[Federal Register Volume 74, Number 7 (Monday, January 12, 2009)]
[Proposed Rules]
[Pages 1153-1155]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E9-314]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-1364; Directorate Identifier 2008-NM-103-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-300, -400, and -500 
Series Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to adopt a new airworthiness directive (AD) for 
certain Boeing Model 737-300, -400, and -500 series airplanes. This 
proposed AD would require modifying the control power wiring of the 
normal supply fan and the low flow sensor for the equipment cooling 
system of the electronic flight instrument system (EFIS). This proposed 
AD results from a report of loss of both the normal EFIS cooling supply 
and the indication of EFIS cooling loss due to a single failure of the 
battery bus, causing eventual power-down of the EFIS displays; the 
standby attitude indication is also powered by this battery bus. We are 
proposing this AD to prevent loss of all attitude indications from both 
the standby indicator and EFIS displays, which could decrease the 
ability of the flightcrew to maintain the safe flight and landing of 
the airplane.

DATES: We must receive comments on this proposed AD by February 26, 
2009.

ADDRESSES: You may send comments by any of the following methods:
     Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590.
     Hand Delivery: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.

[[Page 1154]]

    For service information identified in this AD, contact Boeing 
Commercial Airplanes, Attention: Data & Services Management, P.O. Box 
3707, MC 2H-65, Seattle, Washington 98124-2207; telephone 206-544-5000, 
extension 1, fax 206-766-5680; e-mail [email protected]; Internet 
https://www.myboeingfleet.com. You may review copies of the referenced 
service information at the FAA, Transport Airplane Directorate, 1601 
Lind Avenue SW., Renton, Washington. For information on the 
availability of this material at the FAA, call 425-227-1221 or 425-227-
1152.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The AD docket contains this proposed AD, the regulatory 
evaluation, any comments received, and other information. The street 
address for the Docket Office (telephone 800-647-5527) is in the 
ADDRESSES section. Comments will be available in the AD docket shortly 
after receipt.

FOR FURTHER INFORMATION CONTACT: Suk Jang, Aerospace Engineer, Systems 
and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone 
(425) 917-6511; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2008-1364; 
Directorate Identifier 2008-NM-103-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of this proposed AD. We 
will consider all comments received by the closing date and may amend 
this proposed AD because of those comments.
    We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this proposed AD.

Discussion

    We received a report of loss of both the normal electronic flight 
instrument system (EFIS) cooling supply and the indication of EFIS 
cooling loss due to a single failure of the battery bus, causing 
eventual power-down of the EFIS displays; the standby attitude 
indication is also powered by this battery bus. A single failure of the 
battery bus can cause loss of attitude indications from both the 
standby attitude indicator and EFIS displays. An indication of battery 
bus failure is not displayed on Boeing Model 737-300, -400, and -500 
airplanes. The battery bus energizes the standby horizon, the normal 
supply fan for the equipment cooling system for the EFIS, and the 
cooling air flow sensor. If the fan does not operate, the EFIS will 
start to get hot, and when it gets too hot it will automatically stop 
operation by first going to mono-chromatic, and then, after 60 minutes 
or more, it will power-down. The supply fan off light will not 
illuminate to indicate that the fan has failed because it is also 
powered by the battery bus, which lost power. When this condition 
occurs, the flightcrew could be left without any attitude indication. 
Loss of all attitude indications from both the standby indicator and 
EFIS displays could decrease the ability of the flightcrew to maintain 
safe flight and landing of the airplane.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-21A1156, 
Revision 2, dated December 11, 2008. The service bulletin describes 
procedures for modifying the control power wiring of the normal supply 
fan and the low flow sensor for the equipment cooling system of the 
EFIS. The modification includes the following procedures:
     Rerouting the wire for Group 1 airplanes identified in 
Boeing Alert Service Bulletin 737-21A1156, Revision 1, on which the 
length of the wire in the W018 wire bundle at the P18 load control 
center is adequate. If the length of the wire is inadequate, install 
new wire.
     Rerouting the wire for Group 2 airplanes identified in 
Boeing Alert Service Bulletin 737-21A1156, Revision 1, on which the 
length of the wire in the W018 wire bundle at the P18 load control 
center is adequate. If the length of the wire is inadequate, install 
new wire.
     Modifying wire bundle W044 between the P6 top disconnect 
panel and the P6-1 panel for Group 3 airplanes identified in Boeing 
Alert Service Bulletin 737-21A1156, Revision 1.
     Modifying wire bundle W036 between the P5 forward overhead 
panel and the mid-center ceiling panel for Group 4 airplanes identified 
in Boeing Alert Service Bulletin 737-21A1156, Revision 1.

