Airworthiness directives: Boeing,
[Federal Register: December 24, 1998 (Volume 63, Number 247)]
[Rules and Regulations]
[Page 71214-71216]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr24de98-4]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
[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.
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.
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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:
‹bullet› 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.
‹bullet› 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 filedin 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,
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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
-
The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
-
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. 98-33691Filed12-23-98; 8:45 am]
BILLING CODE 4910-13-U
