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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. FAA-2008-1007; Directorate Identifier 2008-NM-135-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration (FAA), DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM).

# SUMMARY:

We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as: Bombardier Aerospace has completed a system safety review of the CL-600-2C10/CL-600-2D24 aircraft fuel system against new fuel tank safety standards. The assessment showed that due to the close proximity of intrinsically safe fuel system wiring with other wiring, a single failure from wire chafing at various locations of the fuselage could result in an ignition source inside the fuel tank. In addition, chafing of the temperature sensor wiring against the high power wiring in the avionics compartment could lead to overheating of the temperature sensor and hot surface ignition. The presence of an ignition source inside the fuel tank could result in a fuel tank explosion. 

The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI. 

# DATES:

We must receive comments on this proposed AD by October 23, 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:                          (202) 493-2251.                     
      -  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 W12-40, 1200 New Jersey Avenue, SE., Washington, DC, 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 Operations office 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 Operations office (telephone (800) 647-5527) is in the                     **ADDRESSES**                     section. Comments will be available in the AD docket shortly after receipt.                 

# FOR FURTHER INFORMATION CONTACT:

Rocco Viselli, Aerospace Engineer, Airframe and Propulsion Branch, ANE-171, FAA, New York Aircraft Certification Office, 1600 Stewart Avenue, Suite 410, Westbury, New York 11590; telephone (516) 228-7331; fax (516) 794-5531. 

# 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-2008-1007; Directorate Identifier 2008-NM-135-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 based on 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 

Transport Canada Civil Aviation (TCCA), which is the aviation authority for Canada, has issued Canadian Airworthiness Directive CF-2008-25, dated July 3, 2008 (referred to after this as “the MCAI”), to correct an unsafe condition for the specified products. The MCAI states: 

Bombardier Aerospace has completed a system safety review of the CL-600-2C10/CL-600-2D24 aircraft fuel system against new fuel tank safety standards, introduced in Chapter 525 of the Airworthiness Manual through Notice of Proposed Amendment (NPA) 2002-043. The identified non-compliances were assessed using Transport Canada Policy Letter No. 525-001 to determine if mandatory corrective action was required. 

The assessment showed that due to the close proximity of intrinsically safe fuel system wiring with other wiring, a single failure from wire chafing at various locations of the fuselage could result in an ignition source inside the fuel tank. In addition, chafing of the temperature sensor wiring against the high power wiring in the avionics compartment could lead to overheating of the temperature sensor and hot surface ignition. The presence of an ignition source inside the fuel tank could result in a fuel tank explosion. 

To correct the unsafe condition, this directive mandates the installation of conduit and the addition of spacers to protect fuel tank wiring.

You may obtain further information by examining the MCAI in the AD docket. 

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                           ( print page 54750)                        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. 

## Relevant Service Information 

Bombardier has issued Service Bulletin 670BA-24-011, Revision C, dated November 28, 2005. The actions described in this service information are intended to correct the unsafe condition identified in the MCAI. 

## FAA's Determination and Requirements of This Proposed AD 

This product has been approved by the aviation authority of another country, and is approved for operation in the United States. Pursuant to our bilateral agreement with the State of Design Authority, we have been notified of the unsafe condition described in the MCAI and service information referenced above. We are proposing this AD because we evaluated all pertinent information and determined an unsafe condition exists and is likely to exist or develop on other products of the same type design. 

## Differences Between This AD and the MCAI or Service Information 

We have reviewed the MCAI and related service information and, in general, agree with their substance. But we might have found it necessary to use different words from those in the MCAI to ensure the AD is clear for U.S. operators and is enforceable. In making these changes, we do not intend to differ substantively from the information provided in the MCAI and related service information. 

We might also have proposed different actions in this AD from those in the MCAI in order to follow FAA policies. Any such differences are highlighted in a NOTE within the proposed AD. 

## Costs of Compliance 

Based on the service information, we estimate that this proposed AD would affect about 159 products of U.S. registry. We also estimate that it would take about 38 work-hours per product to comply with the basic requirements of this proposed AD. The average labor rate is $80 per work-hour. Required parts would cost about $2,914 per product. Where the service information lists required parts costs that are covered under warranty, we have assumed that there will be no charge for these costs. As we do not control warranty coverage for affected parties, some parties may incur costs higher than estimated here. Based on these figures, we estimate the cost of the proposed AD on U.S. operators to be $946,686, or $5,954 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. 

