[Federal Register Volume 68, Number 182 (Friday, September 19, 2003)]
[Proposed Rules]
[Pages 54874-54876]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-23934]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-360-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-400, 777-200, and 777-
300 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 747-400, 777-
200, and 777-300 series airplanes. This proposal would require, for 
certain airplanes, replacement of the cell stack of the flight deck 
humidifier with a supplier-tested cell stack, or replacement with an 
end plate and subsequent deactivation of the flight deck humidifier. 
For other airplanes, this proposal would require replacement of the 
cell stack with a blanking plate or a new cell stack, or replacement of 
the blanking plate with a supplier-tested cell stack. This action is 
necessary to prevent an increased pressure drop across the humidifier 
and consequent reduced airflow to the flight deck, which could result 
in the inability to clear any smoke that might appear in the flight 
deck. This action is intended to address the identified unsafe 
condition.

DATES: Comments must be received by November 3, 2003.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-360-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9 a.m. and 3 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 2000-NM-360-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 or 2000 or 
ASCII text.
    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: Jeffrey S. Palmer, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056; telephone (425) 917-6481; fax (425) 917-6590.

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 action may be changed in 
light of the comments received.
    Submit comments using the following format:
    [sbull] Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
    [sbull] For each issue, state what specific change to the proposed 
AD is being requested.
    [sbull] Include justification (e.g., reasons or data) for each 
request.
    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.

[[Page 54875]]

    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NM-360-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. 2000-NM-360-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports of sagging cell stack membranes of the 
flight deck humidifiers on certain Boeing Model 747-400, 777-200, and 
777-300 series airplanes. The sagging has been attributed to 
difficulties encountered during the membrane welding process. The 
result of the sagging membranes is an increased pressure drop across 
the humidifier (if it is activated), and consequent reduced airflow to 
the flight deck. These conditions, if not corrected, could result in 
the inability to clear any smoke that might appear in the flight deck.

Explanation of Relevant Service Information

    We have reviewed and approved Boeing Alert Service Bulletin 747-
21A2414, Revision 1, dated October 26, 2000 (for Model 747-400 series 
airplanes), and Boeing Service Bulletin 777-21A0048, Revision 1, dated 
September 7, 2000 (for Model 777-200 and 777-300 series airplanes). 
Service Bulletin 747-21A2414 describes procedures for replacement of 
the cell stack of the flight deck humidifier with a new or reworked 
cell stack, or replacement with an end plate and subsequent 
deactivation of the flight deck humidifier. Service Bulletin 777-
21A0048 describes procedures for replacement of the cell stack with a 
blanking plate or a supplier-tested cell stack, or replacement of the 
blanking plate with a supplier-tested cell stack. Accomplishment of the 
actions specified in the service bulletins is intended to adequately 
address the identified unsafe condition.
    Boeing Service Bulletins 747-21A2414 and 777-21A0048 refer to 
Hamilton Sundstrand Service Bulletins 821486-21-01 and 816086-21-01, 
respectively (both dated March 15, 2000), as additional sources of 
service information for replacement of the cell stack.
    Boeing Service Bulletin 747-21A2414 also refers to Boeing Service 
Bulletin 747-21-2405, which provides information for activation and 
deactivation of the flight deck humidifier. Boeing Service Bulletin 
777-21A0048 refers to Boeing Service Bulletin 777-21-0035, which 
provides information for activation of the flightdeck humidifier.

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 
Boeing Service Bulletins 747-21A2414 and 777-21A0048, described 
previously, except as discussed below.

Differences Between Proposed AD and Service Bulletins

    Boeing Service Bulletins 747-21A2414 and 777-21A0048 recommend 
replacing the cell stack within 60 days; the proposed AD would allow up 
to 90 days. In developing an appropriate compliance time, we considered 
the safety implications and operators' normal maintenance schedules for 
the timely replacement of the cell stack. Therefore, with manufacturer 
concurrence, we have determined that the proposed 90-day compliance 
time represents an appropriate interval to replace the cell stack and 
still maintain an adequate level of safety within the fleet.

Explanation of Certain Alternative Method of Compliance

    Paragraph (c)(1) of this proposed AD would allow replacement of the 
cell stack with a blanking plate provided the humidifier system is 
deactivated. The service bulletin provides no procedures for 
deactivating the humidifier system. Therefore, this option must be done 
in accordance with a method approved by the FAA, or per data meeting 
the type certification basis of the airplane approved by a Boeing 
Company Designated Engineering Representative who has been authorized 
by the FAA to make such findings.

Cost Impact

    There are approximately 35 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 12 airplanes of U.S. registry 
would be affected by this proposed AD. The FAA provides the following 
cost estimates, which would vary depending on the actions chosen by the 
operator, to comply with this proposed AD.

