[Federal Register Volume 64, Number 203 (Thursday, October 21, 1999)]
[Proposed Rules]
[Pages 56709-56712]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-27564]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-186-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 767 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

-----------------------------------------------------------------------

SUMMARY: This document revises an earlier proposed airworthiness 
directive (AD), applicable to certain Boeing Model 767 series 
airplanes, that would have required repetitive inspections to ensure 
the proper condition of the engine thrust link components, and follow-
on corrective action, if necessary; and replacement of the end cap 
assembly with an improved assembly. Such replacement, when 
accomplished, would terminate the repetitive inspections. That proposal 
was prompted by a report of fatigue cracking of end cap bolts caused by 
improper installation. This new action revises the proposed rule by 
adding a repair requirement and by clarifying the type of inspection 
and terminology used in describing the parts to be inspected. The 
actions specified by this new AD are intended to prevent failure of the 
end cap assembly, which could lead to separation of the engine from the 
airplane in the event of a primary thrust linkage failure.

DATES: Comments must be received by November 10, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 97-NM-186-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.
    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. This information may be examined at the FAA, Transport 
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

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:

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.
    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 97-NM-186-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. 97-NM-186-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to 
certain Boeing Model 767 series airplanes, was published as a notice of 
proposed rulemaking (NPRM) in the Federal Register on May 20, 1998 (63 
FR 27696). That NPRM would have required repetitive inspections to 
detect improper installation or fatigue damage of the end cap of the 
forward engine mount, and replacement of the end cap assembly with an 
improved assembly. Such replacement, when accomplished, would terminate 
the repetitive inspections. That NPRM was prompted by a report of 
fatigue cracking of end cap bolts caused by improper installation. That 
condition, if not corrected, could result in failure of the end cap 
assembly, which could lead to separation of the engine from the 
airplane in the event of a primary thrust linkage failure.

Comments

    Due consideration has been given to the comments received in 
response to the NPRM:
    One commenter states that it is not affected by the proposal 
because its Model 767-200ER series airplanes are powered by General 
Electric engines. Another commenter generally supports the proposal.

Request To Withdraw the Original NPRM

    One commenter does not consider that issuance of the original NPRM 
is necessary for the following reasons:
    1. The commenter states that ``regulatory action mandating 
incorporation of Boeing Alert Service Bulletin 767-71A0087 is 
unwarranted for JT9D powered Model 767 aircraft'' for several reasons. 
First, the original

[[Page 56710]]

