[Federal Register Volume 62, Number 208 (Tuesday, October 28, 1997)]
[Rules and Regulations]
[Pages 55732-55736]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-28347]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-229-AD; Amendment 39-10179; AD 97-22-07]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to certain Boeing Model 737 series airplanes, that 
currently requires repetitive inspections to detect cracking of the 
lower skin at the lower row of fasteners in the lap joints of the 
fuselage, and repair of any cracking detected. This amendment requires 
that the inspections be accomplished at more frequent intervals. This 
amendment also adds a requirement for modification of the fuselage lap 
joints at certain locations, which constitutes terminating action for 
repetitive inspections of modified areas. This amendment is prompted by 
reports of numerous fatigue cracks in the lower skin of the fuselage 
lap joints at the lower row of fasteners. The actions specified in this 
AD are intended to prevent such fatigue cracking, which could result in 
sudden decompression of the airplane.

DATES: Effective November 12, 1997.
    The incorporation by reference of certain publications, as listed 
in the regulations, is approved by the Director of the Federal Register 
as of November 12, 1997.
    The incorporation by reference of Boeing Alert Service Bulletin 
737-53A1177, dated November 8, 1994, as listed in the regulations, was 
approved previously by the Director of the Federal Register as of 
December 27, 1994 (59 FR 63716, December 9, 1994).
    Comments for inclusion in the Rules Docket must be received on or 
before December 29, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 97-NM-229-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    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 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.

FOR FURTHER INFORMATION CONTACT: Gregory L. Schneider or Nenita K. 
Odesa, Aerospace Engineers, Airframe Branch, ANM-120S, FAA, Transport 
Airplane Directorate, Seattle Aircraft Certification Office (ACO), 1601 
Lind Avenue, SW., Renton, Washington; telephone (425) 227-2028 or (425) 
227-2557; fax (425) 227-1181.


[[Page 55733]]


SUPPLEMENTARY INFORMATION: On April 28, 1988, a Boeing Model 737 series 
airplane was involved in an accident in which a 15-foot long section of 
fuselage structure peeled open during flight. In light of this, the FAA 
initiated an Aging Fleet Program. The objective of that program is to 
identify and implement procedures to ensure the continuing structural 
airworthiness of aging transport category airplanes.
    As part of the Aging Fleet Program, the airplane manufacturer 
conducted cyclic pressure (fatigue) tests to evaluate the performance 
of the various fuselage skin panel lap joint configurations. The 
fuselage skin panel joint consists of two adjacent panels that overlap 
each other longitudinally and are joined together by three rows of 
fasteners at the overlap (hence, lap joint). Cracks in the upper skin 
of the lap joint led to the structural failure that occurred in the 
1988 accident discussed previously. These ``first generation'' lap 
joints, installed on early Model 737 series airplanes having line 
numbers 1-291, were modified by replacing the countersunk fasteners in 
the upper fastener row of the lap joint with protruding head fasteners 
to correct and prevent cracking in the upper skin of the lap joint. No 
cracking has been detected to date in the lower fastener row of these 
(modified)``first generation'' lap joints.
    In 1994, tests were conducted on ``second generation'' lap joints; 
test results revealed cracks in the lower skin of this lap joint. The 
airplane manufacturer determined that these cracks were caused by 
increased stresses in this area due to the increased bending stresses 
associated with the installation of a doubler on the upper skin. This 
doubler was installed on ``second generation'' lap joints as an 
improvement to the lap joint to prevent cracks in the upper skin. This 
lap joint configuration, which incorporates the additional doubler, was 
installed on Model 737 series airplanes having line numbers 292 through 
2565.
    In light of results of these tests, the manufacturer inspected the 
lap joints of five aging airplanes and detected a total of 273 fatigue 
cracks. The use of eddy current inspection techniques were required as 
the cracks in the lower skin are not detectable visually due to the 
positioning of the lower skin between the upper skin and the 
circumferential tear strap. Many of these cracks were found to have 
occurred simultaneously at adjacent fastener hole locations in the 
lower skin of the fuselage lap joint.
    This type of cracking of the lap joint is known as multiple site 
damage (MSD). MSD is characterized by the simultaneous presence of 
fatigue cracks in the same structural element (such as the lower skin 
panel of the lap joint). Coalescence of cracks at adjacent fastener 
holes in the lower skin can lead to sudden fracture and failure of the 
lap joint, which could result in rapid decompression of the airplane. 
Due to the reduction in the residual strength of a lap joint in the 
presence of MSD. This reduction of the structural integrity of the 
fuselage may occur at loads significantly below those that would be 
expected for structure having a single large crack. The accident 
discussed previously has demonstrated dramatically that small cracks 
acting together can have a significant effect on the residual strength 
of the aircraft structure.

