E8-30518. Airworthiness Directives; Boeing Model 727-281 Airplanes Equipped With Auxiliary Fuel Tanks Installed in Accordance With Supplemental Type Certificate SA3449NM

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 727-281 airplanes. This proposed AD would require deactivation of Rogerson Aircraft Corporation auxiliary fuel tanks. This proposed AD results from fuel system reviews conducted by the manufacturer, which identified potential unsafe conditions but has not provided associated corrective actions. We are proposing this AD to prevent 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.

DATES:

We must receive comments on this proposed AD by February 6, 2009.

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.

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:

Serj Harutunian, Aerospace Engineer, Propulsion Branch, ANM-140L, FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712-4137; 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-2008-1325; Directorate Identifier 2008-NM-157-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” (67 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) design approval) holders to substantiate that their fuel tank systems can prevent ignition sources in the fuel tanks. This requirement applies to design approval 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 another 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 proposed 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.

Rogerson Auxiliary Fuel Tank STCs

The auxiliary fuel tank STCs on affected airplanes are cylindrical and double walled. These tanks use pneumatic air pressure to empty into the airplane center wing tank. All auxiliary tanks use some type of electrical fuel quantity indication system (FQIS), flight deck control and annunciation panels, float level switches, valves and venting systems, electrical wiring connections in the dry bay area, and electrical bonding methods.

FAA's Findings

During the SFAR 88 safety assessment, it was determined that the Rogerson Aircraft Corporation FQIS and float level switch did not meet intrinsically safe electrical energy levels as described in the guidelines of advisory circular (AC) 25.981-1B, Fuel Tank Ignition Source Prevention Guidelines. Rogerson identified potential ignition sources resulting from a combination of single and latent failures for the Rogerson fuel tank subsystems. To prevent high electrical energy levels from the FQIS and float level switch from entering the auxiliary fuel tank, we have determined that the appropriate solution (depending on the type of auxiliary tank) for continued use is a combination of actions. First, installing a transient suppression device (TSD) in the FQIS and float level switches would be needed. In order to maximize wire separation, the TSD must be installed as close as possible to the points where the FQIS and float level switch wires enter the auxiliary tank. Other actions might include replacing high-energy FQISs, and float level switches that are impractical for TSD application, with intrinsically safe FQISs, providing wire separation, conducting a one time inspection and/or replacing aging float level switch conduit assemblies, periodically inspecting the external dry bay system components and wires, and testing the integrity of bonding resistances.

Furthermore, to reduce fuel vapor ignition risks associated with dry running of fuel pumps and fuel pump failures, operational limitations are needed to ensure that the fuel pumps are turned off when the auxiliary tank is emptied. An inspection to detect fuel leakage in the dry bay and vent pipe shrouds needs to be included in the operator's maintenance program. Rogerson Aircraft Corporation has declared all STCs as high-flammability exposure installations, and has reported a few service difficulties with fuel leakage and damage to tank bladders during maintenance activities.

Rogerson has not provided the service information required under SFAR 88 that would lead the FAA to make a finding of compliance; therefore, we must mandate the deactivation of all Rogerson Aircraft Corporation auxiliary fuel tanks.

If operators do not wish to deactivate their auxiliary fuel tanks, we will consider requests for alternative methods of compliance (AMOCs). The most likely requests would be to allow continued use of the tanks by showing compliance with SFAR 88. This would involve obtaining STCs and developing maintenance procedures to address the safety issues identified above.

Once an operator has deactivated the tank as specified in this proposed AD, the operator might wish to remove the tank. This would require a separate design approval, if an approved tank removal procedure does not exist.

Related Rulemaking

AD 2008-12-03, amendment 39-15546 (73 FR 31749, June 4, 2008) applies to various transport category airplanes equipped with auxiliary fuel tanks installed in accordance with the identified Rogerson fuel tank STCs. That AD requires deactivation of Rogerson Aircraft Corporation auxiliary fuel tanks.

We have determined that AD 2008-12-03 does not include STC SA3449NM, which is also subject to the identified unsafe condition, and might be installed on Boeing Model 727-281 airplanes.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other products of this same type design. For this reason, we are proposing this AD, which would require deactivation to prevent usage of auxiliary fuel tanks.

This NPRM proposes the same requirements as AD 2008-12-03, but for airplanes that were not included in the applicability of that AD. In determining whether to supersede that AD or issue a new AD action, we considered the effect on the fleet of superseding AD 2008-12-03, and the consequent workload associated with revising maintenance record entries. In light of this, we have determined that a less burdensome approach is to issue a separate AD action for just the additional airplanes. This proposed AD would therefore not supersede AD 2008-12-03. Airplanes listed in the applicability of AD 2008-12-03 must be in compliance with its requirements. This proposed AD is a separate AD action and applies only to Boeing Model 727-281 airplanes, certificated in any category and equipped with auxiliary fuel tanks installed in accordance with STC SA3449NM.

