[Federal Register Volume 59, Number 234 (Wednesday, December 7, 1994)]
[Unknown Section]
[Page 0]
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