[Federal Register Volume 68, Number 139 (Monday, July 21, 2003)]
[Proposed Rules]
[Pages 43040-43042]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-18418]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-NM-297-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 727-100 and -200; 737-100, 
-200, -200C, -300, -400 and -500; and 747 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 727-100 and -
200; 737-100, -200, -200C, -300, -400 and -500; and 747 series 
airplanes. This proposal would require, among other things, preparation 
of the electrical bonding faying surfaces on the forward and aft 
surfaces of the rear spars of the fuel tanks of the left and right 
wings, a one-time measurement of the electrical bonding resistances, 
and follow-on actions. This action is necessary to ensure adequate 
electrical bonding between the penetration fittings of the hydraulic 
heat exchanger and the rear spars of the fuel tanks. Inadequate 
electrical bonding, in the event of a lightning strike, could cause 
electrical arcing and ignition of fuel vapor in the wing fuel tank, 
which could result in a fuel tank explosion. This action is intended to 
address the identified unsafe condition.

DATES: Comments must be received by September 4, 2003.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2001-NM-297-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. 2001-NM-297-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 for Windows or 
ASCII text.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, PO 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: Sulmo Mariano, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 917-6501; 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.
    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 2001-NM-297-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. 2001-NM-297-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received data from the manufacturer indicating that, 
during an electrical bonding and grounding test of wing fuel tank 
penetrations on certain Boeing Model 747 series airplanes, it was found 
that the penetration fittings of the hydraulic heat exchanger were not 
electrically bonded to the rear spars. Inadequate electrical bonding, 
in the event of a lightning strike, could cause electrical arcing and 
ignition of fuel vapor in the wing fuel tank, which could result in a 
fuel tank explosion.
    The electrical bonding condition of the penetration fittings of the 
hydraulic heat exchanger on certain Model 727 and 737 series airplanes 
may be the same as those on the affected Model 747 series airplanes. 
Therefore, these models may be subject to this same unsafe condition.

Explanation of Relevant Service Information

    The FAA has reviewed and approved the following Boeing alert 
service bulletins:

[[Page 43041]]



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           Service bulletin                 Revision level                Date                    Model
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727-29A0067..........................  Original...............  June 7, 2001...........  727-100 and -200 series
                                                                                          airplanes.
737-29A1096..........................  Original...............  June 7, 2001...........  737-100, -200, -200C, -
                                                                                          300, -400 and -500
                                                                                          series airplanes.
747-29A2104..........................  Original...............  July 19, 2001..........  747 series airplanes.
----------------------------------------------------------------------------------------------------------------

    These service bulletins describe procedures for preparation of the 
electrical bonding faying surfaces on the forward and aft surfaces of 
the rear spars of the fuel tanks of the left and right wings, a one-
time measurement of the electrical bonding resistances between the 
penetration fittings of the hydraulic heat exchanger and the surfaces 
of the rear spars and between the heat exchanger tube and the lower 
wing stringer surfaces, and follow-on actions. The procedures to follow 
before preparation of the faying surfaces include depressurizing the 
hydraulic systems, draining the fuel from the fuel tanks of the left 
and right wings, disconnecting the inlet and outlet tubes of the heat 
exchangers, and removing the heat exchangers. The preparation of the 
faying surfaces is done by sanding the surface areas down to bare metal 
and applying alodine protective coating on the surfaces and re-
installing the heat exchangers. The follow-on actions involve applying 
fillet sealant and protective finishes around the penetration fittings, 
servicing and pressurizing the hydraulic systems and examining for 
signs of hydraulic fluid leakage, and servicing the fuel tank and 
examining for signs of fuel leakage. Accomplishment of the actions 
specified in the service bulletins is intended to adequately address 
the identified unsafe condition.
    The service bulletins reference Boeing 727, 737, and 747 Airplane 
Maintenance Manuals, Standard Wiring Practices Manuals, and Standard 
Overhaul Practices Manuals for the leak check and repair instructions 
if any discrepancy is found.

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.

Difference Between the Service Bulletins and This Proposed AD

    Although the service bulletins recommend accomplishing the 
specified actions at the earliest opportunity when manpower, materials, 
and facilities are available, we have determined that such an imprecise 
compliance time would not address the identified unsafe condition in a 
timely manner. In developing an appropriate compliance time for this 
AD, we considered not only the manufacturer's recommendation, but the 
degree of urgency associated with addressing the subject unsafe 
condition, the average utilization of the affected fleet, and the time 
necessary to perform the required actions (between 44 and 68 work 
hours). In light of all of these factors, we find a 5-year 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.

