AD 2000-04-17

[Federal Register Volume 65, Number 40 (Tuesday, February 29, 2000)]
[Rules and Regulations]
[Pages 10695-10698]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 00-4568]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-366-AD; Amendment 39-11600; AD 2000-04-17]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-100, -200, and -300 
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Boeing Model 747-100, -200, and -300 series 
airplanes. This action requires repetitive inspections to detect 
fatigue cracking in the upper deck floor beams located at certain body 
stations, and repair, if

[[Page 10696]]

necessary. This amendment is prompted by a report by the manufacturer 
that, during a fatigue test, the upper chord and web of the upper deck 
floor beams located at body stations (BS) 340 and 360 were found 
severed at approximately 34,000 total flight cycles. Another report by 
an operator indicated that a severed upper chord and web were found in 
the upper deck floor beam at BS 380 at approximately 33,000 total 
flight cycles. In addition, cracking was found at multiple fastener 
hole locations. The actions specified in this AD are intended to 
prevent failure of the upper deck floor beams at certain body stations 
due to fatigue cracking, which could result in rapid decompression and 
consequent reduced controllability of the airplane.

DATES: Effective March 15, 2000.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 15, 2000.
    Comments for inclusion in the Rules Docket must be received on or 
before May 1, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-366-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    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 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.

FOR FURTHER INFORMATION CONTACT: Rick Kawaguchi, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-1153; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received a report indicating 
that, during a Boeing fatigue test, the upper chord and web of the 
upper deck floor beams located at body stations (BS) 340 and 360 failed 
at approximately 34,000 flight cycles. The FAA also received an 
operator's report of a severed upper chord and web at BS 380, which 
occurred in an upper deck floor beam at approximately 33,000 flight 
cycles. In addition, cracks were found at twelve floor panel attachment 
fastener holes between left buttock line 66.5 and right buttock line 
58.5.
    The manufacturer also reports that one operator found crack 
indications at multiple fastener hole locations during an inspection of 
the upper deck floor beams located at BS 340 and 360 on six airplanes 
having at least 30,000 total flight cycles. Inspections included an 
open-hole high frequency eddy current (HFEC) inspection from above, and 
a visual inspection from below. The majority of the cracks were found 
during open-hole HFEC inspections, and most of such cracking could be 
removed by oversizing the fastener holes; however, repairs were 
required at some locations.
    The report also indicates that the floor beams at BS 340 and 360 
are made from 7075 aluminum, a material which is more susceptible to 
fatigue cracking than 2024 aluminum. The floor beam at BS 380 is made 
from 2024 aluminum, which is considered a more durable material than 
7075 aluminum; however, recent reports of cracking at that body station 
indicate that it is necessary to also require inspections in that area.
    The FAA has been informed that flight-critical wire bundles and 
control cables are routed through the upper deck floor beams at BS 340, 
360, and 380; and that failure of these floor beams could lead to large 
deflection or deformation of the floor and body skin, frames, and 
stringers, which could damage the wire bundles and result in unintended 
inputs to the flight control cables. Failure of the upper deck floor 
beams at BS 340, 360, and 380, due to fatigue cracking, could also 
result in rapid decompression and consequent reduced controllability of 
the airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-53A2431, dated February 10, 2000, which describes procedures for 
repetitive open-hole high frequency eddy current (HFEC) and surface 
HFEC inspections to detect cracking of the upper chords of the upper 
deck floor beams at BS 340 and 360; and repair, if necessary. 
Procedures also include repetitive inspections if no cracking is found. 
The first repetitive inspection threshold may be extended from 3,000 
flight cycles to 10,000 flight cycles if the floor panel attachment 
fastener holes are modified.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other Boeing Model 747-100, -200, and -300 series 
airplanes of the same type design, this AD is being issued to prevent 
failure of the upper deck floor beams at BS 340, 360, and 380 due to 
fatigue cracking that originates from the upper chord fastener holes of 
those floor beams, which could result in rapid decompression and 
consequent reduced controllability of the airplane. This AD requires 
accomplishment of actions specified in the alert service bulletin 
described previously, except as discussed below.

Differences Between the Alert Service Bulletin and This AD

    Operators should note that, although the alert service bulletin 
specifies inspections of the upper chord of the upper deck floor beam 
at BS 340 and 360, the FAA has determined that the same unsafe 
condition also exists on both the left and right sides of the floor 
beam at BS 380 between buttock lines 40 and 76. This determination is 
based on a recent report from an operator that a severed upper chord 
and web were found in an upper deck floor beam at BS 380.
    Operators also should note that, although the alert service 
bulletin specifies that the manufacturer may be contacted for 
disposition of certain repair conditions, this AD requires the repair 
of those conditions to be accomplished in accordance with a method 
approved by the FAA, 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 
FAA to make such findings.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be

[[Page 10697]]

considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 99-NM-366-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    The regulations adopted herein will not have a substantial direct 
effect 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, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket.
    A copy of it, if filed, 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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

2000-04-17  Boeing: Amendment 39-11600. Docket 99-NM-366-AD.

