Airworthiness Directives; Aerospatiale Model ATR72 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-95-AD; Amendment 39-8980; AD 94-15-09]

Airworthiness Directives; Aerospatiale Model ATR72 Series

Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: 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.

DATES: Effective August 8, 1994. The incorporation by reference of

certain publications listed in the regulations is approved by the

Director of the Federal Register as of August 8, 1994.

Comments for inclusion in the Rules Docket must be received on or

before September 20, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-103,

Attention: Rules Docket No. 94-NM-95-AD, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056.

The service information referenced in this AD may be obtained from

Technical Publications Department, Messier-Eram, Zone Aeronautique Luis

Breget, B.P. 10, 78142 Velizy Cedex, France. This information may be

examined 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.

FOR FURTHER INFORMATION CONTACT: Sam Grober, Aerospace Engineer,

Standardization Branch, ANM-113, FAA, Transport Airplane Directorate,

1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206)

227-1187; fax (206) 227-1320.

SUPPLEMENTARY INFORMATION: The Direction Generale 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-Bugatti service 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 on the 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 effectiveness of 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 on the 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.

Air transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

List of Subjects in 14 CFR Part 39

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:

Adoption of the Amendment

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.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

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) Special flight 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.

Issued in Renton, Washington, on July 15, 1994.

S.R. Miller,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-17766 Filed 7-21-94; 8:45 am]

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