[Federal Register Volume 59, Number 23 (Thursday, February 3, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-2410]
[[Page Unknown]]
[Federal Register: February 3, 1994]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 93-NM-183-AD]
Airworthiness Directives; Boeing Model 747 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: This document proposes the supersedure of an existing
airworthiness directive (AD), applicable to certain Boeing Model 747
series airplanes, that currently requires inspecting to detect cracking
in certain lower lobe lap joints, and repair, if necessary; reporting
any findings of discrepancies; replacing certain countersunk fasteners
with protruding head fasteners; and verifying that the airplanes do not
have certain countersunk fasteners. This action would increase the area
to be inspected, delete the reporting requirement, and expand the
applicability. This proposal is prompted by reports of fuselage skin
cracking in certain areas and findings of additional countersunk
fasteners. The actions specified by the proposed AD are intended to
prevent reduced structural integrity of the fuselage.
DATES: Comments must be received by March 30, 1994.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 93-NM-183-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: Steven C. Fox, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (206) 227-2777; 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 93-NM-183-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. 93-NM-183-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
On December 19, 1989, the FAA issued AD 90-01-07, Amendment 39-6440
(55 FR 255, January 4, 1990), applicable to Boeing Model 747 series
airplanes, having line numbers 201 through 765, inclusive, to require:
1. Repetitively inspecting to detect cracking in certain lower lobe
lap joints, and repair, if necessary;
2. Reporting any findings of discrepancies;
3. Replacing certain countersunk fasteners with protruding head
fasteners; and
4. Verifying that airplanes do not have certain countersunk
fasteners.
That action was prompted by reports of cracking in the lap joint of
stringer 34 near the interface with the wing-to-body fairing. The
requirements of that AD are intended to prevent in-flight
depressurization due to undetected cracks in the skin of the airplane.
Since the issuance of that AD, the FAA has received additional
reports of cracking in the upper row of countersunk fasteners in the
lap splice in the area adjacent to the wing-to-body fairing
intersection on Model 747 series airplanes. Additionally, several
airplanes were found to have more than the necessary number of
countersunk fasteners, which were installed during production at the
upper row of the lap splice at stringer 34. These countersunk fasteners
were found in the upper row of fasteners in the lap splice near the
wing-to-body fairing and skin intersection between body station (BS)
768 and the circumferential skin joint at BS 741.
Cracking in locations where countersunk fasteners were installed,
if not corrected, could result in reduced structural integrity of the
fuselage.
The FAA has reviewed and approved Boeing Service Bulletin 747-
53A2312, Revision 2, dated October 8, 1992, that describes procedures
for visually inspecting to determine the number of countersunk
fasteners in the upper row of the lap splice.
If more than the necessary number of countersunk fasteners were
installed during production, this service bulletin specifies conducting
an external high frequency eddy current (HFEC) inspection to detect
cracking in the skin lap splices at the wing-to-body fairing
intersection where countersunk fasteners were found in the upper row of
fasteners. If cracking is found, the service bulletin describes
procedures for modifying the locations where countersunk fasteners were
found by replacing the countersunk fasteners with oversized protruding
head fasteners and repairing the skin. These actions were accomplished,
prior to delivery, on airplanes having line numbers 815 through 919,
inclusive.
If the proper number of countersunk fasteners were installed during
production, repetitive inspections are specified in the service
bulletin until the locations where countersunk fasteners were installed
have been modified.
The service bulletin describes procedures for eventual modification
of all airplanes at the location where countersunk fasteners were
installed, and repetitive inspections following modification.
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 90-01-07 to:
1. Continue to require inspections to detect cracking in certain
lower lobe lap joints, and repair, if necessary;
2. Require visual inspections to determine if countersunk fasteners
had been installed between body stations (BS) 741 and 1000 at Stringers
(S-)34L, S-34R, S-39L, S-39R, and S-44L, S-44R, and between BS 1480 and
1741 at S-34L, S-34R, S-40L, and S-40R on airplanes having line numbers
201 through 814, inclusive;
3. Require HFEC inspections to detect cracking at all locations
where countersunk fasteners were found in the upper row of the lap
splice, and repair, if necessary; and
4. Require modification of all locations where countersunk
fasteners were found.
