[Federal Register Volume 60, Number 1 (Tuesday, January 3, 1995)]
[Proposed Rules]
[Pages 66-69]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-32264]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-208-AD]


Airworthiness Directives; Boeing Model 747 Series Airplanes 
Equipped With General Electric Model CF6-45 or -50 Series Engines, or 
Pratt & Whitney Model JT9D-70 Series 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 747 series 
airplanes. This proposal would require modification of the nacelle 
strut and wing structure, inspections and checks to detect 
discrepancies, and correction of discrepancies. This proposal is 
prompted by the development of a modification of the strut and wing 
structure that improves the fail-safe capability and durability of the 
strut-to-wing attachments, and reduces reliance on inspections of those 
attachments. The actions specified by the proposed AD are intended to 
prevent failure of the strut and subsequent loss of the engine.

DATES: Comments must be received by February 28, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 94-NM-208-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.

FOR FURTHER INFORMATION CONTACT: Tim Backman, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2776; fax (206) 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 94-NM-208-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-103, Attention: Rules 
Docket No. 94-NM-208-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056. [[Page 67]] 

Discussion

    The FAA has received numerous reports of fatigue cracking and/or 
corrosion in the strut-to-wing attachments on Boeing Model 747 series 
airplanes. In two cases, cracking resulted in the failure of a strut 
load path and the subsequent loss of the number 3 engine and strut. In 
both cases, catastrophic accidents occurred when the number 3 engine 
and strut separated from the wing of the airplane and struck the number 
4 engine, causing it to separate from the airplane. Investigation into 
the cause of these accidents and other reported incidents has revealed 
that fatigue cracks and corrosion in the strut-to-wing attachments, if 
not detected and corrected in a timely manner, can result in failure of 
the strut and subsequent separation of the engine from the airplane. 
Investigation also has revealed that the structural fail-safe 
capability of the strut-to-wing attachment is inadequate on these 
airplanes.
    The FAA has previously issued 13 AD's that address various problems 
associated with the strut attachment assembly on Boeing Model 747 
series airplanes that are equipped with General Electric Model CF6-45 
or -50 series engines or Pratt & Whitney Model JT9D-70 series engines. 
These AD's have required, among other things, inspections of the strut, 
strut-to-wing attachment structure, and wing backup structure.

Explanation of Service Information

    Boeing recently has developed a modification of the strut-to-wing 
attachment structure installed on Model 747 series airplanes equipped 
with General Electric Model CF6-45 or -50 series engines or Pratt & 
Whitney Model JT9D-70 series engines. This modification significantly 
improves the load-carrying capability and durability of the strut-to-
wing attachments. Such improvement also will substantially reduce the 
possibility of fatigue cracking and corrosion developing in the 
attachment assembly.
    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-54A2158, dated November 30, 1994, which describes procedures for 
modification of the nacelle strut and wing structure. This modification 
entails the following:
    1. Changing the strut by adding a new titanium dual side load 
fitting to the strut aft bulkhead, replacing the aft end of the midspar 
web with a new 15-5 stainless steel web, installing new 15-5 stainless 
steel midspar fittings on the inboard struts, and replacing the aft 
bulkhead assembly and overhauling the spring beams on the outboard 
struts;
    2. Changing the wing structure by installing a new dual side load 
underwing fitting and new support fitting, and replacing the end 
fitting and installing a new stiffener at the wing midspar for the 
outboard strut location [for certain airplanes, installing new inboard 
backup fittings, installing new titanium outboard underwing fittings at 
all strut positions, and replacing the tee fitting common to the rib at 
wing station (WS) 1140; for certain other airplanes, replacing the tee 
fitting bolts common to the rib at WS 1140];
    3. Changing the electrical wiring and hydraulics by rerouting the 
wire bundles around the new dual side load fitting, splicing additional 
wire to the wire bundles, and installing new hydraulic tubes; and
    4. Installing the strut with a new upper link, a new diagonal 
brace, and new side links.
    This alert service bulletin specifies that the modification of the 
nacelle strut and wing structure is to be accomplished prior to, or 
concurrently with, the terminating actions described in the service 
bulletins listed in paragraph I.C., Table 2, ``Prior or Concurrent 
Service Bulletins,'' on page 7 of this alert service bulletin. These 
terminating actions include the following:
    1. Replacement of the diagonal brace, midspar and upper link fuse 
pins with new third generation 15-5 corrosion resistant steel fuse 
pins;
    2. Replacement of the strut-to-diagonal brace aluminum attach 
fitting on the inboard engine with a steel fitting;
    3. Installation of a large skin doubler and frame stiffener in the 
area of the precooler exhaust vent;
    4. A zero-time overhaul of the springbeams and rework of certain 
fastener holes of the springbeam support fittings of the outboard 
strut;
    5. Inspection and torque check of certain fasteners of the strut-
to-wing attachment fittings; and
    6. Modification of the rib at wing station 669.5.

