AD 2000-07-05

[Federal Register Volume 65, Number 69 (Monday, April 10, 2000)]
[Rules and Regulations]
[Pages 18883-18886]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 00-8518]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-72-AD; Amendment 39-11659; AD 2000-07-05]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 767 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to certain Boeing Model 767 series airplanes, that 
currently 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. That AD also provides optional 
terminating action for the repetitive inspections. This amendment 
requires accomplishment of the previously optional terminating action. 
This amendment is prompted by a report that a fractured diagonal brace 
lug was found during a routine maintenance inspection. The actions 
specified by this AD are intended to prevent 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 May 15, 2000.
    The incorporation by reference of Boeing Alert Service Bulletin 
767-54A0094, dated May 22, 1998, was approved previously by the 
Director of the Federal Register as of April 12, 1999 (64 FR 14578, 
March 26, 1999).

ADDRESSES: 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 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: 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: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) by superseding AD 99-07-06, 
amendment 39-11091 (64 FR 14578, March 26, 1999), which is applicable 
to certain Boeing Model 767 series airplanes, was published in the 
Federal Register on June 23, 1999 (64 FR 33437). The action proposed to 
supersede AD 99-07-06 to continue to require 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. That 
action also proposed to require accomplishment of the previously 
optional terminating action.

Comments

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

Support for the Proposal

    Two commenters support the proposed rule.

[[Page 18884]]

Requests To Revise Compliance Time

    One commenter requests that the compliance time for the repetitive 
inspection intervals specified in paragraph (b)(1) of the proposed AD 
be extended. The commenter suggests that the inspection intervals 
should coincide with its current heavy maintenance program, which 
specifies that inspections be performed between 1,200 and 1,300 flight 
cycles. The commenter further states that to carry out the inspection 
at intervals not to exceed 1,000 flight cycles would be considered 
punitive action as it is prior to the normally scheduled maintenance.
    The FAA does not concur with the commenter's request to extend the 
compliance time for accomplishment of the repetitive inspection 
intervals to between 1,200 and 1,300 flight cycles after the initial 
inspection. In developing an appropriate compliance time for the 
repetitive inspections, the FAA considered not only the degree of 
urgency associated with addressing cracking or damage of the forward 
and aft lugs of the diagonal brace of the nacelle strut, but other 
factors as well. Those factors include the recommendations of the 
manufacturer, and the practical aspect of accomplishing the repetitive 
inspections within an interval of time coinciding with normally 
scheduled maintenance for the majority of affected operators. 
Considering those factors, the FAA has determined that the compliance 
time of 1,000 flight cycles after the accomplishment of the initial 
inspection represents the maximum interval in which the affected 
airlines can continue to operate without compromising safety. In view 
of those factors, and the amount of time that has already elapsed since 
issuance of the notice of proposed rulemaking, the FAA has determined 
that further delay of these inspections is, in general, not 
appropriate. The FAA may, however, approve a request for an adjustment 
of the compliance time under the provisions of paragraph (f) of this 
final rule if data are submitted to substantiate that such an 
adjustment would provide an equivalent level of safety. No change to 
the final rule is necessary in this regard.
    Another commenter requests that the compliance times for the 
replacement of the diagonal brace specified in paragraphs (d) and (e) 
of the proposed rule be changed to reflect the flight cycle threshold 
formula specified in the structural inspection program service 
bulletin, 767-54-0081, Figure 1, which is to be released soon. The 
commenter also notes that the threshold formula could be placed in an 
appendix to the proposal.
    The FAA does not concur with the commenter's request. Boeing 
Service Bulletin 767-54-0081 states that the threshold formula may be 
used in lieu of the calendar threshold specified in the identified 
service bulletins. The formula in service bulletin 767-54-0081 was FAA-
approved based on the fact that certain airplanes (e.g., those that 
have extended flights) would reach the 20-year calendar threshold long 
before they accumulated the flight cycle threshold of 37,500 total 
flight cycles specified in that service bulletin. The FAA notes that 
there is no comparable threshold in calendar time contained in this 
final rule for which the proposed threshold formula can be used as a 
substitute. The FAA considered many factors (as stated previously) 
before developing an appropriate compliance time for this AD, and the 
FAA has determined that the compliance time for the replacement 
required by paragraphs (d) and (e) of the final rule represents the 
maximum interval in which the affected airlines can continue to operate 
without compromising safety. Therefore, no change to the final rule is 
necessary.
    Another commenter requests the compliance time in paragraph (b)(2) 
of the proposal be revised to read, ``* * * diagonal brace has 
accumulated 24,000 flight cycles * * *'' to agree with the alert 
service bulletin. The FAA does not concur. The alert service bulletin 
specifies that the initial inspection for Group 2 airplanes be 
performed prior to the accumulation of 24,000 flight cycles, or within 
90 days after receipt of the service bulletin; and the repetitive 
inspections be performed at intervals not to exceed 3,000 flight cycles 
until the diagonal brace has accumulated 32,000 flight cycles. 
Therefore, the final rule agrees with the alert service bulletin and no 
change is necessary in this regard.

