[Federal Register Volume 64, Number 227 (Friday, November 26, 1999)]
[Proposed Rules]
[Pages 66426-66428]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-30798]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-307-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 777-200 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the adoption of a new airworthiness
directive (AD) that is applicable to certain Boeing Model 777-200
series airplanes. This proposal would require one-time inspections to
detect cracking of the aft wheel well bulkhead, and corrective actions,
if necessary. This proposal also would require modification of the aft
wheel well bulkhead. For certain airplanes, this proposal also would
require a one-time visual inspection to detect excess sealant covering
the outer flange of the side fitting and lower chord and splice area of
the aft wheel well bulkhead, and corrective actions, if necessary. This
proposal is prompted by a report indicating that numerous fatigue
cracks were found in the aft wheel well bulkhead. The actions specified
by the proposed AD are intended to prevent fatigue cracking of the aft
wheel well bulkhead, which could result in rapid in-flight
decompression of the airplane.
DATES: Comments must be received by January 10, 2000.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 99-NM-307-AD, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056. Comments may be inspected at this
location between 9:00 a.m. and 3:00 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: Stan Wood, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-2772; fax (425) 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
[[Page 66427]]
must submit a self-addressed, stamped postcard on which the following
statement is made: ``Comments to Docket Number 99-NM-307-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-114, Attention: Rules
Docket No. 99-NM-307-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
The FAA has received a report indicating numerous fatigue cracks
have been found in the aft wheel well bulkhead of a Boeing Model 777-
200 test airplane. During full-scale fatigue testing of the airplane,
cracks between 0.15 to 1.5 inches long occurred at 55,186 flight
cycles. The cracks were detected at the bulkhead web cut-out for the
air driven pump duct, at the side fitting to lower chord splice area,
and both sides of the splice joint of the aft wheel well bulkhead. At
110,000 flight cycles, cracks were detected in the vertical flange of
the lower chord at the fairing support bracket attachment. Such fatigue
cracking, if not detected and corrected, could result in rapid in-
flight decompression of the airplane.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin
777-53A0015, dated June 17, 1999, which describes procedures for a one-
time visual inspection to detect cracking of the adjacent structure of
the aft wheel well bulkhead, and a one-time high frequency eddy current
(HFEC) inspection to detect cracking of certain fastener holes in the
web, side fitting, and outer chord of the aft wheel well bulkhead, and
corrective actions, if necessary. The corrective actions involve, for
certain airplanes, removing additional fasteners, oversizing the
cracked fastener holes, performing additional HFEC inspections, and
replacing the fasteners with new fasteners.
For certain airplanes, Boeing Alert Service Bulletin 777-53A0015,
dated June 17, 1999, describes procedures for modification of the aft
wheel well bulkhead. The modification involves cold working certain
fastener holes; replacing the fairing support brackets and splice
plates with revised fairing support brackets and splice plates; and
installing new web doublers and, if necessary, shims.
Additionally, for certain airplanes, Boeing Alert Service Bulletin
777-53A0015, dated June 17, 1999, describes procedures for a one-time
visual inspection to detect excess sealant covering the outer flange of
the side fitting and lower chord and splice of the aft wheel well
bulkhead, and corrective actions, if necessary. The corrective actions
involve removing the excess sealant between stringers S-27L to S-27R
prior to accomplishing the inspections and modification of the aft
wheel well bulkhead.
Accomplishment of the actions specified in the alert service
bulletin is intended to adequately address the identified unsafe
condition.
Explanation of Requirements of Proposed Rule
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 require accomplishment of the actions specified in
the alert service bulletin described previously, except as discussed
below.
Differences Between Proposed Rule and Alert Service Bulletin
Operators should note that, although the Boeing alert service
bulletin specifies that the manufacturer may be contacted for
disposition of certain cracking conditions, this proposal would require
the repair of those conditions to be accomplished in accordance with a
method approved by the FAA.
Additionally, operators also should note that, this proposed AD
would require, removal of excess sealant in the remaining area between
stringers S-27L and S-27R, prior to further flight, upon completion of
the aft wheel well bulkhead modification. The alert service bulletin
recommends that the excess sealant be removed prior to the threshold
specified for fatigue inspections in Section 9 of the Maintenance
Planning Document (MPD). In developing the appropriate compliance time,
the FAA considered the manufacturer's recommendation and the degree of
urgency associated with addressing the subject unsafe condition. In
light of these factors, the FAA finds that the compliance time
specified by this proposed AD to be appropriate.
Cost Impact
There are approximately 109 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 35 airplanes of U.S. registry
would be affected by this proposed AD.
For all airplanes, it would take approximately 2 work hours per
airplane to accomplish the general visual and HFEC inspections at an
average labor rate of $60 per work hour. Based on these figures, the
cost impact of the these inspections proposed by this AD on U.S.
operators is estimated to be $120 per airplane.
For all airplanes, it would take approximately 28 work hours per
airplane to accomplish the proposed modification at an average labor
rate of $60 per work hour. Required parts would be approximately $6,013
per airplane. Based on these figures, the cost impact of the
modification proposed by this AD on U.S. operators is estimated to be
$7,693 per airplane.
