E6-18573. Airworthiness Directives; Bombardier Model DHC-8-400 Series Airplanes

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 Bombardier Model DHC-8-400 series airplanes. This proposed AD would require inspecting to determine the manufacturer's date of certain V-band clamps on the engine exhaust shroud assembly, and doing related investigative/corrective actions if necessary. This proposed AD results from a report of a discrepancy found during a maintenance inspection on a V-band clamp located on the engine exhaust duct shroud. The clamp ends were touching (although the correct fastener torque had been applied), resulting in reduced clamp force on the flanges. We are proposing this AD to prevent vibration in the duct shroud and fretting of the V-band clamp and flanges, which could result in cracking of the flanges and consequent release of hot exhaust gases from the engine tailpipe and damage to adjacent structure. This situation could trigger the fire warning system and result in an in-flight emergency, such as the flightcrew shutting down the engine and activating the fire suppression system.

DATES:

We must receive comments on this proposed AD by December 4, 2006.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD.

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC 20590.
• Fax: [phone].
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

Contact Bombardier, Inc., Bombardier Regional Aircraft Division, 123 Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada, for service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT:

Richard Fiesel, Aerospace Engineer, Airframe and Propulsion Branch, ANE-171, FAA, New York Aircraft Certification Office, 1600 Stewart Avenue, Suite 410, Westbury, New York 11590; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the ADDRESSES section. Include the docket number “FAA-2006-26241; Directorate Identifier 2006-NM-155-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that Web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov.

Examining the Docket

You may examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone [phone]) is located on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the Docket Management System receives them.

Discussion

Transport Canada Civil Aviation (TCCA), which is the airworthiness authority for Canada, notified us that an unsafe condition may exist on certain Bombardier Model DHC-8-400 series airplanes. TCCA advises of a report of a discrepancy found during a maintenance inspection on a V-band clamp located on the engine exhaust duct shroud. The clamp ends were touching (although the correct fastener torque had been applied), resulting in reduced clamp force on the flanges. Investigation revealed that a batch of V-band clamps were not manufactured to the drawing specifications. These clamps may cause vibration and fretting of the V-band clamp flanges to occur, leading to flange cracking and local area overheating. These conditions, if not corrected, could result in cracking of the flanges and consequent release of hot exhaust gases from the engine tailpipe and damage to adjacent structure. This situation could trigger the fire warning system and result in an in-flight emergency, such as the flightcrew shutting down the engine and activating the fire suppression system.

Relevant Service Information

Bombardier has issued Service Bulletin 84-78-01, Revision ‘A,’ dated September 15, 2005. The service bulletin describes procedures for inspecting to determine the manufacturer's date of certain V-band clamps on the engine exhaust shroud assembly, and doing related investigative and corrective actions if necessary. The related investigative action is measuring the gap between the clamp loops at the T-bolt and trunnion. The related corrective actions are as follows:

• If both clamp loops touch when the clamp is tightened to the specified torque value: Replace the V-band clamp with a serviceable clamp.
• If the gap between the clamp loops is less than 0.050 inch when the clamp is tightened to the specified torque value: Replace the V-band clamp on or before the next C-check.

The corrective actions also include inspecting the flange of the shroud assemblies for any of the following discrepancies:

• Indication(s) of exhaust gas leakage.
• Damage to surrounding structure or adjacent assemblies as a result of gas leakage.
• Indication(s) of chafing, fretting, or cracking at the flanges of the related shrouds.

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition. TCCA mandated the service information and issued Canadian airworthiness directive CF-2006-06, dated April 4, 2006, to ensure the continued airworthiness of these airplanes in Canada.

FAA's Determination and Requirements of the Proposed AD

These airplane models are manufactured in Canada and are type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, TCCA has kept the FAA informed of the situation described above. We have examined TCCA's findings, evaluated all pertinent information, and determined that we need to issue an AD for airplanes of this type design that are certificated for operation in the United States.

Therefore, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between the Proposed AD and Service Information.”

Differences Between the Proposed AD and Service Information

The service bulletin specifies to contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require repairing those conditions using a method that we or TCCA (or its delegated agent) approve. In light of the type of repair that would be required to address the unsafe condition, and consistent with existing bilateral airworthiness agreements, we have determined that, for this proposed AD, a repair we or TCCA approve would be acceptable for compliance with this proposed AD.

The service bulletin specifies replacing the V-band clamp “on or before the next C-check” as part of the corrective actions. This proposed AD would require doing all corrective actions before further flight.

Costs of Compliance

This proposed AD would affect about 21 airplanes of U.S. registry. The proposed actions would take about 3 work hours per airplane, at an average labor rate of $80 per work hour. Required parts cost would be minimal. Based on these figures, the estimated cost of the proposed AD for U.S. operators is $5,040, or $240 per airplane.

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):

Bombardier, Inc. (Formerly de Havilland, Inc.): Docket No. FAA-2006-26241; Directorate Identifier 2006-NM-155-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by December 4, 2006.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Bombardier Model DHC-8-400 series airplanes, certificated in any category; as identified in Bombardier Service Bulletin 84-78-01, Revision ‘A,’ dated September 15, 2005.

Unsafe Condition

(d) This AD results from a report of a discrepancy found during a maintenance inspection on a V-band clamp located on the engine exhaust duct shroud. The clamp ends were touching (although the correct fastener torque had been applied), resulting in reduced clamp force on the flanges. We are issuing this AD to prevent vibration in the duct shroud and fretting of the V-band clamp and flanges, which could result in cracking of the flanges and consequent release of hot exhaust gases from the engine tailpipe and damage to adjacent structure. This situation could trigger the fire warning system and result in an in-flight emergency, such as the flightcrew shutting down the engine and activating the fire suppression system.

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.

Inspection/Investigative and Corrective Actions

(f) Within 5,000 flight hours after the effective date of this AD: Inspect to determine the part number (P/N) of the V-band clamps on the engine exhaust duct shroud in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-78-01, Revision ‘A,’ dated September 15, 2005. For any V-band clamp having P/N VC1642A-2030-A or VC1642A-1875-A, before further flight, determine the manufacturer's date and do all applicable related investigative and corrective actions (including inspecting the flange of the shroud assemblies for discrepancies), by accomplishing all the actions specified in the Accomplishment Instructions of the service bulletin; except as provided by paragraph (g) of this AD. Do all applicable related investigative and corrective actions before further flight.

(g) If, during the accomplishment of the corrective actions required by paragraph (f) of this AD, the service bulletin specifies contacting the manufacturer for repair instructions, before further flight, repair in accordance with a method approved by either the Manager, New York Aircraft Certification Office (ACO), FAA; or Transport Canada Civil Aviation (TCCA) (or its delegated agent).

Actions Accomplished According to Previous Issue of Service Bulletin

(h) Actions accomplished before the effective date of this AD according to Bombardier Service Bulletin 84-78-01, dated March 22, 2005, are considered acceptable for compliance with the corresponding actions specified in paragraph (f) of this AD.

Parts Installation

(i) As of the effective date of this AD, no person may install a V-band clamp, P/N VC1642A-2030-A or VC1642A-1875-A, with a manufacturer batch stamp dated before “08-02,” on any airplane.

Alternative Methods of Compliance (AMOCs)

(j)(1) The Manager, New York ACO, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19.

(2) Before using any AMOC approved in accordance with § 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office.

Related Information

(k) Canadian airworthiness directive CF-2006-06, dated April 4, 2006, also addresses the subject of this AD.

Issued in Renton, Washington, on October 26, 2006.

Kalene C. Yanamura,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.