NPRM was issued solely because the part numbers of the end caps and 
bolts on Model 767 and Model 747-400 series airplanes are the same. 
Second, the alert service bulletin was issued on the basis of one 
report of broken end cap bolts by one operator of a Model 747-400 
series airplane.
    The FAA does not concur that the original NPRM should be withdrawn. 
Issuance of the original NPRM was not based on the fact that both end 
caps have the same part number, but on the fact that the configuration 
of the end cap assembly is identical. The configuration of the end cap 
assembly for Model 767 and 747 series airplanes is identical in all 
relevant respects. Therefore, if an end cap assembly is installed 
incorrectly in either of those airplane models, the same unsafe 
condition is likely to occur. In addition, the unsafe condition is 
likely to occur regardless of whether the airplane is powered by Pratt 
& Whitney Model JT9D or Model PW4000 series engines, as the 
installations of those airplane engines also are identical. In light of 
this, the FAA has determined that an unsafe condition exists. No change 
to the supplemental NPRM is necessary in this regard.
    2. The commenter states that the cause of the bolt failure on a 
Model 747-400 series airplane was attributed to a personnel error when 
the end cap was installed backwards. The commenter adds that one 
isolated incident involving a personnel error ``does not warrant 
drastic repetitive inspections.''
    The FAA does not concur that the original NPRM should be withdrawn. 
While personnel error was involved in the mis-installation of the end 
cap, it is the ease by which an end cap can be installed backwards that 
makes it likely that this condition could exist on other airplanes. For 
this reason, the FAA considers that an unsafe condition is likely to 
develop on other airplane models of the same design, and that issuance 
of this AD and the repetitive inspections required by this AD are 
necessary to ensure continued operational safety. No change to the 
supplemental NPRM is necessary in this regard.
    3. The commenter states that the end cap and bolts are routinely 
inspected for defects when they are removed from the assembly. In 
addition, in the entire operating history of Model 767 series airplanes 
powered by Pratt & Whitney Model JT9D series engines, there is no 
documented event of any operator experiencing failure of an end cap or 
bolt. Further, there is no evidence that the end caps were ever 
installed backwards on any Model 767 series airplane.
    The FAA does not concur that the original NPRM should be withdrawn. 
Even though the operator may conduct a routine inspection of the end 
cap and bolts for defects, additional inspections are required because 
of the possibility of early fatigue failure. The FAA considers this AD 
necessary in order to address two major concerns:
     First, if an end cap were installed incorrectly, it would 
automatically pick up thrust loads on every flight and result in an 
early fatigue failure of the end cap assembly. Thus, if the primary 
load path provided by the thrust links, evener bar, and engine lugs 
were to then experience a failure, the engine would separate from the 
airplane almost immediately.
     Second, investigation has revealed that even a properly 
installed end cap assembly has an inadequate fatigue life. Analysis and 
testing indicate that if the primary load path fails, the end cap 
assembly then would react all of the new loads and cause the end cap 
assembly to fail within a relatively small number of flight cycles. 
Such failure would occur even if the end cap assembly had been entirely 
intact at the time the primary load path failed. For this reason, the 
original NPRM specifies repetitive inspections of the primary load path 
(i.e., the thrust link, evener bar, and engine lugs) until 
accomplishment of the replacement action specified in Work Packages 3 
or 4.
    The FAA considers that the lack of defects found in the operator's 
end caps implies merely that the original end caps were installed 
correctly, as a properly installed end cap would not react any loads 
during normal flight operations, thereby making it unlikely that any 
fatigue damage would have occurred. However, because it has been 
determined that the existing end cap assembly has an inadequate fatigue 
life, the FAA considers that the requirements of this AD are necessary 
to ensure the operational safety of the fleet. No change to the 
supplemental NPRM is necessary in this regard.
    4. The commenter states that the alert service bulletin mandates a 
visual check and an ultrasonic on-wing [non-destructive test (NDT)] 
inspection of the evener bar and thrust links for the engine mounts for 
Pratt & Whitney Model JT9D series engines, but no on-wing ultrasonic 
inspection is specified for Model PW4000 series engines. If repetitive 
on-wing ultrasonic inspections are waived for the higher thrust Model 
PW4000 series engines, there is no justification to require those 
inspections for the lower thrust Model JT9D series engines. Further, 
the operating history of airplanes powered by Model JT9D series engines 
does not support any regulatory action regarding the forward lower 
engine mount.
    The FAA does not concur that the original NPRM should be withdrawn. 
The FAA points out that the original NPRM makes it clear in the 
``Differences'' paragraph that the two airplane groups for Model 767 
series airplanes, Group 1 airplanes (with JT9D engines) and Group 2 
airplanes (with PW4000 engines), are to be treated exactly the same. 
According to the manufacturer's fleet utilization data base, there 
should never be a case of any Group 2 airplane ever reaching the 
threshold of 16,000 flight cycles before it reaches the 3-year 
compliance time for the mandatory terminating action. Although the 
logic diagram in Figure 1 of the alert service bulletin specifies that 
operators of Group 2 airplanes (i.e., airplanes with Model PW4000 
series engines) [with more than 16,000 flight cycles] should contact 
the manufacturer, the FAA considers that this instruction was included 
on the off-chance that an airplane might fall into this category. 
However, this does not imply that any such airplanes would be waived 
from the NDT inspection requirements. On the contrary, such airplanes 
would be handled on a case-by-case basis, with every expectation that 
NDT inspections would be required at shorter inspection intervals 
because of the higher fatigue damage that could be caused by the higher 
thrust Model PW4000 series engines. No change to the supplemental NPRM 
is necessary.

