[Federal Register Volume 64, Number 58 (Friday, March 26, 1999)]
[Rules and Regulations]
[Pages 14578-14580]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-7117]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-39-AD; Amendment 39-11091; AD 99-07-06]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 767 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 certain Boeing Model 767 series airplanes. This action 
requires repetitive inspections to detect cracking or damage of the 
forward and aft lugs of the diagonal brace of the nacelle strut, and 
follow-on actions, if necessary. This action also provides optional 
terminating action for the repetitive inspections. This amendment is 
prompted by a report that a fractured diagonal brace lug was found 
during a routine maintenance inspection. The actions specified in this 
AD are intended to detect and correct cracking of the diagonal brace of 
the nacelle strut, which could result in failure of the diagonal brace, 
and consequent fatigue failure of a strut secondary load path and 
separation of the engine and strut.

DATES: Effective April 12, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of April 12, 1999.
    Comments for inclusion in the Rules Docket must be received on or 
before May 26, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-39-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056.
    The service information referenced in this AD may be obtained from 
Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 
98124-2207. 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: James G. Rehrl, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2783; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received a report indicating 
that a fractured lug of the diagonal brace of the nacelle strut was 
found during a routine visual inspection of a Boeing Model 767 series 
airplane. The affected airplane had accumulated 36,247 flight hours and 
17,677 flight cycles.
    Such cracking has been attributed to migration of a bushing inside 
the lug bore. A migrated bushing could cause fretting damage to the lug 
bore, which could lead to the initiation of a crack. Subsequent 
propagation of that crack due to fatigue loading could result in 
complete fracture of the lug and consequent failure of the diagonal 
brace. Failure of the diagonal brace would place increased stress on 
the strut secondary load paths. Continued operation of the airplane 
with a failed diagonal brace could result in fatigue failure of a strut 
secondary load path. This condition, if not corrected, could result in 
separation of the engine and strut.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
767-54A0094, dated May 22, 1998, which describes procedures for 
repetitive detailed visual inspections to detect cracking or damage of 
the forward and aft lugs of the diagonal brace of the nacelle strut, 
and follow-on actions, if necessary. Follow-on actions include, if 
cracking or damage is detected, replacement of the existing one-piece 
diagonal brace with a new three-piece diagonal brace, which eliminates 
the need for the repetitive inspections, and additional inspections of 
the strut secondary load paths to detect damage. For airplanes on which 
no cracking or damage is detected, the alert service bulletin describes 
procedures for optional rework of the diagonal brace, which allows 
repetitive inspections to be deferred, provided that the one-piece 
diagonal brace is replaced with a three-piece diagonal brace prior to 
the accumulation of 37,500 total flight cycles.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design, this AD is 
being issued to detect and correct cracking of the diagonal brace of 
the nacelle strut, which could result in failure of the diagonal brace, 
and consequent failure of a secondary load path and loss of the engine 
and strut. This AD requires repetitive detailed visual inspections to 
detect cracking or damage of the forward and aft lugs of the diagonal 
brace of the nacelle strut, and follow-on actions, if necessary. If no 
cracking or damage is detected, this AD provides for optional rework of 
the diagonal brace, which would allow the repetitive inspection 
threshold to be increased from 1,000 or 3,000 flight cycles, as 
applicable, to 12,000 flight cycles. If any cracking or damage is 
detected, this AD requires replacement of the existing one-piece 
diagonal brace with a new three-piece diagonal brace, which constitutes 
terminating action for the repetitive inspections; additional 
inspections of the strut secondary load paths to detect damage; and 
corrective actions, if necessary. This AD also provides for an optional 
replacement of the one-piece diagonal brace with a new three-piece 
diagonal brace, which constitutes terminating action for the repetitive 
inspection requirements of this AD. The actions are required to be 
accomplished in accordance with the alert service bulletin described 
previously, except as discussed below.

Differences Between Alert Service Bulletin and This AD

    Operators should note that the effectivity listing of the alert 
service bulletin is divided into four groups. However, Figure 1 of the 
alert service bulletin specifies procedures only for Groups 1, 2, and 
3. The FAA has determined that airplanes in Group 4 are subject to the 
detailed visual inspection at the same threshold (12,000 total flight 
cycles), and the same corrective actions, if necessary, as airplanes in 
Groups 1 and 3.
    Operators also should note that, if the optional rework of the 
diagonal brace is accomplished, this AD requires reinspection to detect 
cracking or damage of the diagonal brace lugs within 12,000 flight 
cycles. The alert service bulletin identifies the optional rework as 
``zero time rework''; however, the alert service bulletin does not

[[Page 14579]]

clearly specify that the detailed visual inspection of the diagonal 
brace lugs should be repeated within 12,000 flight cycles after 
accomplishment of the rework. The FAA finds that, to ensure the safety 
of the fleet of affected airplanes, it is necessary to clarify the 
requirement to repeat the inspection of the diagonal brace within 
12,000 flight cycles after rework.
    Operators also should note that, although the alert service 
bulletin specifies that the manufacturer may be contacted for 
disposition of certain repair conditions, this AD requires the repair 
of those conditions to be accomplished in accordance with a method 
approved by the FAA, or in accordance with data meeting the type 
certification basis of the airplane approved by a Boeing Company 
Designated Engineering Representative who has been authorized by the 
FAA to make such findings.