Costs of Compliance

This proposed AD would affect about 17 U.S.-registered airplanes. The following table provides the estimated costs to comply with this proposed AD.

Estimated Costs

Action	Work hours	Average labor rate per hour	Parts	Cost per airplane	Fleet cost
Report	1	$80	None	$80	$1,360.
Preparation of tank deactivation procedure	80	80	None	6,400	Up to $108,800.
Physical tank deactivation	30	80	$1,200	3,600	Up to $61,200.

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 have 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 that the 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.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation.

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 Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2008-1325; Directorate Identifier 2008-NM-157-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by February 6, 2009.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 727-281 airplanes, certificated in any category and equipped with auxiliary fuel tanks installed in accordance with Supplemental Type Certificate (STC) SA3449NM.

Unsafe Condition

(d) This AD results from fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent 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.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Report

(f) Within 60 days after the effective date of this AD, submit a report to the Manager, Los Angeles Aircraft Certification Office (ACO), FAA. Information collection requirements in this AD are approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.) and are assigned OMB Control Number 2120-0056. The report must include the following information:

(1) The airplane registration and auxiliary tank STC number installed.

(2) The usage frequency in terms of total number of flights per year and total number of flights for which the auxiliary tank is used.

Prevent Usage of Auxiliary Fuel Tanks

(g) Within 90 days after the effective date of this AD, deactivate the auxiliary fuel tanks, in accordance with a deactivation procedure approved by the Manager of the Los Angeles ACO. Any auxiliary tank component that remains on the airplane must be secured and must have no effect on the continued operational safety and airworthiness of the airplane. Deactivation may not result in the need for additional instructions for continued airworthiness.

Note 1:

Appendix A of this AD provides criteria that might need to be included in the deactivation procedure. Timely approval is dependent on early submittal of the deactivation procedures.

Note 2:

For technical information, contact Dan Zevallos, Director of Program Management, Rogerson Aircraft Corporation, 2201 Alton Parkway, Irvine, California 92606; phone [phone]; fax [phone].

Alternative Methods of Compliance (AMOCs)

(h)(1) The Manager, Los Angeles Aircraft Certification Office (ACO), FAA, ATTN: Serj Harutunian, Aerospace Engineer, Propulsion Branch, ANM-140L, FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712-4137; 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.

Material Incorporated by Reference

(i) None.

Appendix A

Deactivation Criteria

The auxiliary fuel tank deactivation procedure required by paragraph (g) of this AD might need to address the following actions.

(1) Permanently drain auxiliary fuel tanks, and clear them of fuel vapors to eliminate the possibility of out-gassing of fuel vapors from the emptied auxiliary tank.

Note:

If applicable, removing the bladder might help eliminate out-gassing.

(2) Disconnect all electrical connections from the fuel quantity indication system (FQIS), fuel pumps if applicable, float switches, and all other electrical connections required for auxiliary tank operation, and stow them at the auxiliary tank interface.

(3) Disconnect all pneumatic connections if applicable, cap them at the pneumatic source, and secure them.

(4) Disconnect all fuel feed and fuel vent plumbing interfaces with airplane original equipment manufacturer (OEM) tanks, cap them at the airplane tank side, and secure them in accordance with a method approved by the FAA; one approved method is specified in AC 25-8 Fuel Tank Systems Installations. In order to eliminate the possibility of structural deformation during cabin decompression, leave open and secure the disconnected auxiliary fuel tank vent lines.

(5) Pull and collar all circuit breakers used to operate the auxiliary tank.

(6) Revise the weight and balance document, if required, and obtain FAA approval.

(7) Amend the applicable sections of the applicable airplane flight manual (AFM) to indicate that the auxiliary fuel tank is deactivated. Remove auxiliary fuel tank operating procedures to ensure that only the OEM fuel system operational procedures are contained in the AFM. Amend the Limitations Section of the AFM to indicate that the AFM Supplement for the STC is not in effect. Place a placard in the flight deck indicating that the auxiliary tank is deactivated. The AFM revisions specified in this paragraph may be accomplished by inserting a copy of this AD into the AFM.

(8) Amend the applicable sections of the applicable airplane maintenance manual to remove auxiliary tank maintenance procedures.

(9) After the auxiliary fuel tank is deactivated, accomplish procedures such as leak checks and pressure checks deemed necessary before returning the airplane to service. These procedures must include verification that the airplane FQIS and fuel distribution systems have not been adversely affected.

(10) Include with the operator's proposed procedures any relevant information or additional steps that are deemed necessary by the operator to comply with the deactivation and return the airplane to service.

Issued in Renton, Washington, on December 14, 2008.

Michael J. Kaszycki,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.