Request To Clarify Inspection Requirements and Components To Be 
Inspected

    One commenter, the manufacturer, requests certain changes to the 
``Explanation of Relevant Service Information'' paragraph in the 
original NPRM. The commenter contends that the AD should refer to 
inspections of the ``engine thrust link components'' rather than to 
inspections of the ``end cap.''
    The FAA concurs that the commenter's suggested changes add clarity 
and technical accuracy to the supplemental NPRM. Additionally, Boeing 
Alert Service Bulletin 767-71A0087, dated October 10, 1996, does not 
specify inspections of the ``end cap,'' but only includes inspections 
of the ``forward engine mount'' to ensure that the thrust links, evener 
bar, associated engine lugs, and attaching hardware are firmly 
attached. Although the ``Explanation of Relevant Service Information'' 
paragraph is not included

[[Page 56711]]

in this supplemental NPRM, the FAA has determined that certain changes 
are necessary in this AD for several reasons.
    The FAA considers that requiring operators ``to ensure the proper 
condition of the engine thrust link components'' more accurately 
describes the action required for the inspection rather than ``to 
detect improper installation or fatigue damage of the end cap of the 
forward engine mount.'' The FAA points out that ``fatigue damage of the 
end cap of the forward engine mount,'' which involves the secondary 
load path, could not be detected until the forward engine mount was 
disassembled. In addition, the inspections specified by the alert 
service bulletin are for ``engine thrust link components,'' not the 
``end cap'' itself.
    This supplemental NPRM correlates the corrective action to the 
presence or absence of damage to the engine thrust link components. In 
addition, the engine thrust link components, which involve the primary 
load path, can be inspected with no disassembly of the forward engine 
mount. In light of this information, the FAA has made the appropriate 
changes to the ``Summary'' paragraph of this supplemental NPRM.

Request To Include Repair of Discrepancies

    One commenter, the manufacturer, requests that paragraph (d) of the 
original NPRM be revised to require that all discrepancies or damage 
found be repaired in accordance with an approved FAA procedure.
    The FAA concurs partially. The action required by paragraph (d) of 
the original NPRM is now included in paragraphs (c), (c)(1), and (c)(2) 
of the supplemental NPRM. The repair requirement is added in paragraph 
(c)(1), and the action for accomplishment of Work Package 3 is included 
in paragraph (c)(2). Because the repair procedures are not specified in 
Work Package 3 of the alert service bulletin, it is necessary for this 
supplemental NPRM to require that any repairs be accomplished in 
accordance with a method approved by the Manager, Seattle Aircraft 
Certification Office (ACO).

Explanation of Changes Made to the Supplemental NPRM

    The FAA has clarified one of the inspection requirements contained 
in the original NPRM. Whereas the original NPRM specified the 
accomplishment of Work Package 1 (visual inspection of the forward 
engine mount), the FAA has revised this supplemental NPRM to clarify 
that its intent is to require a detailed visual inspection. 
Additionally, a note has been added to the supplemental NPRM to define 
that inspection.
    The FAA has deleted the reference to paragraph (c) that was 
included in paragraph (a) of the original NPRM, which stated that 
``Where Boeing Alert Service Bulletin 767-71A0087, dated October 10, 
1996, specifies that the actions required by this AD may be 
accomplished in accordance with an operator's equivalent procedure,' 
the actions must be accomplished in accordance with Chapter 71-00-00 of 
the Boeing 767 Airplane Maintenance Manual (AMM), as specified in the 
alert service bulletin.'' The FAA has determined that the required 
inspections and replacement actions specified in paragraphs (a), (b), 
and (c)(2) of the supplemental NPRM are adequately addressed in the 
alert service bulletin. Therefore, reference to a specific chapter of 
the AMM is not necessary.
    Paragraphs (a)(1) and (a)(2) of this supplemental NPRM have been 
revised to clarify the inspection requirements.

Explanation of Changes Made to This Final Rule

    The FAA has clarified the inspection requirement contained in the 
proposed AD. Whereas the proposal specified a visual inspection, the 
FAA has revised this final rule to clarify that its intent is to 
require a detailed visual inspection. Additionally, a note has been 
added to the final rule to define that inspection.

Conclusion

    Since these changes expand the scope of the originally proposed 
rule, the FAA has determined that it is necessary to reopen the comment 
period to provide additional opportunity for public comment.