Issuance of Previous Rule

    On December 2, 1994, the FAA issued AD 94-25-05, amendment 39-9089 
(59 FR 63716, December 9, 1994), applicable to certain Boeing Model 737 
series airplanes, to require repetitive eddy current inspections to 
detect cracking of the lower skin at the lower row of fasteners in the 
lap joints of the fuselage between body stations 259.50 and 1016, and 
repair of any cracking detected. That AD was prompted by reports of 
fatigue cracking occurring simultaneously at adjacent fastener hole 
locations in the lower skin of the fuselage lap joint. The actions 
required by AD 94-25-05 are intended to prevent sudden decompression of 
the airplane due to undetected cracking of the fuselage skin.

Actions Since Issuance of Previous Rule

    Since the issuance of AD 94-25-05, the FAA has received additional 
reports of fatigue cracking in the lower skin of the lap joints of the 
fuselage on airplanes previously inspected in accordance with that AD. 
The FAA received reports of numerous cracks on a number of airplanes 
that had accumulated between 52,000 and 78,000 total flight cycles and 
that had been inspected using low frequency eddy current (LFEC) 
inspection techniques. The majority of these cracks occurred at left 
and right stringers 4, 10, and 14.
    The FAA also received recent reports indicating that extensive 
cracking was found on three airplanes on which high frequency eddy 
current (HFEC) inspections and modification of the lap joints had been 
accomplished in accordance with Revision 1 of Boeing Alert Service 
Bulletin 737-53A1177. Approximately eight months had elapsed since the 
initial LFEC inspections required by AD 94-25-05 had been accomplished. 
These airplanes had accumulated between 76,000 and 84,400 total flight 
cycles. The total number of cracks reported was between 246 and 360 on 
these three airplanes, and the majority of these cracks occurred at 
left and right stringers 4, 10, and 14. On one of these airplanes, 
cracking was found along a 111-inch section of stringer 4L at every 
fastener hole in the lower row of fasteners in the lower skin that had 
not been repaired during the previous LFEC inspection (82% of the total 
fastener holes).
    In the preamble to AD 94-25-05, the FAA specified that the actions 
required by that AD were considered ``interim action'' and that the 
manufacturer was developing a modification to positively address the 
unsafe condition. The FAA indicated that it may consider further 
rulemaking action once the modification was developed, approved, and 
available. The manufacturer now has developed such a modification, and 
the FAA has determined that further rulemaking action is indeed 
necessary; this AD follows from that determination.

Explanation of Relevant Service Information

    Since the issuance of AD 94-25-05, the FAA has reviewed and 
approved Boeing Alert Service Bulletin 737-53A1177, Revision 1, dated 
September 19, 1996; Revision 2, dated July 24, 1997; and Revision 3, 
dated September 18, 1997; which describe procedures for inspections 
similar to those specified in the original issue of the alert service 
bulletin. (The original issue of the alert service bulletin was cited 
in AD 94-25-05 as the appropriate source of service information).
    Revision 1 of the alert service bulletin describes procedures for 
modification of the lap joints at the lower row of fasteners in the 
lower skin of the fuselage [reference Part III (``Preventive Change'') 
of the Accomplishment Instructions of the alert service bulletin].
    The relevant changes in Revision 2 of the alert service bulletin 
include procedures for more frequent repetitive inspections of the 
lower skin at the lower row of fasteners in the lap joints of the 
fuselage.
    For certain lap joint locations on Model 737-200 series airplanes 
only, Revision 2 of the alert service bulletin also describes 
procedures for an option to the modification (``Preventive Change'') 
described in Revision 1 of the alert service bulletin. This option 
[reference Part IV (``Lap Joint Repair'') of the Accomplishment 
Instructions of the alert service bulletin] involves installing a lap 
joint repair on the entire length of the skin panel at certain lap 
joint locations.

