[Federal Register Volume 64, Number 41 (Wednesday, March 3, 1999)]
[Rules and Regulations]
[Pages 10205-10208]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-4892]



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 Rules and Regulations
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  Federal Register / Vol. 64, No. 41 / Wednesday, March 3, 1999 / Rules 
and Regulations  

[[Page 10205]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-76-AD; Amendment 39-11054; AD 99-05-06]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to certain Boeing Model 747 series airplanes, that 
currently requires a one-time inspection to detect cracking and 
corrosion of various areas at all four nacelle struts; and repair, if 
necessary. This amendment requires new repetitive inspections to detect 
fatigue cracking or loose or missing fasteners of the aft torque 
bulkheads of the outboard nacelle struts; and repair, if necessary. In 
addition, this action expands the applicability of the existing AD to 
include additional airplanes. This amendment is prompted by a report 
indicating that cracking was found in the aft torque bulkheads of the 
outboard nacelle struts, and by the availability of new service 
instructions for detecting fatigue cracking that would not have been 
detected by the required actions of the existing AD. The actions 
specified in this AD are intended to detect and correct such fatigue 
cracking and loose or missing fasteners, which could result in failure 
of an outboard nacelle strut diagonal brace load path and possible 
separation of the nacelle from the wing.

DATES: Effective March 18, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
March 18, 1999.
    Comments for inclusion in the Rules Docket must be received on or 
before May 3, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-76-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: Tamara L. Anderson, Aerospace 
Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane 
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, 
SW., Renton, Washington 98055-4056; telephone (425) 227-2771; fax (425) 
227-1181.

SUPPLEMENTARY INFORMATION: On December 31, 1996, the FAA issued AD 96-
26-51, amendment 39-9876 (62 FR 1038, January 8, 1997), applicable to 
Boeing Model 747 series airplanes equipped with Rolls-Royce-type 
engines, to require a one-time detailed visual inspection to detect 
cracking and corrosion of various areas at all four nacelle struts; and 
repair, if necessary. That action was prompted by reports of cracking 
of the aft torque bulkhead at the number 1 and number 2 nacelle struts. 
The actions required by that AD are intended to detect and correct 
cracking of an inboard or outboard nacelle strut, which could result in 
failure of the nacelle strut and consequent separation of the nacelle 
from the wing.

Actions Since Issuance of Previous Rule

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to include an airworthiness directive (AD) that is 
applicable to certain Boeing Model 747 series airplanes was published 
in the Federal Register on November 24, 1998 (63 FR 64915). That notice 
of proposed rulemaking (NPRM) proposed to supersede AD 96-26-51 to 
require new repetitive inspections to detect fatigue cracking or loose 
or missing fasteners of the aft torque bulkheads of the outboard 
nacelle struts; and repair, if necessary. In addition, that action 
proposed to expand the applicability of the existing AD to include 
additional airplanes.
    As stated in the NPRM, subsequent to the issuance of the previous 
rule, the FAA learned of several new findings: The outboard, but not 
inboard, strut is susceptible to fatigue cracking of the aft torque 
bulkhead; additional fatigue cracking was found on another Model 747 
series airplane (which also was equipped with Rolls-Royce Model RB211 
series engines) at certain locations on the number 4 nacelle strut; 
outboard struts equipped with other types of engines also may be 
susceptible to fatigue cracking; and additional nacelle struts were 
found to have loose fasteners at the attachment between the vertical 
flange of the lower spar fitting and the aft torque bulkhead.
    Since the issuance of that NPRM, the manufacturer reported that 
cracking of the aft torque bulkhead was recently found at the number 4 
pylon on a Model 747-300 series airplane. The aft torque bulkhead web 
and vertical chords (into the chord radius) were fractured above the 
lower spar fitting. That airplane had accumulated 43,266 total flight 
hours and 10,673 total flight cycles, and was powered by Rolls-Royce 
Model RB211 series engines.

FAA's Determination

    In consideration of this new finding of cracking at a threshold 
lower than that specified by the NPRM, the FAA has determined that, for 
airplanes powered by Rolls-Royce Model RB211 series engines, the 
compliance time for accomplishment of the actions required by this AD 
should be reduced from 12,000 total flight cycles or 90 days to 8,000 
total flight cycles or 30 days.
    It should be noted that Boeing Alert Service Bulletin 747-54A2184, 
dated July 3, 1997 (which was cited in the NPRM as the appropriate 
source of service information), recommends accomplishing the visual 
inspection within 12,000 total flight cycles. However, for the reasons 
stated below, the FAA has determined that an interval of 12,000 total 
flight cycles will not address the identified unsafe condition in a 
timely manner, and has revised the AD accordingly.

