[Federal Register Volume 60, Number 25 (Tuesday, February 7, 1995)]
[Proposed Rules]
[Pages 7140-7143]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-2930]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-252-AD]


Airworthiness Directives; Boeing Model 747 Series Airplanes 
Equipped with Rolls Royce Model RB211 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 March 6, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 94-NM-252-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-121S, 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 
[[Page 7141]] 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-252-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-252-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

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 9 AD's that address various problems 
associated with the strut attachment assembly on Boeing Model 747 
series airplanes that are equipped with Rolls Royce Model RB211 series 
engines. These AD's have required, among other things, inspections of 
the strut, and strut-to-wing attachment 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 Rolls Royce Model RB211 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 
747-54A2157, dated January 12, 1995, 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, 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 replacing the tee fitting bolts common to the rib at wing 
station (WS) 1140 [and for certain airplanes, installing a new 
stiffener at the wing midspar];
    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 5 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. Installation of improved bushings in the strut-to-wing 
attachment fittings;
    3. Replacement of certain strut-to-wing attachment fitting 
fasteners; and
    4. Inspection and torque check of certain fasteners of the strut-
to-wing attachment fittings.
    Paragraph III, NOTES 8, 9, and 13 of the Accomplishment 
Instructions on pages 109 and 110 of the alert service bulletin also 
describes procedures for inspections and checks to detect discrepancies 
of the adjacent structure and correction of any discrepancies.

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:

                                                                                                                
[[Page 7142]]                                                                                                   
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                                                                  Federal Register                              
                  AD No.                      Amendment No.           citation            Date of publication   
----------------------------------------------------------------------------------------------------------------
93-17-07-................................            39-8678-  58 FR 45827-           August 31, 1993.          
93-03-14-................................            39-8518-  58 FR 14513-           March 18, 1993.           
92-24-51-................................            39-8439-  57 FR 60118-           December 18, 1992.        
90-20-20-................................            39-6725-  55 FR 37859-           September 14, 1990.       
89-07-15-................................            39-6167-  54 FR 11693-           March 22, 1989.           
87-04-13 R1-.............................            39-5836-  53 FR 2005-            January 26, 1988.         
86-05-11 R1-.............................            39-5334-  51 FR 21900-           June 17, 1986.            
86-23-01-................................            39-5450-  51 FR 37712-           October 26, 1986.         
79-17-07-................................            39-3533-  44 FR 50033-           August 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

    Currently, there are no Model 747 series airplanes of the affected 
design, equipped with Rolls Royce Model RB211 series engines, on the 
U.S. Register. However, should an affected airplane be imported and 
placed on the U.S. Register in the future, it would require 
approximately 6,545 work hours to accomplish the required actions, at 
an average labor charge of $60 per work hour. The manufacturer would 
incur the cost of labor, on a pro-rated basis, with 20 years being the 
expected life of these airplanes. The median age for the fleet of Model 
747 series airplanes equipped with Rolls Royce Model RB211 series 
engines is estimated to be 6 years. Required parts would be supplied by 
the manufacturer at no cost to operators. Based on these figures, the 
total cost impact of this AD would be $117,810 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 5 of Boeing Alert Service Bulletin 747-54A2157, dated January 12, 
1995, 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 
[[Page 7143]] 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. 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-252-AD.

    Applicability: Model 747 series airplanes having line positions 
292 through 1033 inclusive, equipped with Rolls Royce Model RB211 
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 (c) 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-
54A2157, dated January 12, 1995, at the time specified in paragraph 
(a)(1) or (a)(2) of this AD, as applicable. All of the terminating 
actions described in the service bulletins listed in paragraph I.C., 
Table 2, ``Prior or Concurrent Service Bulletins,'' on page 5 of 
Boeing Alert Service Bulletin 747-54A2157, dated January 12, 1995, 
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.
    (1) For Model 747-400 series airplanes having line positions 705 
through 1033 inclusive, equipped with Rolls Royce Model RB211-524G 
and H engines: Within 80 months after the effective date of this AD.
    (2) For all other Model 747 series airplanes equipped with Rolls 
Royce Model RB211 series engines not subject to the requirements of 
paragraph (a)(1) of this AD: Within 56 months after the effective 
date of this AD.
    (b) Perform the inspections and checks specified in paragraph 
III, NOTES 8, 9, and 13 of the Accomplishment Instructions on pages 
109 and 110 of Boeing Alert Service Bulletin 747-54A2157, dated 
January 12, 1995, 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-
54A2157, dated January 12, 1995, constitutes terminating action for 
the inspections required by the following AD's:

----------------------------------------------------------------------------------------------------------------
                                                                  Federal Register                              
                  AD No.                      Amendment No.           citation            Date of publication   
----------------------------------------------------------------------------------------------------------------
93-17-07-................................            39-8678-  58 FR 45827-           August 31, 1993.          
93-03-14-................................            39-8518-  58 FR 14513-           March 18, 1993.           
92-24-51-................................            39-8439-  57 FR 60118-           December 18, 1992.        
90-20-20-................................            39-6725-  55 FR 37859-           September 14, 1990.       
89-07-15-................................            39-6167-  54 FR 11693-           March 22, 1989.           
87-04-13 R1-.............................            39-5836-  53 FR 2005-            January 26, 1988.         
86-05-11 R1-.............................            39-5334-  51 FR 21900-           June 17, 1986.            
86-23-01-................................            39-5450-  51 FR 37712-           October 26, 1986.         
79-17-07-................................            39-3533-  44 FR 50033-           August 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 February 1, 1995.

Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-2930 Filed 2-6-95; 8:45 am]
BILLING CODE 4910-13-U