Airworthiness Directives; Aerospatiale Model ATR72 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 Aerospatiale Model ATR72 airplanes. This proposed AD would require a one-time general visual inspection for contamination of the surface of the upper arms of the main landing gear (MLG) secondary side brace assemblies; and repetitive eddy current inspections for cracking of the upper arms, and related specified and corrective actions if necessary. This proposed AD also would mandate eventual replacement of aluminum upper arms with steel upper arms, which would end the repetitive inspections. This proposed AD is prompted by two reports of rupture of the upper arm of the MLG secondary side brace due to fatigue cracking. We are proposing this AD to prevent cracking of the upper arms of the secondary side brace assemblies of the MLG, which could result in collapse of the MLG during takeoff or landing, damage to the airplane, and possible injury to the flightcrew and passengers.

DATES:

We must receive comments on this proposed AD by August 22, 2005.

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.
• By fax: (202) 493-2251.
• 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.

For service information identified in this proposed AD, contact Aerospatiale, 316 Route de Bayonne, 31060 Toulouse, Cedex 03, France.

You can examine the contents of this AD docket on the Internet at http://dms.dot.gov , or in person at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., room PL-401, on the plaza level of the Nassif Building, Washington, DC. This docket number is FAA-2005-21909; the directorate identifier for this docket is 2005-NM-059-AD.

FOR FURTHER INFORMATION CONTACT:

Tom Rodriguez, Aerospace Engineer, International Branch, ANM-116, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1137; fax (425) 227-1149.

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 under ADDRESSES. Include “Docket No. FAA-2005-21909; Directorate Identifier 2005-NM-059-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 submitted 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 our docket 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 can review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you can visit http://dms.dot.gov .

Examining the Docket

You can 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 (800) 647-5227) 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 (DMS) receives them.

Discussion

The Direction Générale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, notified us that an unsafe condition may exist on certain Aerospatiale Model ATR72 airplanes. The DGAC advises that there were two reports of rupture of the upper arm of the main landing gear (MLG) secondary side brace assembly. Fatigue cracking has been determined to be the cause of the ruptures. This cracking, if not corrected, could result in collapse of the MLG during takeoff or landing, damage to the airplane, and possible injury to the flightcrew and passengers.

Relevant Service Information

Messier-Dowty has issued Special Inspection Service Bulletin 631-32-178, Revision 1, dated September 30, 2004. The service bulletin describes procedures for, among other things, a one-time general visual inspection for contamination of the surface of the upper arms of the MLG secondary side brace assemblies, and an eddy current inspection for cracking of the upper arms. The service bulletin also recommends sending an inspection report to Messier-Dowty.

Aerospatiale has issued Avions de Transport Regional Service Bulletin ATR72-32-1046, Revision 1, dated October 7, 2004. The service bulletin contains no Accomplishment Instructions, but describes procedures for replacing the upper arms of the MLG secondary side brace assemblies. The service bulletin refers to Messier-Dowty Service Bulletin 631-32-183, dated October 6, 2004, as the source of service information for accomplishing the replacement. Service Bulletin 631-32-183 describes procedures for replacing aluminum upper arms of the MLG secondary side brace assemblies with steel upper arms, and engraving a new suffix on the identification plate on the assembly.

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition. The DGAC mandated the service information and issued French airworthiness directive F-2004-164, dated October 13, 2004, to ensure the continued airworthiness of these airplanes in France.

The French airworthiness directive refers to Messier-Bugatti Service Bulletin 631-32-085, dated August 21, 1992, as the source of service information for replacing the press-fitted ball cages of the lower and upper arms of the MLG secondary side brace assemblies with ball cages that are shrink-fitted and bonded with adhesive. For airplanes on which this replacement has been accomplished, the compliance time for the replacement of the aluminum upper arms is extended.

FAA's Determination and Requirements of the Proposed AD

This airplane model is manufactured in France and is 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, the DGAC has kept the FAA informed of the situation described above. We have examined the DGAC's findings, evaluated all pertinent information, and determined that we need to issue an AD for products 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 Avions de Transport Regional Service Bulletin ATR72-32-1046, Revision 1; Messier-Dowty Special Inspection Service Bulletin 631-32-178, Revision 1; and Messier-Dowty Service Bulletin 631-32-183; described previously; except as discussed under “Differences Between the Proposed AD and Messier-Dowty Special Inspection Service Bulletin 631-32-178.” In addition, this proposed AD would require, for replacement of aluminum upper arms, an eddy current inspection and investigative or corrective actions. Replacement with steel arms would end the repetitive inspections, and replacement with aluminum arms would require repeating the eddy current inspections.

Differences Among Proposed AD, French Airworthiness Directive, and Messier-Dowty Service Information

Although the French airworthiness directive requires replacing any defective upper arm of the MLG secondary side brace assemblies with a new or serviceable aluminum arm, or a new steel arm, there are no procedures specified in Service Bulletin 631-32-183 for replacing the defective arm with an aluminum arm. The service bulletin does reference the ATR Component Maintenance Manual (CMM), Chapter 32-18-41, Revision 3, dated September 30, 2002, for procedures for replacing the affected arm with a new steel arm. Therefore, this proposed AD will reference the CMM for procedures for replacement of any defective aluminum upper arm with a new or serviceable aluminum upper arm. Chapter 32-18-41 provides procedures for replacement of affected upper arms with either steel or aluminum upper arms. This difference has been coordinated with the DGAC.

Special Inspection Service Bulletin 631-32-178, Revision 1, recommends sending an inspection report to Messier-Dowty, but this proposed AD does not contain that requirement.

Special Inspection Service Bulletin 631-32-178, Revision 1, refers only to a “visual inspection” for contamination of the surface. We have determined that the procedures in the service bulletin should be described as a “general visual inspection.” A note has been included in this AD to define this type of inspection.

Costs of Compliance

This proposed AD would affect about 18 airplanes of U.S. registry.

The proposed initial and repetitive inspections would take about 1 work hour per airplane, at an average labor rate of $65 per work hour. Based on these figures, the estimated cost of the proposed inspections for U.S. operators is $1,170, or $65 per airplane, per inspection cycle.

The proposed replacement would take about 4 work hours per airplane (2 work hours per upper arm), at an average labor rate of $65 per work hour. Required parts would cost about $4,948 per airplane ($2,474 per upper arm). Based on these figures, the estimated cost of the proposed replacement for U.S. operators is $93,744, or $5,208 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. 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.