E8-24542. Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

We propose to adopt a new airworthiness directive (AD) for certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes. This proposed AD would require adding two new indicator lights on the P10 panel to inform the captain and first officer of a low pressure condition in the left and right override/jettison pumps of the center wing tanks. This proposed AD would also require replacing the left and right override/jettison switches on the M154 fuel control module on the P4 panel with improved switches and doing the associated wiring changes. This proposed AD would also require a revision to the FAA-approved maintenance program to incorporate airworthiness limitation No. 28-AWL-22. This proposed AD results from fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent uncommanded operation of the override/jettison pumps of the center wing tanks, which could lead to an unwanted ignition source inside the center wing tank. This condition, in combination with flammable fuel vapors, could result in a center fuel tank explosion and consequent loss of the airplane.

DATES:

We must receive comments on this proposed AD by December 1, 2008.

ADDRESSES:

You may send comments by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Sulmo Mariano, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2008-1098; Directorate Identifier 2008-NM-108-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.

Discussion

The FAA has examined the underlying safety issues involved in fuel tank explosions on several large transport airplanes, including the adequacy of existing regulations, the service history of airplanes subject to those regulations, and existing maintenance practices for fuel tank systems. As a result of those findings, we issued a regulation titled “Transport Airplane Fuel Tank System Design Review, Flammability Reduction and Maintenance and Inspection Requirements” (66 FR 23086, May 7, 2001). In addition to new airworthiness standards for transport airplanes and new maintenance requirements, this rule included Special Federal Aviation Regulation No. 88 (“SFAR 88,” Amendment 21-78, and subsequent Amendments 21-82 and 21-83).

Among other actions, SFAR 88 requires certain type design (i.e., type certificate (TC) and supplemental type certificate (STC)) holders to substantiate that their fuel tank systems can prevent ignition sources in the fuel tanks. This requirement applies to type design holders for large turbine-powered transport airplanes and for subsequent modifications to those airplanes. It requires them to perform design reviews and to develop design changes and maintenance procedures if their designs do not meet the new fuel tank safety standards. As explained in the preamble to the rule, we intended to adopt airworthiness directives to mandate any changes found necessary to address unsafe conditions identified as a result of these reviews.

In evaluating these design reviews, we have established four criteria intended to define the unsafe conditions associated with fuel tank systems that require corrective actions. The percentage of operating time during which fuel tanks are exposed to flammable conditions is one of these criteria. The other three criteria address the failure types under evaluation: Single failures, single failures in combination with a latent condition(s), and in-service failure experience. For all four criteria, the evaluations included consideration of previous actions taken that may mitigate the need for further action.

We have determined that the actions identified in this AD are necessary to reduce the potential of ignition sources inside fuel tanks, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.

Currently, there are lights on the flight engineer's P4 panel to provide pressure indication for the override/jettison pumps of the left and right center wing tanks. These lights are illuminated to inform the flight engineer that a low pressure or no fuel flow condition exists. A pump uncommanded-on is an event that may result in the pump running dry and illumination of the associated low pressure light. This event requires the flight engineer to manually pull the pump circuit breaker to shut off the pump. To limit the potential of the pump running dry for an extended period of time, Boeing has found that two new indicator lights must be added to the forward panel on the flight deck to inform the captain and first officer of a low pressure condition in the override/jettison pumps. The P4 panel must also be modified to provide the flight engineer with switches to shut off the override/jettison pumps and the new indicator lights.

Uncommanded operation of the override/jettison pumps of the center wing tanks could lead to an unwanted ignition source inside the center wing tank. These conditions, if not corrected, in combination with flammable fuel vapors, could result in a center fuel tank explosion and consequent loss of the airplane.

Other Related Rulemaking

On April 28, 2008, we issued AD 2008-10-07, amendment 39-15513 (73 FR 25977, May 8, 2008), applicable to certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes. That AD requires revising the FAA-approved maintenance program by incorporating new airworthiness limitations (AWLs) for fuel tank systems to satisfy SFAR 88 requirements. That AD also requires the initial accomplishment of certain repetitive AWL inspections to phase in those inspections, and repair if necessary. As an optional action, that AD also allows incorporating AWL No. 28-AWL-22 into the FAA-approved maintenance program. Incorporating AWL No. 28-AWL-22 into the FAA-approved maintenance program in accordance with paragraph (g) of AD 2008-10-07 would terminate the action specified in paragraph (g) of this proposed AD.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-28A2288, dated March 20, 2008. The service bulletin describes procedures for adding two indicator lights on the P10 panel to inform the captain and first officer of a low pressure condition in the left and right override/jettison pumps of the center wing tanks. The service bulletin also describes procedures for replacing the left and right override/jettison switches on certain M154 fuel control modules on the P4 panel with improved switches, and doing the associated wiring changes.

For airplanes equipped with certain other M154 fuel control modules, Boeing Alert Service Bulletin 747-28A2288 refers to the BAE Systems service bulletins in the following table as additional sources of service information for replacing the switches and doing the associated wiring changes, as applicable:

Additional Sources of Service Information

Service Bulletin	Date
BAE Systems Service Bulletin 65B46124-28-01	February 16, 2006.
BAE Systems Service Bulletin 65B46124-28-02	March 28, 2007.
BAE Systems Service Bulletin 65B46124-28-03	March 28, 2007.
BAE Systems Service Bulletin 65B46214-28-01	February 16, 2006.
BAE Systems Service Bulletin 65B46214-28-02	March 28, 2007.
BAE Systems Service Bulletin 65B46214-28-03	March 28, 2007.