[[Page 55734]]

    Revision 3 of the alert service bulletin is essentially the same as 
Revision 2; however, Revision 3 corrects a particular fastener size 
specified in Part IV of the Accomplishment Instructions of the alert 
service bulletin.
    Accomplishment of the modification eliminates the need for the 
repetitive inspections only of those areas that have been modified. 
Accomplishment of the actions specified in the alert service bulletin 
is intended to adequately address the identified unsafe condition.

FAA's Determinations

    Based on reports of numerous cracks detected on airplanes inspected 
previously, the FAA finds that, for certain airplanes, the repetitive 
LFEC inspections required currently by AD 94-25-05 must be accomplished 
at more frequent intervals to detect cracks that, in the presence of 
MSD, could propagate to the point of structural failure of the lap 
joints and result in rapid decompression of the airplane.
    Based upon reports of extensive MSD found in the lower skin of the 
lap joints located at stringers 4, 10, and 14, there may be a 
significant reduction in the residual strength of these lap joints. 
Because of this reduction in strength, in combination with the 
possibility that cracks may go undetected due to human factors, the FAA 
finds that the reduced inspection interval provided by this AD may not 
be adequate to detect cracks which could propagate to the point of 
structural failure. As a result, for airplanes that have accumulated 
70,000 or more total flight cycles, the FAA has concluded that 
modifications of the lap joints at stringers 4, 10, and 14 (as required 
by this AD) on which the most severe cracking has been detected, must 
be required on an emergency basis.

Explanation of Requirements of Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of this same type design, this AD 
supersedes AD 94-25-05 to continue to require repetitive inspections to 
detect cracking of the lower skin at the lower row of fasteners in the 
lap joints of the fuselage, and repair of any cracking detected. This 
AD requires that the inspections be accomplished at more frequent 
intervals.
    This AD also requires modification of the fuselage lap joints at 
certain locations. Accomplishment of the modification constitutes 
terminating action for the repetitive inspections only of those areas 
that have been modified in accordance with this AD.
    The inspections and modification are required to be accomplished in 
accordance with the alert service bulletin described previously.

Explanation of Compliance Time for Initial Inspection

    Operators should note that, for certain airplanes, the compliance 
time for accomplishment of the initial inspection required by this AD 
is approximately 120 days. That number of days is usually sufficient to 
allow for prior notice to the public and a brief comment period before 
adoption of a final rule. In this AD, however, that compliance time was 
selected because of:
     The large number of aircraft affected by the AD;
     The large number of work hours required to accomplish the 
inspection; and
     The availability of an adequate number of maintenance 
facilities able to accommodate scheduling the fleet for inspection.
    A shorter compliance time might have resulted in the unnecessary 
removal of airplanes from service pending scheduling. Nevertheless, the 
FAA has determined that immediate adoption is necessary in this case 
because of the importance of initiating the required inspections and 
modification as soon as possible.

Differences Between the AD and the Relevant Service Bulletins

    Operators should note that, for airplanes that have accumulated 
between 60,000 and 65,000 total flight cycles, the alert service 
bulletin specifies a repetitive inspection of 3,500 flight cycles until 
the airplane has accumulated 65,000 total flight cycles. However, for 
that group of airplanes, this AD requires that repetitive inspections 
be accomplished at intervals not to exceed 1,200 flight cycles. The FAA 
has determined that, because of the safety implications and 
consequences of multiple site damage associated with fatigue cracking 
of the fuselage skin, it is necessary to require earlier repetitive 
inspections to ensure the continued operational safety of the fleet.
    For Boeing Model 737-200 series airplanes only, Part IV of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1177, Revision 3, dated September 18, 1997, recommends installation 
of a support cradle at station 540. However, this installation is not 
intended to support the weight of the airplane. Therefore, this AD does 
not require installation of this support cradle. In addition, to 
clarify the reference in the alert service bulletin for supporting the 
airplane in the jig position, paragraph (g)(2) of this AD explicitly 
requires that, prior to conducting the repair of the lap joint, the 
airplane be supported in the jig position, including support (removal) 
of the engine weight. This action is required to be accomplished in 
accordance with Boeing Document D6-15565, ``737 Structural Repair 
Manual (SRM),'' Chapter 51, Subject 51-50-1, Revision 70, dated July 5, 
1997.

