AD 94-02-07

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AD Number:
94-02-07
Document Type:
AD Final Rules
Docket Number:
93-NM-67-AD
Subject Heading:
Airworthiness Directives; McDONNELL DOUGLAS MD-11 Series Airplanes
Subject:
Center Gear Drag Link
Status:
Current
Citation:
This information is not available.
Citation Publish Date:
Effective Date:
02/28/1994
Make:
The Boeing Company
Model:
MD-11 | MD-11F
Product Type:
Aircraft
Product Subtype:
Large Airplane
Affected AD:
Superseded AD:
Affected By:
Superseded By:
Service/Office:
Office of Primary Responsibility:
CFR Part Reference:
Part 39
Comments:
AIRWORTHINESS DIRECTIVES FINAL RULES: 94-02-07
CITATION:   This information is not available.

PAGE NUMBER:  

DOCKET NUMBER:   93-NM-67-AD

AMENDMENT:   39-8805

AD NUMBER:   94-02-07

SUBJECT HEADING:   Airworthiness Directives; McDONNELL DOUGLAS MD-11 Series Airplanes

ACTION:   Final rule.

SUMMARY:   This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model MD-11 series airplanes, that requires replacing the anti-skid control unit. This amendment is prompted by three reports of failure of the center landing gear drag link, after which the center landing gear swung aft and struck the fuselage. The actions specified by this AD are intended to prevent failure of the center landing gear drag link, which could result in extensive damage to the fuselage structure.

DATES:   Effective February 28, 1994. The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of February 28, 1994.

ADDRESSES:   The service information referenced in this AD may be obtained from McDonnell Douglas Corporation, P.O. Box 1771, Long Beach, California 90801-1771, Attention: Business Unit Manager, Technical Publications - Technical Administrative Support, C1-L5B. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Transport Airplane Directorate, Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT:   Andrew Gfrerer, Aerospace Engineer, Systems and Equipment Branch, ANM-131L, FAA, Transport Airplane Directorate, Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California 90806-2425; telephone (310) 988-5338; fax (310) 988-5210.

SUPPLEMENTARY INFORMATION:   A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model MD-11 series airplanes was published in the Federal Register on July 16, 1993 (58 FR 38321). That action proposed to require replacing the anti-skid control unit.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

One commenter supports the proposal.

One commenter suggests that the proposed AD action is inappropriate for two reasons:

1. Drag link failures occur only with the use of autobraking. Therefore, if only manual brakes are used, there should be no requirement to modify the anti-skid control unit.

2. Failure of the center landing gear drag link does not pose sufficient risk to the airframe to warrant AD action.

The FAA does not concur with the commenter's suggestion that this AD action is not warranted. As for the commenter's Item 1, the FAA points out that there has been at least one case of failure of the center gear with the application of manual brakes prior to touchdown of the nose gear wheel. By replacing the Part Number (P/N) 6005304-1 control unit with the P/N 6005304-2 unit (as required by this AD), center gear braking is inhibited both manually and through the use of autobrakes until nose gear touchdown.

As for the commenter's Item 2, the FAA notes that there have been at least three in-service failures of center landing gear drag links that have caused significant structural damage to the airplane. In each occurrence, the failed drag link allowed the center landing gear to swing aft and strike the fuselage. Additionally, there are numerous other possible scenarios involving similar failures that could result in damage to the hydraulic and electrical systems of the airplane. The center landing gear is also needed to properly distribute the airplane's weight for heavy weight landings. For these reasons, the FAA considers that failure of the center landing gear drag link does present an unsafe condition sufficient to warrant mandated corrective action. The appropriate vehicle for mandating such corrective action is the airworthiness directive.

Two commenters request that the proposed compliance time of 9 months be extended to 12 months. The manufacturer has indicated that the fleet of affected Model MD-11's could not be retrofitted within 9 months, given the current schedule of modifying the subject part on a rotatable basis and the capacity of the manufacturer to modify the control units. The FAA concurs with the commenter's request. Extending the compliance time an additional 3 months will not adversely affect safety and will allow the affected fleet to be modified in an orderly manner, thereby minimizing the costs associated with special airplane scheduling. Paragraph (a) of the final rule has been revised to specify a compliance time of 12 months.

One commenter requests that the wording of references to the anti-skid control unit be clarified. The preamble to the notice referred to "the anti-skid control unit for the center landing gear;" however, this control unit controls all of the landing gears, not just the center landing gear. The FAA agrees that clarification of this point is needed and, where appropriate, has changed the wording in this final rule accordingly.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

There are approximately 86 McDonnell Douglas Model MD-11 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 32 airplanes of U.S. registry will be affected by this AD, that it will take approximately 1 work hour per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Required parts will be provided by the manufacturer at no cost to the operator. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $1,760, or $55 per airplane. This total cost figure assumes that no operator has yet accomplished the requirements of this AD.

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.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under 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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it 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 14 CFR part 39 of the Federal Aviation Regulations 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:

REGULATORY TEXT:   94-02-07 McDONNELL DOUGLAS: Amendment 39-8805. Docket 93-NM-67-AD.

Applicability: Model MD-11 series airplanes, as listed in McDonnell Douglas MD-11 Service Bulletin 32-30, dated March 3, 1993; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent potential failure of the center gear drag link, which could lead to extensive damage to the fuselage structure, accomplish the following:

(a) Within 12 months after the effective date of this AD, replace the anti-skid control unit, part number 6005304-1, with a new anti-skid control unit, part number 6005304-2, in accordance with McDonnell Douglas MD-11 Service Bulletin 32-30, dated March 3, 1993.

(b) 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, Los Angeles Certification Office (ACO), 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, Los Angeles ACO.

NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles ACO.

(c) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished.

(d) The replacement shall be done in accordance with McDonnell Douglas MD-11 Service Bulletin 32-30, dated March 3, 1993. 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 McDonnell Douglas Corporation, P.O. Box 1771, Long Beach, California 90801-1771, Attention: Business Unit Manager, Technical Publications - Technical Administrative Support, C1-L5B. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Transport Airplane Directorate, Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(e) This amendment becomes effective on February 28, 1994.

FOOTER: