[Federal Register Volume 59, Number 234 (Wednesday, December 7, 1994)]
[Unknown Section]
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From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-30086]
[[Page Unknown]]
[Federal Register: December 7, 1994]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-159-AD]
Airworthiness Directives; Boeing Model 737-100 and -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 737-100 and -
200 series airplanes. This proposal would require various inspections
for cracks in the outboard chord of the frame at Body Station (BS) 727
and in the outboard chord of Stringer 18A; and repair or replacement of
cracked parts. This proposal is prompted by reports of fatigue cracks
in those outboard chords. The actions specified by the proposed AD are
intended to prevent such fatigue cracking, which could result in
reduced structural integrity of the outboard chords, and subsequent
rapid decompression of the airplane.
DATES: Comments must be received by February 3, 1995.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-ANM-159-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: Thomas Rodriguez, Aerospace Engineer,
Airframe Branch, ANM-120S, Seattle Aircraft Certification Office, FAA,
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (206) 227-2779; fax (206) 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 94-NM-159-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-103, Attention: Rules
Docket No. 94-NM-159-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
The FAA has received several reports of cracking on Boeing Model
737-100 and -200 series airplanes in the outboard chord of the frame at
Body Station (BS) 727 where Stringer 18A is attached. There also have
been reports of cracking in the outboard chord of Stringer 18A. These
cracks were found on eight airplanes that had accumulated between
39,000 and 54,100 flight hours, and between 56,200 and 73,200 flight
cycles. The cracks have been determined to be caused by fatigue that
was initiated by fretting of adjacent parts. Fatigue cracks in the
chords, if not detected and corrected in a timely manner, could result
in reduced structural integrity of the structure, and subsequent rapid
decompression of the airplane.
The FAA has reviewed and approved Boeing Alert Service Bulletin
737-53A1166, dated June 30, 1994, which describes procedures for the
following repetitive inspections:
1. Close visual inspections to detect cracking of the edge of the
forward flange of the outboard chord of the frame at BS 727;
2. High frequency eddy current (HFEC) inspections to detect
cracking of the fastener holes in the outboard chord of the frame at BS
727;
3. Pulse echo shear wave (PESW) inspections to detect cracking in
the area of the two forward lower fastener holes in the outboard chord
where Stringer 18A is attached; and
4. HFEC inspections to detect cracking of the outboard surface of
the outboard chord of Stringer 18A at Station 727 and of the surface
around the heads of two fasteners.
The alert service bulletin also describes procedures for either the
installation of a time-limited repair or the replacement of the chords,
if any crack is found in the outboard chord of the frame at BS 727.
(The alert service bulletin references Boeing Service Bulletin 737-53-
1088 as an additional source of service information for replacement of
the outboard chords.) In addition, the alert service bulletin describes
procedures for installation of a preventative modification, which, when
accomplished, eliminates the need for repetitive inspections.
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 various inspections for cracks in the
outboard chord of the frame at BS 727 and in the outboard chord of
Stringer 18A; and repair or replacement of cracked parts. The proposed
AD would also provide for an optional terminating action for the
required inspections. The actions would be required to be accomplished
in accordance with the service bulletin described previously.
As a result of recent communications with the Air Transport
Association (ATA) of America, the FAA has learned that, in general,
some operators may misunderstand the legal effect of AD's on airplanes
that are identified in the applicability provision of the AD, but that
have been altered or repaired in the area addressed by the AD. Under
these circumstances, at least one operator appears to have incorrectly
assumed that its airplane was not subject to an AD. On the contrary,
all airplanes identified in the applicability provision of an AD are
legally subject to the AD. If an airplane has been altered or repaired
in the affected area in such a way as to affect compliance with the AD,
the owner or operator is required to obtain FAA approval for an
alternative method of compliance with the AD, in accordance with the
paragraph of each AD that provides for such approvals. A note has been
included in this notice to clarify this requirement.
There are approximately 999 Boeing Model 737-100 and -200 series
airplanes of the affected design in the worldwide fleet. The FAA
estimates that 296 airplanes of U.S. registry would be affected by this
proposed AD, that it would take approximately 4 work hours per airplane
to accomplish each of the proposed inspections, and that the average
labor rate is $60 per work hour. Based on these figures, the total cost
impact of the inspection requirements of this proposed AD on U.S.
operators is estimated to be $71,040, or $240 per airplane, per
inspection cycle.