Subsequent Rulemaking

    The FAA may consider separate rulemaking action for airplanes that 
have accumulated more than 70,000 total flight cycles to require 
modification of the lap joints at the remaining locations specified in 
Part III (``Preventive Change'') of the Accomplishment Instructions of 
the alert service bulletin.
    In addition, for airplanes that have accumulated less than 70,000 
total flight cycles, the FAA may consider requiring accomplishment of 
this modification at all locations specified in the alert service 
bulletin.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the rule. All comments submitted will be 
available, both before and after the closing date for comments, in the 
rules docket for examination by

[[Page 55735]]

interested persons. A report that summarizes each FAA-public contact 
concerned with the substance of this AD will be filed in the rules 
docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 97-NM-229-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    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.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the rules docket. 
A copy of it, if filed, 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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing amendment 39-9089 (59 FR 
63716, December 9, 1994), and by adding a new airworthiness directive 
(AD), amendment 39-10179, to read as follows:

97-22-07  Boeing: Amendment 39-10179. Docket 97-NM-229-AD. 
Supersedes AD 94-25-05, Amendment 39-9089.

    Applicability: Model Boeing 737 series airplanes having line 
numbers 292 through 2565 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 
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 (i) 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 sudden decompression of the airplane, accomplish the 
following:
    (a) Perform a low frequency eddy current inspection to detect 
cracking of the lower skin at the lower row of fasteners in the lap 
joints of the fuselage at the time specified in paragraph (b) or (c) 
of this AD, as applicable, in accordance with Part I 
(``Inspection'') of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1177, dated November 8, 1994; Revision 1, 
dated September 19, 1996; Revision 2, dated July 24, 1997; or 
Revision 3, dated September 18, 1997.
    (b) For airplanes that have accumulated 70,000 total flight 
cycles or more as of the effective date of this AD: Perform the 
inspection required by paragraph (a) of this AD at the later of the 
times specified in paragraphs (b)(1) and (b)(2) of this AD.
    (1) Within 100 flight cycles after the effective date of this 
AD.
    (2) Within 300 flight cycles after the last inspection 
accomplished in accordance with AD 94-25-05, amendment 39-9089.
    (c) For airplanes that have accumulated less than 70,000 total 
flight cycles as of the effective date of this AD: Perform the 
inspection required by paragraph (a) of this AD at the later of the 
times specified in paragraphs (c)(1) and (c)(2) of this AD.
    (1) Prior to the accumulation of 60,000 total flight cycles.
    (2) At the earliest of the times specified in paragraph 
(c)(2)(i), (c)(2)(ii), and (c)(2)(iii) of this AD.
    (i) Within 3,500 flight cycles after the last inspection 
accomplished in accordance with AD 94-25-05, amendment 39-9089.
    (ii) Within 1,200 flight cycles after the effective date of this 
AD.
    (iii) Prior to the accumulation of 70,300 total flight cycles.
    (d) If any cracking is detected during the inspection required 
by paragraph (a) of this AD, prior to further flight, repair it in 
accordance with Part II (``Crack Repair'') of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1177, dated 
November 8, 1994; Revision 1, dated September 19, 1996; Revision 2, 
dated July 24, 1997; or Revision 3, dated September 18, 1997.
    (e) Repeat the inspection required by paragraph (a) of this AD 
at the time specified in paragraph (e)(1) or (e)(2) of this AD, as 
applicable, until the modification required by paragraph (f) or (g) 
of this AD, as applicable, is accomplished.
    (1) If the airplane had accumulated less than 70,000 total 
flight cycles at the time of the immediately preceding inspection, 
perform the next inspection within 1,200 flight cycles or prior to 
the accumulation of 70,300 total flight cycles, whichever occurs 
first.
    (2) If the airplane had accumulated 70,000 or more total flight 
cycles at the time of the immediately preceding inspection, perform 
the next inspection within 300 flight cycles.
    (f) Except as provided by paragraph (g) of this AD, modify the 
fuselage lap joints at the lower row of fasteners at stringer 
locations right/left stringer 4 between body station (BS) 360 and BS 
1016; and right/left stringers 10 and 14 between BS 360 and BS 540, 
and between BS 727 and BS 1016; in accordance with Part III 
(``Preventive Change'') of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1177, Revision 1, dated September 19, 
1996; Revision 2, dated July 24, 1997; or Revision 3, dated 
September 18, 1997; at the time specified in paragraph (h) of this 
AD. Accomplishment of this modification constitutes terminating 
action for the repetitive inspections only for the areas that have 
been modified in accordance with this AD.
    (g) For Boeing Model 737-200 series airplanes only:
    (1) Except as provided in paragraphs (g)(2) and (g)(3) of this 
AD, in lieu of accomplishing the modification (``Preventive 
Change'') specified in paragraph (f) of this AD, installation of the 
lap joint repair in accordance with Part IV (``Lap Joint Repair'') 
of the Accomplishment Instructions of Boeing Alert Service Bulletin 
737-53A1177, Revision 3, dated September 18, 1997, at the locations 
specified in Part IV of the alert service bulletin, may be 
accomplished. Accomplishment of the repair constitutes terminating 
action for the repetitive inspections only for the areas that have 
been modified in accordance with this AD.
    (2) Prior to conducting the repair, support the airplane in the 
jig position, including support (removal) of the engine weight, in 
accordance with Boeing Document D6-15565, ``737 Structural Repair 
Manual (SRM),'' Chapter 51, Subject 51-50-1, Revision 70, dated July 
5, 1997.

