[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]


-----------------------------------------------------------------------

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.

-----------------------------------------------------------------------

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]
BILLING CODE 4910-13-P