Request To Revise Paragraphs (a), (b), and (c) of the Proposed Rule

    Three commenters request that the word ``damage'' be deleted from 
or clarified in paragraphs (a), (b), and (c) of the proposal.
    The first commenter states that, if any damage is detected, even if 
it is minor and repairable, replacement of the diagonal brace is 
required, as specified in paragraph (c) of the proposal. The commenter 
further states that the alert service bulletin referenced in the 
proposal specifies an inspection to detect cracking of the diagonal 
brace lugs only, and does not specify inspecting for damage; therefore, 
the word ``damage'' should be deleted.
    The second commenter states that if the words ``or damage'' are not 
removed, paragraphs (a), (b), and (c) of the proposal should 
specifically clarify what should be searched for (cracks, fracture) 
during the inspection. The same commenter requests the addition of a 
requirement in paragraph (c) of the proposal to specify that damage to 
the lug bores (including wear, cracks, or surface corrosion) be 
repaired in accordance with Part 2 of the Accomplishment Instructions 
of the alert service bulletin.
    The third commenter states that the word ``damage'' is undefined in 
the proposed rule, and notes that the alert service bulletin specifies 
that cracks originated in the lug bore of the diagonal brace caused by 
bushing motion and subsequent fretting of the lug bore, indicating that 
the damage that caused the cracks was fretting of the lug bore. The 
commenter also notes that the detailed visual inspection required by 
paragraph (a) of the proposal does not inspect the lug bore; therefore, 
the fretting or ``damage'' will not be found. The commenter indicates 
that, without any damage limit guidelines, even very minor damage (tool 
marks, scratched paint) will make it necessary for operators to perform 
costly additional inspections. The commenter notes that the inspection 
should be limited to the unsafe condition that is caused by fretting of 
the lug bore, which can be found by crack indications.
    The FAA does not concur with the commenters' requests concerning 
removal of the word ``damage'' as referenced in paragraphs (a), (b), 
and (c) of the final rule. The FAA has reviewed this issue and has 
determined that the inspection to detect cracks or damage as required 
by paragraphs (a) and (b) of the final rule, is necessary. Certain 
types of damage, if detected, specifically fretting and bushing motion, 
must be corrected in accordance with the Manager, Seattle Aircraft 
Certification Office. These types of damage are two links in a 
sequential chain of events that can ultimately result in a fractured 
lug, or other possible failure modes. Other types of damage (tool 
marks, scratched paint) are not related to the unsafe condition 
specified in this AD, and would be defined as superficial. The FAA has, 
however, added a ``NOTE 2'' to the final rule to define the word 
``damage.''
    The FAA concurs with the second commenter's request to add another 
requirement to paragraph (c) of the final rule, which states that 
damage can be repaired in accordance with the applicable service 
bulletin. Paragraph

[[Page 18885]]

(c) of the final rule has been revised to give the operator the option 
of either repair or replacement of the diagonal brace if any cracking 
or damage is detected, following accomplishment of any inspection 
required by paragraph (a) or (b) of the AD.

