[Federal Register Volume 65, Number 196 (Tuesday, October 10, 2000)]
[Proposed Rules]
[Pages 60124-60126]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-25968]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-157-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 767 Series Airplanes 
Powered by General Electric or Pratt & Whitney Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 767 series 
airplanes powered by General Electric or Pratt & Whitney engines. This 
proposal would require repetitive inspections to detect discrepancies 
of the aft-most fastener holes in the horizontal tangs of the midspar 
fitting of the strut, and corrective actions, if necessary. This 
proposal also provides for optional terminating action for the 
repetitive inspections. This action is necessary to prevent fatigue 
cracking in primary strut structure and reduced structural integrity of 
the strut, which could result in separation of the strut and engine. 
This action is intended to address the identified unsafe condition.

DATES: Comments must be received by November 24, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-157-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 2000-NM-157-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 for Windows or 
ASCII text.
    The service information referenced in the proposed rule 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.

FOR FURTHER INFORMATION CONTACT: James Rehrl, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-2783; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed 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 above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Submit comments using the following format:
     Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
     For each issue, state what specific change to the proposed 
AD is being requested.
     Include justification (e.g., reasons or data) for each 
request.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NM-157-AD.'' The postcard will be date stamped 
and returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 2000-NM-157-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

[[Page 60125]]

Discussion

    The FAA has received a report indicating fatigue cracking of an 
inboard midspar fitting on the number two pylon of a Boeing Model 767 
series airplane powered by General Electric engines. The crack was 
detected during replacement of a midspar fitting bushing, and the 
airplane had accumulated 21,375 total flight hours and 11,563 total 
flight cycles. A cracked midspar fitting could result in a fractured 
fitting and drooping of the strut at the strut-to-wing interface. 
Structural assessment indicates that the actual operational loads 
applied to the nacelle strut and wing structure are higher than the 
analytical loads that were used during the initial design. Subsequent 
analysis and service history, which includes numerous reports of 
fatigue cracking on certain strut and wing structure, indicate that 
fatigue cracking can occur on the primary strut structure before an 
airplane reaches its design service objective of 20 years or 50,000 
total flight cycles. Analysis also indicates that such cracking, if it 
were to occur, would grow at a much greater rate than originally 
expected. This condition, if not corrected, could result in reduced 
structural integrity of the strut and separation of the strut and 
engine.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 767-
54A0101, Revision 1, dated February 3, 2000, which describes procedures 
for accomplishment of either repetitive detailed visual or high 
frequency eddy current inspections to detect discrepancies (cracking, 
incorrect fastener hole diameter), of the aft-most fastener holes in 
the horizontal tangs of the midspar fitting of the strut, and 
corrective actions. The corrective actions consist of rework of the 
aft-most fastener holes or replacement of the midspar fittings of the 
strut. The service bulletin references the strut improvement program 
(SIP) for accomplishment of the replacement. The service bulletin also 
specifies contacting the manufacturer for accomplishment of certain 
repairs. Accomplishment of the actions specified in the service 
bulletin is intended to adequately address the identified unsafe 
condition.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require accomplishment of the actions specified in 
the service bulletin described previously, except as discussed below.

Differences Between Proposed Rule and Service Bulletin

    Operators should note that, although the service bulletin describes 
procedures for inspections of the two aft-most fastener holes of the 
midspar fitting to detect cracking, this proposed AD would require 
inspections of the four aft-most fastener holes of the midspar fitting. 
The FAA has determined that this is necessary due to the service 
history of cracking on the Model 747 series airplane midspar fittings, 
which are made of the same material as the midspar fittings on the 
Model 767 series airplane and are also subject to similar loading 
conditions.
    Operators also should note that, although the service bulletin 
specifies that the manufacturer may be contacted for disposition of 
certain repair conditions; this proposed AD would require 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.
    This proposed AD also would allow operators the option, if cracking 
is detected, of either repair of the midspar fitting or replacement 
with a serviceable fitting in accordance with a method approved by the 
FAA. This is due to the fact that parts are not always readily 
available and operators required to accomplish the strut improvement 
program before further flight could have a problem obtaining these 
parts.

Cost Impact

    There are approximately 636 Model 767 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 235 
airplanes of U.S. registry would be affected by this proposed AD.
    It would take approximately 1 work hour per airplane to accomplish 
the proposed detailed visual inspection, at an average labor rate of 
$60 per work hour. Based on these figures, the cost impact of the 
proposed inspection on U.S. operators is estimated to be $14,100, or 
$60 per airplane, per inspection cycle.
    It would take approximately 3 work hours per airplane to accomplish 
the proposed eddy current inspection, at an average labor rate of $60 
per work hour. Based on these figures, the cost impact of the proposed 
inspection on U.S. operators is estimated to be $42,300, or $180 per 
airplane, per inspection cycle.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the proposed requirements 
of this AD action, and that no operator would accomplish those actions 
in the future if this proposed AD were not adopted. The cost impact 
figures discussed in AD rulemaking actions represent only the time 
necessary to perform the specific actions actually required by the AD. 
These figures typically do not include incidental costs, such as the 
time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.