We have also reviewed the Boeing 747-100/200/300/SP Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D6-13747-CMR, Revision March 2008 (hereafter referred to as “Document D6-13747-CMR”). (For the purposes of Document D6-13747-CMR, the Model 747SR series airplane is basically a Model 747-100 series airplane with certain modifications to improve fatigue life.) Section D of Document D6-13747-CMR describes AWLs for fuel tank systems. Section D of Document D6-13747-CMR includes fuel system AWL No. 28-AWL-22, which is a repetitive inspection (test) to verify continued functionality of the low pressure indicator lights on the P10 panel for the override/jettison pumps of the center wing tanks.

FAA's Determination and Requirements of This Proposed AD

We are proposing this AD because we evaluated all relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the(se) same type design(s). This proposed AD would require accomplishing the following actions:

• Adding two new indicator lights on the P10 panel to inform the captain and first officer of a low pressure condition in the left and right override/jettison pumps of the center wing tanks.
• Replacing the left and right override/jettison switches on the M154 fuel control module on the P4 panel with improved switches and doing the associated wiring changes.
• Revising the FAA-approved maintenance program to incorporate AWL No. 28-AWL-22, which is a repetitive inspection to verify continued functionality of the low pressure indicator lights on the P10 panel for the override/jettison pumps of the center wing tanks.

Costs of Compliance

We estimate that this proposed AD would affect 185 airplanes of U.S. registry. We also estimate that it would take up to 28 work-hours per product to comply with this proposed AD. The average labor rate is $80 per work-hour. Required parts would cost up to $2,668 per product. Based on these figures, we estimate the cost of this proposed AD to the U.S. operators up to $907,980, or $4,908 per product.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. “Subtitle VII: Aviation Programs,” describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in “Subtitle VII, Part A, Subpart III, Section 44701: General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD 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.

For the reasons discussed above, I certify 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. 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.

You can find our regulatory evaluation and the estimated costs of compliance in the AD Docket.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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.

§ 39.13

[Amended]

2. The FAA amends § 39.13 by adding the following new AD:

Boeing: Docket No. FAA-2008-1098; Directorate Identifier 2008-NM-108-AD.

Comments Due Date

(a) We must receive comments by December 1, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 747-28A2288, dated March 20, 2008.

Note 1:

This AD requires revisions to certain operator maintenance documents to include a new inspection. Compliance with this inspection is required by 14 CFR 91.403(c). For airplanes that have been previously modified, altered, or repaired in the areas addressed by this inspection, the operator may not be able to accomplish the inspections described in the revisions. In this situation, to comply with 14 CFR 91.403(c), the operator must request approval for an alternative method of compliance (AMOC) according to paragraph (j) of this AD. The request should include a description of changes to the required inspection that will ensure the continued operational safety of the airplane.

Unsafe Condition

(d) This AD results from fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent uncommanded operation of the override/jettison pumps of the center wing tanks, which could lead to an unwanted ignition source inside the center wing tank. This condition, in combination with flammable fuel vapors, could result in a center fuel tank explosion and consequent loss of the airplane.

Compliance

(e) Comply with this AD within the compliance times specified, unless already done.

Installation of Indicator Lights and Replacement of Switches

(f) Within 36 months after the effective date of this AD: Add two new indicator lights on the P10 panel to inform the captain and first officer of a low pressure condition in the left and right override/jettison pumps of the center wing tanks; and replace the left and right override/jettison switches on the M154 fuel control module on the P4 panel with improved switches and do the associated wiring changes; by accomplishing all of the applicable actions specified in the Accomplishment Instructions of Boeing Alert Service Bulletin 747-28A2288, dated March 20, 2008.

Note 2:

For airplanes equipped with certain M154 fuel control modules, paragraph 2.C.2 of Boeing Alert Service Bulletin 747-28A2288 refers to the BAE Systems service bulletins identified in Table 1 of this AD, as applicable, as additional sources of service information for replacing the switches.

Table 1—Additional Sources of Service Information

Service Bulletin	Date
BAE Systems Service Bulletin 65B46124-28-01	February 16, 2006.
BAE Systems Service Bulletin 65B46124-28-02	March 28, 2007.
BAE Systems Service Bulletin 65B46124-28-03	March 28, 2007.
BAE Systems Service Bulletin 65B46214-28-01	February 16, 2006.
BAE Systems Service Bulletin 65B46214-28-02	March 28, 2007.
BAE Systems Service Bulletin 65B46214-28-03	March 28, 2007.

Maintenance Program Revision

(g) Concurrently with accomplishing the actions required by paragraph (f) of this AD, revise the FAA-approved maintenance program by incorporating Airworthiness Limitation (AWL) No. 28-AWL-22 of Section D of the Boeing 747-100/200/300/SP Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D6-13747-CMR, Revision March 2008.

No Alternative Inspections or Inspection Intervals

(h) After accomplishing the action specified in paragraph (g) of this AD, no alternative inspections or inspection intervals may be used unless the inspections or inspection intervals are approved as an AMOC in accordance with the procedures specified in paragraph (j) of this AD.

Terminating Action for Maintenance Program Revision

(i) Incorporating AWL No. 28-AWL-22 into the FAA-approved maintenance program in accordance with paragraph (g) of AD 2008-10-07, amendment 39-15513, terminates the action required by paragraph (g) of this AD.

Alternative Methods of Compliance (AMOCs)

(j)(1) The Manager, Seattle ACO, FAA, ATTN: Sulmo Mariano, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone]; has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19.

(2) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO.

Issued in Renton, Washington, on October 7, 2008.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.