[Federal Register Volume 64, Number 113 (Monday, June 14, 1999)]
[Proposed Rules]
[Pages 31762-31764]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-14934]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-47-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 737-100, -200, -300, -400,
and -500 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: This document proposes the adoption of a new airworthiness
directive (AD) that is applicable to certain Boeing Model 737-100, -
200, -300, -400, and -500 series airplanes. For certain airplanes, this
proposal would require installation of a transient suppression diode in
the wiring circuit of the refueling valve-to-float switch of each fuel
tank. For certain other airplanes, this proposal would require
replacement of the existing transient suppression diode with an
improved diode. This proposal also would require a functional test to
verify proper installation of each diode, and corrective action, if
necessary. This proposal is prompted by incidents of electrical fire
during fueling of the airplane, due to a short circuit and overheating
of a transient suppression diode. The actions specified by the proposed
AD are intended to prevent such conditions, which could result in
electrical arcing and ignition of fuel vapors at the refueling
receptacle for the fuel tanks, and consequent fire during airplane
fueling.
DATES: Comments must be received by July 29, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 99-NM-47-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 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: Dorr Anderson, Aerospace Engineer,
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate,
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-2684; 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-47-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-47-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
The FAA has received reports indicating that electrical fires have
been detected during fueling of two Boeing Model 737 series airplanes.
The affected airplanes have transient suppression diodes installed in
the wiring circuit of the refueling valve-to-float switch of the fuel
tanks to prevent electrical transients from entering the fuel tanks.
Investigation revealed that a short circuit in the transient
suppression diode of the number 1 fuel tank caused electrical arcing,
and consequent fire. The diode is located 17 inches from the P15
pressure fueling panel. In the event
[[Page 31763]]
of a short circuit of a transient suppression diode and consequent
electrical fire, the proximity of the diode to the pressure fueling
panel could result in ignition of fuel vapors at the fueling receptacle
during fueling. The fuel valve circuit, of which the diode is part, is
powered only during pressure fueling on the ground; therefore, the
diode is most likely to short circuit and overheat during airplane
fueling.
Inspection of production diodes by the manufacturer revealed that
the manufacturing process may be the cause of the failure of the diodes
during normal operation of the airplane. The failures appear to be
caused by stresses on the internal leads and end caps of the diode by
the placement of the wire crimps next to the glass body of the diode.
The manufacturer replaced the deficient diodes with improved diodes
during production of Model 737 series airplanes having line numbers
3017 and subsequent.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Service Bulletin 737-28-
1115, dated March 4, 1999, which describes procedures for installation
of a transient suppression diode in the wiring circuit of the refueling
valve-to-float switch of each fuel tank on certain airplanes, and
replacement of the existing transient suppression diode with an
improved diode, on certain other airplanes. The service bulletin also
describes procedures for a functional test to verify proper
installation of each diode. 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 require accomplishment of the actions specified in
the service bulletin described previously, except as discussed below.
Differences Between Proposed Rule and Service Bulletin
Operators should note that, although the service bulletin
recommends installation of the improved diodes as soon as manpower and
materials are available, the FAA has determined that a 12-month
compliance time would address the identified 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 subject unsafe
condition, the average utilization of the affected fleet, and the time
necessary to perform the modification. In light of all of these
factors, the FAA finds a 12-month compliance time for completion of the
proposed replacement 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 bulletin does
not specify corrective action if any discrepancy is detected during the
functional test of the transient suppression diode, this proposal would
require replacement of the discrepant diode to be accomplished in
accordance with the procedures specified in the service bulletin.
Cost Impact
There are approximately 2,897 airplanes of the affected design in
the worldwide fleet. The FAA estimates that 1,126 airplanes of U.S.
registry would be affected by this proposed AD.
For all airplanes, it would take approximately 7 work hours per
airplane to accomplish the proposed replacement or installation (as
applicable), and the functional test to verify proper installation, at
an average labor rate of $60 per work hour. Required parts would cost
approximately $50 per airplane. Based on these figures, the cost impact
of the proposed AD on U.S. operators is estimated to be $529,220, or
$470 per airplane.
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-47-AD.
Applicability: Model 737-100, -200, -300, -400, and -500 series
airplanes, line numbers 1 through 3016 inclusive, 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 (e) 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 prevent a short circuit and overheating of the transient
suppression diode, which could result in electrical arcing and
ignition of fuel vapors at the fueling receptacle for the fuel
tanks, and consequent fire during airplane fueling, accomplish the
following:
Corrective Action
(a) For Group 1 airplanes, as identified in Boeing Service
Bulletin 737-28-1115, dated March 4, 1999: Within 12 months after
the
[[Page 31764]]
effective date of this AD, install a transient suppression diode,
part number (P/N) 69-58806-4, in the wire bundle (W264) of the
refueling valve-to-float switch of each fuel tank, in accordance
with the service bulletin.
(b) For Groups 2, 3, and 4 airplanes, as identified in Boeing
Service Bulletin 737-28-1115, dated March 4, 1999: Within 12 months
after the effective date of this AD, replace the existing transient
suppression diode, P/N 69-58806-1 or 69-58806-3, installed in the
wire bundle (W264) of the refueling valve-to-float switch of each
fuel tank, with an improved diode, P/N 69-58806-4, in accordance
with the service bulletin.
(c) Prior to further flight following accomplishment of the
actions requied by paragraph (a) or (b) of this AD, perform a
functional test to verify proper installation of each diode in
accordance with Boeing Service Bulletin 737-28-1115, dated March 4,
1999. If any discrepancy is detected during any functional test,
prior to further flight, replace the discrepant diode and repeat the
functional test, in accordance with the service bulletin.
Spares Paragraph
(d) As of the effective date of this AD, no person shall install
a transient suppression diode having P/N 69-58806-1 or 69-58806-3 on
any airplane.
Alternative Methods of Compliance
(e) 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 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 Permits
(f) 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 June 7, 1999.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-14934 Filed 6-11-99; 8:45 am]
BILLING CODE 4910-13-P
