[Federal Register Volume 59, Number 125 (Thursday, June 30, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-15619]


[[Page Unknown]]

[Federal Register: June 30, 1994]


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Part II





Department of Transportation





_______________________________________________________________________



Federal Aviation Administration



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14 CFR Part 23




Airworthiness Standards; Powerplant Proposals Based on European Joint 
Aviation Requirements; Proposed Rule
DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. 27804; Notice No. 94-19]
RIN: 2120-AE60

 
Airworthiness Standards; Powerplant Proposals Based on European 
Joint Aviation Requirements Proposals

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking.

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SUMMARY: This notice proposes changes to the powerplant airworthiness 
standards for normal, utility, acrobatic, and commuter category 
airplanes. These proposals arise from the joint effort of the Federal 
Aviation Administration (FAA) and the European Joint Aviation 
Authorities (JAA) to harmonize the Federal Aviation Regulations (FAR) 
and the Joint Aviation Requirements (JAR) for airplanes that will be 
certificated in these categories. The proposed changes would provide 
nearly uniform powerplant airworthiness standards for airplanes 
certificated in the United States under 14 CFR part 23 (part 23) and in 
the JAA countries under Joint Aviation Requirements 23 (JAR 23) 
simplifying airworthiness approvals for import and export purposes.

DATES: Comments must be submitted on or before October 28, 1994.

ADDRESSES: Comments on this notice should be mailed in triplicate to: 
Federal Aviation Administration, Office of the Chief Counsel, 
Attention: Rules Docket (AGC-200), Docket No. 27804, 800 Independence 
Avenue SW., Washington, DC 20591. Comments delivered must be marked 
Docket No. 27804. Comments may be inspected in Room 915G weekdays 
between 8:30 a.m. and 5:00 p.m., except on Federal holidays.
    In addition, the FAA is maintaining a duplicate information docket 
of comments in the Office of the Assistant Chief Counsel, ACE-7, 
Federal Aviation Administration, Central Region, 601 East 12th Street, 
Kansas City, Missouri 64106. Comments in the duplicate information 
docket may be inspected in the Office of the Assistant Chief Counsel 
weekdays, except Federal holidays, between the hours of 7:30 a.m. and 
4:00 p.m.

FOR FURTHER INFORMATION CONTACT:
Norman Vetter, ACE-112, Small Airplane Directorate, Aircraft 
Certification Service, Federal Aviation Administration, 601 East 12th 
Street, Kansas City, Missouri 64106; telephone (816) 426-5688.

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. Comments relating to the environmental, energy, or 
economic impact that might result from adopting the proposals in this 
notice are also invited. Substantive comments should be accompanied by 
cost estimates. Comments should identify the regulatory docket or 
notice number and should be submitted in triplicate to the Rules Docket 
address specified above. All comments received on or before the 
specified closing date for comments will be considered by the 
Administrator before taking action on this proposed rulemaking. The 
proposals contained in this notice may be changed in light of comments 
received. All comments received 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 docket. Commenters wishing the FAA to acknowledge receipt of their 
comments submitted in response to this notice must include a 
preaddressed, stamped postcard on which the following statement is 
made: ``Comments to Docket No. 27804.'' The postcard will be date 
stamped and returned to the commenter.

Availability of NPRM

    Any person may obtain a copy of this Notice of Proposed Rulemaking 
(NPRM) by submitting a request to the Federal Aviation Administration, 
Office of Public Affairs, Attention: Public Inquiry Center, APA-200, 
800 Independence Avenue, SW., Washington, DC 20591, or by calling (202) 
267-3484. Communications must identify the notice number of this NPRM.
    Persons interested in being placed on the mailing list for future 
NPRM's should request, from the above office, a copy of Advisory 
Circular No. 11-2A, Notice of Proposed Rulemaking Distribution System, 
which describes the application procedure.