Interim Action

    This is considered to be interim action. The FAA currently is 
considering requiring the replacement of the existing one-piece 
diagonal brace with a new three-piece diagonal brace, which would 
constitute terminating action for the repetitive inspections required 
by this AD action. However, the planned compliance time for the 
installation of the three-piece diagonal brace is sufficiently long so 
that notice and opportunity for prior public comment will be 
practicable.

Determination of Rule's Effective Date

    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 99-NM-39-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    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.

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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

99-07-06  Boeing: Amendment 39-11091. Docket 99-NM-39-AD.

    Applicability: Model 767 series airplanes; as listed in Boeing 
Alert Service Bulletin 767-54A0094, dated May 22, 1998; certificated 
in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (f) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To detect and correct cracking of the diagonal brace of the 
nacelle strut, which could result in failure of the diagonal brace, 
and consequent fatigue failure of a strut secondary load path and 
separation of the engine and strut, accomplish the following:

Initial Inspection

    (a) Perform a detailed visual inspection to detect cracking or 
damage of the forward and aft lugs of the diagonal brace of the 
nacelle strut, on the left and right sides of the airplane, in 
accordance with Boeing Alert Service Bulletin 767-54A0094, dated May 
22, 1998. Perform the inspection at the time specified in paragraph 
(a)(1) or (a)(2) of this AD, as applicable.
    (1) For airplanes in Groups 1, 3, and 4: Inspect prior to the 
accumulation of 12,000 total flight cycles, or within 90 days after 
the effective date of this AD, whichever occurs later.
    (2) For airplanes in Group 2: Inspect prior to the accumulation 
of 24,000 total flight cycles, or within 90 days after the effective 
date of this AD, whichever occurs later.

Follow-On Actions

    (b) If no cracking or damage is detected during the inspection 
required by paragraph (a) of this AD, repeat the inspection 
thereafter at the interval specified in paragraph (b)(1) or (b)(2) 
of this AD, as applicable, in accordance

[[Page 14580]]

with Boeing Alert Service Bulletin 767-54A0094, dated May 22, 1998. 
Repeat the inspection until the actions specified by paragraph (d) 
or (e) of this AD have been accomplished.
    (1) For airplanes in Groups 1, 3, and 4; and for airplanes in 
Group 2 on which the diagonal brace has accumulated more than 32,000 
total flight cycles: Repeat the inspection at intervals not to 
exceed 1,000 flight cycles.
    (2) For airplanes in Group 2 on which the diagonal brace has 
accumulated 32,000 or fewer total flight cycles: Repeat the 
inspection at intervals not to exceed 3,000 flight cycles.
    (c) If any cracking or damage is detected during any inspection 
required by paragraph (a) or (b) of this AD, prior to further 
flight, remove the diagonal brace and perform additional inspections 
to detect damage of the strut secondary load paths, in accordance 
with Part 4 of Boeing Alert Service Bulletin 767-54A0094, dated May 
22, 1998; and accomplish the requirements of paragraphs (c)(1) and, 
if applicable, (c)(2) of this AD.
    (1) Prior to further flight, replace the one-piece diagonal 
brace with a new three-piece diagonal brace, in accordance with Part 
3 of the Accomplishment Instructions of the alert service bulletin. 
Such replacement constitutes terminating action for the requirements 
of this AD.
    (2) If any additional damage of the alternate load paths is 
detected, prior to further flight, repair in accordance with a 
method approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate; or in accordance 
with data meeting the type certification basis of the airplane 
approved by a Boeing Company Designated Engineering Representative 
who has been authorized by the Manager, Seattle ACO, to make such 
findings.
    (d) For airplanes on which no cracking is detected during the 
inspection required by paragraph (a) of this AD, in lieu of 
accomplishing repetitive inspections in accordance with paragraph 
(b) of this AD, rework of the forward and aft lugs of the diagonal 
brace may be accomplished in accordance with Part 2 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 767-
54A0094, dated May 22, 1998. If such rework is accomplished: Within 
12,000 flight cycles after the rework, repeat the inspection 
required by paragraph (a) of this AD; and, prior to the accumulation 
of 37,500 total flight cycles on the diagonal brace, replace the 
one-piece diagonal brace with a new three-piece diagonal brace, in 
accordance with Part 3 of the Accomplishment Instructions of the 
alert service bulletin. Such replacement constitutes terminating 
action for the requirements of this AD.

Optional Terminating Action

    (e) Replacement of the one-piece diagonal brace with a new 
three-piece diagonal brace, in accordance with Part 3 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 767-
54A0094, dated May 22, 1998, constitutes terminating action for the 
requirements of this AD.

Alternative Methods of Compliance

    (f) 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 ACO. 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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

Special Flight Permits

    (g) 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.

Incorporation by Reference

    (h) Except as specified by paragraph (c)(2) of this AD, the 
actions shall be done in accordance with Boeing Alert Service 
Bulletin 767-54A0094, dated May 22, 1998. 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 Boeing Commercial Airplane Group, P.O. Box 3707, 
Seattle, Washington 98124-2207. 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.

Effective Date

    (i) This amendment becomes effective on April 12, 1999.

    Issued in Renton, Washington, on March 17, 1999.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-7117 Filed 3-25-99; 8:45 am]
BILLING CODE 4910-13-U