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it 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 

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

**Bombardier, Inc. (Formerly Canadair):**                                 Docket No. FAA-2008-1007; Directorate Identifier 2008-NM-135-AD.                             

## Comments Due Date 

(a) We must receive comments by October 23, 2008. 

## Affected ADs 

(b) None. 

## Applicability 

(c) This AD applies to the airplanes identified in paragraphs (c)(1) and (c)(2) of this AD, certificated in any category. 

(1) Bombardier Model CL-600-2C10 (Regional Jet Series 700, 701, & 702) airplanes, serial numbers 10003 through 10169 inclusive. 

(2) Bombardier Model CL-600-2D24 (Regional Jet Series 900) airplanes, serial numbers 15001 through 15030 inclusive. 

## Subject 

(d) Air Transport Association (ATA) of America Code 24: Electrical Power. 

## Reason 

(e) The mandatory continuing airworthiness information (MCAI) states: 

                                Bombardier Aerospace has completed a system safety review of the CL-600-2C10/CL-600-2D24 aircraft fuel system against new fuel tank safety standards, introduced in Chapter 525 of the Airworthiness Manual through Notice of Proposed Amendment                                       ( print page 54751)                                    (NPA) 2002-043. The identified non-compliances were assessed using Transport Canada Policy Letter No. 525-001 to determine if mandatory corrective action was required.                             

The assessment showed that due to the close proximity of intrinsically safe fuel system wiring with other wiring, a single failure from wire chafing at various locations of the fuselage could result in an ignition source inside the fuel tank. In addition, chafing of the temperature sensor wiring against the high power wiring in the avionics compartment could lead to overheating of the temperature sensor and hot surface ignition. The presence of an ignition source inside the fuel tank could result in a fuel tank explosion. 

To correct the unsafe condition, this directive mandates the installation of conduit and the addition of spacers to protect fuel tank wiring. 

## Actions and Compliance 

(f) Unless already done, do the following actions. 

(1) Within 4,500 flight hours after the effective date of this AD, modify the fuel system wiring along the fuselage and in the avionics compartment by installing protective conduit and spacers, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 670BA-24-011, Revision C, dated November 28, 2005. 

(2) Actions done before the effective date of this AD in accordance with Bombardier Service Bulletin 670BA-24-011, dated September 7, 2004; Revision A, dated December 14, 2004; or Revision B, dated February 28, 2005; are acceptable for compliance with the corresponding requirements of this AD. 

## FAA AD Differences 

# Note:

This AD differs from the MCAI and/or service information as follows: No differences.

## Other FAA AD Provisions 

(g) The following provisions also apply to this AD: 

(1) Alternative Methods of Compliance (AMOCs): The Manager, New York Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Rocco Viselli, Aerospace Engineer, Airframe and Propulsion Branch, ANE-171, FAA, New York ACO, 1600 Stewart Avenue, Suite 410, Westbury, New York 11590; telephone (516) 228-7331; fax (516) 794-5531. 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. 

(2) Airworthy Product: For any requirement in this AD to obtain corrective actions from a manufacturer or other source, use these actions if they are FAA-approved. Corrective actions are considered FAA-approved if they are approved by the State of Design Authority (or their delegated agent). You are required to assure the product is airworthy before it is returned to service. 

(3) Reporting Requirements: For any reporting requirement in this AD, under the provisions of the Paperwork Reduction Act, the Office of Management and Budget (OMB) has approved the information collection requirements and has assigned OMB Control Number 2120-0056. 

## Related Information 

(h) Refer to MCAI Canadian Airworthiness Directive CF-2008-25, dated July 3, 2008, and Bombardier Service Bulletin 670BA-24-011, Revision C, dated November 28, 2005, for related information.

Issued in Renton, Washington, on September 12, 2008. 

Michael Kaszycki, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. E8-22218 Filed 9-22-08; 8:45 am] 

BILLING CODE 4910-13-P