----------------------------------------------------------------------------------------------------------------
                                                                         Work      Hourly     Parts     Cost per
          Model/series                          Action                  hours       rate       cost     airplane
----------------------------------------------------------------------------------------------------------------
747-400........................  Replace cell stack with supplier-            5        $65     $5,100     $5,425
                                  tested cell stack.
747-400........................  Replace cell stack with end plate            6         65          0        390
                                  and deactivate humidifier.
777-200........................  Replace cell stack with blanking             5         65          0        325
777-300........................   plate.
777-200........................  Replace cell stack with supplier-            5         65      6,053      6,378
777-300........................   tested cell stack.
777-200........................  Replace blanking plate with                  3         65      6,053      6,248
777-300........................   supplier-tested cell stack.
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    The cost impact figures discussed above are 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 proposed AD were not adopted. The cost impact 
figures discussed in AD rulemaking actions represent only the time 
necessary to perform the specific actions actually required by the AD. 
These figures typically do not include incidental costs, such as the 
time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.

Regulatory Impact

    The regulations proposed herein would not have a substantial direct 
effect 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,

[[Page 54876]]

it is determined that this proposal would not have federalism 
implications under Executive Order 13132.
    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 2000-NM-360-AD.

    Applicability: Model 747-400 series airplanes listed in Boeing 
Alert Service Bulletin 747-21A2414, Revision 1, dated October 26, 
2000; and Model 777-200 and -300 series airplanes listed in Boeing 
Service Bulletin 777-21A0048, Revision 1, dated September 7, 2000; 
certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent an increased pressure drop across the humidifier and 
consequent reduced airflow to the flight deck, which could result in 
the inability to clear any smoke that might appear in the flight 
deck, accomplish the following:

Cell Stack Replacement: Model 747-400

    (a) For Model 747-400 series airplanes: Within 90 days after the 
effective date of this AD, do the actions specified in either 
paragraph (a)(1) or (a)(2) of this AD.
    (1) Replace the cell stack of the flight deck humidifier with a 
supplier-tested cell stack, in accordance with Part 1 of Boeing 
Alert Service Bulletin 747-21A2414, Revision 1, dated October 26, 
2000.
    (2) Replace the cell stack with an end plate and before further 
flight deactivate the flight deck humidifier, in accordance with 
Part 2 of the alert service bulletin. Replacement of the cell stack 
with a supplier-tested cell stack in accordance with the 4 
requirements of paragraph (a)(1) of this AD, if accomplished, 
terminates the requirement to deactivate the humidifier.

    Note 1: Boeing Alert Service Bulletin 747-21A2414 refers to 
Boeing Service Bulletin 747-21-2405 as an additional source of 
service information for deactivating the humidifier.

    (b) Replacement of the cell stack before the effective date of 
this AD in accordance with Boeing Alert Service Bulletin 747-
21A2414, dated April 13, 2000, is acceptable for compliance with the 
applicable requirements of paragraph (a) of this AD.

Cell Stack Replacement: Model 777-200 and -300

    (c) For Model 777-200 and 777-300 series airplanes: Within 90 
days after the effective date of this AD, do the actions specified 
in paragraph (c)(1) or (c)(2) or (c)(3) of this AD, in accordance 
with Boeing Service Bulletin 777-21A0048, Revision 1, dated 
September 7, 2000.
    (1) Replace the cell stack with a blanking plate, in accordance 
with Part 1 of the service bulletin; and deactivate the humidifier 
system before further flight in accordance with a method approved by 
the Manager, Seattle Aircraft Certification Office (ACO), FAA; or 
per data meeting the type certification basis of the airplane 
approved by a Boeing Company Designated Engineering Representative 
who has been authorized by the Manager, Seattle ACO, to make such 
findings. For a deactivation method to be approved, the approval 
must specifically reference this AD.
    (2) Replace the cell stack with a supplier-tested cell stack, in 
accordance with Part 2 of the service bulletin.
    (3) Replace the blanking plate with a supplier-tested cell 
stack, in accordance with Part 3 of the service bulletin.

    Note 2: Boeing Service Bulletins 747-21A2414 and 777-21A0048 
refer to Hamilton Sundstrand Service Bulletins 821486-21-01 and 
816086-21-01, respectively, as additional sources of service 
information for the cell stack replacement.

Part Installation

    (d) On Model 747-400 series airplanes: As of the effective date 
of this AD, no person may install a flight deck humidifier cell 
stack having part number (P/N) 821482-1, unless ``DEV 13433'' is 
also marked next to the cell stack part number.
    (e) On Model 777-200 and 777-300 series airplanes: As of the 
effective date of this AD, no person may install a flight deck 
dehumidifier cell stack having P/N 822976-2, unless ``DEV 13433'' is 
also marked next to the cell stack part number.

Alternative Methods of Compliance

    (f) In accordance with 14 CFR 39.19, the Manager, Seattle ACO, 
FAA, is authorized to approve alternative methods of compliance for 
this AD.

    Issued in Renton, Washington, on September 15, 2003.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-23934 Filed 9-18-03; 8:45 am]
BILLING CODE 4910-13-P