[Federal Register Volume 64, Number 224 (Monday, November 22, 1999)]
[Proposed Rules]
[Pages 63757-63759]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-30370]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-85-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-200 and -300 Series 
Airplanes Equipped With Cargo Doors Installed in Accordance With 
Supplemental Type Certificate (STC) SA2969SO

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing 
airworthiness directive (AD), applicable to certain Boeing Model 737-
200 and -300 series airplanes, that currently requires repetitive 
inspections to detect cracking in the radii on the support angles on 
the lower jamb (latch lug fittings) of the main deck cargo door, and 
replacement of cracked parts. This action would add a requirement for 
installation of redesigned lower jamb latch support angles in the main 
cargo door surround structure, which would terminate the repetitive 
inspections. This proposal is prompted by the development of a 
modification that will provide better protection of the subject area 
against effects of structural fatigue. The actions specified by the 
proposed AD are intended to prevent in-flight separation of the main 
deck cargo door from the airplane due to fatigue cracking on the 
support angles on the lower door jamb.

DATES: Comments must be received by January 6, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-85-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 Pemco Aeroplex, Inc., P.O. Box 2287, Birmingham, Alabama 
35201-2287. This information may be examined at the FAA, Transport 
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at 
the FAA, Small Airplane Directorate, Atlanta Aircraft Certification 
Office, One Crown

[[Page 63758]]

Center, 1895 Phoenix Boulevard, suite 450, Atlanta, Georgia.

FOR FURTHER INFORMATION CONTACT: Paul Sconyers, Manager, Airframe and 
Propulsion Branch, ACE-117A; FAA, Small Airplane Directorate, Atlanta 
Aircraft Certification Office, One Crown Center, 1895 Phoenix 
Boulevard, suite 450, Atlanta, Georgia 30337-2748; telephone (770) 703-
6076; fax (770) 703-6097.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 99-NM-85-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 99-NM-85-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On December 29, 1994, the FAA issued AD 95-01-06, amendment 39-9117 
(60 FR 2323, January 9, 1995), as revised by AD 95-01-06 R1, amendment 
39-9449 (60 FR 62192, December 5, 1995), applicable to certain Boeing 
Model 737-200 and -300 series airplanes [those equipped with main deck 
cargo doors installed in accordance with supplemental type certificate 
(STC) SA2969SO]. That AD requires repetitive visual inspections to 
detect cracking in the radii on the support angles on the lower jamb 
(latch lug fittings) of the main deck cargo door, and replacement of 
cracked parts with new parts. That action was prompted by reports of 
premature fatigue cracking on the support angles on the lower jamb of 
the main deck cargo door. The requirements of that AD are intended to 
prevent in-flight separation of the main deck cargo door from the 
airplane due to fatigue cracking on the support angles on the lower 
door jamb.

Actions Since Issuance of Previous Rule

    When the FAA originally issued AD 95-01-06R1, it was noted in the 
preamble that the AD was considered interim action until final action 
was identified, at which time the FAA might consider further 
rulemaking. Since the issuance of that AD, the STC holder for the cargo 
door airplane modification has generated a design change for the lower 
latch lug fitting support angles for the main cargo door surround 
structure. This design change, consisting of the installation of new 
lower jamb latch support angles in the main cargo door surround 
structure, would eliminate the need for the repetitive inspections (as 
required by AD 95-01-06R1). Upon consideration, the FAA has determined 
that installation of the design change is necessary to correct the 
unsafe condition addressed by AD 95-01-06R1.
    The FAA has determined that long-term continued operational safety 
will be better assured by modifications or design changes to remove the 
source of the problem, rather than by repetitive inspections. Long term 
inspections may not be providing the degree of safety assurance 
necessary for the transport airplane fleet. This, coupled with a better 
understanding of the human factors associated with numerous repetitive 
inspections, has led the FAA to consider placing less emphasis on 
special procedures and more emphasis on design improvements. The 
proposed design change requirement is in consonance with these 
considerations.
    The actions specified by the proposed AD are intended to prevent 
in-flight separation of the main deck cargo door from the airplane due 
to fatigue cracking on the support angles on the lower door jamb.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Pemco Service Bulletin 737-53-
0003, Revision 4, dated February 22, 1995, and Revision 5, dated March 
25, 1999, which describe, among other things, procedures for 
installation of new, improved lower jamb latch support angles in the 
main cargo door surround structure. Accomplishment of the actions 
specified in the service bulletin is intended to adequately address the 
identified unsafe condition.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would supersede AD 95-01-06 R1 to continue to require the 
repetitive visual inspections to detect cracking in the radii on the 
support angles on the lower jamb (latch lug fittings) of the main deck 
cargo door, and replacement of cracked parts with new parts. The 
proposed AD would also add a requirement for accomplishment of the 
design change specified in the service bulletins described previously, 
which would terminate the repetitive visual inspections. The actions 
would be required to be accomplished in accordance with the service 
information described previously, except as discussed below.
    The FAA has clarified the inspection requirement contained in AD 
95-01-06 R1. Whereas that AD specified a visual inspection, the FAA has 
revised this proposed AD to clarify that its intent is to require a 
detailed visual inspection. Additionally, a note has been added to the 
proposed rule to define that inspection.

Differences Between Proposed Rule and Service Information

    Operators should note that, unlike the procedures described in 
Pemco Alert Service Letter 737-53-0003, Revision 3, dated December 22, 
1994, this proposed AD would not permit further flight if cracks are 
detected in the affected area of the cargo door installation. The FAA 
has determined that, because of the safety implications and 
consequences associated with such cracking, any affected area of the 
cargo door installation that is found to be cracked must be repaired or 
modified prior to further flight.

Cost Impact

    There are approximately 32 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 2 airplanes of U.S. registry 
would be affected by this proposed AD.
    The inspection that is currently required by AD 95-01-06 R1 and 
retained in this proposed AD takes approximately 8 work hours per

[[Page 63759]]

airplane to accomplish, at an average labor rate of $60 per work hour. 
Based on these figures, the cost impact of the currently required 
actions on U.S. operators is estimated to be $480 per airplane, per 
inspection cycle.
    The new installation that is proposed in this AD action would take 
approximately 500 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Required parts would cost 
approximately $9,700 per airplane. Based on these figures, the cost 
impact of the proposed requirements of this AD on U.S. operators is 
estimated to be $79,400, or $39,700 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the current or proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.

Regulatory Impact

    The regulations proposed herein would not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) Is not a ``significant regulatory action'' under 
Executive Order 12866; (2) Is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) If promulgated, will not have a significant economic impact, 
positive or negative, on a substantial number of small entities under 
the criteria of the Regulatory Flexibility Act. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing amendment 39-9449 (60 FR 
62192, December 5, 1995), and by adding a new airworthiness directive 
(AD), to read as follows:

Boeing: Docket 99-NM-85-AD. Supersedes AD 95-01-06 R1, Amendment 39-
9449.

    Applicability: Model 737-200 and -300 series airplanes equipped 
with main deck cargo doors installed in accordance with supplemental 
type certificate (STC) SA2969SO, 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 use the authority 
provided in paragraph (c)(1) of this AD 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 in-flight separation of the main deck cargo door from 
the airplane, accomplish the following:

    Note 2: This AD references Pemco Alert Service Letter 737-53-
0003, Revision 3, dated December 22, 1994; Pemco Service Bulletin 
737-53-0003, Revision 4, dated February 22, 1995; and Pemco Service 
Bulletin 737-53-0003, Revision 5, dated March 25, 1999; for 
information concerning inspection and replacement procedures. In 
addition, this AD specifies replacement requirements different from 
those included in the service letter or service bulletin. Where 
there are differences between the AD and the service letter or 
service bulletin, the AD prevails.

Restatement of Requirements of AD 95-01-06R1, Amendment 39-9449

Repetitive Inspections

    (a) Within 50 flight cycles after January 24, 1995 (the 
effective date of AD 95-01-06, amendment 39-9117), or within 50 
flight cycles after installation of STC SA2969SO, whichever occurs 
later, perform a detailed visual inspection to detect cracking in 
the radii on the support angles on the lower jamb of the main deck 
cargo door, in accordance with Pemco Alert Service Letter 737-53-
0003, Revision 3, dated December 22, 1994.
    (1) If no cracking is detected, repeat the detailed visual 
inspection thereafter at intervals not to exceed 450 flight cycles.
    (2) If any cracking is detected, prior to further flight, 
replace the cracked part with a new part in accordance with the 
alert service letter. Repeat the detailed visual inspection 
thereafter at intervals not to exceed 450 flight cycles.

    Note 3: For the purposes of this AD, a detailed visual 
inspection is defined as: ``An intensive visual examination of a 
specific structural area, system, installation, or assembly to 
detect damage, failure, or irregularity. Available lighting is 
normally supplemented with a direct source of good lighting at 
intensity deemed appropriate by the inspector. Inspection aids such 
as mirror, magnifying lenses, etc., may be used. Surface cleaning 
and elaborate access procedures may be required.''

New Requirements of This AD

Terminating Action

    (b) Within 1,500 flight cycles after the effective date of this 
AD, install redesigned lower jamb latch lug support angles in the 
main cargo door surround structure in accordance with Pemco Service 
Bulletin 737-53-0003, Revision 4, dated February 22, 1995, or 
Revision 5, dated March 25, 1999. This action constitutes 
terminating action for the requirements of this AD.

Alternative Methods of Compliance

    (c)(1) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, FAA, Small Airplane Directorate, 
Atlanta Aircraft Certification Office (ACO). Operators shall submit 
their requests through an appropriate FAA Principal Maintenance 
Inspector, who may add comments and then send it to the Manager, 
Atlanta ACO.
    (c)(2) Alternative methods of compliance, approved previously in 
accordance with AD 95-01-06 R1, amendment 39-9449, are approved as 
alternative methods of compliance with paragraphs (a) and (b) of 
this AD.

    Note 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Atlanta ACO.

Special Flight Permits

    (d) Special flight permits may be issued in accordance with 
Secs. 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 November 16, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-30370 Filed 11-19-99; 8:45 am]
BILLING CODE 4910-13-U