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Proposed Rule

Airworthiness Directives; Boeing Model 747 Series Airplanes

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AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to all Boeing Model 747 series airplanes, that currently 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. That AD was 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. For certain airplanes, this action would require installation of improved fuel pumps, which would terminate the requirements of the existing AD. This proposal is prompted by new information received from the fuel pump manufacturer. The actions specified by the proposed 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, 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:

Comments must be received by January 4, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-158-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. Comments may be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2000-NM-158-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

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

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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 action may be changed in light of the comments received.

Submit comments using the following format:

  • Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
  • For each issue, state what specific change to the proposed AD is being requested.
  • Include justification (e.g., reasons or data) for each request.

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 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 action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NM-158-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. 2000-NM-158-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On December 15, 1998, the FAA issued AD 98-25-52, amendment 39-10957 (63 FR 71214, December 24, 1998), applicable to all Boeing Model 747 series airplanes, to require 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. That action was 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 requirements of that 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). Start Printed Page 69719

Actions Since Issuance of Previous Rule

In the preamble to AD 98-25-52, the FAA indicated that the actions required by that AD were considered “interim action” and that further rulemaking action was being considered. The FAA now has determined that further rulemaking action is indeed necessary, and this proposed AD follows from that determination.

Since the issuance of AD 98-25-52, the FAA has received information from the fuel pump manufacturer indicating that it has now determined the cause of the premature wear of the thrust carbon bearings of the center wing tank override/jettison fuel pumps, and the horizontal stabilizer tank transfer pumps. The thrust washer located in the pump shaft thrust bearing was coated with aluminum oxide, applied using a plasma spray method, and investigation revealed that this method has a life limit of less than 500 flight hours. Further investigation revealed that aluminum oxide coating applied to the thrust washer using a D-gun spray method has a life limit of more than 15,000 flight hours.

During operation at normal fuel pump rotation speeds (7,000 to 8,000 RPM), the steel-to-steel contact may produce sparks or hot spots sufficient to ignite fuel vapor from the center wing tank or horizontal stabilizer tank, when the pump is running dry. The center wing fuel tank pumps on 747-400 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 747-400 series airplanes uses the same pumps and is also run out dry each time it is used. Replacement of the existing pumps with improved pumps having the correct thrust washers installed enhances airplane safety in that it eliminates the possibility that pumps with bad washers will be operated when the pump is running dry.

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 supersede AD 98-25-52 to continue to require 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. For certain airplanes, the proposed AD also would require the installation of improved fuel pumps, which would terminate the requirements of the existing AD.

Cost Impact

There are approximately 1,100 Model 747 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 250 airplanes of U.S. registry would be affected by this proposed AD.

The AFM revisions that are currently required by AD 98-25-52 take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions on U.S. operators is estimated to be $15,000, or $60 per airplane.

The replacements that are proposed in this new AD action would take approximately 25 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would be provided by the manufacturer at no cost to the operators. Based on these figures, the cost impact of the proposed requirements of this AD on U.S. operators is estimated to be $375,000, or $1,500 per airplane.

The cost impact figures discussed above are based on assumptions that no 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. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

Regulatory Impact

The regulations proposed herein would not have a substantial direct effect 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, it is determined that this proposal would not have federalism implications under Executive Order 13132.

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.

Start List of Subjects

List of Subjects in 14 CFR Part 39

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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:

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PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Start Authority

Authority: 49 U.S.C. 106(g), 40113, 44701.

End Authority
[Amended]

2. Section 39.13 is amended by removing amendment 39-10957 (63 FR 71214, December 24, 1998), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 2000-NM-158-AD. Supersedes AD 98-25-52, amendment 39-10957.

Applicability: All Model 747 series airplanes, 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)(1) 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 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: Start Printed Page 69720

Restatement of Requirements of AD 98-25-52

Airplane Flight Manual (AFM) Revisions

(a) Within 7 days after December 29, 1998 (the effective date of AD 98-25-52, amendment 39-10957), revise the Limitations Section of the FAA-approved 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).”

New Requirements of This AD

Determination of Correct Thrust Washer

(b) For airplanes having center wing fuel tank override/jettison pumps and, if installed, horizontal stabilizer tank transfer pumps, and all pumps meet the criteria specified in paragraph (b)(1), (b)(2), or (b)(3) of this AD (i.e., the correct thrust washer is installed), no further action is required by this AD.

(1) Verify the serial number on the pump data plate. The first four digits of the pump serial number represent the month and year of manufacture (e.g., 0697 indicates a pump manufactured in June 1997). If the serial number date code indicates that the pump was manufactured prior to July 1996, or after November 1998, and if the operator can determine that the pump was not overhauled or repaired after July 31, 1996, then the pump has the correct thrust washer installed. If the pump was overhauled or repaired after July 31, 1996, and the operator has maintenance/overhaul records showing that the thrust washer was not replaced, or was replaced with the correct thrust washer, as specified in paragraph (c) of this AD, then the pump has the correct thrust washer installed.

(2) For airplanes having a date of manufacture prior to July 1996, if the operator can determine that the pump was not overhauled or repaired after July 31, 1996; and the pump was not replaced with a new pump manufactured between July 1996 and November 1998, then the pump has the correct thrust washer installed. If the pump was overhauled or repaired after July 31, 1996, and the operator has maintenance/overhaul records showing that the thrust washer was not replaced, or was replaced with the correct thrust washer, as specified in paragraph (c) of this AD, then the pump has the correct thrust washer installed.

(3) For airplanes having pumps installed containing a serial number on the pump data plate with the suffix “P,” the pump has the correct thrust washer installed.

Terminating Action

(c) For airplanes that do not meet the requirements specified in paragraph (b)(1), (b)(2), or (b)(3) of this AD; or if the serial number on the pump data plate of any fuel pump cannot be determined: Within 24 months after the effective date of this AD, replace the applicable center wing fuel tank override/jettison pumps and horizontal stabilizer tank transfer pumps with Crane Hydro-Aire fuel pumps having a thrust washer, part number 60-06561, with a date code of 9848 (“98” indicates the year 1998, and “48” indicates the 48th week in 1998), or higher, etched on the outside diameter of the thrust washer. Accomplishment of this paragraph terminates the requirements of paragraph (a) of this AD.

Alternative Methods of Compliance

(d)(1) An alternative method of compliance (AMOC) 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. Operators shall submit their requests through an appropriate FAA Principal Operations Inspector or Principal Maintenance Inspector, as applicable, who may add comments and then send it to the Manager, Seattle ACO.

(2) With the exception of FAA AMOC letter to Boeing (No. 98-140-437, dated December 9, 1998), AMOC's approved previously in accordance with AD 98-25-52, amendment 39-10957, are approved as alternative methods of compliance with paragraph (a) of this AD.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

Special Flight Permits

(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.

Start Signature

Issued in Renton, Washington, on November 13, 2000.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 00-29498 Filed 11-17-00; 8:45 am]

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