[Federal Register Volume 59, Number 113 (Tuesday, June 14, 1994)]
[Unknown Section]
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From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-14362]
[[Page Unknown]]
[Federal Register: June 14, 1994]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-30-AD]
Airworthiness Directives; Boeing Model 747 Series Airplanes
Equipped With General Electric CF6 Series Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the supersedure of an existing
airworthiness directive (AD), applicable to certain Boeing Model 747
series airplanes, that currently requires inspections of the strut skin
in the area of the precooler exhaust vent for cracks on the inboard and
outboard struts, and repair, if necessary. This action would require
inspections of an expanded area for certain airplanes, and inspections
of airplanes on which a skin doubler has been installed as terminating
action for the existing AD. This proposal is prompted by reports of
strut skin fatigue cracks and heat damage found aft of the edges of
skin doublers installed on certain Model 747 series airplanes. The
actions specified by the proposed AD are intended to prevent separation
of an engine due to overheating and subsequent cracking of the engine
strut.
DATES: Comments must be received by August 8, 1994.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-NM-30-AD, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056. Comments may be inspected at this location
between 9 a.m. and 3 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-30-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-30-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
On January 28, 1987, the FAA issued AD 87-04-21, Amendment 39-5543
(52 FR 3793, February 6, 1987), applicable to certain Boeing Model 747
series airplanes, to require repetitive inspections of the strut skin
in the area of the precooler exhaust vent to detect cracks on the
inboard and outboard struts, and repair, if necessary. That action also
provides for an optional terminating modification (installation of
frame stiffeners and skin doublers) for the repetitive inspections.
That action was prompted by reports of extensive damage to struts on
several airplanes. The requirements of that AD are intended to prevent
separation of an engine due to overheating and subsequent cracking of
the engine strut.
Since the issuance of that AD, the FAA has received reports of
fatigue cracks found in the strut skin and heat damage found aft of the
edges of skin doublers. These skin doublers had been installed on
certain Model 747 series airplanes as terminating action for certain
requirements contained in AD 87-04-21 and AD 90-06-06, amendment 39-
6490 (55 FR 8374, March 7, 1990). (AD 90-06-06 requires, in part,
incorporation of certain structural modifications specified in the
original issue, Revision 1, or Revision 2 of Boeing Service Bulletin
747-54-2091.) Further, cracking of the skin doublers and the underlying
number 3 stringer also was found on one of these airplanes.
Subsequently, the FAA has reviewed and approved Boeing Service
Bulletin 747-54-2091, Revision 5, dated April 26, 1990, that describes
procedures for a visual inspection of the strut skin and internal
structure in the area of the precooler exhaust vent for cracks, heat
discoloration, and wrinkles on the inboard and outboard struts of
certain airplanes, and on the outboard struts of certain other
airplanes. The service bulletin also describes procedures for
repetitive inspections if no crack, heat discoloration, or wrinkle is
found; and installation of a skin doubler if any crack, heat
discoloration, or wrinkle is found.
The FAA finds that the inspection areas specified in the Boeing
service bulletin must be expanded since cracks and heat damage have
been reported in locations beyond those inspection areas.
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 supersede AD 87-04-21 to require the following:
1. For airplanes on which a frame stiffener and a skin doubler
specified in certain revisions of Boeing Service Bulletin 747-54-2091
have been installed: Repetitive visual inspections to detect cracks,
heat discoloration, or wrinkles of the strut skin and internal
structure in the area of the precooler exhaust vent from the edge of
the skin doubler to nacelle station (NAC STA) 300 on the inboard and
outboard struts, and repair, if necessary. This inspection area has
been expanded beyond the zone described in Revision 5 of the service
bulletin to cover a 30-inch width from the doubler edge to NAC STA 300.
(This inspection zone excludes the area covered by the skin doubler.)
2. For airplanes on which a frame stiffener and a skin doubler
specified in certain revisions of Boeing Service Bulletin 747-54-2091
have not been installed: Repetitive visual inspections to detect
cracks, heat discoloration, or wrinkles of the strut skin and internal
structure in the area of the precooler exhaust vent from NAC STA 230 to
NAC STA 300 on the inboard and outboard struts, and repair, if
necessary. This inspection area has been expanded beyond the zone
described in Revision 5 of the service bulletin to cover a 30-inch
width from NAC STA 230 to NAC STA 300.
The actions would be required to be accomplished in accordance with
procedures described in the service bulletin described previously.
There are approximately 250 Model 747 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 4
airplanes of U.S. registry would be affected by this proposed AD.
The inspections that were previously required by AD 87-04-21, and
retained in this AD, will take approximately 4 work hours per airplane
to accomplish, at an average labor rate of $55 per work hour. Based on
these figures, the total cost impact of that inspection requirement on
U.S. operators is estimated to be $880, or $220 per airplane, per
inspection cycle.
The new inspections that would be added by this AD action would
take approximately 4 work hours per airplane to accomplish, at an
average labor rate of $55 per work hour. Based on these figures, the
total cost impact of the proposed inspection requirements of this AD on
U.S. operators is estimated to be $880, or $220 per airplane.
The total 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 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. 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 removing amendment 39-5543 (52 FR
3793, February 6, 1987), and by adding a new airworthiness directive
(AD), to read as follows:
Boeing: Docket 94-NM-30-AD. Supersedes AD 87-04-21, Amendment 39-
5543.
