[Federal Register Volume 59, Number 95 (Wednesday, May 18, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-10115]


[[Page Unknown]]

[Federal Register: May 18, 1994]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-164-AD; Amendment 39-8902; AD 94-09-13]

 

Airworthiness Directives; Boeing Model 747 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 Boeing Model 747 series airplanes, that requires 
replacement of certain pneumatic duct couplings with redesigned 
couplings. This amendment is prompted by reports of failures of certain 
duct couplings installed on the wing leading edge pneumatic duct. The 
actions specified by this AD are intended to prevent such failures, 
which could lead to structural damage to the wing leading edge, flight 
control problems, or fire.

DATES: Effective June 17, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of June 17, 1994.

ADDRESSES: The service information referenced in this AD may be 
obtained from PTI Technologies, Inc., 950 Rancho Conejo Boulevard, 
Newbury Park, California 91320. 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 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Barbara Mudrovich, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane 
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, 
SW., Renton, Washington 98055-4056; telephone (206) 227-2670; fax (206) 
227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations to include an airworthiness directive (AD) that is 
applicable to certain Boeing Model 747 series airplanes was published 
in the Federal Register on December 9, 1993 (58 FR 64707). That action 
proposed to require replacement of certain pneumatic duct couplings 
installed on the wing leading edge pneumatic duct.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    Two commenters support the proposal.
    One commenter requests that the proposal be revised to permit 
operators to perform repetitive dye penetrant inspections to detect 
fatigue cracking of the duct couplings at intervals of 15 months, in 
lieu of the proposed mandatory replacement of the couplings at 15 
months. This commenter states that it has found only one failure of a 
duct coupling, but the failed coupling was at a location different from 
that addressed by the proposal. Additionally, the commenter found 
excess misalignment of the pneumatic ducts at the location of the 
failed duct, and considers that this situation contributed to the 
coupling failure. The commenter has already performed a dye penetrant 
inspection of the wing leading edge pneumatic duct couplings on its 
fleet of affected airplanes, but has found no fatigue cracking. The FAA 
does not concur with the commenter's request for several reasons. 
First, dye penetrant inspections have not been shown to be a reliable 
method for detecting cracks in the couplings. Second, the couplings in 
the vicinity of the struts (addressed by this AD action) are of highest 
concern, because of the increased risk of damage in that area, should a 
duct burst. Third, the misalignment referred to by the commenter has 
been found to be associated with maintenance activity; this problem has 
been addressed with improved installation instructions that have been 
added recently to the Model 747 Maintenance Manual. While misalignment 
has been shown to be a contributing factor in the coupling failures, 
fatigue cracking is the main concern. The new design couplings that 
were installed on airplanes beginning at line number 220, and that are 
required to be installed in accordance with this AD, have not exhibited 
any fatigue or other failures. In light of these items, the FAA has 
determined that installation of the new design couplings is both 
appropriate and warranted.
    Another commenter requests that the proposal be revised to include 
the option of performing an aided visual inspection of the subject 
couplings within 15 months and replacement of the couplings within 24 
months. The FAA does not concur. The FAA does not consider a visual 
inspection to be adequate for detecting critical cracks in the 
couplings, even as an interim measure. The FAA has determined that 
replacement of the couplings with the new design couplings is the only 
method to effectively address the unsafe condition presented by failure 
of the subject couplings.
    One commenter requests that the proposed compliance time of 15 
months be extended to 18 months in order to allow the replacement to be 
accomplished during the time of this commenter's regularly scheduled 
``C'' check. The commenter states that the adoption of the proposed 
compliance time of 15 months would require that special times be 
scheduled for the accomplishment of this replacement, at additional 
expense. The FAA does not concur. The proposed compliance time was 
selected based on the average ``C'' check interval for the majority of 
affected operators. It was also selected based on the degree of urgency 
associated with addressing the subject unsafe condition, the 
availability of required parts, and the practical aspect of replacing 
the required parts within a maximum interval of time allowable for all 
affected airplanes to continue to operate without compromising safety. 
In light of these items, the FAA has determined that 15 months for 
compliance is appropriate. However, paragraph (b) of the final rule 
does provide affected operators the opportunity to apply for an 
adjustment of the compliance time if sufficient data are presented to 
justify such an adjustment.
    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 as proposed.
    There are approximately 219 Model 747 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 132 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 12 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 $8,486 per airplane. Based on 
these figures, the total cost impact of the AD on U.S. operators is 
estimated to be $1,207,272, or $9,146 per airplane.
    The number of required work hours for the replacement of the duct 
couplings, as indicated above, is presented as if the accomplishment of 
that action was to be conducted as a ``stand alone'' action. However, 
the 15-month compliance time specified in paragraph (a) of this AD 
should allow ample time for the duct coupling replacement to be 
accomplished coincidentally with scheduled major airplane inspection 
and maintenance activities, thereby minimizing the costs associated 
with special airplane scheduling.
    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 FAA recognizes that the obligation to maintain aircraft in an 
airworthy condition is vital, but sometimes expensive. Because AD's 
require specific actions to address specific unsafe conditions, they 
appear to impose costs that would not otherwise be borne by operators. 
However, because of the general obligation of operators to maintain 
aircraft in an airworthy condition, this appearance is deceptive. 
Attributing those costs solely to the issuance of this AD is 
unrealistic because, in the interest of maintaining safe aircraft, most 
prudent operators would accomplish the required actions even if they 
were not required to do so by the AD.
    A full cost-benefit analysis has not been accomplished for this AD. 
As a matter of law, in order to be airworthy, an aircraft must conform 
to its type design and be in a condition for safe operation. The type 
design is approved only after the FAA makes a determination that it 
complies with all applicable airworthiness requirements. In adopting 
and maintaining those requirements, the FAA has already made the 
determination that they establish a level of safety that is cost-
beneficial. When the FAA, as in this AD, makes a finding of an unsafe 
condition, this means that this cost-beneficial level of safety is no 
longer being achieved and that the required actions are necessary to 
restore that level of safety. Because this level of safety has already 
been determined to be cost-beneficial, a full cost-benefit analysis for 
this AD would be redundant and unnecessary.
    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:

94-09-13 Boeing: Amendment 39-8902. Docket 93-NM-164-AD.

    Applicability: Model 747 series airplanes, line position 1 
through 219 inclusive; certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of duct couplings installed on the wing 
leading edge pneumatic duct installed in the vicinity of the strut, 
which could lead to structural damage to the wing leading edge, 
flight control problems, or fire, accomplish the following:
    (a) Within 15 months after the effective date of this AD, 
replace duct couplings having part number (P/N) 7540600 and 7540602, 
with duct couplings having P/N 7541749 and 7541751, in accordance 
with Purolator Service Bulletin FSC-912, dated December 1972, at the 
following locations:
    (1) The coupling that connects the tee duct at the inboard 
struts to the pneumatic ducting of the engine in the struts;
    (2) The coupling that connects the tee duct at the inboard 
struts to the pneumatic ducting of the wing leading edge outboard of 
the inboard struts; and
    (3) The coupling that connects the pneumatic ducting of the wing 
leading edge to the pneumatic ducting of the engine in the outboard 
struts.
    (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, Seattle 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, Seattle ACO.

    Note: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle 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 replacement shall be done in accordance with Purolator 
Service Bulletin FSC-912, dated December 1972. 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 PTI Technologies, Inc., 950 Rancho Conejo Boulevard, 
Newbury Park, California 91320. 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.
    (e) This amendment becomes effective on June 17, 1994.

    Issued in Renton, Washington, on April 21, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-10115 Filed 5-17-94; 8:45 am]
BILLING CODE 4910-13-U