[[Page 10206]]

    In developing an appropriate compliance time for this AD, the FAA 
considered not only the manufacturer's recommendation, but the degree 
of urgency associated with addressing the subject unsafe condition, the 
average utilization of the affected fleet, and the time necessary to 
perform the inspection. In light of all of these factors, as discussed 
earlier, the FAA finds a compliance time of 8,000 total flight cycles 
or 30 days to be warranted for initiating the required actions (for 
Groups 1 and 2 airplanes), in that the revised compliance time 
represents an appropriate interval of time allowable for affected 
airplanes to continue to operate without compromising safety.
    In making this revision, the FAA finds that, with respect to the 
reduced compliance time, since a situation exists that requires the 
immediate adoption of this regulation, notice and opportunity for prior 
public comment hereon are impracticable, and good cause exists for 
making this amendment effective in less than 30 days.

Comments

    Due consideration has been given to the comments received regarding 
the NPRM.

Support for the Proposal

    One commenter supports the proposed AD.

Request to Revise Unsafe Condition

    One commenter requests that the FAA expand the details of the 
identified unsafe condition to more fully describe the failure 
sequence. Specifically, the commenter requests a revision of the NPRM 
to specify that fatigue cracking or loose or missing fasteners could 
result first in failure of the diagonal brace load path, and then 
possible separation of the nacelle from the wing.
    The FAA agrees that the requested language helps to clarify the 
sequence of possible failures. The unsafe condition in this AD has been 
revised accordingly.

Request to Defer Inspection for Certain Airplanes

    One commenter states that certain airplanes have already 
accomplished the terminating action required by AD 95-13-05, amendment 
39-9285 (60 FR 33333, June 28, 1995). The commenter requests that those 
airplanes be allowed to defer inspection until 12,000 flight cycles 
after completing that terminating action. As justification for its 
request, the commenter explains that, after modification in accordance 
with AD 95-13-05, the chords are replaced with new chords. Therefore, 
the commenter requests that inspections start 12,000 flight cycles 
after accomplishment of the terminating modification in accordance with 
AD 95-13-05.
    The FAA concurs partially. The FAA concurs that accomplishment of 
the initial inspections required by paragraphs (a) and (b) of this AD 
may be deferred, for Groups 1 and 2 airplanes, following accomplishment 
of the terminating action in accordance with AD 95-13-05. This AD has 
been revised accordingly, as shown in paragraphs (a) and (b). However, 
as stated previously, the compliance time for these actions has been 
reduced from 12,000 to 8,000 flight cycles.

Request for Clarification

    One commenter requests a revision to the section of the NPRM titled 
``Actions Since Issuance of Previous Rule.'' Specifically, the 
commenter requests that the statement ``* * * analysis shows that this 
is not the case for many of the different types that can be installed 
on the outboard strut'' be changed to ``* * * analysis shows sufficient 
similarities for many * * *'' The FAA agrees that this language more 
accurately reflects relevant conditions. However, because this section 
of the preamble to an NPRM is not restated in this AD, no change to 
this AD is necessary.

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.

Explanation of Requirements of Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of this same type design, this AD 
supersedes AD 96-26-51 to require new repetitive inspections to detect 
fatigue cracking or loose or missing fasteners of the aft torque 
bulkheads of the outboard nacelle struts; and repair, if necessary. In 
addition, this AD expands the applicability of the existing AD to 
include additional airplanes. The actions are required to be 
accomplished in accordance with Boeing Alert Service Bulletin 747-
54A2184, except as discussed previously and in the NPRM.

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 98-NM-76-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

[[Page 10207]]

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 removing amendment 39-9876 (62 FR 
1038, January 8, 1997), and by adding a new airworthiness directive 
(AD), amendment 39-11054, to read as follows:

99-05-06  Boeing: Amendment 39-11054. Docket 98-NM-76-AD. Supersedes 
AD 96-26-51, Amendment 39-9876.