Applicability: Model 747 series airplanes equipped with General
Electric CF6 series engines, certificated in any category.
Compliance: Required as indicated, unless accomplished
previously.
To prevent separation of an engine due to overheating and
subsequent cracking of the engine strut, accomplish the following:
(a) For airplanes listed in Boeing Service Bulletin 747-54-2091,
Revision 1, dated October 22, 1984: Prior to the accumulation of
10,000 total hours time-in-service, or within the next 7\1/2\ months
after March 13, 1987 (the effective date of AD 87-04-21, Amendment
39-5543), whichever occurs later, perform a visual inspection to
detect cracks of the strut skin in the area of the precooler exhaust
vent on the inboard and outboard struts of Group 1 airplanes, and on
the outboard struts of Group 2 airplanes, as defined in the service
bulletin, in accordance with Boeing Service Bulletin 747-54-2091,
Revision 1, dated October 22, 1984; Revision 2, dated March 24,
1988; Revision 3, dated July 27, 1989; Revision 4, dated December
14, 1989; or Revision 5, dated April 26, 1990. After the effective
date of this AD, the inspection shall be accomplished in accordance
with paragraph (b) of this AD.
(1) If no crack is found, repeat the inspection required by
paragraph (a) of this AD thereafter at intervals not to exceed 15
months, until the inspection required by paragraph (b) or (c) of
this AD, as applicable, is accomplished.
(2) If any crack is found, prior to further flight, repair in
accordance with FAA-approved data, and repeat the inspection
required by paragraph (a) of this AD thereafter at intervals not to
exceed 15 months, until the inspection required by paragraph (b) or
(c) of this AD, as applicable, is accomplished.
(b) For airplanes on which a frame stiffener and a skin doubler
have not been installed during production or in accordance with
Boeing Service Bulletin 747-54-2091, Revision 1, dated October 22,
1984; Revision 2, dated March 24, 1988; Revision 3, dated July 27,
1989; Revision 4, dated December 14, 1989; or Revision 5, dated
April 26, 1990: Perform a visual inspection to detect cracks, heat
discoloration, or wrinkles of the strut skin and internal structure
in the area of the precooler exhaust vent from nacelle station (NAC
STA) 230 to NAC STA 300 on the inboard and outboard struts of Group
1 airplanes and on the outboard struts of Group 2 airplanes, in
accordance with the inspection procedures described in Figure 3 of
Boeing Service Bulletin 747-54-2091, Revision 5, dated April 26,
1990; at the time specified in paragraph (b)(1) or (b)(2) of this
AD, whichever occurs later. Accomplishment of this inspection
terminates the repetitive inspections required by paragraph (a) of
this AD.
(1) Prior to the accumulation of 10,000 total hours time-in-
service on the airplane strut, or within 120 days after the
effective date of this AD, whichever occurs later. Or
(2) Within 12 months after the immediately preceding inspection
accomplished in accordance with paragraph (a) of this AD.
Note 1: Paragraph (b) of this AD specifies an inspection zone
that is expanded beyond the zone described in Revision 5 of the
service bulletin to cover a 30-inch width from NAC STA 230 to NAC
STA 300.
(c) For airplanes on which a frame stiffener and a skin doubler
have been installed during production or in accordance with Boeing
Service Bulletin 747-54-2091, Revision 1, dated October 22, 1984;
Revision 2, dated March 24, 1988; Revision 3, dated July 27, 1989;
Revision 4, dated December 14, 1989; or Revision 5, dated April 26,
1990: Within 120 days after the effective date of this AD, perform a
visual inspection to detect cracks, heat discoloration, or wrinkles
of the strut skin and internal structure in the area of the
precooler exhaust vent from the edge of the doubler to NAC STA 300
on the inboard and outboard struts of Group 1 airplanes and on the
outboard struts of Group 2 airplanes, in accordance with the
inspection procedures described in Figure 3 of Boeing Service
Bulletin 747-54-2091, Revision 5, dated April 26, 1990.
Note 2: Paragraph (c) of this AD specifies an inspection zone
that is expanded beyond the zone described in Revision 5 of the
service bulletin to cover a 30-inch width from the doubler edge to
NAC STA 300.
(d) If no crack, heat discoloration, or wrinkle is found during
the inspection required by paragraph (b) or (c) of this AD, repeat
that inspection thereafter at intervals not to exceed 15 months.
(e) If any crack, heat discoloration, wrinkle, or previously
stop-drilled crack is found during the inspection required by
paragraph (b) or (c) of this AD, prior to further flight, repair
using either the small skin doubler and frame stiffener or the large
skin doubler and frame stiffener specified in Boeing Service
Bulletin 747-54-2901, Revision 5, dated April 26, 1990, in
accordance with that service bulletin; or in accordance with a
method approved by the Manager, Seattle Aircraft Certification
Office (ACO), FAA, Transport Airplane Directorate. Thereafter,
repeat that inspection at intervals not to exceed 15 months.
(f) Installation of a frame stiffener and a skin doubler
referred to in Boeing Service Bulletin 747-54-2091 as ``terminating
action'' does not constitute terminating action for the inspection
requirements of this AD.
(g) 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 3: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(h) Special flight permits may be issued in accordance with
Secs. 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 June 8, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-14362 Filed 6-13-94; 8:45 am]
BILLING CODE 4910-13-U