Should an operator elect to accomplish the optional terminating
action that would be provided by this AD action, it would take
approximately 50 work hours to accomplish it, at an average labor rate
of $60 per work hour. Required parts would cost approximately $3,680
per airplane. Based on these figures, the total cost impact of this
optional terminating action is estimated to be $6,680 per airplane.
The total cost impact figure discussed above is 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.
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. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
Boeing: Docket 94-NM-159-AD.
Applicability: Model 737-100 and -200 series airplanes; line
numbers 1 through 999, inclusive; 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 use the authority
provided in paragraph (h) to request approval from the FAA. This
approval may address either no action, if the current configuration
eliminates the unsafe condition; or different actions necessary to
address the unsafe condition described in this AD. Such a request
should include an assessment of the effect of the changed
configuration on the unsafe condition addressed by this AD. In no
case does the presence of any modification, alteration, or repair
remove any airplane from the applicability of this AD.
Compliance: Required as indicated, unless accomplished
previously.
To prevent reduced structural integrity of the outboard chords,
and subsequent rapid decompression of the airplane, accomplish the
following:
(a) For airplanes on which the upper outboard chord has been
replaced in accordance with Boeing Service Bulletin 737-53-1088:
Prior to the accumulation of 30,000 total flight cycles since
replacement of the upper outboard chord, or within 4,500 flight
cycles after the effective date of this AD, whichever occurs later,
perform close visual, pulse echo shear wave (PESW), and high
frequency eddy current (HFEC) inspections to detect cracks in the
outboard chord of the frame at Body Station (BS) 727 and in the
outboard chord of Stringer 18A , in accordance with Part I of the
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1166, dated June 30, 1994.
(b) Repeat the inspections required by paragraph (a) of this AD
as follows, until the optional terminating action described in
paragraph (g) of this AD is accomplished:
(1) If, at the time of the most recent inspection required by
paragraph (a) or (b) of this AD, the airplane has accumulated 27,000
or more flight cycles, but fewer than 50,000 flight cycles, since
the replacement of the outboard chord: Perform the next inspection
within 15,000 flight cycles. Repeat the inspection thereafter at
intervals not to exceed 15,000 flight cycles until the airplane has
accumulated 50,000 or more flight cycles since the replacement of
the outboard chord; then perform the inspections required by
paragraph (b)(2) of this AD.
(2) If, at the time of the most recent inspection required by
paragraph (a) or (b) of this AD, the airplane has accumulated 50,000
or more flight cycles, but fewer than 60,000 flight cycles, since
the replacement of the outboard chord: Perform the next inspection
within 7,500 flight cycles. Repeat the inspection thereafter at
intervals not to exceed 7,500 flight cycles until the airplane has
accumulated 60,000 or more flight cycles since the replacement of
the outboard chord; then perform the inspections required by
paragraph (b)(3) of this AD.
(3) If, at the time of the most recent inspection required by
paragraph (a) or (b) of this AD, the airplane has accumulated 60,000
or more flight cycles, but fewer than 70,000 flight cycles, since
the replacement of the outboard chord: Perform the next inspection
within 5,000 flight cycles. Repeat the inspection thereafter at
intervals not to exceed 5,000 flight cycles until the airplane has
accumulated 70,000 or more flight cycles since the replacement of
the outboard chord; then perform the inspections required by
paragraph (b)(4) of this AD.
(4) If, at the time of the most recent inspection required by
paragraph (a) or (b) of this AD, the airplane has accumulated 70,000
or more flight cycles since replacement of the outboard chord:
Perform the next inspection within 3,000 flight cycles. Repeat the
inspection thereafter at intervals not to exceed 3,000 flight
cycles.
(c) For airplanes on which the outboard chord has not been
replaced or on which only the lower outboard chord has been replaced
in accordance with Boeing Service Bulletin: 737-53-1088: Perform
close visual, pulse echo shear wave (PESW), and high frequency eddy
current (HFEC) inspections to detect cracks in the outboard chord of
the frame at BS 727 and in the outboard chord of Stringer 18A, in
accordance with Part I of the Accomplishment Instructions of Boeing
Alert Service Bulletin 737-53A1166, dated June 30, 1994. Perform
these inspections initially at the time specified in paragraph
(c)(1), (c)(2), (c)(3), or (c)(4), as applicable. Repeat these
inspections thereafter at the intervals specified in paragraph (d)
of this AD.
(1) For airplanes that have accumulated 27,000 or more total
flight cycles, but fewer than 50,000 total flight cycles, as of the
effective date of this AD: Inspect prior to the accumulation of
4,500 flight cycles after the effective date of this AD.