Regulatory Impact

    The regulations proposed herein would 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 proposal would not have federalism implications 
under Executive Order 13132.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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.

[[Page 60126]]

Sec. 39.13  [Amended]

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

Boeing: Docket 2000-NM-157-AD.

    Applicability: Model 767 series airplanes, certificated in any 
category, as listed in Boeing Service Bulletin 767-54A0101, Revision 
1, dated February 3, 2000.

    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 (d) 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 fatigue cracking in primary strut structure and 
reduced structural integrity of the strut, which could result in 
separation of the strut and engine, accomplish the following:

Repetitive Inspections/Corrective Actions

    (a) Before the accumulation of 10,000 total flight cycles, or 
within 600 flight cycles after the effective date of this AD, 
whichever occurs later: Accomplish the inspections required by 
paragraph (a)(1) or (a)(2) of this AD, as applicable.
    (1) Perform a detailed visual inspection of the four aft-most 
fastener holes in the horizontal tangs of the midspar fitting of the 
strut to detect cracking, in accordance with Part 1, ``Detailed 
Visual Inspection,'' of the Accomplishment Instructions of Boeing 
Service Bulletin 767-54A0101, Revision 1, dated February 3, 2000. If 
no cracking is detected, repeat the inspection thereafter at the 
applicable intervals specified in Table 1, ``Reinspection Intervals 
for Part 1--Detailed Visual Inspection'' included in Figure 1 of the 
service bulletin.

    Note 2: For the purposes of this AD, a detailed visual 
inspection is defined as: ``An intensive visual examination of a 
specific structural area, system, installation, or assembly to 
detect damage, failure, or irregularity. Available lighting is 
normally supplemented with a direct source of good lighting at 
intensity deemed appropriate by the inspector. Inspection aids such 
as mirror, magnifying lenses, etc., may be used. Surface cleaning 
and elaborate access procedures may be required.''

    (2) Perform a high frequency eddy current inspection of the four 
aft-most fastener holes in the horizontal tangs of the midspar 
fitting of the strut to detect discrepancies (cracking, incorrect 
fastener hole diameter), in accordance with Part 2, ``High Frequency 
Eddy Current (HFEC) Inspection,'' of the Accomplishment Instructions 
of the service bulletin. Accomplish the requirements specified in 
paragraph (a)(2)(i) or (a)(2)(ii) of this AD, as applicable; and 
repeat the inspection thereafter at the applicable intervals 
specified in Table 2, ``Reinspection Intervals for Part 2--HFEC 
Inspection'' included in Figure 1 of the service bulletin.
    (i) If no cracking is detected and the fastener hole diameter is 
less than or equal to 0.5322 inch, rework the hole in accordance 
with Part 3 of the Accomplishment Instructions of the service 
bulletin.
    (ii) If no cracking is detected and the fastener hole diameter 
is greater than 0.5322 inch, accomplish the requirements specified 
in either paragraph (b)(1) or (b)(2) of this AD.
    (b) If any cracking is detected after accomplishment of any 
inspection required by paragraph (a) of this AD, before further 
flight, accomplish the requirements specified in either paragraph 
(b)(1) or (b)(2) of this AD.
    (1) Accomplish the terminating action specified in Part 4 of the 
Accomplishment Instructions of Boeing Service Bulletin 767-54A0101, 
Revision 1, dated February 3, 2000. Accomplishment of this paragraph 
terminates the requirements of this AD.
    (2) Replace the midspar fitting of the strut with a serviceable 
part, or repair in accordance with a method approved by the Manager, 
Seattle Aircraft Certification Office (ACO), FAA. Repeat the 
applicable inspection thereafter at the applicable time specified in 
paragraph (a)(1) or (a)(2) of this AD.
    (c) If any discrepancies (cracking, incorrect fastener hole 
diameter) are detected after accomplishment of any inspection 
required by paragraph (a) of this AD, for which the service bulletin 
specifies that the manufacturer may be contacted for disposition of 
those repair conditions: Before further flight, accomplish the 
corrective actions (including fastener hole rework and/or midspar 
fitting replacement) 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 
Designated Engineering Representative who has been authorized by the 
Manager, Seattle ACO, to make such findings.

Alternative Methods of Compliance

    (d) 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 Permit

    (e) 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.

    Issued in Renton, Washington, on October 3, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-25968 Filed 10-6-00; 8:45 am]
BILLING CODE 4910-13-U