[Federal Register Volume 59, Number 77 (Thursday, April 21, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-8175]


[[Page Unknown]]

[Federal Register: April 21, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-20-AD; Amendment 39-8874; AD 94-08-03]

 

Airworthiness Directives; McDonnell Douglas Model MD-11 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain McDonnell Douglas Model MD-11 series airplanes, 
that requires visual inspection to detect inward buckling of the left 
and right main landing gear (MLG) pistons, and modification or 
replacement of the rebound check valves with new valves. If inward 
buckling is detected, this AD also requires replacement of the MLG 
piston with a serviceable piston. This amendment is prompted by 
failures of the MLG piston on Model DC-10 series airplanes. The actions 
specified by this AD are intended to prevent failure of the MLG piston 
and the subsequent reduced controllability of the airplane during 
landing.

DATES: Effective May 23, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of May 23, 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 
Administrative Support, Department L51, M.C. 2-98. 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: Maureen Moreland, Aerospace Engineer, 
Airframe Branch, ANM-121L, FAA, Transport Airplane Directorate, Los 
Angeles Aircraft Certification Office, 3229 East Spring Street, Long 
Beach, California 90806-2425; telephone (310) 988-5238; 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 September 29, 1993 (58 FR 
50871). That action proposed to require visual inspection to detect 
inward buckling of the left and right main landing gear (MLG) pistons, 
and modification or replacement of the rebound check valves with new 
valves. If inward buckling is detected, that action also proposed to 
require replacement of the MLG piston with a serviceable piston.
    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 proposed rule.
    One commenter, the Air Transport Association (ATA) of America, on 
behalf of one of its member operators, objects to the proposed 
requirement to modify or replace rebound check valves on the MLG 
pistons with new valves. This commenter suggests that the requirement 
is unnecessary, due to the fact that the piston assemblies installed on 
the Model MD-11 series airplanes are substantially stronger than those 
installed on the Model DC-10 series airplanes. The FAA does not concur 
that this rule is unnecessary. Although the pistons installed on Model 
MD-11 series airplanes are generally stronger than those installed on 
Model DC-10 series airplanes, the FAA has reviewed an analysis 
conducted by the manufacturer, which supports the FAA's finding that 
the thicker piston walls (a few thousandths of an inch) on pistons 
installed on Model MD-11 series airplanes will not adequately prevent 
inward buckling of MLG pistons. Model MD-11 series airplanes have a 
higher maximum landing weight than Model DC-10 series airplanes. Under 
certain conditions, these higher landing weights result in higher 
pressure loads in the rebound chamber. Therefore, the FAA has 
determined that the installation of new or modified rebound check 
valves will prevent failure of MLG pistons and the subsequent reduced 
controllability of the airplane during landing.
    Several commenters request extensions of the proposed two-year 
compliance time. One of these commenters requests that the proposed 
compliance time be extended to eight years, which would allow operators 
to accomplish the proposed modification or replacement of the rebound 
check valves coincidentally with the operator's regularly scheduled 
maintenance (``D'' check) at which time the MLG would be scheduled to 
be changed. Another commenter requests that the compliance time 
coincide with AD 92-27-18, Amendment 39-8453 (58 FR 5259, January 21, 
1993), which is applicable to certain DC-10 series airplanes, to 
require visual inspection to detect inward buckling of the left and 
right MLG pistons, and modification or replacement of the rebound check 
valves with new valves.
    The FAA does not concur with these commenters' request to extend 
the compliance time. The FAA has determined that the compliance time, 
as proposed, represents the maximum interval of time allowable for the 
affected airplanes to continue to operate prior to accomplishing the 
required modification or replacement of the rebound check valves 
without compromising safety. Additionally, the FAA finds that the 
integrity of the MLG cannot be ensured for a period of eight years 
without modifying or replacing the rebound check valves. Further, in 
light of the reported incident during which the MLG piston on a Model 
DC-10-10 series airplane failed, and the safety implications of a 
failed MLG piston and the subsequent reduced controllability of the 
airplane during landing, the FAA finds that an extension of the 
compliance time would adversely affect safety of the affected 
airplanes. Although the MLG's installed on Model DC-10 series airplanes 
and Model MD-11 series airplanes are similar in basic design, the 
ultimate strength capability of the MLG's differ significantly. In 
developing the compliance time of 24 months, the FAA based its finding 
upon, among other factors, the potential of the affected airplanes to 
be exposed to conditions that may result in buckling of the MLG 
pistons. The FAA finds that the higher landing maximum weights of the 
Model MD-11 series airplanes may result in higher pressure loads in the 
rebound chamber, which may result in a greater rate of failure on these 
MLG's. Therefore, the FAA finds the 24-month compliance time 
justifiable and appropriate to address this unsafe condition.
    Several commenters note that the economic impact information in the 
proposal was inaccurate. One of these commenters states that the FAA's 
estimate of 9.5 work hours per airplane to accomplish the proposed 
actions is extremely low. One operator estimates that its cost to 
implement the actions proposed by this AD will be approximately 
$65,000. One commenter states that a more accurate estimation would be 
30 work hours, as is specified in McDonnell Douglas MD-11 Service 
Bulletin 32-19, Revision 1, dated August 12, 1993 (referenced in the 
proposal as the appropriate source of service information). The FAA 
concurs, in part, with these commenters observations. The approximate 
number of work hours required to accomplish the required actions, which 
was presented in the economic impact information of the notice, was 
provided to the FAA by the manufacturer, and was based on the best data 
available at that time. The FAA now recognizes that the number used in 
the proposal did not include the .5 work hour required to inspect the 
MLG pistons, although it did include the time required to modify and 
install the rebound check valves. In light of this, the number of work 
hours in the economic impact information, below, has been increased to 
10 work hours. The cost analysis in AD rulemaking actions typically 
does not include planning time, aircraft preparation time, time to gain 
access and remove parts, or time to raise and lower the aircraft; 
accordingly, the cost estimate, below, does not include this data.
    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 63 Model MD-11 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 22 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 10 work hours per airplane to accomplish the 
required actions, and that the average labor rate is $55 per work hour. 
Required parts will cost approximately $1,251 per airplane. Based on 
these figures, the total cost impact of the AD on U.S. operators is 
estimated to be $39,622, or $1,801 per airplane.
    The total cost impact figure discussed above is based on 
assumptions that no operator has yet accomplished any of the 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.
    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.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