Cost Impact

    There are approximately 5,085 airplanes of the affected design in 
the worldwide fleet. We estimate that 2,251 airplanes of U.S. registry 
would be affected by this proposed AD. The following table shows the 
estimated cost impact to do the proposed actions for airplanes affected 
by this proposed AD. The average labor rate is $60 per work hour. The 
estimated maximum total cost for all airplanes affected by this 
proposed AD is $6,302,640.

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                                               Number of U.S.-                                     Maximum fleet
                   Model                          registered        Work hours      Labor cost         cost
                                                  airplanes         (estimated)     (estimated)     (estimated)
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727........................................                  910              44          $2,640      $2,402,400
737........................................                1,091              44           2,640       2,880,240
747........................................                  250              68           4,080       1,020,000
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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 
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, 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.

[[Page 43042]]

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 2001-NM-297-AD.

    Applicability: This AD applies to the airplanes listed in Table 
1 of this AD, certificated in any category:

                         Table 1.--Applicability
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                Model--                           As listed in--
------------------------------------------------------------------------
727-100 and -200 series airplanes......  Boeing Alert Service Bulletin
                                          727-29A0067, dated June 7,
                                          2001.
737-100, -200, -200C, -300, -400 and -   Boeing Alert Service Bulletin
 500 series airplanes.                    737-29A1096, dated June 7,
                                          2001.
747 series airplanes...................  Boeing Alert Service Bulletin
                                          747-29A2104, dated July 19,
                                          2001.
------------------------------------------------------------------------


    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 ensure adequate electrical bonding between the penetration 
fittings of the hydraulic heat exchanger and the rear spars of the 
fuel tanks of the left and right wings, accomplish the following:

Prepare Electrical Bonding Faying Surfaces/Measure Electrical Bonding

    (a) Within 5 years after the effective date of this AD: Prepare 
the electrical bonding faying surfaces on the forward and aft 
surfaces of the rear spars of the fuel tanks of the left and right 
wings, and do a one-time measurement of the electrical bonding 
resistances between the penetration fittings of the hydraulic heat 
exchanger and the rear spars, and between the heat exchanger tube 
and the lower wing stringer surfaces, per the Accomplishment 
Instructions of the applicable Boeing alert service bulletin listed 
in Table 2 of this AD. The procedures include the following: 
Depressurize the hydraulic systems; drain the fuel from the fuel 
tanks; disconnect the inlet and outlet tubes of the heat exchangers 
and remove the heat exchangers; prepare the faying surface by 
sanding the surface areas down to bare metal and apply alodine 
protective coating on the surfaces, and re-install the heat 
exchangers. Before further flight, do the corrective action for any 
incorrect bonding resistance per the Accomplishment Instructions of 
the applicable service bulletin listed in Table 2 of this AD, as 
follows:

                                           Table 2.--Service Bulletins
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              Model                     Service bulletin           Revision level                 Date
----------------------------------------------------------------------------------------------------------------
727-100 and -200.................  727-29A0067                Original................  June 7, 2001.
737-100, -200, -200C, -300, -400   737-29A1096                Original................  June 7, 2001.
 and -500.
747..............................  747-29A2104                Original................  July 19, 2001.
----------------------------------------------------------------------------------------------------------------

Follow-On Actions

    (b) Before further flight after accomplishment of paragraph (a) 
of this AD: Apply fillet sealant and protective finishes around the 
penetration fittings of the hydraulic heat exchanger per the 
Accomplishment Instructions of the applicable Boeing alert service 
bulletin listed in Table 2 of this AD ( per Figure 4 of Boeing Alert 
Service Bulletin 727-29A0067, per Figure 4 Boeing Alert Service 
Bulletin 747-29A2104, or per Figure 8 of Boeing Alert Service 
Bulletin 737-29A1096, as applicable); then service and pressurize 
the hydraulic systems and examine for signs of hydraulic fluid 
leakage; and service the fuel tank and examine for signs of fuel 
leakage per the Accomplishment Instructions of the applicable 
service bulletin listed in Table 2 of this AD. Repair any leaks 
found before further flight, per the applicable service bulletin 
listed in Table 2 of this AD.

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

Special Flight Permit

    (d) Special flight permits may be issued in accordance with 
Sec. Sec.  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 July 15, 2003.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-18418 Filed 7-18-03; 8:45 am]
BILLING CODE 4910-13-P