[Federal Register Volume 64, Number 155 (Thursday, August 12, 1999)]
[Proposed Rules]
[Pages 43950-43953]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-20881]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-84-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 737-200, -200C, -300, and
-400 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the supersedure of an existing
airworthiness directive (AD), applicable to certain Boeing Model 737-
200, -200C, -300, and -400 series airplanes, that currently requires
repetitive visual inspections to detect cracking of the corners of the
door frame and the cross beams of the aft cargo door, and corrective
actions, if necessary. That AD also provides an optional terminating
action for certain repetitive inspections. This action would add
requirements for repetitive high frequency eddy current (HFEC)
inspections, and corrective actions, if necessary. This action also
would mandate accomplishment of the previously optional terminating
action. The actions specified by the proposed AD are intended to
prevent fatigue cracking of the corners of the door frame and the cross
beams of the aft cargo door, which could result in rapid
depressurization of the airplane.
DATES: Comments must be received by September 27, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 99-NM-84-AD, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056. Comments may be inspected at this location
between 9 a.m. and 3 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: 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:
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 must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 99-NM-84-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-84-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
[[Page 43951]]
Discussion
On November 30, 1998, the FAA issued AD 98-25-06, amendment 39-
10931 (63 FR 67769, December 9, 1998), applicable to certain Boeing
Model 737-200, -200C, -300, and -400 airplanes, to require repetitive
inspections to detect cracking of the corners of the door frame and the
cross beams of the aft cargo door, and corrective actions, if
necessary. That action also provides an optional terminating action for
the repetitive inspection requirement of that AD. That action was
prompted by reports indicating that fatigue cracks have been detected
in the corners of the door frame and the cross beams of the aft cargo
door on several in-service airplanes, and by another report indicating
that rapid depressurization occurred during flight on one of those
airplanes. The requirements of that AD are intended to prevent fatigue
cracking of the corners of the door frame and the cross beams of the
aft cargo door, which could result in rapid depressurization of the
airplane.
Actions Since Issuance of Previous Rule
Since the issuance of AD 98-25-06, the FAA has received a report
indicating that during a high frequency eddy current inspection a one-
inch crack was detected in the forward corner frame of the aft cargo
door. Further investigation revealed a crack in the aft corner frame
and cracks in the lower cross beam. No cracking was detected during a
detailed visual inspection of these areas that was accomplished
approximately 925 flight cycles prior to an incident of rapid
depressurization of the airplane. In light of this information, the FAA
has determined that the detailed visual inspections of the door frame
and the cross beams of the aft cargo door required by the existing AD
are not providing the degree of safety assurance necessary for the
affected airplanes.
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 supersede AD 98-25-06 to continue to require
repetitive visual inspections to detect cracking of the corners of the
door frame and the cross beams of the aft cargo door, and corrective
actions, if necessary. This proposed AD would add requirements for
repetitive high frequency eddy current (HFEC) inspections of the
corners of the aft cargo door frame, and corrective actions, if
necessary. This proposal also would mandate accomplishment of the
previously optional terminating action.
The HFEC inspections would be required to be accomplished in
accordance with the procedures specified in Boeing 737 Nondestructive
Test Manual, Part 6, Chapter 51-00-00 (Figure 4 or Figure 23).
Modification of the door frame would be required to be accomplished in
accordance with Boeing Service Bulletin 737-52-1079, Revision 5, dated
May 16, 1996. Repairs of the outer chord of the upper and lower cross
beams would be required to be accomplished 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 Designated Engineering Representative.
Other Relevant Rulemaking
The FAA previously has issued AD 90-06-02, amendment 39-6489 (55 FR
8372, March 7, 1990), applicable to certain Boeing Model 737 series
airplanes. AD 90-06-02 requires accomplishment of certain structural
modifications, which constitutes terminating action for the repetitive
inspection requirements of this proposed AD.
Differences Between Service Bulletin and This Proposed AD
As stated in AD 98-25-06, operators should note that,
unlike the procedures described in the service bulletin, this proposed
AD would not permit further flight with stop-drilled cracks in the
frame of the aft cargo door. The FAA has determined that, because of
the safety implications and consequences associated with such cracking,
any subject aft cargo door frame that is found to be cracked must be
permanently repaired and modified prior to further flight.
As stated in AD 98-25-06, operators should note that the
effectivity listing of the service bulletin includes Boeing Model 737-
200 and -200C series airplanes having line numbers 6 through 873
inclusive. The applicability of this proposed AD includes not only
those airplanes listed in the effectivity listing of the service
bulletin, but also Boeing Model 737-200, -200C, -300, and -400 series
airplanes; having line numbers 874 through 1642 inclusive; that have
certain replacement doors installed and that have not been modified in
accordance with Boeing Service Bulletin 737-52-1079.
