 747 series airplanes. These conditions still exist, and the 
AD is hereby published in the Federal Register as an amendment to 
section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to 
make it effective to all persons.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the rule. All comments submitted will be 
available, both before and after the closing date for comments, in the 
Rules Docket for examination by interested persons. A report that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-NM-360-AD.'' The postcard will be date stamped and 
returned to the commenter.

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,

[[Page 71216]]

it is determined that this final rule does not have sufficient 
federalism implications to warrant the preparation of a Federalism 
Assessment.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, 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, 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.


Sec. 39.13  [Amended]

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

98-25-52  Boeing: Amendment 39-10957. Docket 98-NM-360-AD.

    Applicability: 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]
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