    Note 2: Chapter 51, Subject 51-50-1 of the referenced SRM 
references Subjects 51-50-2, 51-50-3, and 51-60 of the referenced 
SRM as additional sources of service information.

    (3) Notwithstanding the Accomplishment Instructions of Boeing 
Alert Service Bulletin

[[Page 55736]]

737-53A1177, Revision 3, dated September 18, 1997, the repair 
described in paragraph (g)(1) of this AD may be accomplished without 
installing a support cradle at station 540.
    (h) Accomplish the modification required by paragraph (f) or (g) 
of this AD, as applicable, at the latest of the times specified in 
paragraphs (h)(1), (h)(2), and (h)(3) of this AD.
    (1) Prior to the accumulation of 70,000 total flight cycles.
    (2) Within 600 flight cycles after the effective date of this 
AD.
    (3) Within 80 days after the effective date of this AD.
    (i) 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.

    (j) 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.
    (k) The actions shall be done in accordance with Boeing Alert 
Service Bulletin 737-53A1177, dated November 8, 1994; Boeing Alert 
Service Bulletin 737-53A1177, Revision 1, dated September 19, 1996; 
Boeing Alert Service Bulletin 737-53A1177, Revision 2, dated July 
24, 1997; Boeing Alert Service Bulletin 737-53A1177, Revision 3, 
dated September 18, 1997; and Boeing Document D6-15565, ``737 
Structural Repair Manual (SRM),'' Chapter 51, Subject 51-50-1, 
Revision 70, dated July 5, 1997, which contains the following list 
of effective pages (NOTE: The issue date and revision level of the 
SRM are indicated only on the Title Page; no other page of the 
document contains this information.):

------------------------------------------------------------------------
                                   Revision level shown   Date shown on 
             Page No.                     on page              page     
------------------------------------------------------------------------
Title page.......................  70..................  July 5, 1997.  
1................................  Not shown...........  Feb. 5, 1989.  
2, 3, 11, 12.....................  Not shown...........  Aug. 5, 1988.  
4................................  Not shown...........  Feb. 1, 1978.  
5, 6, 8-10.......................  Not shown...........  Aug. 1, 1968.  
7................................  Not shown...........  Feb. 1, 1975.  
------------------------------------------------------------------------

    (1) The incorporation by reference of Boeing Alert Service 
Bulletin 737-53A1177, Revision 1, dated September 19, 1996; Boeing 
Alert Service Bulletin 737-53A1177, Revision 2, dated July 24, 1997; 
Boeing Alert Service Bulletin 737-53A1177, Revision 3, dated 
September 18, 1997; and Boeing Document D6-15565, ``737 Structural 
Repair Manual (SRM),'' Chapter 51, Subject 51-50-1, Revision 70, 
dated July 5, 1997; is approved by the Director of the Federal 
Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) The incorporation by reference of Boeing Alert Service 
Bulletin 737-53A1177, dated November 8, 1994, was approved 
previously by the Director of the Federal Register as of December 
27, 1994 (59 FR 63716, December 9, 1994).
    (3) 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.
    (l) This amendment becomes effective on November 12, 1997.

    Issued in Renton, Washington, on October 21, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-28347 Filed 10-27-97; 8:45 am]
BILLING CODE 4910-13-U