[Federal Register Volume 59, Number 141 (Monday, July 25, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-17592]


[[Page Unknown]]

[Federal Register: July 25, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-183-AD; Amendment 39-8977; AD 94-15-06]

 

Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes 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 amendment requires inspection of an 
expanded area, deletion of the reporting requirement, and expansion of 
the applicability to include additional airplanes. This amendment is 
prompted by reports of cracking of the fuselage skin in certain areas 
and findings of additional countersunk fasteners. The actions specified 
by this AD are intended to prevent reduced structural integrity of the 
fuselage.

DATES: Effective August 24, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of August 24, 1994.

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 1601 Lind Avenue SW., Renton, Washington; or at the Office of 
the Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.

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: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) by superseding AD 90-01-07, 
amendment 39-6440 (55 FR 255, January 4, 1990), which is applicable to 
certain Boeing Model 747 series airplanes, was published in the Federal 
Register on February 3, 1994 (59 FR 5139). The action proposed to 
require inspection of an expanded area, deletion of the reporting 
requirement, and expansion of the applicability.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    One commenter supports the proposed rule.
    Two commenters request that proposed paragraph (e) be revised to 
reduce the area of inspection to coincide with the area specified in 
the service bulletin (Boeing Service Bulletin 747-53A2312, Revision 2, 
dated October 8, 1992) referenced in the proposal as the appropriate 
source of service information. The FAA does not concur. An FAA 
investigation has revealed that countersunk fasteners may be installed 
in areas other than those specified in the referenced service bulletin. 
Therefore, the FAA has determined that a one-time inspection along the 
entire lap joint of the skin panel must be accomplished to positively 
confirm the exact location of these countersunk fasteners.
    One commenter requests an extension to the proposed compliance time 
of 11,000 total landings to conduct the high frequency eddy current 
(HFEC) inspection required by paragraph (g) of the proposal. The 
commenter states that the compliance time should coincide with the time 
recommended in the service bulletin (Boeing Service Bulletin 747-
53A2312, Revision 2, dated October 8, 1992) referenced in the proposal 
as the appropriate source of service information. The compliance time 
in the service bulletin specifies that, for airplanes on which only the 
minimum number of countersunk fasteners have been installed, the HFEC 
inspection should commence at 20,000 total flight cycles. The commenter 
notes that for airplanes on which only the minimum number of 
countersunk fasteners have been installed, the potential for widespread 
multi-site damage is significantly lessened than for airplanes on which 
more than the minimum number of countersunk fasteners have been 
installed.
    The FAA does not concur with the commenter's request to extend the 
compliance time. In developing an appropriate compliance time for this 
action, the FAA considered the safety implications of any cracking in 
this area. The FAA acknowledges that cracking in the upper row of 
countersunk fasteners in the lap splice in the area adjacent to the 
wing-to-body fairing intersection may not result in catastrophic 
consequences; however, the FAA finds that any cracking in this area has 
the potential for developing into an unsafe condition. This AD is 
issued to address that unsafe condition, which may result in reduced 
structural integrity of the fuselage of the airplane as a result of 
cracking in these areas. Further, since cracking has been found in this 
area on in-service airplanes that had accumulated less than 20,000 
total flight cycles, the FAA has determined that 11,000 total landings 
represent the maximum interval of time allowable wherein the inspection 
can reasonably be accomplished and an acceptable level of safety can be 
maintained.
    One commenter requests clarification of the proposed compliance 
time for reinspection of previously modified lap joints. The commenter 
requests that the HFEC inspections required by proposed paragraph (k) 
commence from the time the lap joint was modified in accordance with AD 
90-01-07, rather than from the time the lap joint is modified in 
accordance with proposed paragraph (j). The FAA finds that 
clarification is warranted. Paragraph (k) of the final rule has been 
revised to state that HFEC inspections are to be performed prior to the 
accumulation of 10,000 total landings following modifications (of 
locations where countersunk fasteners were found) accomplished in 
accordance with Boeing Service Bulletin 747-53A2312, dated June 12, 
1989, Revision 1, dated March 29, 1990, or Revision 2, dated October 8, 
1992, which includes modifications accomplished in accordance with AD 
90-01-07 or in accordance with paragraph (j) of this AD.
    Two commenters question the necessity for the inspections following 
modification of the lap joints required by proposed paragraph (k). One 
of these commenters does not see adequate justification for requiring 
these inspections since AD 90-01-07 terminated the inspections after 
accomplishment of the modification. The other commenter states that, 
since other lap joints are not required to be inspected following 
modification, this lap joint should not be inspected following 
modification. From these comments, the FAA infers that these commenters 
are requesting that the requirement to inspect following modification 
be deleted. The FAA does not concur. An FAA evaluation of currently 
available inspection techniques reveals that current technology may not 
be able to adequately detect cracking beneath protruding head 
fasteners. Further, in-service experience has demonstrated that 
cracking has gone undetected beneath these protruding head fasteners. 
Therefore, the FAA's intent in requiring these inspections following 
the modification are to detect any cracking that may develop after 
accomplishment of the modification and to repair any cracking prior to 
it adversely affecting the structural integrity of the fuselage of the 
airplane.
    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the change previously 
described. The FAA has determined that this change will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.
    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 will be affected by this AD.
    The inspections that were previously required by AD 90-01-07, and 
retained in this AD, take approximately 14 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 $140,910, or $770 per 
airplane, per inspection cycle.
    The additional new inspections that are required by this AD will 
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, per 
inspection cycle.
    The modification required by this AD will take approximately 124 
work hours per airplane to accomplish, at an average labor rate of $55 
per work hour. Required parts will 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.
    The total cost impact figure discussed above is based on 
assumptions that no operator has yet accomplished any of the 
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 modification will require a large 
number of work hours to accomplish. However, the 20,000-landings 
compliance time specified in paragraph (j) of this AD should allow 
ample time for the modification of all countersunk fasteners locations 
to be accomplished coincidentally with scheduled major airplane 
inspection and maintenance activities, thereby minimizing the costs 
associated with special airplane scheduling.
    The regulations adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 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 39-6440 (55 FR 
255, January 4, 1990), and by adding a new airworthiness directive 
(AD), amendment 39-    , to read as follows:

94-15-06 BOEING: Amendment 39-8977. 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 total 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 during the inspections required 
by paragraph (a) of this AD, 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 during the inspection required by paragraph (e) of this 
AD, no further action is required by this AD.
    (g) If any countersunk fastener is found in the upper row of the 
lap splice during the inspection required by paragraph (e) of this 
AD, 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), and (k) of this AD, at any location where a 
countersunk fastener was found, repeat the inspection thereafter 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 in accordance with Boeing Service Bulletin 747-53A2312, 
dated June 12, 1989, or Revision 1, dated March 29, 1990, or 
Revision 2, dated October 8, 1992, perform an HFEC inspection at all 
locations where countersunk fasteners were found, and repeat this 
inspection thereafter 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 
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.
    (n) The actions shall be done in accordance with Boeing Service 
Bulletin 747-53A2312, including the ``ADDENDUM,'' Revision 2, dated 
October 8, 1992. This incorporation by reference was approved by the 
Director of the Federal Register in accordance with 5 U.S.C. 552(a) 
and 1 CFR part 51. Copies may be obtained from Boeing Commercial 
Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. 
Copies may be inspected at the FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington; or at the Office of the 
Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.
    (o) This amendment becomes effective on August 24, 1994.

    Issued in Renton, Washington, on July 13, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-17592 Filed 7-22-94; 8:45 am]
BILLING CODE 4910-13-U