[Federal Register Volume 63, Number 226 (Tuesday, November 24, 1998)]
[Proposed Rules]
[Pages 64913-64915]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-31327]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-144-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

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 repetitive inspections of the 
outboard nacelle struts to detect fatigue cracking of the strut skin 
and spring beam support fittings, and to detect cracked or loose 
fasteners of the support fittings; and corrective actions, if 
necessary. This proposal also provides for optional terminating action 
for the repetitive inspection requirements. This proposal is prompted 
by reports indicating that several cracked or broken spring beam 
support fittings were found on the outboard nacelle struts. The actions 
specified by the proposed AD are intended to detect and correct such 
fatigue cracking and loose fasteners, which could result in failure of 
the outboard nacelle struts and consequent separation of the engine.

DATES: Comments must be received by January 8, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-144-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: Tamara L. Anderson, Aerospace 
Engineer, Airframe Branch, ANM-120S, FAA, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056; telephone (425) 227-2771; 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 98-NM-144-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRM's

    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. 98-NM-144-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports from three operators indicating 
findings of six cracked or broken spring beam support fittings on the 
outboard struts of Model 747 series airplanes. Four of the cracked or 
broken support fittings were found on strut number 1 (left outboard 
strut), and two others were found on strut number 4 (right outboard 
strut).
    An operator of a Model 747-200 combi airplane that had accumulated 
76,372 total flight hours and 14,501 total flight cycles reported 
finding a 5-inch crack in the inboard skin panel during a preflight 
check on the number 1 strut, and further investigation revealed a 
fractured support fitting on the inboard side of that strut. An 
operator of a Model 747-200F airplane equipped with General Electric 
CF6-50 series engines, which had accumulated 71,609 total flight hours 
and 14,808 total flight cycles, reported findings of a severed support 
fitting on the number 1 strut.
    Another operator of a Model 747-200F airplane equipped with Pratt & 
Whitney JT9D-70 series engines reported findings of two broken support 
fittings, one on the number 1 strut and one on the number 4 strut. A 
report indicated that, during a heavy maintenance preliminary check, a 
misaligned stripe on the outboard nacelle strut was found. Further 
investigation revealed a broken spring beam on the outboard side of the 
number 4 strut and a broken support fitting. This airplane had 
accumulated 72,426 total flight hours and 18,142 total flight cycles. 
An inspection of the remaining fleet of similar airplanes revealed 
findings of two fractured support fittings on an airplane that had 
accumulated 66,035 total flight hours and 16,709 total flight cycles.
    All of these operators reported findings of cracked or severed 
spring beam support fittings located on the inboard side of the strut 
and attached to the strut skin. These conditions, if not corrected, 
could cause fatigue cracking of the strut skin and spring beam support 
fittings on the outboard nacelle struts, which could result in failure 
of the outboard nacelle struts and consequent separation of the engine.

Other Relevant Rulemaking

    The FAA has previously issued AD 95-13-07, amendment 39-9287 (60 FR 
33336, June 28, 1995), which currently requires modification of the 
nacelle strut and wing structure, inspections and checks to detect 
discrepancies, and correction of discrepancies. The corrective action 
specified by that AD included a modification to improve the damage 
tolerance capability and durability of the strut-to-wing attachments, 
reduce reliance on non-routine inspections of those attachments, and 
prevent failure of the strut and consequent separation of the engine. 
Although the accomplishment of the modification required by that AD 
constitutes terminating action for the requirements of that AD, this 
proposed AD specifies that same modification as an optional terminating 
action.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-

[[Page 64914]]