    Applicability: Model 747-100, -200, and -300 series airplanes as 
listed in Boeing Alert Service Bulletin 747-53A2431; certificated in 
any category.


    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
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 (b) 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.


    Note 2:
    The actions specified by Boeing Alert Service Bulletin 747-
53A2431, dated February 10, 2000, for the upper deck floor beams 
located at body stations (BS) 340 and 360, also are applicable to 
both the left and right sides of the floor beam at BS 380 between 
buttock lines (BL) 40 and 76.


    To prevent failure of the upper deck floor beams due to fatigue 
cracking at BS 340, 360, and 380; which could result in rapid 
decompression and consequent reduced controllability of the 
airplane; accomplish the following:

Inspections and Repair

    (a) Prior to the accumulation of 28,000 total flight cycles, or 
within 60 days after the effective date of this AD, whichever occurs 
later, perform the inspections required by either paragraph (a)(1) 
or (a)(2) of this AD, as applicable.
    (1) Gain access to the upper deck floor beams from above the 
upper deck floor, and perform an open-hole high frequency eddy 
current (HFEC) inspection to detect cracking of the upper deck floor 
beams at BS 340 and 360, and on both the left and right sides of the 
floor beam at BS 380 between BL 40 and 76; in accordance with Part 1 
of the Accomplishment Instructions of Boeing Alert Service Bulletin 
747-53A2431, dated February 10, 2000.
    (i) If no cracking is found, perform the actions required by 
either paragraph (a)(1)(i)(A) or (a)(1)(i)(B) of this AD, in 
accordance with the alert service bulletin.
    (A) Repeat the inspection required by paragraph (a)(1) of this 
AD thereafter at intervals not to exceed 3,000 flight cycles.
    (B) Modify (oversize) the floor panel attachment fastener holes 
as specified in Figure 5 of the alert service bulletin, and repeat 
the inspection required by paragraph (a)(1) of this AD within 10,000 
flight cycles. Thereafter, repeat the inspection at intervals not to 
exceed 3,000 flight cycles.
    (ii) If any cracking is found, 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 (DER) who has been authorized 
by the FAA to make such findings. For a repair method to be approved 
by the Manager, Seattle ACO, as required by this paragraph, the 
Manager's approval letter must specifically reference this AD.
    (2) Gain access to the upper deck floor beams from below the 
upper deck floor; modify the floor panel attachment clipnuts at BS 
340 and 360, and on both the left and right sides of the floor beam 
at BS 380 between BL 40 and 76; and perform a surface HFEC 
inspection to detect cracking of the floor beams at those body 
stations; in accordance with Part 2 of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 747-53A2431, dated 
February 10, 2000.
    (i) If no cracking is found, repeat the inspection required by 
paragraph (a)(2) of this AD thereafter at intervals not to exceed 
750 flight cycles.
    (ii) If any cracking is found, prior to further flight, repair 
in accordance with a method approved by the Manager, Seattle ACO, or 
in accordance with data meeting the type certification basis of the 
airplane approved by a Boeing Company DER who has been authorized by 
the FAA to make such findings. For a repair method to be approved by 
the Manager, Seattle ACO, as required by this paragraph, the 
Manager's approval letter must specifically reference this AD.

Alternative Methods of Compliance

    (b)(1) 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.
    (2) An alternative method of compliance for paragraphs 
(a)(1)(ii) and (a)(2)(ii) of this AD that provides an acceptable 
level of safety may be used in accordance with data meeting the type 
certification basis of the airplane

[[Page 10698]]

approved by a Boeing Company DER who has been authorized by the 
Manager, Seattle ACO, to make such findings.


    Note 3:
    Information concerning the existence of approved alternative 
methods of compliance with this AD, if any, may be obtained from the 
Seattle ACO.

Special Flight Permits

    (c) 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.

Incorporation by Reference

    (d) Except as specified in paragraphs (a)(1)(ii) and (a)(2)(ii), 
the actions shall be done in accordance with Boeing Alert Service 
Bulletin 747-53A2431, dated February 10, 2000. 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.
    (e) This amendment becomes effective on March 15, 2000.

    Issued in Renton, Washington, on February 22, 2000.
Donald L. Riggin,
Acting Manager Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-4568 Filed 2-28-00; 8:45 am]
BILLING CODE 4910-13-U