Explanation of the Provisions of the Proposed AD

    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 modification of the nacelle strut and wing 
structure, inspections and checks to detect discrepancies in the 
adjacent structure, and correction of discrepancies. The actions would 
be required to be accomplished in accordance with the alert service 
bulletin described previously.
    The FAA has determined that long term continued operational safety 
will be better assured by design changes to remove the source of the 
problem, rather than by repetitive inspections. Long term inspections 
may not be providing the degree of safety assurance necessary for the 
transport airplane fleet. This, coupled with a better understanding of 
the human factors associated with numerous continual inspections, has 
led the FAA to consider placing less emphasis on inspections and more 
emphasis on design improvements. The proposed modification requirement 
is in consonance with these considerations.
    Accomplishment of the modification of the nacelle strut and wing 
structure would terminate the inspections required by the following 
AD's:

------------------------------------------------------------------------
                      Amendment   Federal Register                      
       AD No.            No.          citation-      Date of Publication
------------------------------------------------------------------------
94-22-08...........      39-9057  59 FR 58761.....  Nov. 15, 1994.      
93-17-07...........      39-8678  58 FR 45827.....  Aug. 31, 1993.      
93-03-14...........      39-8518  58 FR 14513.....  Mar. 18, 1993.      
92-24-51...........      39-8439  57 FR 60118.....  Dec. 18, 1992.      
90-20-20...........      39-6725  55 FR 37859.....  Sept. 14, 1990.     
89-07-15...........      39-6167  54 FR 11693.....  Mar. 22, 1989.      
87-04-13 R1-.......      39-5836  53 FR 2005......  Jan. 26, 1988.      
86-23-01...........      39-5450  51 FR 37712.....  Oct. 24, 1986.      
86-08-03...........      39-5289  51 FR 12836.....  Apr. 16, 1986.      
86-07-06...........      39-5270  51 FR 10821.....  Mar. 31, 1986.      
86-05-11 R1-.......      39-5334  51 FR 21900-....  June 17, 1986.      
[[Page 68]]                                                             
                                                                        
80-08-02...........      39-3738  45 FR 24450.....  Apr. 10, 1980.      
79-17-07...........      39-3533  44 FR 50033.....  Aug. 27, 1979.      
------------------------------------------------------------------------


    As a result of recent communications with the Air Transport 
Association (ATA) of America, the FAA has learned that, in general, 
some operators may misunderstand the legal effect of AD's on airplanes 
that are identified in the applicability provision of the AD, but that 
have been altered or repaired in the area addressed by the AD. The FAA 
points out that all airplanes identified in the applicability provision 
of an AD are legally subject to the AD. If an airplane has been altered 
or repaired in the affected area in such a way as to affect compliance 
with the AD, the owner or operator is required to obtain FAA approval 
for an alternative method of compliance with the AD, in accordance with 
the paragraph of each AD that provides for such approvals. A note has 
been included in this notice to clarify this requirement.

Cost Estimate

    There are approximately 145 Model 747 series airplanes of the 
affected design, equipped with General Electric Model CF6-45 or -50 
series engines or Pratt & Whitney Model JT9D-70 series engines in the 
worldwide fleet. The FAA estimates that 12 airplanes of U.S. registry 
would be affected by this proposed AD.
    The proposed modification may take as many as 6,600 to 7,151 work 
hours to accomplish, depending upon the configuration of the airplane. 
The manufacturer would incur the cost of labor, on a pro-rated basis, 
with 20 years being the expected life of these airplanes. The total 
cost impact of the proposed AD on U.S. operators is based on the median 
age for the fleet of Model 747 series airplanes equipped with General 
Electric Model CF6-45 or -50 series engines or Pratt & Whitney Model 
JT9D-70 series engines, which is estimated to be 15 years. The average 
labor rate is estimated to be $60 per work hour. Required parts would 
be supplied by the manufacturer at no cost to the operator. Based on 
these figures, the cost impact of this proposal on U.S. operators is 
estimated to be between $3,564,000 ($297,000 per airplane) and 
$3,861,540 ($321,795 per airplane).
    This cost impact figure does not reflect the cost of the 
terminating actions described in the service bulletins listed in 
paragraph I.C., Table 2, ``Prior or Concurrent Service Bulletins,'' on 
page 7 of Boeing Alert Service Bulletin 747-54A2158, dated November 30, 
1994, that are proposed to be accomplished prior to or concurrently 
with the modification of the nacelle strut and wing structure. Since 
some operators may have accomplished certain modifications on some or 
all of the airplanes in its fleet, while other operators may not have 
accomplished any of the modifications on any of the airplanes in its 
fleet, the FAA is unable to provide a reasonable estimate of the cost 
of accomplishing the terminating actions described in the service 
bulletins listed in Table 2 of the Boeing alert service bulletin. As 
indicated earlier in this preamble, the FAA invites comments 
specifically on the overall economic aspects of this proposed rule. Any 
data received via public comments to this notice will aid the FAA in 
developing an accurate accounting of the cost impact of the rule.
    The cost impact figure discussed above is 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 AD were not adopted.
    The FAA recognizes that the obligation to maintain aircraft in an 
airworthy condition is vital, but sometimes expensive. Because AD's 
require specific actions to address specific unsafe conditions, they 
appear to impose costs that would not otherwise be borne by operators. 
However, because of the general obligation of operators to maintain 
aircraft in an airworthy condition, this appearance is deceptive. 
Attributing those costs solely to the issuance of this AD is 
unrealistic because, in the interest of maintaining safe aircraft, 
prudent operators would accomplish the required actions even if they 
were not required to do so by the AD.
    A full cost-benefit analysis has not been accomplished for this 
proposed AD. As a matter of law, in order to be airworthy, an aircraft 
must conform to its type design and be in a condition for safe 
operation. The type design is approved only after the FAA makes a 
determination that it complies with all applicable airworthiness 
requirements. In adopting and maintaining those requirements, the FAA 
has already made the determination that they establish a level of 
safety that is cost-beneficial. When the FAA, as in this proposed AD, 
makes a finding of an unsafe condition, this means that the original 
cost-beneficial level of safety is no longer being achieved and that 
the proposed actions are necessary to restore that level of safety. 
Because this level of safety has already been determined to be cost-
beneficial, a full cost-benefit analysis for this proposed AD would be 
redundant and unnecessary.

