[Federal Register Volume 63, Number 79 (Friday, April 24, 1998)]
[Rules and Regulations]
[Pages 20311-20313]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-10919]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-127-AD; Amendment 39-10498; AD 98-09-17]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747-200F and -200C 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 all Boeing Model 747-200F and -200C series airplanes.
This action requires repetitive inspections or a one-time inspection to
detect cracking of certain areas of the upper deck floor beams; and
corrective actions, if necessary. This amendment is prompted by reports
indicating that fatigue cracks were found in the upper chord and web of
upper deck floor beams. The actions specified in this AD are intended
to prevent such fatigue cracking and the resultant failure of such
floor beams. Failure of the floor beam could result in damage to
critical flight control cables and wire bundles that pass through the
floor beam, and consequent reduced controllability of the airplane;
failure of the floor beam also could result in the failure of the
adjacent fuselage frames and skin, and consequent rapid decompression
of the airplane.
DATES: Effective May 11, 1998.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of May 11, 1998.
Comments for inclusion in the Rules Docket must be received on or
before June 23, 1998.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 98-NM-127-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: Bob Breneman, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-2776; fax (425) 227-1181.
SUPPLEMENTARY INFORMATION: The FAA has received two reports indicating
that, during modification of Boeing Model 747-200F series airplanes,
fatigue cracking was found in the upper chord and web of the upper deck
floor beams at body stations (BS) 340, 360, 380, and 400. One of these
airplanes had accumulated approximately 19,100 total flight cycles, and
the other approximately 18,500 total flight cycles. In addition, cracks
were found at BS 380 on a 747-200F series airplane that had accumulated
11,586 total flight cycles.
The subject cracking was found in the upper chord of the upper deck
floor beams, at the fastener location common to the fuselage frame
inner chord. Cracks in this location are not detectable by visual
inspection until the crack propagates to the horizontal flange of the
chord. Analysis has demonstrated that, when a crack of the upper chord
reaches the horizontal flange, the crack would propagate extremely
rapidly, allowing little time to detect the crack prior to complete
failure of the upper chord.
The upper deck floor beams are attached to the adjacent fuselage
frames and provide a significant contribution to the structural
integrity of the flat-sided fuselage. These floor beams also contain
critical flight control cables and wire bundles that originate from the
flight deck and flight engineer's control panel. The subject upper deck
floor beams are made from 7075-T6511 aluminum, which is less durable
and more susceptible to fatigue cracking than 2024 aluminum, which is
used on passenger airplanes.
Unsafe Conditions
Fatigue cracking of the upper chord and web, if not corrected could
result in failure of the upper deck floor beams and consequent damage
to critical flight control cables and wire bundles that pass through
the floor beams. Such damage could lead to uncommanded input to flight
controls and reduced controllability of the airplane.
In addition, because the subject fatigue cracking has been found at
multiple adjacent floor beam locations, failure of one floor beam could
precipitate the failure of adjacent floor beams. Failure of these floor
beams could cause the failure of the adjacent fuselage frames and skin,
which could result in rapid decompression of the airplane.
Similar Models
Boeing Model 747-200C series airplanes have the same upper deck
floor beam configuration to that on the affected Model 747-200F series
airplanes. Therefore, both of these models may be subject to the same
unsafe condition.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin
747-53A2420, dated March 26, 1998, which describes procedures for
performing repetitive detailed visual inspections to detect cracks of
the upper chord, web, and strap of the upper deck floor beams at BS 340
through BS 520 inclusive; and repair, if necessary. The alert service
bulletin also describes procedures for a one-time open hole high
frequency eddy current (HFEC) inspection to detect cracking at BS 340
through BS 420 inclusive, which would eliminate the need for the
repetitive detailed visual inspections.
Explanation of the Requirements of the Rule
Since an unsafe condition has been identified that is likely to
exist or develop on other airplanes of the same type design, this AD is
being issued to prevent reduced controllability of the airplane and/or
rapid decompression of the airplane due to fatigue cracking in the
upper deck floor beams. This AD requires accomplishment of the actions
specified in the alert service bulletin described previously, except as
provided below.
Differences Between Rule and Alert Service Bulletin
This AD differs from the alert service bulletin in the following
three respects:
[[Page 20312]]
1. The alert service bulletin specifies that the manufacturer may
be contacted for disposition of repair conditions. However, this AD
requires the repair of those conditions to be accomplished in
accordance with a method approved by the FAA.
2. The alert service bulletin requires a visual inspection of the
upper deck floor beams at BS 460 and BS 480. This AD does not require
inspection of this area because the upper chords of these floor beams
are made from a 2024 material, which is more durable than the other
upper deck floor beams and is less susceptible to the same type of
fatigue cracking.