Cost Impact

    There are approximately 239 Model 767 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 96 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 37 work hours per airplane (18.5 work hours per 
engine) to accomplish the required inspections, and that the average 
labor rate is $60 per work hour. Based on these figures, the cost 
impact of the AD on U.S. operators is estimated to be $213,120, or 
$2,220 per airplane, per inspection cycle.
    It will take approximately 135 work hours per airplane (67.5 work 
hours per engine) to accomplish the required replacement of the forward 
engine mount end cap and bolts, and the average labor rate is $60 per 
work hour. Required parts would cost approximately $1,000 per airplane. 
Based on these figures, the cost impact of the AD on U.S. operators is 
estimated to be $873,600, or $9,100 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 proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    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.


Sec. 39.13  [Amended]

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

Boeing: Docket 97-NM-186-AD.


[[Page 56712]]


    Applicability: Model 767 series airplanes, powered by Pratt & 
Whitney Model JT9D or Model PW4000 series engines, as listed in 
Boeing Alert Service Bulletin 767-71A0087, dated October 10, 1996; 
certificated in any category.

    Note: 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 (e) 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 possible separation of the engine from the airplane 
in the event of a primary thrust linkage failure, accomplish the 
following:

Initial and Repetitive Inspections

    (a) For Groups 1 and 2 airplanes: Accomplish paragraphs (a)(1), 
(a)(2), and (a)(3) of this AD, as applicable, in accordance with 
Boeing Alert Service Bulletin 767-71A0087, dated October 10, 1996.
    (1) Within 500 flight hours or 300 flight cycles after the 
effective date of this AD, whichever occurs later: Accomplish Work 
Package 1 (a detailed visual inspection of the forward engine mount 
to ensure that the thrust link, evener bar, associated lugs, and 
attaching hardware are firmly attached). Thereafter, repeat Work 
Package 1 at the intervals specified in the alert service bulletin 
until the requirements of either paragraph (a)(2) or (a)(3) of this 
AD are accomplished.

    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 an 
intensity deemed appropriate by the inspector. Inspection aids such 
as mirrors, magnifying lenses, etc. may be used. Surface cleaning 
and elaborate access procedures may be required.''

    (2) Prior to the accumulation of 16,000 total flight cycles on 
any engine or within 500 flight hours or 300 flight cycles after the 
effective date of this AD, whichever occurs latest: Accomplish Work 
Package 2 (non-destructive test inspection of the forward engine 
mount to ensure the proper condition of the engine thrust link 
components). Thereafter, repeat Work Package 2 on that engine at the 
intervals specified in the alert service bulletin until the 
requirements of paragraph (a)(3) of this AD are accomplished. 
Accomplishment of Work Package 2 constitutes terminating action for 
the repetitive inspections required by paragraph (a)(1) of this AD 
for that engine.

Replacement and Terminating Action

    (3) Within 3 years after the effective date of this AD: 
Accomplish Work Package 3 (end cap and bolt replacement of the 
forward engine mount). Accomplishment of Work Package 3 constitutes 
terminating action for the requirements of this AD for Groups 1 and 
2 airplanes.
    (b) For Group 3 airplanes: Within 3 years after the effective 
date of this AD, accomplish Work Package 4 (bolt replacement) in 
accordance with Boeing Alert Service Bulletin 767-71A0087, dated 
October 10, 1996.

Repair and Replacement Action

    (c) For all airplanes: If any discrepancy (including an 
improperly installed or damaged engine thrust link component) is 
found during any inspection required by this AD, prior to further 
flight, accomplish the actions required by paragraphs (c)(1) and 
(c)(2) of this AD.
    (1) Repair any discrepancies in accordance with a method 
approved by the Manager, Seattle Aircraft Certification Office 
(ACO), FAA, Transport Airplane Directorate. For a repair method to 
be approved by the Manager, Seattle ACO, as required by this 
paragraph, the Manager's approval letter must specifically reference 
this AD.
    (2) Accomplish Work Package 3 in accordance with Boeing Alert 
Service Bulletin 767-71A0087, dated October 10, 1996.

Spares

    (d) As of the effective date of this AD, no person shall install 
a forward engine mount end cap having part number 310T3026-1 on any 
airplane.

Alternative Method of Compliance

    (e) 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, 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 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

    (f) 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 15, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-27564 Filed 10-20-99; 8:45 am]
BILLING CODE 4910-13-p