94-08-03 McDonnell Douglas: Amendment 39-8874. Docket 93-NM-20-AD.

    Applicability: Model MD-11 series airplanes, as listed in 
McDonnell Douglas MD-11 Service Bulletin 32-19, Revision 1, dated 
August 12, 1993, certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the main landing gear (MLG) piston and the 
subsequent reduced controllability of the airplane during landing, 
accomplish the following:
    (a) Within 2 years after the effective date of this AD, perform 
a visual inspection to detect inward buckling of the left and right 
MLG pistons, in accordance with McDonnell Douglas MD-11 Service 
Bulletin 32-19, Revision 1, dated August 12, 1993.
    (1) If any piston is found to be buckled inwardly, prior to 
further flight, accomplish the requirements of paragraphs (a)(1)(i) 
and (a)(1)(ii) of this AD, in accordance with McDonnell Douglas MD-
11 Service Bulletin 32-19, Revision 1, dated August 12, 1993:
    (i) Replace that MLG piston with a serviceable piston; and
    (ii) Modify or replace the rebound check valves with new valves.
    (2) If no piston is found to be buckled inwardly, prior to 
further flight, modify or replace the rebound check valves with new 
valves in accordance with McDonnell Douglas MD-11 Service Bulletin 
32-19, Revision 1, dated August 12, 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 Aircraft 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 
Federal Aviation Regulations (FAR) 21.197 and 21.199 to operate the 
airplane to a location where the requirements of this AD can be 
accomplished.
    (d) The inspection, replacement, and modification shall be done 
in accordance with McDonnell Douglas MD-11 Service Bulletin 32-19, 
Revision 1, dated August 12, 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 
Administrative Support, Department L51, M.C. 2-98. 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 ACO, 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 May 23, 1994.

    Issued in Renton, Washington, on March 31, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-8175 Filed 4-20-94; 8:45 am]
BILLING CODE 4910-13-U