Operators also should note that, although the service
bulletin specifies that the manufacturer may be contacted for
disposition of certain repair conditions, this proposed AD would
require 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.
Operators should note that, although the service bulletin
describes accomplishment of a visual inspection of the corners of the
door frame and the cross beams of the aft cargo door, for the reasons
discussed previously, the FAA has determined that accomplishment of a
visual inspection only is inadequate to detect cracking in certain
areas. Therefore, this proposed AD would add repetitive high frequency
eddy current inspections to detect cracking of the four corners of the
aft cargo door frame.
Operators should note that this AD proposes to mandate,
within 4 years after the effective date of this AD, the modification of
the door frame of the aft cargo door described in Boeing Service
Bulletin 737-52-1079, Revision 5, dated May 16, 1996, as terminating
action for the repetitive inspections of the door frame. The FAA has
determined that long-term continued operational safety will be better
assured by design changes to remove the source of the problem, rather
than by repetitive inspections. Long-term inspections may not be
providing the degree of safety assurance necessary for the transport
airplane fleet. This, coupled with a better understanding of the human
factors associated with numerous continual inspections, has led the FAA
to consider placing less emphasis on inspections and more emphasis on
design improvements. The proposed modification is in consonance with
these conditions.
Cost Impact
There are approximately 1,636 Model 737 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 707
airplanes of U.S. registry would be affected by this proposed AD.
The detailed visual inspections that currently are required by AD
98-25-06, and retained in this proposed AD, take approximately 2 work
hours per airplane to accomplish, at an average labor rate of $60 per
work hour. Based on these figures, the cost impact of the currently
required inspections on U.S. operators is estimated to be $84,840, or
$120 per airplane, per inspection cycle.
The new high frequency eddy current inspections that are proposed
in this AD action would take approximately 4 work
[[Page 43952]]
hours per airplane to accomplish, at an average labor rate of $60 per
work hour. Based on these figures, the cost impact of the new
inspections proposed by this AD on U.S. operators is estimated to be
$169,680, or $240 per airplane, per inspection cycle.
The modification that is proposed in this AD action would take
approximately 144 work hours per airplane to accomplish, at an average
labor rate of $60 per work hour. Required parts would cost
approximately $4,530 per airplane. Based on these figures, the cost
impact of the modification proposed by this AD on U.S. operators is
estimated to be $9,311,190, or $13,170 per airplane.
The cost impact figures discussed above are based on assumptions
that no operator has yet accomplished any of the current or 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.
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 removing amendment 39-10931 (63 FR
67769, December 9, 1998), and by adding a new airworthiness directive
(AD), to read as follows:
Boeing: Docket 99-NM-84-AD. Supersedes AD 98-25-06, Amendment 39-
10931.
Applicability: The following airplane models, certificated in
any category:
Model 737-200 and -200C series airplanes, line numbers
6 through 873 inclusive;
Model 737-200, -200C, -300, and -400 series airplanes;
line numbers 874 through 1642 inclusive; equipped with an aft cargo
door having Boeing part number (P/N) 65-47952-1 or P/N 65-47952-524;
excluding:
1. Those airplanes on which that door has been modified in
accordance with Boeing Service Bulletin 737-52-1079; or
2. Those airplanes on which the door assembly having P/N 65-
47952-524 includes four straps (P/N's 65-47952-139, 65-47952-140,
65-47952-141, and 65-47952-142) and a thicker lower cross beam web
(P/N 65-47952-157).
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 (f)(1)
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 corners of the door frame and
the cross beams of the aft cargo door, which could result in rapid
depressurization of the airplane, accomplish the following:
Restatement of the Requirements of AD 98-25-06:
Inspections and Corrective Actions
(a) Within 90 days or 700 flight cycles after December 24, 1998
(the effective date of AD 98-25-06, amendment 39-10931), whichever
occurs later, perform an internal detailed visual inspection to
detect cracking of the corners of the door frame and the cross beams
of the aft cargo door, in accordance with Boeing Service Bulletin
737-52-1079, Revision 5, dated May 16, 1996.
(1) If no cracking is detected, accomplish the requirements of
either paragraph (a)(1)(i) or (a)(1)(ii) of this AD.
(i) Repeat the internal visual inspection thereafter at
intervals not to exceed 4,500 flight cycles. Or
(ii) Prior to further flight, modify the corners of the door
frame and the cross beams of the aft cargo door in accordance with
the service bulletin. Accomplishment of such modification
constitutes terminating action for the repetitive inspection
requirements of paragraph (a)(1)(i) of this AD.