Request for Clarification of Paragraph (c) of the Proposed Rule

    One commenter requests that the wording in paragraph (c) of the 
proposal be revised to read, ``* * * and if one or more ligaments of 
the lugs are fractured perform additional inspections to detect damage 
of the strut secondary load paths * * *'' The commenter notes that 
cracking, rather than fractures, will not increase the load in the 
secondary load path.
    Another commenter requests clarification of the requirements in 
paragraph (c) of the proposal. The commenter questions which two lugs 
out of the four lugs (two lugs on the forward end and two lugs on the 
aft end) of the diagonal brace must be fractured before the extensive 
follow-on inspections of the secondary load path structure (Figure 8 of 
the service bulletin) are necessary. The commenter's interpretation is 
that the inspections specified in Figure 8 of the service bulletin are 
necessary only if both lugs on one of the ends of the diagonal brace 
are fractured, and if only one lug on each end of the diagonal brace is 
fractured, the inspections specified in Figure 7 of the service 
bulletin would be necessary.
    The FAA agrees that clarification is necessary in order to better 
define the requirements in paragraph (c) of the AD. Paragraph (c) of 
the final rule has been revised to provide a detailed explanation of 
the inspection area and procedures.

Conclusion

    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.

Cost Impact

    There are approximately 208 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 105 airplanes of U.S. registry 
will be affected by this AD.
    The inspections that are currently required by AD 99-07-06, and 
retained in this AD, take approximately 1 work hour per airplane to 
accomplish, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the currently required inspections on 
U.S. operators is estimated to be $6,300, or $60 per airplane, per 
inspection cycle.
    The replacement that is required in this AD action takes 
approximately 8 work hours (4 work hours for each strut) per airplane 
to accomplish, at an average labor rate of $60 per work hour. Required 
parts will cost approximately $50,000 per airplane. Based on these 
figures, the cost impact of the required replacement required by this 
AD on U.S. operators is estimated to be $5,300,400, or $50,480 per 
airplane.
    The cost impact figures discussed above are 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.

Regulatory Impact

    The regulations adopted herein will not have a substantial direct 
effect 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, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    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 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 removing amendment 39-11091 (64 FR 
14578, March 26, 1999), and by adding a new airworthiness directive 
(AD), amendment 39-11659, to read as follows:

2000-07-05  Boeing: Amendment 39-11659. Docket 99-NM-72-AD. 
Supersedes AD 99-07-06, amendment 39-11091.

    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 prevent 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.

    Note 2: The word ``damage'' as referenced in this AD, is defined 
as fretting and/or bushing motion.

    (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 
April 12, 1999 (the effective date of AD 99-07-06, amendment 39-
11091), 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 April 12, 
1999, whichever occurs later.

Follow-On Actions

    (b) If no cracking or damage is detected during the inspection 
required by paragraph

[[Page 18886]]

(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 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 paragraph (c)(1) or 
(c)(2) of this AD; as applicable.
    (1) If any cracking is detected: Prior to further flight, 
accomplish the requirements of paragraph (c)(1)(i), (c)(1)(ii), or 
(c)(1)(iii) of this AD, as applicable.
    (i) If one lug on one or both ends of the diagonal brace is 
fractured (Figure 7 of the alert service bulletin), or if two lugs 
on either end of the diagonal brace are fractured (Figure 8 of the 
alert service bulletin), prior to further flight: Rework the forward 
and aft lugs of the diagonal brace in accordance with the rework 
limits specified in Part 2 of the Accomplishment Instructions of the 
alert service bulletin.
    (ii) 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.
    (iii) If any additional damage of the alternate load paths is 
detected, 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 (DER) who has been authorized 
by the Manager, Seattle ACO, to make such findings.
    (2) If any damage is detected: Prior to further flight, repair 
in accordance with a method approved by the Manager, Seattle ACO; or 
in accordance with data meeting the type certification basis of the 
airplane approved by a Boeing Company DER 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.

Terminating Action

    (e) Prior to the accumulation of 37,500 total flight cycles, or 
within 180 days after the effective date of this AD, whichever 
occurs later: Replace 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. Such replacement 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 3: 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 
Secs. 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 provided by paragraphs (c)(1)(i) and (c)(3) of 
this AD, the actions shall be done in accordance with Boeing Alert 
Service Bulletin 767-54A0094, dated May 22, 1998. The incorporation 
by reference of this service bulletin was approved previously by the 
Director of the Federal Register as of April 12, 1999 (64 FR 14578, 
March 26, 1999). 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.
    (i) This amendment becomes effective on May 15, 2000.

    Issued in Renton, Washington, on March 31, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-8518 Filed 4-7-00; 8:45 am]
BILLING CODE 4910-13-U