Although the actions and compliance times of this proposed AD would
differ from the manufacturer's recommendations specified in the service
bulletin, the actions themselves would be required to be accomplished
in accordance with the procedures of the service bulletin described
previously.
There are approximately 723 Boeing Model 747 series airplanes of
the affected design in the worldwide fleet. The FAA estimates that 183
airplanes of U.S. registry would be affected by this AD.
The inspections that were previously required by AD 90-01-07, and
retained in this AD, take approximately 14 workhours per airplane to
accomplish, at an average labor rate of $55 per work hour. Based on
these figures, the total cost impact of these inspection requirements
of this AD on U.S. operators is estimated to be $140,910 or $770 per
airplane, per inspection cycle.
The additional new inspections that would be required by this AD
would take approximately 82 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 these inspection requirements of this AD on U.S.
operators is estimated to be $825,330, or $4,510 per airplane
The modification required by this AD would take approximately 124
work hours per airplane to accomplish, at an average labor rate of $55
per work hour. Required parts would be nominal in cost. Based on these
figures, the total cost impact of the modification requirements of this
AD on U.S. operators is estimated to be $1,248,060, or $6,820 per
airplane.
Based on the above figures, the total cost impact of the inspection
and modification requirements of this AD on U.S. operators is estimated
to be $2,214,300, or $11,407 per airplane. This total cost figure
assumes that no operator has yet accomplished the proposed requirements
of this AD action.
The FAA recognizes that the proposed modification would require a
large number of work hours to accomplish. However, the 20,000-flight
cycle compliance time specified in paragraph (j) of this proposed AD
should allow ample time for the modification of all locations where
countersunk fasteners were found to be accomplished coincidentally with
scheduled major airplane inspection and maintenance activities, thereby
minimizing the costs associated with special airplane scheduling.
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 14
CFR part 39 of the Federal Aviation Regulations 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 39-6440 (55 FR
255, January 4, 1990), and by adding a new airworthiness directive
(AD), to read as follows:
Boeing: Docket 93-NM-183-AD. Supersedes AD 90-01-07, Amendment 39-
6440.
Applicability: Model 747 series airplanes, having line numbers
201 through 814 inclusive, certificated in any category.
Compliance: Required as indicated, unless accomplished
previously.
To prevent reduced structural integrity of the fuselage,
accomplish the following:
Restatement of Requirements of AD 90-01-07, Amendment 39-6440
(a) For airplanes having line numbers 201 through 765: Conduct a
high frequency eddy current (HFEC) inspection to detect cracking of
the lower lobe lap joints in the vicinity of the wing-to-body
fairing in accordance with Boeing Alert Service Bulletin 747-
53A2312, dated June 12, 1989; or Revision 1, dated March 29, 1990;
or Revision 2, dated October 8, 1992; at the time specified in
paragraph (a)(1), (a)(2), (a)(3), or (a)(4) of this AD, as
applicable. Repeat this inspection thereafter at intervals not to
exceed 4,000 landings until the inspection required by paragraph (e)
of this AD is accomplished.
(1) For airplanes that have accumulated less than 11,200 total
landings as of February 5, 1990 (the effective date of AD 90-01-07):
Prior to the accumulation of 11,000 landings or within the next
1,000 landings after February 5, 1990, whichever occurs later.
(2) For airplanes that have accumulated 11,200 or more total
landings but less than 15,201 total landings as of February 5, 1990
(the effective date of AD 90-01-07): Within the next 1,000 landings
after February 5, 1990, or prior to the accumulation of 15,500 total
landings, whichever occurs earlier.
(3) For airplanes that have accumulated 15,201 or more total
landings but less than 18,200 total landings as of February 5, 1990:
Within the next 300 landings after February 5, 1990, or prior to the
accumulation of 18,250 total landings, whichever occurs earlier.
(4) For airplanes that have accumulated 18,200 or more landings
as of February 5, 1990: Within the next 50 landings after February
5, 1990.
(b) For airplanes having line numbers 201 through 765:
Accomplish the requirements of paragraphs (b)(1) and (b)(2) of this
AD.
(1) If any cracking is detected, prior to further flight, repair
in accordance with Boeing Alert Service Bulletin 747-53A2312, dated
June 12, 1989; or Revision 1, dated March 29, 1990; or Revision 2,
dated October 8, 1992.
