E8-23668. Airworthiness Directives; Boeing Model 727 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 727 airplanes. This proposed AD would require, among other actions, installing new ground fault interrupter (GFI) relays for the main fuel tanks and the auxiliary fuel tank pumps. This proposed AD also would require revising the FAA-approved maintenance program to incorporate new Airworthiness Limitations (AWLs) for the GFI of the boost pumps and for the uncommanded on system for the auxiliary fuel tank pumps. This proposed AD results from fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent an electrical fault in the fuel pump system, which might cause a connector or end cap to burn through and a subsequent fire or explosion inside the fuel pump or wing spar area. We are also proposing this AD to prevent uncommanded operation of the auxiliary fuel tank pumps, which can cause them to run dry. This condition will increase pump temperature and could supply an ignition source to fumes in the fuel tank, which can result in a consequent fire or explosion.

DATES:

We must receive comments on this proposed AD by November 21, 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:

Binh Tran, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, 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-2008-1065; Directorate Identifier 2008-NM-126-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.

We have determined that the fuel pump control system on certain Model 727 airplanes must be changed by installing ground fault interrupter (GFI) relays that will interrupt the electrical power to the fuel pumps when a ground fault is detected. The GFI relays will remove the 115VAC power from the fuel pumps before electrical arcing can occur. An electrical fault in the fuel pump system, if not corrected, might cause a connector or end cap to burn through and a subsequent fire or explosion inside the fuel pump or wing spar area.

In addition, we have determined that electrical faults within the fuel tank pump system on certain Model 727-100 and -200 series airplanes can cause a pump to operate when the pump switch is in the “OFF” position (referred to as “uncommanded on” (UCO) pump operation). Uncommanded operation of the auxiliary fuel tank pumps can cause them to run dry, which will increase pump temperature and could supply an ignition source to fumes in the fuel tank, and result in a consequent fire or explosion.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 727-28A0128, dated April 4, 2008. The service bulletin describes procedures for installing new GFI relays for the main fuel tanks and the auxiliary fuel tank pumps and doing other specified actions. The other specified actions include installing new wires and modifying some existing wires to support the installation of the new GFI relays.

We also have reviewed Boeing Alert Service Bulletin 727-28A0130, dated April 30, 2008. The service bulletin describes procedures for:

• Installing new ground blocks, track, switch mounting bracket, relay mounting bracket, toggle switches, and relays, and making changes to the wire bundles in the GFI relay panel in the electronic equipment bay; and
• Installing new circuit breakers and lights and making changes to wire bundles on the third crewman's P6 and P4 panels in the flight compartment.

For certain airplanes identified in Boeing Alert Service Bulletin 727-28A0128, the procedures specified in Boeing Alert Service Bulletin 727-28A0130 must be done concurrently with the procedures specified in Boeing Alert Service Bulletin 727-28A0128.

In addition, we have reviewed “Boeing 727-100/200 Airworthiness Limitations (AWLs),” D6-8766-AWL, Revision August 2007 (hereafter referred to as “Document D6-8766-AWL”). Document D6-8766-AWL describes, among other actions, new AWLs for the GFI of the boost pumps (i.e., 28-AWL-16) and for the Auxiliary Tanks Boost Pump Uncommanded On System (i.e., 28-AWL-17).

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 the following actions:

• Installing new GFI relays for the main fuel tanks and the auxiliary fuel tank pumps.
• For certain airplanes, installing new ground blocks, track, switch mounting bracket, relay mounting bracket, toggle switches, and relays, and changing the wire bundles in the GFI relay panel in the electronic equipment bay.
• For certain airplanes, installing new circuit breakers and lights and changing wire bundles on the third crewman's P6 and P4 panels in the flight compartment.
• Revising the FAA-approved maintenance program to incorporate AWL numbers 28-AWL-16 and 28-AWL-17, which would require repetitive inspections of the GFI of the boost pumps and of the uncommanded on system for the auxiliary fuel tank pumps, respectively.

Costs of Compliance

We estimate that this proposed AD would affect 199 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

Table—Estimated Costs

Action	Work hours	Average labor rate per hour (dollars)	Parts	Cost per product	Number of U.S.- registered airplanes	Fleet cost
Installation of new GFI relays	Between 202 and 416 1	$80	Between $30,619 and $59,785 1	Between $46,779 and $93,065 1	199	Between $9,309,021 and $18,519,935 1.
Concurrent Requirements	Between 68 and 209 1	80	Between $1,292 and $10,470 1	Between $6,732 and $27,190 1	35	Between $235,620 and $951,650 1.
Revision of FAA-approved maintenance program	1	80	None	$80	199	$15,920.
1 Depending on the airplane configuration.

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-2008-1065; Directorate Identifier 2008-NM-126-AD.

Comments Due Date

(a) We must receive comments by November 21, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 727, 727C, 727-100, 727-100C, 727-200, and 727-200F series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 727-28A0128, dated April 4, 2008.

Note 1:

This AD requires revisions to certain operator maintenance documents to include new inspections. Compliance with these inspections is required by 14 CFR 91.403(c). For airplanes that have been previously modified, altered, or repaired in the areas addressed by these inspections, 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 inspections 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 an electrical fault in the fuel pump system, which might cause a connector or end cap to burn through and a subsequent fire or explosion inside the fuel pump or wing spar area. We are also issuing this AD to prevent uncommanded operation of the auxiliary fuel tank pumps, which can cause them to run dry. This condition will increase pump temperature and could supply an ignition source to fumes in the fuel tank, which can result in a consequent fire or explosion.

Compliance

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

Installation

(f) Within 60 months after the effective date of this AD, install new ground fault interrupter (GFI) relays for the main fuel tanks and the auxiliary fuel tank pumps and do all the other specified actions by accomplishing all the applicable actions specified in the Accomplishment Instructions of Boeing Alert Service Bulletin 727-28A0128, dated April 4, 2008.

Concurrent Requirements

(g) For airplanes identified as Groups 5 through 18 inclusive, in Boeing Alert Service Bulletin 727-28A0128, dated April 4, 2008: Concurrently with the installation required by paragraph (f) of this AD, do the actions specified in paragraphs (g)(1) and (g)(2) of this AD in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 727-28A0130, dated April 30, 2008.

(1) Install new ground blocks, track, switch mounting bracket, relay mounting bracket, toggle switches, and relays, and make changes to the wire bundles in the GFI relay panel in the electronic equipment bay.

(2) Install new circuit breakers and lights and make changes to wire bundles on the third crewman's P6 and P4 panels in the flight compartment.

Maintenance Program Revision

(h) Concurrently with accomplishing the installation required by paragraph (f) of this AD, revise the FAA-approved maintenance program by incorporating AWLs numbers 28-AWL-16 and 28-AWL-17 of Section D of the “Boeing 727-100/200 Airworthiness Limitations (AWLs),” D6-8766-AWL, Revision August 2007 (hereafter referred to as “Document D6-8766-AWL.”)

No Alternative Inspection or Inspection Intervals

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

Alternative Methods of Compliance (AMOCs)

(j)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, ATTN: Binh Tran, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, 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 September 18, 2008.

Michael Kaszycki,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.