(2) If any cracking is detected in the upper or lower cross
beams, prior to further flight, modify the cracked beam in
accordance with paragraph III.C. of Part I of the Accomplishment
Instructions of the service bulletin. Accomplishment of such
modification constitutes terminating action for the repetitive
inspection requirements of paragraph (a)(1)(i) of this AD for the
repaired beam.
(3) If any cracking is detected in the forward or aft upper door
frame, prior to further flight, repair the frame and modify the
corners of the door frame of the aft cargo door, in accordance with
paragraph III.E. of Part I of the Accomplishment Instructions of the
service bulletin, except as provided by paragraph (b) of this AD.
Accomplishment of such modification constitutes terminating action
for the repetitive inspection requirements of paragraph (a)(1)(i) of
this AD for the upper door frame.
Note 2: Cracks of the forward or aft upper door frame,
regardless of length, must be repaired prior to further flight in
accordance with paragraph III.E. of Part I of the Accomplishment
Instructions of the service bulletin.
(4) If any cracking is detected in the forward or aft lower door
frame, prior to further flight, replace the damaged frame with a new
frame, and modify the corners of the door frame of the aft cargo
door, in accordance with paragraph III.F. of Part I of the
Accomplishment Instructions of the service bulletin. Accomplishment
of such modification constitutes terminating action for the
repetitive inspection requirements of paragraph (a)(1)(i) of this AD
for the lower door frame.
(b) Where Boeing Service Bulletin 737-52-1079, Revision 5, dated
May 16, 1996, specifies that certain repairs are to be accomplished
in accordance with instructions received from Boeing, this AD
requires that, prior to further flight, such repairs be accomplished
in accordance with a method approved by the Manager, Seattle
Aircraft Certification Office (ACO), FAA, Transport Airplane
Directorate.
New Requirements of This AD:
Inspections and Corrective Actions
(c) If any cracking of the outer chord of the upper or lower
cross beams of the aft cargo door is detected as a result of any
inspection required by paragraph (a) of this AD, 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
Designated Engineering Representative who has been authorized by the
FAA to make such findings.
[[Page 43953]]
(d) Within 4,500 flight cycles or one year after the effective
date of this AD, whichever occurs later: Perform a high frequency
eddy current inspection (HFEC) to detect cracking of the four
corners of the door frame of the aft cargo door, in accordance with
the procedures specified in Boeing 737 Nondestructive Test Manual,
Part 6, Chapter 51-00-00 (Figure 4 or Figure 23) .
(1) If no cracking of the corners of the door frame of the aft
cargo door is detected, repeat the HFEC inspections thereafter at
intervals not to exceed 4,500 flight cycles until accomplishment of
the modification specified in paragraph (e) of this AD.
(2) If any cracking of the corners of the door frame of the aft
cargo door is detected, prior to further flight, replace the damaged
frame with a new frame, and modify the four corners of the door
frame, in accordance with Parts II and III of the Accomplishment
Instructions of Boeing Service Bulletin 737-52-1079, Revision 5,
dated May 16, 1996. Accomplishment of such modification constitutes
terminating action for the repetitive inspection requirements of
paragraph (d)(1) of this AD for that door frame.
Terminating Action
(e) Within 4 years after the effective date of this AD: Modify
the four corners of the door frame and the cross beams of the aft
cargo door, in accordance with Part II of the Accomplishment
Instructions of Boeing Service Bulletin 737-52-1079, Revision 5,
dated May 16, 1996. Accomplishment of such modification constitutes
terminating action for the repetitive inspection requirements of
this AD.
Note 3: Accomplishment of the modification required by paragraph
(a) of AD 90-06-02, amendment 39-6489, is considered acceptable for
compliance with paragraph (e) of this AD.
Note 4: Modification of the corners of the door frame and the
cross beams of the aft cargo door accomplished prior to the
effective date of this AD in accordance with Boeing Service Bulletin
737-52-1079, dated December 16, 1983; Revision 1, dated December 15,
1988; Revision 2, dated July 20, 1989; Revision 3, dated May 17,
1990; or Revision 4, dated February 21, 1991; is considered
acceptable for compliance with paragraph (e) of this AD.
Alternative Methods of Compliance
(f)(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.
(f)(2) Alternative methods of compliance, approved previously in
accordance with AD 98-25-06, amendment 39-10931, are approved as
alternative methods of compliance with this AD.
Note 5: 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
(g) 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.
Issued in Renton, Washington, on August 6, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-20881 Filed 8-11-99; 8:45 am]
BILLING CODE 4910-13-P