(2) Prior to the accumulation of 20,000 total landings or within
the next 3,000 landings after February 5, 1990 (the effective date
of AD 90-01-07), whichever occurs later, modify the airplane by
replacing countersunk fasteners in the upper row of the lower lobe
lap joints in the vicinity of the wing-to-body fairing with
protruding head fasteners, in accordance with the procedures
described in the Boeing Alert Service Bulletin 747-53A2312, dated
June 12, 1989; or Revision 1, dated March 29, 1990; or Revision 2,
dated October 8, 1992.
(c) For purposes of complying with paragraphs (a) and (b) of
this AD, the number of landings may be determined to equal the
number of pressurization cycles where the cabin pressure
differential was greater than 2.0 p.s.i.
(d) For Model 747SR airplanes only: Based on continued mixed
operation of lower cabin differentials, the inspection and
modification compliance times specified paragraphs (a) and (b) of
this AD may be multiplied by a 1.2 adjustment factor.
New Requirements of This AD
(e) Prior to the accumulation of 11,000 total landings, or
within 1,000 landings after the effective date of this AD, whichever
occurs later, unless previously accomplished within the last 3,000
landings prior to the effective date of this AD, conduct a visual
inspection to determine if countersunk fasteners have been installed
in the area defined in either paragraph (e)(1) or (e)(2), as
applicable, in accordance with the procedures described in Boeing
Service Bulletin 747-53A2312, Revision 2, dated October 8, 1992.
Accomplishment of this inspection terminates the inspection
requirements of paragraph (a) of this AD.
(1) For Model 747-100, -200, -300, -400, and 747SR series
airplanes: From body stations (BS) 741 to 1000 at Stringers (S-)34L,
S-34R, S-39L, S-39R, S-44L, and S-44R, and from BS 1480 to 1741 at
S-34L, S-34R, S-40L, and S-40R.
(2) For Model 747SP series airplanes: From BS 520 to 1000 at S-
34L, S-34R, S-39L, S-39R, S-44L, and S-44R, and from BS 1480 to 1741
at S-34L, S-34R, S-40L, and S-40R.
(f) If no countersunk fastener is found in the upper row of the
lap splice, no further action is required by this AD.
(g) If any countersunk fastener is found in the upper row of the
lap splice, prior to further flight, perform an HFEC inspection to
detect cracking at all locations where countersunk fasteners were
found, in accordance with the procedures described in Boeing Service
Bulletin 747-53A2312, Revision 2, dated October 8, 1992.
(h) If no cracking is detected during any inspection required by
paragraphs (g), (h), (i), and (k) of this AD, at any location where
a countersunk fastener was found, thereafter repeat the inspection
at intervals not to exceed 4,000 landings, in accordance with the
procedures described in the Boeing Service Bulletin 747-53A2312,
Revision 2, dated October 8, 1992.
(i) If cracking is detected during any inspection required by
paragraphs (g), (h), (i), and (k) of this AD, at any location where
a countersunk fastener was found, prior to further flight, repair
and modify that lap joint in accordance with Boeing Service Bulletin
747-53A2312, Revision 2, dated October 8, 1992.
(j) Prior to the accumulation of 20,000 total landings or within
1,000 landings after the effective date of this AD, whichever occurs
later, modify all locations where countersunk fasteners were found,
in accordance with the procedures described in Boeing Service
Bulletin 747-53A2312, Revision 2, dated October 8, 1992. For
purposes of complying with the requirements of this paragraph,
locations that were previously modified, in accordance with
paragraph (b) of this AD, do not need to be modified again.
(k) Prior to the accumulation of 10,000 total landings following
modification of the locations where countersunk fasteners were
installed, perform an HFEC inspection at all locations where
countersunk fasteners were found, and thereafter, repeat this
inspection at intervals not to exceed 4,000 landings, in accordance
with the procedures described in Boeing Service Bulletin 747-
53A2312, Revision 2, dated October 8, 1992.
(l) 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: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(m) Special flight permits may be issued in accordance with FAR
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 January 28, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-2410 Filed 2-2-94; 8:45 am]
BILLING CODE 4910-13-P