    Applicability: Model 747 series airplanes, as listed in Boeing 
Alert Service Bulletin 747-54A2184, dated July 3, 1997; 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 (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 detect and correct fatigue cracking and loose or missing 
fasteners of the aft torque bulkheads of the outboard nacelle 
struts, which could result in failure of an outboard nacelle strut 
diagonal brace load path and possible separation of the nacelle from 
the wing, accomplish the following:
    (a) For airplanes identified as Groups 1 and 2 airplanes in 
Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: Prior 
to the accumulation of 8,000 total flight cycles, or within 8,000 
flight cycles since modification in accordance with AD 95-13-05, 
amendment 39-9285, or within 30 days after the effective date of 
this AD, whichever occurs latest, perform a detailed visual 
inspection of the aft torque bulkheads of the number 1 and number 4 
nacelle struts to detect fatigue cracking and loose or missing 
fasteners. The inspection shall be accomplished in accordance with 
Part I of the Accomplishment Instructions of Boeing Alert Service 
Bulletin 747-54A2184, dated July 3, 1997.

    Note 2: There is a typographical error on Sheet 3 of Figure 1 of 
the alert service bulletin. The words ``Group 1 airplanes'' should 
read ``Groups 1 and 2 airplanes.''

    (1) If no cracking, and no loose or missing fastener, is found, 
repeat the inspection thereafter at the intervals specified in 
Figure 1 of the alert service bulletin.
    (2) If any cracking, or any loose or missing fastener, is found, 
prior to further flight, repair in accordance with Part III of the 
alert service bulletin. Repeat the inspection thereafter at the 
intervals specified in Figure 1 of the alert service bulletin. Where 
the service bulletin specifies that the manufacturer may be 
contacted for disposition of certain repair conditions, 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.
    (b) For airplanes identified as Groups 1 and 2 airplanes in 
Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: Prior 
to the accumulation of 8,000 total flight cycles, or within 8,000 
flight cycles since modification in accordance with AD 95-13-05, 
amendment 39-9285, or within 30 days after the effective date of 
this AD, whichever occurs latest, perform a non-destructive test 
(NDT) inspection of the aft torque bulkheads of the number 1 and 
number 4 nacelle struts to detect fatigue cracking. The NDT 
inspection shall be accomplished in accordance with Part II of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 747-
54A2184, dated July 3, 1997.

    Note 3: The alert service bulletin refers to a variety of NDT 
inspections, consisting of ultrasonic inspections, surface eddy 
current inspections, and open-hole eddy current inspections. The 
logic diagram in Figure 1 of the alert service bulletin states the 
conditions under which each of these inspections is to be performed.

    (1) If no cracking is found, repeat the inspection thereafter at 
the intervals specified in Figure 1 of the alert service bulletin.
    (2) If any cracking is found, prior to further flight, repair in 
accordance with Part III of the alert service bulletin. Repeat the 
inspection thereafter at the intervals specified in Figure 1 of the 
alert service bulletin. Where the alert service bulletin specifies 
that the manufacturer may be contacted for disposition of certain 
repair conditions, 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.
    (c) For airplanes identified as Groups 3 and 4 airplanes in 
Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: Prior 
to the accumulation of 12,000 total flight cycles, or within 90 days 
after the effective date of this AD, whichever occurs later, perform 
a detailed visual inspection of the aft torque bulkheads of the 
number 1 and number 4 nacelle struts to detect fatigue cracking and 
loose or missing fasteners. The inspection shall be accomplished in 
accordance with Part I of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 747-54A2184, dated July 3, 1997.
    (1) If no cracking, and if no loose or missing fastener is 
found, repeat the inspection thereafter at the intervals specified 
in Figure 1 of the alert service bulletin, until the applicable 
requirements of paragraph (d) are accomplished.
    (2) If any cracking, or if any loose or missing fastener is 
found, prior to further flight, repair in accordance with Part III 
of the alert service bulletin. Where the alert service bulletin 
specifies that the manufacturer may be contacted for disposition of 
certain repair conditions, 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 identified as Groups 3 and 4 airplanes in 
Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: 
Accomplishment of the nacelle strut modifications required in AD 95-
13-07, amendment 39-9287 (applicable to airplanes equipped with 
either General Electric CF6-45/50 or Pratt & Whitney JT9D-70 nacelle 
struts), constitutes terminating action for the requirements of this 
AD.
    (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. 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 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.
    (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.
    (g) Except as provided in paragraphs (a)(2), (b)(2), and (c)(2) 
of this AD, the actions shall be done in accordance with Boeing 
Alert Service Bulletin 747-54A2184, dated July 3, 1997. This 
incorporation by reference was

[[Page 10208]]

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.
    (h) This amendment becomes effective on March 18, 1999.

    Issued in Renton, Washington, on February 22, 1999.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-4892 Filed 3-2-99; 8:45 am]
BILLING CODE 4910-13-U