[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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