3. The alert service bulletin does not require repeat detailed
visual inspections or any open hole eddy current inspection of the
upper deck floor beams at BS 440 through BS 520. For this area, this AD
requires that the detailed visual inspection, if accomplished, be
repetitively performed; and also requires that an open hole HFEC
inspection eventually be accomplished. The floor beams at BS 440
through BS 520 (with the exception of floor beams at BS 460 and BS 480)
are made from the same, less durable 7075-T6511 material and are
subjected to the same operational loads as the floor beams with
reported fatigue cracking; therefore, these beams are subject to the
same type of fatigue cracking. Operators should note that procedures
specified in Figures 2 and 4 of the alert service bulletin are
identical.
Interim Action
This is considered to be interim action. The manufacturer advises
that it currently is developing a preventive modification that will
positively address the unsafe condition addressed by this AD. Once this
modification is developed, approved, and available, the FAA may
consider additional rulemaking.
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 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 98-NM-127-AD.'' The postcard will be date stamped and
returned to the commenter.
Regulatory Impact
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.
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:
98-09-17 Boeing: Amendment 39-10498. Docket 98-NM-127-AD.
Applicability: All Model 747-200F and -200C series airplanes,
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 (d) 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.
To prevent reduced controllability of the airplane and/or rapid
decompression of the airplane due to fatigue cracking in the upper
deck floor beams, accomplish the following:
Note 2: For this AD, ``flight cycles'' are considered to be
flight cycles with a cabin pressure differential greater than 2.0
pounds per square inch.
(a) For airplanes that have accumulated less than 18,000 total
flight cycles as of the effective date of this AD: Prior to the
accumulation of 15,000 total flight cycles, or within 250 flight
cycles after the effective date of this AD, whichever occurs later,
inspect the upper chord, web, and strap of the upper deck floor
beams at body station (BS) 340 through BS 440 inclusive, and the
upper deck floor beams at BS 500 and BS 520, on the right and left
sides of the airplane, in accordance with paragraph (a)(1) or (a)(2)
of this AD. The inspections shall be
[[Page 20313]]
accomplished in accordance with Boeing Alert Service Bulletin 747-
53A2420, dated March 26, 1998.
(1) Perform a detailed visual inspection to detect cracks in
accordance with Figure 2 of the alert service bulletin.
(i) Repeat the detailed visual inspection thereafter at
intervals not to exceed 25 flight cycles, until the requirements of
paragraph (a)(1)(ii) are accomplished.
(ii) Within 500 flight cycles after accomplishment of the
initial detailed visual inspection, accomplish paragraph (a)(2) of
this AD.
(2) Perform a one-time open hole high frequency eddy current
(HFEC) inspection to detect cracks in accordance with Figure 3 of
the alert service bulletin.
Accomplishment of this action constitutes terminating action for
the repetitive inspection requirements of this AD.
(b) For airplanes that have accumulated 18,000 or more total
flight cycles as of the effective date of this AD: Within 25 flight
cycles after the effective date of this AD, inspect the upper chord,
web, and strap of the upper deck floor beams at BS 340 through BS
440 inclusive, and the upper deck floor beams at BS 500 and BS 520,
on the right and left sides of the airplane, in accordance with
paragraph (b)(1) or (b)(2) of this AD. The inspections shall be
accomplished in accordance with Boeing Alert Service Bulletin 747-
53A2420, dated March 26, 1998.
(1) Perform a detailed visual inspection to detect cracks in
accordance with Figure 2 of the alert service bulletin.
(i) Repeat the detailed visual inspection thereafter at
intervals not to exceed 25 flight cycles, until the requirements of
paragraph (b)(1)(ii) are accomplished.
(ii) Within 250 flight cycles after accomplishment of the
initial detailed visual inspection, accomplish paragraph (b)(2) of
this AD.
(2) Perform a one-time open hole HFEC inspection to detect
cracks in accordance with Figure 3 of the alert service bulletin.
Accomplishment of this action constitutes terminating action for the
repetitive inspection requirements of this AD.
(c) If any cracking is found during any inspection required by
this AD, prior to further flight, repair in accordance with a method
approved by the Manager, Seattle Aircraft Certification Office, FAA,
Transport Airplane Directorate.
(d) 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.
(e) 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.
(f) The inspections shall be done in accordance with Boeing
Alert Service Bulletin 747-53A2420, dated March 26, 1998. 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.
(g) This amendment becomes effective on May 11, 1998.
Issued in Renton, Washington, on April 20, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 98-10919 Filed 4-23-98; 8:45 am]
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