AD 94-15-09

This amendment adopts a new airworthiness directive (AD) that is applicable to all Aerospatiale Model ATR72 series airplanes. This action requires inspections to detect damage, corrosion, or cracking of the hinge pin on each shock absorber on the main landing gear (MLG), and repair or replacement of the pins, if necessary. This amendment is prompted by reports of rupture of certain hinge pins due to stress corrosion of the pins in the shock absorber on the MLG on Model ATR72 series airplanes. The actions specified in this AD are intended to prevent loss of the MLG during a hard landing due to malfunction of the shock absorber on the MLG.

Final rule; request for comments.

94-15-09 AEROSPATIALE: Amendment 39-8980. Docket 94-NM-95-AD.

Applicability: All Model ATR72 series airplanes, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent loss of the main landing gear (MLG) during a hard landing, accomplish the following:

(a) Perform a visual inspection (using a borescope) to detect damage to the protective treatments on the inside diameter of the upper hinge pins on each shock absorber on the MLG, in accordance with Messier-Bugatti Service Bulletin 631-32-099, dated April 12, 1994, at the time specified in paragraph (a)(1), (a)(2), or (a)(3) of this AD, as applicable. Repeat this inspection thereafter at intervals not to exceed 4,000 landings.

(1) For airplanes on which the MLG has accumulated more than 9,000 total landings as of the effective date of this AD: Inspect within 300 landings after the effective date of this AD.

(2) For airplanes on which the MLG has accumulated 6,000 or more total landings but less than or equal to 9,000 total landings as of the effective date of this AD: Inspect prior to the accumulation of 9,300 total landings, or within 1,000 landings after the effective date of this AD, whichever occurs first.

(3) For airplanes on which the MLG has accumulated less than 6,000 total landings as of the effective date of this AD: Inspect prior to the accumulation of 7,000 total landings, or within 3,000 landings after the effective date of this AD, whichever occurs later.

(b) If no damaged protective treatment is found, prior to further flight, reinstall the grease duct and fill the cavity between the pin and the grease duct with grease in accordance with Messier-Bugatti Service Bulletin 631-32-099, dated April 12, 1994. Thereafter, perform the repetitive inspections required by paragraph (a) of this AD.

(c) If any damaged protective treatment is found, prior to further flight, strip the damaged protective treatment to determine if the base metal is corroded, in accordance with Messier-Bugatti Service Bulletin 631-32-099, dated April 12, 1994.

(1) If no corrosion of the base metal is found, within 250 landings, complete a paint scheme of the damaged area, reinstall the grease duct, and fill the cavity between the pin and the grease duct with grease in accordance with the service bulletin. Thereafter, perform the repetitive inspections required by paragraph (a) of this AD.

(2) If any corrosion of the base metal is found, prior to further flight, remove the corrosion, and perform a dye penetrant or a fluorescent penetrant inspection to detect cracking of the pin, in accordance with the service bulletin.

(i) If no crack is found, accomplish either paragraph (c)(2)(i)(A) or (c)(2)(i)(B) of this AD in accordance with the service bulletin. Thereafter, perform the repetitive inspections required by paragraph (a) of this AD.

(A) Prior to further flight, repair the hinge pin; or

(B) Within 50 landings after performing the inspection required by paragraph (c)(2) of this AD, replace the hinge pin with a serviceable pin.

(ii) If any crack is found, prior to further flight, replace the hinge pin with a serviceable pin in accordance with the service bulletin. Thereafter, perform the repetitive inspections required by paragraph (a) of this AD.

(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Standardization Branch, ANM-113.

NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

(e) Specialflight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

(f) The actions shall be done in accordance with Messier-Bugatti Service Bulletin 631- 32-099, dated April 12, 1994. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Technical Publications Department, Messier-Eram, Zone Aeronautique Luis Breget, B.P. 10, 78142 Velizy Cedex, France. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(g) This amendment becomes effective on August 8, 1994.

The Direction G n rale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, recently notified the FAA that an unsafe condition may exist on all Aerospatiale Model ATR72 series airplanes. The DGAC advises that it has received reports of rupture of the upper hinge pins in the shock absorber on the main landing gear (MLG) on Model ATR72 series airplanes. Investigation revealed that these hinge pins ruptured due to stress corrosion inside the pin. Corrosion inside the hinge pins, if not detected and corrected in a timely manner, could result in malfunction of the shock absorber on the MLG. This condition, if not corrected, could result in loss of the MLG during a hard landing.

Avions de Transport Regional (ATR) has issued Service Bulletin ATR72-32-1025, dated April 5, 1994. This service bulletin references Messier-Bugatti Service Bulletin 631-32-099, dated April 12, 1994, for additional service information. The Messier-Bugattiservice bulletin describes procedures for repetitive visual inspections (using a borescope) to detect damage to the protective treatments on the inside diameter of the hinge pin on each shock absorber on the MLG. The service bulletin describes procedures for stripping any damaged protective treatments to determine if the base metal is corroded, completing a paint scheme of the damaged area, and reinstalling any pin on which no corrosion of the base metal is found. For pins on which the base metal is corroded, the service bulletin describes procedures for removal of the corrosion and a dye penetrant or fluorescent penetrant inspection to detect cracking of the pin; repair or replacement of any uncracked pin; and replacement of any cracked pin with a serviceable pin.

The DGAC classified these service bulletins as mandatory and issued French Airworthiness Directive 94-065-020(B), dated March 30, 1994, in order to assure the continued airworthiness of these airplanes in France.

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. The FAA has examined the findings of the DGAC, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, this AD is being issued to prevent loss of the MLG during a hard landing. This AD requires repetitive visual inspections (using a borescope) to detect damage to the protective treatments on the inside diameter of the hinge pin on each shock absorber onthe MLG. This AD also requires stripping any damaged protective treatments to determine if the base metal is corroded. For pins on which the base metal is not corroded, this AD requires completion of a paint scheme of the damaged area and reinstallation of the pin. For pins on which the base metal is corroded, this AD requires removal of the corrosion and a dye penetrant or fluorescent penetrant inspection to detect cracking of the pin; repair or replacement of any uncracked pin; and replacement of any cracked pin with a serviceable pin. The actions are required to be accomplished in accordance with the Messier-Bugatti service bulletin described previously.

Messier-Bugatti advises that a modification of the link between the shock absorber and the universal joint is currently under study. Therefore, this AD is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking.

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectivenessof the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 94-NM-95-AD." The postcard will be date stamped and returned to the commenter.

The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or onthe distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (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. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.
39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: