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

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]

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