54A2172, dated February 23, 1995, and Boeing Service Bulletin 747-
54A2172, Revision 1, dated January 4, 1996, which describe similar 
procedures for detecting cracks of the strut skin and spring beam 
support fittings, or detecting cracked or loose fasteners of the 
support fittings; and corrective actions, if necessary.
    The initial inspections differ from the repetitive inspections. The 
initial inspections include a visual inspection of the four spring beam 
support fittings, a detailed visual inspection of the support fitting 
at the fasteners using a borescope, a visual inspection of the 
fasteners, and a detailed visual inspection of the strut skin. The 
repetitive inspections include an inspection of the support fitting at 
fasteners through the horizontal flange, an inspection of the fasteners 
through the vertical flange for loose collars, an external visual 
inspection for loose fastener heads, and a detailed visual inspection 
of the strut skin.
    The terminating action in both service bulletins specifies an open-
hole high frequency eddy current (HFEC) inspection and, if no cracks 
are found, rework of the fastener holes and installation of new 
fasteners. For airplanes on which any cracks are found during the HFEC 
inspection, Part III of the Accomplishment Instructions of the Boeing 
alert service bulletin specifies contacting the manufacturer for repair 
instructions. However, for those same airplanes, Revision 1 of the 
Boeing service bulletin adds a new section to the Accomplishment 
Instructions (``Part IV. Replacement''), which specifies procedures for 
replacing any cracked spring beam support fitting with a new support 
fitting. Accomplishment of this replacement action would eliminate the 
need for the repetitive inspections of that new support fitting.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other Boeing Model 747 series airplanes of this 
same type design, the proposed AD would require accomplishment of the 
actions specified by the service bulletins described previously, except 
as discussed below. The proposed AD also provides for several optional 
terminating actions. If no cracks are found, rework of the fastener 
holes and installation of new fasteners would constitute terminating 
action for the repetitive inspection requirements of this AD. If cracks 
are found during an open-hole HFEC inspection, replacement of the 
spring beam support fittings with new fittings constitutes optional 
terminating action for the repetitive inspection requirements of this 
AD.

Differences Between Proposed Rule and Service Information

    Operators should note the following differences between the 
proposed rule and the service information:
    Boeing Alert Service Bulletin 747-54A2172, dated February 23, 1995, 
and Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4, 
1996, provide procedures for terminating actions for the repetitive 
inspections. However, this proposed AD specifies those actions as 
optional terminating actions since the FAA has previously issued AD 95-
13-07, which requires a terminating modification that is considered 
acceptable for compliance with the optional terminating action 
specified by this AD.
    Although the Boeing alert service bulletin specifies that the 
manufacturer may be contacted for the disposition of certain repair 
conditions, this proposal would require that the repair of those 
conditions be accomplished in accordance with a method approved by the 
FAA.

Cost Impact

    There are approximately 145 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 9 airplanes of U.S. registry 
would be affected by this proposed AD, that it would take approximately 
16 work hours per airplane to accomplish the proposed inspection, and 
that the average labor rate is $60 per work hour. Based on these 
figures, the cost impact of the proposed AD on U.S. operators is 
estimated to be $8,640, or $960 per airplane, per inspection cycle.
    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.
    Should an operator elect to accomplish the fastener hole inspection 
and modification, it would take approximately 20 work hours (excluding 
removal of the strut and spring beam) to accomplish it, at an average 
labor rate of $60 per hour. Based on these figures, the cost impact of 
this optional terminating action is estimated to be $1,200 per strut.
    Should an operator elect to accomplish the replacement of the 
spring beam support fittings with new support fittings, it would take 
approximately 108 work hours (excluding removal of the strut and spring 
beam) to accomplish it, at an average labor rate of $60 per hour. Based 
on these figures, the cost impact of this optional terminating action 
is estimated to be $6,480 per support fitting.

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 98-NM-144-AD.

    Applicability: Model 747 series airplanes, line numbers 202 
through 886 inclusive, equipped with General Electric Model CF6-45/
50 and Pratt & Whitney Model JT9D-70 series engines; on which the 
strut/wing modification has not been accomplished in accordance with 
AD 95-13-07, amendment 39-9287; certificated in any category.


[[Page 64915]]