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:

    [[Page 69]] Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 
U.S.C. 106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

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

BOEING: Docket 94-NM-208-AD.

    Applicability: Model 747 series airplanes, equipped with General 
Electric Model CF6-45 or -50 series engines, or Pratt & Whitney 
Model JT9D-70 series engines; 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 use the authority 
provided in paragraph (d) to request approval from the FAA. This 
approval may address either no action, if the current configuration 
eliminates the unsafe condition; or different actions necessary to 
address the unsafe condition described in this AD. Such a request 
should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any airplane from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the strut and subsequent loss of the 
engine, accomplish the following:
    (a) Accomplish the modification of the nacelle strut and wing 
structure in accordance with Boeing Alert Service Bulletin 747-
54A2158, dated November 30, 1994, within 56 months after the 
effective date of this AD. All of the terminating actions described 
in the service bulletins listed in paragraph I.C., Table 2, ``Prior 
or Concurrent Service Bulletins,'' on page 7 of Boeing Alert Service 
Bulletin 747-54A2158, dated November 30, 1994, must be accomplished 
in accordance with those service bulletins prior to, or concurrently 
with, the accomplishment of the modification of the nacelle strut 
and wing structure required by this paragraph.
    (b) Perform the inspections and checks specified in paragraph 
III, NOTES 8, 9, 10, and 11 of the Accomplishment Instructions on 
page 129 of Boeing Alert Service Bulletin 747-54A2158, dated 
November 30, 1994, concurrently with the modification of the nacelle 
strut and wing structure required by paragraph (a) of this AD. Prior 
to further flight, correct any discrepancies found in accordance 
with the alert service bulletin.
    (c) Accomplishment of the modification of the nacelle strut and 
wing structure in accordance with Boeing Alert Service Bulletin 747-
54A2158, dated November 30, 1994, constitutes terminating action for 
the inspections required by the following AD's:

------------------------------------------------------------------------
                      Amendment   Federal Register                      
       AD No.            No.          citation-      Date of Publication
------------------------------------------------------------------------
94-22-08...........      39-9057  59 FR 58761.....  Nov. 15, 1994.      
93-17-07...........      39-8678  58 FR 45827.....  Aug. 31, 1993.      
93-03-14...........      39-8518  58 FR 14513.....  Mar. 18, 1993.      
92-24-51...........      39-8439  57 FR 60118.....  Dec. 18, 1992.      
90-20-20...........      39-6725  55 FR 37859.....  Sept. 14, 1990.     
89-07-15...........      39-6167  54 FR 11693.....  Mar. 22, 1989.      
87-04-13 R1........      39-5836  53 FR 2005......  Jan. 26, 1988.      
86-23-01...........      39-5450  51 FR 37712.....  Oct. 24, 1986.      
86-08-03...........      39-5289  51 FR 12836.....  Apr. 16, 1986.      
86-07-06...........      39-5270  51 FR 10821.....  Mar. 31, 1986.      
86-05-11 R1-.......      39-5334  51 FR 21900-....  Jun. 17, 1986.      
80-08-02...........      39-3738  45 FR 24450.....  Apr. 10, 1980.      
79-17-07...........      39-3533  44 FR 50033.....  Aug. 27, 1979.      
------------------------------------------------------------------------


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

    (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 December 27, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-32264 Filed 12-30-94; 8:45 am]
BILLING CODE 4310-13-P