Airworthiness Directives; Boeing Model 737 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-02-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 737 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 series

airplanes. This proposal would require a one-time detailed visual

inspection of the upper decompression panel on the flight deck door to

verify that a minimum overlap dimension exists, and corrective action,

if necessary. This proposal is prompted by reports indicating that,

during production, some upper decompression panels were installed

incorrectly on the flight deck door. The actions specified by the

proposed AD are intended to detect an incorrectly installed upper

decompression panel, which could cause the emergency exit panel on the

flight deck door to become inoperable, thereby preventing crewmembers

from performing essential duties during an emergency evacuation.

DATES: Comments must be received by October 4, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-114,

Attention: Rules Docket No. 99-NM-02-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.

[[Page 45471]]

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: Mike Thompson, Aerospace Engineer,

Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle

Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056; telephone (425) 227-1157; fax (425) 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 99-NM-02-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-02-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

During a pre-delivery interior compliance inspection, the FAA

discovered that the emergency exit panel installed on the flight deck

door of a Boeing Model 737 series airplane did not open properly. The

emergency exit panel contains an upper decompression panel that allows

pressure to equalize in the event of a rapid decompression. This panel

also serves as an alternate escape path from the crew cabin if the

flight deck door is damaged during an emergency landing. Subsequent

investigation revealed that if the upper decompression panel is

installed incorrectly, an interference between this panel and a

decorative channel could cause the emergency exit panel to bind. Such

binding could cause the panel to become inoperable as an emergency

exit; however, the panel would still function properly in the event of

a rapid decompression. The FAA found this problem on two airplanes

prior to delivery, and has determined that it could also exist on

certain Model 737-300/-400/-500 series airplanes, as well as on certain

Model 737-600/-700/-800 series airplanes, that have already been

delivered. The actions specified by the proposed AD are intended to

detect an incorrectly installed upper decompression panel, which could

cause the emergency exit panel on the flight deck door to become

inoperable, thereby preventing crewmembers from performing essential

duties during an emergency evacuation.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 737-52-

1128, dated April 22, 1999, which describes procedures to inspect the

upper decompression panel on the flight deck door of certain Model 737-

300/-400/-500 series airplanes to verify that a minimum overlap

dimension of 0.05 inch exists. If the minimum overlap does not exist,

the service bulletin provides instructions to adjust the upper

decompression panel and, if necessary, an adjacent decorative channel,

to establish the correct overlap dimension.

The FAA has also reviewed and approved Boeing Service Bulletin 737-

52-1137, dated May 13, 1999, which describes procedures to inspect the

upper decompression panel on the flight deck door of certain Model 737-

600/-700/-800 series airplanes to verify that a minimum overlap

dimension of 0.05 inch exists. If the minimum overlap does not exist,

the service bulletin provides instructions to adjust the upper

decompression panel and, if necessary, an adjacent decorative channel,

to establish the correct overlap dimension.

Accomplishment of the actions specified in the two service

bulletins discussed above, as applicable, 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 require accomplishment of the actions specified in

the service bulletins described previously, except as discussed below.

Differences Between Proposed Rule and the Service Bulletins

Operators should note that, although the service bulletins

recommend that the inspection be performed at the next convenient

maintenance opportunity, the FAA has determined that an unspecified

maintenance interval would not address the unsafe condition in a timely

manner. In developing an appropriate compliance time for this AD, the

FAA considered not only the manufacturer's recommendation, but the

degree of urgency associated with addressing the unsafe condition, the

average utilization of the affected fleet, and the time necessary to

perform the inspection (1 hour). In light of all of these factors, the

FAA finds an 18-month compliance time for completing the required

actions to be warranted, in that it represents an appropriate interval

of time allowable for affected airplanes to continue to operate without

compromising safety.

Operators also should note that, although the service bulletins

specify accomplishment of an inspection of the upper decompression

panel on the flight deck door to verify that a minimum overlap

dimension of 0.05 inch exists, this proposed AD refers to that

inspection as a detailed visual inspection. The FAA finds that

``detailed visual inspection'' is the appropriate terminology for the

inspection described in the service bulletins. Additionally, a

definition of a detailed visual inspection is included in Note 2 of

this proposed AD.

Cost Impact

There are approximately 1299 airplanes of the affected design in

the worldwide fleet. The FAA estimates that 901 airplanes of U.S.

registry would be affected by this proposed AD, that it would take

approximately 1 work hour per airplane to accomplish the proposed

inspection, and that the average labor rate is $60 per work hour. Based

on these figures, the cost impact of the inspection proposed by this AD

on U.S. operators is estimated to be $54,060, or $60 per airplane.

[[Page 45472]]

The 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.

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 adding the following new

airworthiness directive:

Boeing: Docket 99-NM-02-AD.

Applicability: Model 737 series airplanes, as listed in Boeing

Service Bulletin 737-52-1128, dated April 22, 1999, or in Boeing

Service Bulletin 737-52-1137, dated May 13, 1999; 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 request approval for an

alternative method of compliance in accordance with paragraph (c) 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 detect an incorrectly installed upper decompression panel,

which could cause the emergency exit panel on the flight deck door

to become inoperable, thereby preventing crewmembers from performing

essential duties during an emergency evacuation, accomplish the

following:

One-Time Inspection

(a) Within 18 months after the effective date of this AD,

perform a one-time detailed visual inspection of the upper

decompression panel on the flight deck door to verify that a minimum

overlap dimension of 0.05 inch exists, as specified in Boeing

Service Bulletin 737-52-1128, dated April 22, 1999 (for Model 737-

300/-400/-500 series airplanes); or Boeing Service Bulletin 737-52-

1137, dated May 13, 1999 (for Model 737-600/-700/-800 series

airplanes); as applicable.

Note 2: 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.''

Corrective Action

(b) If a minimum overlap dimension of 0.05 inch is not found

during the inspection required by paragraph (a) of this AD, prior to

further flight, adjust the decompression panel and, as applicable,

the adjacent decorative channel, in accordance with Boeing Service

Bulletin 737-52-1128, dated April 22, 1999 (for Model 737-300/-400/-

500 series airplanes); or Boeing Service Bulletin 737-52-1137, dated

May 13, 1999 (for Model 737-600/-700/-800 series airplanes); as

applicable.

Alternative Methods of Compliance

(c) 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.

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 August 16, 1999.

D. L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-21691 Filed 8-19-99; 8:45 am]

BILLING CODE 4910-13-U