FAA's Determination and Requirements of This Proposed AD

    We are proposing this AD because we evaluated all relevant 
information and determined the unsafe condition described previously is 
likely to exist or develop in other products of these same type 
designs. This proposed AD would require accomplishing the actions 
specified in the service information described previously.

Costs of Compliance

    We estimate that this proposed AD would affect 263 airplanes of 
U.S. registry. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD.

                                                                     Estimated Costs
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                                                                                                                          Number of U.S.-
                  Action/airplane group                     Work hours     Average labor       Parts         Cost per       registered      Fleet cost
                                                                           rate per hour                      product        airplanes
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Groups 1 & 2 modification...............................               3             $80               0            $240             153         $36,720
Group 4 modification....................................               2              80               0             160             113          18,080
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Currently, there are no Group 3 airplanes on the U.S. Register. 
However, if an affected airplane is imported and placed on the U.S. 
Register in the future, the required actions would take about 5 work 
hours, at an average labor rate of $80 per work hour. Based on these 
figures, we estimate the cost of this AD for Group 3 airplanes to be 
$400 per airplane.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I,

[[Page 1155]]

section 106, describes the authority of the FAA Administrator. 
``Subtitle VII: Aviation Programs,'' describes in more detail the scope 
of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
``Subtitle VII, Part A, Subpart III, Section 44701: General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

Regulatory Findings

    We determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD 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.
    For the reasons discussed above, I certify 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. 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.
    You can find our regulatory evaluation and the estimated costs of 
compliance in the AD Docket.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 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. The FAA amends Sec.  39.13 by adding the following new AD:

Boeing: Docket No. FAA-2008-1364; Directorate Identifier 2008-NM-
103-AD.

Comments Due Date

    (a) We must receive comments by February 26, 2009.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-300, -400, and -500 
series airplanes, certificated in any category; as identified in 
Boeing Alert Service Bulletin 737-21A1156, Revision 2, dated 
December 11, 2008.

Unsafe Condition

    (d) This AD results from a report of loss of both the normal 
electronic flight instrument system (EFIS) cooling supply and the 
indication of EFIS cooling loss due to a single failure of the 
battery bus, causing eventual power-down of the EFIS displays; the 
standby attitude indication is also powered by this battery bus. We 
are issuing this AD to prevent loss of all attitude indications from 
both the standby indicator and EFIS displays, which could decrease 
the ability of the flightcrew to maintain the safe flight and 
landing of the airplane.

Compliance

    (e) Comply with this AD within the compliance times specified, 
unless already done.

Modification

    (f) Within 24 months after the effective date of this AD: Modify 
the control power wiring of the normal supply fan and the low flow 
sensor for the equipment cooling system of the EFIS, by doing all 
the applicable actions specified in the Accomplishment Instructions 
of Boeing Alert Service Bulletin 737-21A1156, Revision 2, dated 
December 11, 2008.

Credit for Actions Done Using Previous Service Information

    (g)(1) Actions done before the effective date of this AD in 
accordance with Boeing Alert Service Bulletin 737-21A1156, Revision 
1, dated October 23, 2007, are acceptable for compliance with the 
corresponding requirements of this AD.
    (2) For Groups 1 and 2 airplanes identified in Boeing Alert 
Service Bulletin 737-21A1156, Revision 1, dated October 23, 2007: 
Actions done before the effective date of this AD in accordance with 
Boeing Alert Service Bulletin 737-21A1156, dated June 20, 2006, are 
acceptable for compliance with the corresponding requirements of 
this AD.

Alternative Methods of Compliance (AMOCs)

    (h)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, ATTN: Suk Jang, Aerospace Engineer, Systems and Equipment 
Branch, ANM-130S, FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, 
Washington 98057-3356; telephone (425) 917-6511; fax (425) 917-6590; 
has the authority to approve AMOCs for this AD, if requested using 
the procedures found in 14 CFR 39.19.
    (2) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.

    Issued in Renton, Washington, on December 18, 2008.
Stephen P. Boyd,
Assistant Manager, Transport Airplane Directorate, Aircraft 
Certification Service.
[FR Doc. E9-314 Filed 1-9-09; 8:45 am]
BILLING CODE 4910-13-P