(2) For airplanes that have accumulated 50,000 or more total
flight cycles, but fewer than 60,000 total flight cycles, as of the
effective date of this AD: Inspect prior to the accumulation of
2,500 flight cycles after the effective date of this AD.
(3) For airplanes that have accumulated 60,000 or more total
flight cycles, but fewer than 70,000 total flight cycles as of the
effective date of this AD: Inspect prior to the accumulation of
1,500 flight cycles after the effective date of this AD.
(4) For airplanes that have accumulated 70,000 or more total
flight cycles as of the effective date of this AD: Inspect prior to
the accumulation of 500 flight cycles or within 90 days after the
effective date of this AD, whichever occurs first.
(d) Repeat the inspections required by paragraph (c) of this AD
as follows, until the optional terminating action described in
paragraph (g) of this AD is accomplished:
(1) If, at the time of the most recent inspection required by
paragraph (c) or (d) of this AD, the airplane has accumulated 27,000
or more total flight cycles, but fewer than 50,000 total flight
cycles: Perform the next inspection within 15,000 flight cycles.
Repeat the inspection thereafter at intervals not to exceed 15,000
flight cycles until the airplane has accumulated 50,000 or more
total flight cycles; then perform the inspections required by
paragraph (d)(2) of this AD.
(2) If, at the time of the most recent inspection required by
paragraph (c) or (d) of this AD, the airplane had accumulated 50,000
or more total flight cycles, but fewer than 60,000 total flight
cycles: Perform the next inspection within 7,500 flight cycles.
Repeat the inspection thereafter at intervals not to exceed 7,500
flight cycles until the airplane has accumulated 60,000 or more
total flight cycles; then perform the inspections required by
paragraph (d)(3) of this AD.
(3) If, at the time of the most recent inspection required by
paragraph (c) or (d) of this AD, the airplane had accumulated 60,000
or more total flight cycles, but fewer than 70,000 total flight
cycles: Perform the next inspection within 5,000 flight cycles.
Repeat the inspection thereafter at intervals not to exceed 5,000
flight cycles until the airplane has accumulated 70,000 or more
total flight cycles; then perform the inspections required by
paragraph (b)(4) of this AD.
(4) If, at the time of the most recent inspection required by
paragraph (c) or (d) of this AD, the airplane had accumulated 70,000
or more total flight cycles: Perform the next inspection within
3,000 flight cycles. Repeat the inspection thereafter at intervals
not to exceed 3,000 flight cycles.
(e) If any crack is found in the outboard chord of Stringer 18A
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.
(f) If any crack is found in the outboard chord of the frame at
BS 727 during any inspection required by this AD, accomplish
paragraph (f)(1) or (f)(2) of this AD, as applicable, in accordance
with Boeing Alert Service Bulletin 737-53A1166, dated June 30, 1994.
(1) For any crack that extends from the forward edge of the
chord or from the forward fastener hole, but that does not extend
past the second fastener hole, accomplish either paragraph (f)(1)(i)
or (f)(1)(ii) of this AD. Thereafter, perform initial and repetitive
inspections in accordance with paragraphs (a) and (b) of this AD.
(i) Prior to further flight, install the time limited repair.
Prior to the accumulation of 4,500 flight cycles or within 18
months, after accomplishing the time-limited repair, whichever
occurs first, replace the outboard chord. Or
(ii) Prior to further flight, replace the outboard chord.
Note 4: Boeing Alert Service Bulletin 737-53A1166 references
Boeing Service Bulletin 737-53-1088 as an additional source of
service information for procedures to replace the chord.
(2) For any crack that extends from the forward edge of the
chord, or from the forward fastener hole, and that extends past the
second fastener hole, prior to further flight, replace the outboard
chord in accordance with the alert service bulletin. Thereafter,
perform initial and repetitive inspections in accordance with
paragraphs (a) and (b) of this AD.
(g) Accomplishment of the following actions in accordance with
Boeing Alert Service Bulletin 737-53A1166, dated June 30, 1994,
constitutes terminating actions for the requirements of this AD:
(1) For airplanes on which no crack is found: Install the
preventative modification in accordance with the alert service
bulletin.
(2) For airplanes on which any crack is found: Prior to further
flight, replace the outboard chords and install the preventative
modification in accordance with the alert service bulletin.
(h) 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 Aircraft Certification
Office (ACO), FAA, Transport Airplane Directorate. 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 5: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(i) 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 December 1, 1994.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-30086 Filed 12-6-94; 8:45 am]
BILLING CODE 4910-13-U
