[Federal Register Volume 60, Number 138 (Wednesday, July 19, 1995)]
[Rules and Regulations]
[Pages 36981-36983]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-14167]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 94-NM-159-AD; Amendment 39-9268; AD 95-12-17]


Airworthiness Directives; Boeing Model 737-100 and -200 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 737-100 and -200 series airplanes, 
that requires 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 
amendment is prompted by reports of fatigue cracks in those outboard 
chords. The actions specified by this 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: Effective August 18, 1995. -
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of August 18, 1995.

ADDRESSES: 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 Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 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: 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: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain Boeing Model 737-100 and -
200 series airplanes was published in the Federal Register on December 
7, 1994 (59 FR 63065). That action proposed to 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. That action also provides for an 
optional terminating action for the required inspections. -
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received. -
    Two commenters support the proposed rule. -
    The manufacturer requests that, in the Discussion section of the 
proposed rule, a reference to ``chords'' be changed to ``chord.'' The 
FAA acknowledges that ``chord'' would be more accurate. However, since 
the Discussion section does not appear in the final rule, no change to 
the final rule is necessary. -
    The manufacturer also requests that certain clarifications be made 
to the proposed rule. The manufacturer notes that the addition of the 
words ``BS 727'' in paragraphs (a) and (c) will clarify that it is the 
BS 727 upper outboard chord, not the S-18A chord, that is being 
referred to. The manufacturer also notes that changing the words 
``outboard chords'' with ``cracked chord'' in paragraph (g)(2) would 
clarify the intent of the replacement requirements of that paragraph. 
The FAA concurs, and has revised the final rule accordingly. -
    Two commenters request that the final rule reference a new revision 
of Boeing Service Bulletin 737-53A1166 that includes procedures for 
repair of cracking in the S-18A outer chord. The commenters note that 
the service bulletin specified in the proposed rule only describes the 
inspection of S-18A and does not provide repair instructions in the 
event that cracking is detected. The FAA concurs. Since issuance of the 
proposed rule, the FAA has reviewed and approved Boeing Service 
Bulletin 737-53A1166 Revision 1, dated May 25, 1995, which describes 
repair procedures for cracking of stringer 18A outer chord. Paragraph 
(e) of the final rule has been changed to add a reference to this 
revised service bulletin as an additional source of service 
information. -
    One commenter states that the proposed Pulse Echo Shear Wave (PESW) 
inspection is redundant, since the proposed rule also would require a 
High Frequency Eddy Current (HFEC) inspection. The commenter also 
states that the HFEC inspection is more accurate for detecting cracks 
than the PESW inspection. The commenter therefore requests that the FAA 
remove the requirement to perform the PESW inspection from the proposed 
rule. The FAA does not concur. The PESW inspection is necessary to 
detect cracking that is not common to the fastener holes; the HFEC 
inspection only would detect cracks that extend into the fastener hole. 
-
    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD. -
    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 will be affected by this 
AD, that it will take approximately 4 work hours per airplane to 
accomplish the required inspections, and that the average labor rate is 
$60 per work hour. Based on these figures, the total cost impact of the 
AD on U.S. operators is estimated to be $71,040, or $240 per airplane, 
per inspection cycle. -
    The total cost impact figure discussed above is based on 
assumptions that no operator has yet accomplished any of the 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted. -
    Should an operator elect to accomplish the optional terminating 
action that will be provided by this AD action, it will take 
approximately 50 work hours to accomplish it, at an average labor rate 
of $60 per work hour. Required parts will 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 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. -
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a 

[[Page 36982]]
``significant rule'' under DOT Regulatory Policies and Procedures (44 
FR 11034, February 26, 1979); and (3) 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 final 
evaluation has been prepared for this action and it is contained in the 
Rules Docket. A copy of it 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. 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:

95-12-17 Boeing: Amendment 39-9268. Docket 94-NM-159-AD.

    -Applicability: Model 737-100 and 200 series airplanes, line 
numbers 1 through 999, 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 body station (BS) 727 frame 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 either Boeing Alert Service 
Bulletin 737-53A1166, dated June 30, 1994; or Boeing Service 
Bulletin 737-53A1166, Revision 1, dated May 25, 1995. -
    (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 total flight cycles, but fewer than 50,000 total 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 total 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 total flight cycles, but fewer than 60,000 total 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 total 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 total flight cycles, but fewer than 70,000 total 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 total 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 total 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 BS 727 frame 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, PESW, and 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 either Boeing Alert Service Bulletin 737-53A1166, 
dated June 30, 1994; or Boeing Service Bulletin 737-53A1166, 
Revision 1, dated May 25, 1995. 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 

[[Page 36983]]
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, repair prior to further 
flight, in accordance with either paragraph (e)(1) or (e)(2) of this 
AD. -
    (1) Boeing Service Bulletin 737-53A1166, Revision 1, dated May 
25, 1995, or -
    (2) 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 either Boeing Alert Service Bulletin 737-53A1166, dated June 
30, 1994; or Boeing Service Bulletin 737-53A1166, Revision 1, dated 
May 25, 1995. -
    (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 2: 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 
either Boeing Alert Service Bulletin 737-53A1166, dated June 30, 
1994, or Revision 1, dated May 25, 1995, 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 cracked chord 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 3: 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. -
    (j) The inspections and replacement shall be done in accordance 
with either Boeing Alert Service Bulletin 737-53A1166, dated June 
30, 1994, including Addendum, or Boeing Service Bulletin 737-
53A1166, Revision 1, dated May 25, 1995, including Addendum. 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. -
    (k) This amendment becomes effective on August 18, 1995.

    Issued in Renton, Washington, on June 5, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-14167 Filed 7-18-95; 8:45 am]
BILLING CODE 4910-13-U