    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 (h) 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 of the strut skin and 
spring beam support fittings on the outboard nacelle struts, and 
cracked or loose fasteners of the support fittings, which could 
result in failure of the outboard nacelle struts and consequent 
separation of the engine, accomplish the following:
    (a) Prior to the accumulation of 13,000 total flight cycles, or 
within 6 months after the effective date of this AD, whichever 
occurs later, perform a detailed visual inspection of the outboard 
nacelle struts, as specified by paragraphs (a)(1), (a)(2), (a)(3), 
and (a)(4) of this AD, in accordance with Boeing Alert Service 
Bulletin 747-54A2172, dated February 23, 1995, or Boeing Service 
Bulletin 747-54A2172, Revision 1, dated January 4, 1996.
    (1) Inspect the spring beam support fittings to detect cracks of 
the support fittings.
    (2) Inspect the spring beam support fittings at the fasteners, 
using a borescope to detect cracks of the support fittings.
    (3) Inspect the fasteners of the outer spring beam support 
fittings to detect cracked or loose fasteners.
    (4) Inspect the strut skin to detect cracks.
    (b) If no discrepancy is found during any inspection required by 
paragraph (a) of this AD, perform detailed visual inspections of the 
outboard nacelle struts to detect any discrepancies specified in 
paragraphs (b)(1), (b)(2), (b)(3), and (b)(4) of this AD, in 
accordance with Boeing Alert Service Bulletin 747-54A2172, dated 
February 23, 1995; or Boeing Service Bulletin 747-54A2172, Revision 
1, dated January 4, 1996. Perform the inspection at the times 
specified in paragraph (c) or (d) of this AD, as applicable.
    (1) Perform a detailed visual inspection, using a borescope, of 
only the outer spring beam support fittings at the fasteners through 
the horizontal flange to detect cracks of the support fittings.
    (2) Perform a detailed visual inspection, using a borescope, of 
the fasteners through the vertical flange of only the outer spring 
beam support fittings to detect loose collars.
    (3) Perform an external detailed visual inspection of only the 
outer spring beam support fittings to detect cracked or loose 
fastener heads.
    (4) Perform a detailed visual inspection of the strut skin to 
detect cracks.
    (c) For Model 747-SR series airplanes equipped with General 
Electric Model CF6-45 series engines, on which no discrepancy is 
found during any inspection required by paragraph (a) of this AD: 
Perform the inspection required by paragraph (b) of this AD within 
1,600 flight cycles following the accomplishment of the inspection 
required by paragraph (a) of this AD; and thereafter at intervals 
not to exceed 1,600 flight cycles until accomplishment of the 
optional terminating action specified in paragraph (g) of this AD.
    (d) For Model 747 series airplanes other than those identified 
in paragraph (c) of this AD, on which no discrepancy is found during 
any inspection required by paragraph (a) of this AD: Perform the 
inspection required by paragraph (b) of this AD within 1,000 flight 
cycles following the accomplishment of the inspection required by 
paragraph (a) of this AD; and thereafter at intervals not to exceed 
1,000 flight cycles until accomplishment of the optional terminating 
action specified in paragraph (g) of this AD.
    (e) If any cracking is found in the spring beam support fittings 
during any inspection required by this AD, prior to further flight, 
replace the support fitting with a new support fitting, in 
accordance with the Accomplishment Instructions in Part IV. of 
Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4, 
1996. Accomplishment of this replacement constitutes terminating 
action for the repetitive inspection requirements of this AD for 
only the new support fitting. Continue the repetitive inspections 
required by paragraph (b) of this AD for the other support fitting 
locations until accomplishment of the terminating action specified 
by paragraph (g)(1) or (g)(2) of this AD, as applicable.
    (f) If any crack is found on the strut skin, or if any cracked 
or loose fastener or collar is found during any inspection required 
by this AD, prior to further flight, 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 
who has been authorized by the Manager, Seattle ACO, to make such 
findings.
    (g) Accomplishment of an open-hole high frequency eddy current 
(HFEC) inspection, in accordance with Boeing Alert Service Bulletin 
747-54A2172, dated February 23, 1995, or Boeing Service Bulletin 
747-54A2172, Revision 1, dated January 4, 1996; and either paragraph 
(g)(1) or (g)(2) of this AD, as applicable; constitutes terminating 
action for the requirements of this AD.
    (1) If no discrepancy is found during the HFEC inspection, prior 
to further flight, rework the fastener holes and install new 
fasteners, in accordance with Figures 6 and 7 of Boeing Alert 
Service Bulletin 747-54A2172, dated February 23, 1995, or Boeing 
Service Bulletin 747-54A2172, Revision 1, dated January 4, 1996.
    (2) If any cracking is found during the HFEC inspection, prior 
to further flight, replace any cracked spring beam support fitting 
with a new support fitting, in accordance with Part IV. of the 
Accomplishment Instructions specified by Boeing Service Bulletin 
747-54A2172, Revision 1, dated January 4, 1996.
    (h) 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. 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.

    (i) 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 November 18, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-31327 Filed 11-23-98; 8:45 am]
BILLING CODE 4910-13-U