For certain airplanes, it would take 3 work hours per airplane to
accomplish the proposed inspection to detect excess sealant at an
average labor rate of $60 per work hour. Based on these figures, the
cost impact of the this inspection proposed by this AD on U.S.
operators is estimated to be $180 per airplane.
The cost impact figures discussed above are based on assumptions
that no operator has yet accomplished any of the proposed requirements
of this AD action, and that no operator would accomplish those actions
in the future if this AD were not adopted.
Regulatory Impact
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.
[[Page 66428]]
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
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:
Boeing: Docket 99-NM-307-AD.
Applicability: Model 777-200 series airplanes having line
numbers 1 through 144; certificated in any category.
Note 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
otherwise 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 (c) 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 fatigue cracking of the aft wheel well bulkhead,
which could result in rapid in-flight decompression of the airplane,
accomplish the following:
General Visual Inspection
(a) For Group 1 airplanes, as identified in Boeing Alert Service
Bulletin 777-53A0015, dated June 17, 1999: Prior to the accumulation
of 11,000 total flight cycles, or within 4,000 flight cycles after
the effective date of this AD, whichever occurs later, perform a
one-time general visual inspection to detect excess sealant covering
the outer flange of the side fitting and lower chord and splice of
the aft wheel well bulkhead, in accordance with Part I of the
Accomplishment Instructions of the alert service bulletin.
Note 2: For the purposes of this AD, a general visual inspection
is defined as: ``A visual examination of an interior or exterior
area, installation, or assembly to detect obvious damage, failure,
or irregularity. This level of inspection is made under normally
available lighting conditions such as daylight, hangar lighting,
flashlight, or drop-light, and may require removal or opening of
access panels or doors. Stands, ladders, or platforms may be
required to gain proximity to the area being checked.''
(1) If no excess sealant is detected, no further action is
required by this paragraph.
(2) If any excess sealant is detected, prior to further flight,
remove the excess sealant from the aft wheel well bulkhead area in
accordance with the alert service bulletin.
Inspections/Modification
(b) For Groups 1 and 2 airplanes, as identified in Boeing Alert
Service Bulletin 777-53A0015, dated June 17, 1999: Prior to the
accumulation of 11,000 total flight cycles, or within 4,000 flight
cycles after the effective date of this AD, whichever occurs later,
perform a one-time general visual inspection to detect cracking of
the adjacent structure of the aft wheel well bulkhead and perform a
one-time high frequency eddy current (HFEC) inspection to detect
cracking of the fastener holes in the web, side fitting, and outer
chord of the aft wheel well bulkhead, in accordance with Part II of
the Accomplishment Instructions of the alert service bulletin.
(1) If no cracking is detected during the general visual and
HFEC inspections, prior to further flight, modify the aft wheel well
bulkhead (including cold working; replacing the fairing support
bracket and splice plates with revised fairing support brackets and
splice plates; and installing new web doublers and, if necessary,
shims), in accordance with Part II of the Accomplishment
Instructions of the alert service bulletin.
(2) If any cracking is detected during the general visual
inspection, prior to further flight, accomplish the requirements of
paragraph (c) of this AD.
(3) If any cracking is detected during the one-time HFEC
inspection, prior to further flight, remove additional fasteners,
and perform a second HFEC inspection to detect cracking of the
fastener holes, in accordance with Part II of the Accomplishment
Instructions of the alert service bulletin.
(i) If no cracking is detected during the second HFEC
inspection, prior to further flight, oversize all the holes to the
diameter specified in the alert service bulletin, and perform a
third HFEC inspection to detect cracking of the fastener holes, in
accordance with Part II of the Accomplishment Instructions of the
alert service bulletin.
(A) If no cracking is detected during the third HFEC inspection,
prior to further flight, replace the fasteners with new fasteners
and modify the aft wheel well bulkhead (including cold working;
replacing the fairing support bracket and splice plates with revised
fairing support brackets and splice plates; and installing new web
doublers and, if necessary, shims), in accordance with Part II of
the Accomplishment Instructions of the alert service bulletin.
(B) If any cracking is detected during the third HFEC
inspection, prior to further flight, accomplish the requirements of
paragraph (c) of this AD.
(ii) If any cracking is detected during the second HFEC
inspection, prior to further flight, accomplish the requirements of
paragraph (c) of this AD.
(c) For airplanes on which cracking has been detected during any
inspection required by paragraph (b)(2), (b)(3)(i)(B), or
(b)(3)(ii), prior to further flight, repair in accordance with a
method approved by the Manager, Seattle Airplane 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
who has been authorized by the Manager, Seattle ACO, 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.
(d) For Group 1 airplanes, as identified in Boeing Alert Service
Bulletin 777-53A0015, dated June 17, 1999, on which excess sealant
was detected and removed in accordance with paragraph (a) of this
AD: Prior to further flight following the accomplishment of the
modification required by paragraph (b) of this AD, remove any excess
sealant in the remaining area of the lower lobe of the aft wheel
well bulkhead between stringers S-27L and S-27R, in accordance with
the alert service bulletin.
Alternative Methods of Compliance
(e) 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.
Special Flight Permits
(f) Special flight permits may be issued in accordance with
Secs. 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.
Issued in Renton, Washington, on November 19, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-30798 Filed 11-24-99; 8:45 am]
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