[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]


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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).

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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 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