Background

    At the June 1990 meeting of the JAA Council (consisting of JAA 
members from European countries) and the FAA, the FAA Administrator 
committed the FAA to support the harmonization of the FAR with the JAR 
being developed for use by the European authorities who are members of 
the JAA. In response to this commitment, the FAA Small Airplane 
Directorate established an FAA Harmonization Task Force to work with 
the JAR 23 Study Group to harmonize part 23 and the proposed JAR 23. 
The General Aviation Manufacturers Association (GAMA) also established 
a JAR 23/part 23 Committee to provide technical assistance in this 
effort.
    Following a review of the first draft of proposed JAR 23, members 
of the FAA Harmonization Task Force and the GAMA Committee met in 
Brussels, Belgium for the October 1990 meeting of the JAR 23 Study 
Group. Representatives from the Association Europeenne des 
Constructeures de Material Aerospatial (AECMA), an organization of 
European airframe manufacturers, also attended. The main agenda item 
for this meeting was the establishment of procedures to accomplish 
harmonization of the airworthiness standards for normal, utility, and 
acrobatic category airplanes. The JAA had decided that its initial 
rulemaking effort should be limited to these three categories and that 
commuter category airworthiness standards should be addressed 
separately.
    After that meeting, technical representatives from each of the four 
organizations (GAMA, AECMA, FAA and JAA) met to resolve differences 
between the proposed JAR and part 23. This portion of the harmonization 
effort involved a number of separate meetings of specialists in the 
flight, airframe, powerplant, and systems disciplines. These meetings 
showed that harmonization would require revisions to both part 23 and 
the proposed JAR 23.
    Near the end of the effort to harmonize the normal, utility, and 
acrobatic category airplane airworthiness standards, the JAA requested 
and received recomendations from its member countries on proposed 
airworthiness standards for commuter category airplanes. The JAA and 
the FAA held specialist and study group meetings to discuss these 
recommendations, which resulted in proposals to revise portions of the 
part 23 commuter category airworthiness standards.
    Unlike the European rules, where commuter category airworthiness 
standards are separate, for U.S. rulemaking it is advantageous to adopt 
normal, utility, acrobatic, and commuter category airworthiness 
standards simultaneously, since commuter category airworthiness 
standards are already contained in part 23. Accordingly, this NPRM 
proposes to revise the powerplant airworthiness standards for all part 
23 airplanes.
    During the part 23 Harmonization effort, the FAA established an 
Aviation Rulemaking Advisory Committee (ARAC) (56 FR 2190, January 22, 
1991), which held its first meeting on May 23, 1991. The ARAC on 
General Aviation and Business Airplane (GABA) Issues was established at 
that meeting to provide advice and recommendations to the Director, 
Aircraft Certification Service, FAA, regarding the airworthiness 
standards in part 23 as well as related provisions of parts 91 and 135 
of the regulations.
    The FAA announced, on June 2-5, 1992, at the JAA/FAA Harmonization 
Conference in Toronto, Ontario, Canada, that it would consolidate 
within the ARAC structure an ongoing objective to ``harmonize'' the JAR 
and the FAR. Coinciding with that announcement, the FAA assigned the 
ARAC on GABA Issues those rulemaking projects related to JAR/part 23 
harmonization that were in final coordination between the JAA and the 
FAA. The harmonization process included the intention to present the 
results of JAA/FAA coordination to the public as NPRM's. Subsequently, 
the ARAC on GABA Issues established on ARAC-JAR 23 Study Group.
    The JAR 23 Study Group made recommendations to the ARAC on GABA 
Issues concerning the FAA's disposition of the rulemaking issues 
coordinated between the JAA and the FAA. The draft NPRM's previously 
prepared by the FAA harmonization team were made available to the 
harmonization working group to assist them in their effort.
    A notice of the formation of the JAR/FAR 23 Harmonization Working 
Group was published on November 30, 1992 (54 FR 56626). The group held 
its first meeting on February 2, 1993. These efforts resulted in the 
proposals for powerplant airworthiness standards contained in this 
notice. The ARAC on GABA Issues agreed with these proposals.
    The FAA received unsolicited comments from the JAA dated January 
20, 1994, concerning issues that were left unresolved with the JAR 23 
Study Group. The JAR/FAR 23 Harmonization Working Group did not address 
some of the unresolved issues because the JAA had not yet reached 
positions on those issues. Unresolved issues will be dealt with at 
future FAR/JAR Harmonization meetings. With respect to other issues 
unresolved by the JAR 23 Study Group, the JAR/FAR Harmonization Working 
Group recommendations did not reflect harmonization, but reflected the 
technical discussion of the merits of each issue that had been 
thoroughly debated at the JAR/FAR 23 Harmonization meetings. (The 
Working Group Chairperson had been present at the Harmonization 
meetings.) The JAA comments have been placed in the docket for this 
proposal, and will be considered along with those received during the 
comment period.
    Following completion of these harmonization efforts, the FAA 
determined that the proposed revisions to part 23 were too numerous for 
a single NPRM. The FAA decided to simplify the issues by issuing four 
NPRM's. These NPRM's address the airworthiness standards in the 
specific areas of systems and equipment, powerplant, flight, and 
airframe. These NPRM's propose changes in all seven subparts of part 
23. Since there is some overlap, interested persons are advised to 
review all four NPRM's to identify all proposed changes to a particular 
section.

Discussion of the Proposals

Section 23.777  Cockpit Controls

    The current requirements of Sec. 23.777 address the location of 
powerplant controls on tandem-seated airplanes. For single-engine 
airplanes that are designed for a single cockpit occupant, the 
powerplant controls should be located in the same position as they are 
for tandem-seated airplanes. Therefore, Sec. 23.777(c)(2) would be 
revised to include single-seated airplanes.

Section 23.779  Motion and Effect of Cockpit Controls

    Current Sec. 23.779(b)(1) provides requirements for ``powerplant 
controls,'' including direction of travel and effect. This proposal 
would revise Sec. 23.779(b)(1) by adding a new item ``fuel'' to the 
table. This proposal would require that any fuel shutoff control other 
than mixture must move forward to open.

Section 23.901  Installation

    Section 23.901(d)(1), as amended in Amendment 23-43, requires that 
each turbine engine installation must be constructed and arranged to 
result in vibration characteristics that do not exceed those 
established during the type certification of the engine. This 
requirement would be revised to add the word ``carcass'' before 
vibration. This change would restrict analyses to those vibrations that 
are caused by external excitation to the main engine frame or 
``carcass.'' While the word ``carcass'' has not traditionally been used 
in this context in the United States, it is used in Europe and is 
proposed here in the interest of harmonization.
    Section 23.901(d)(2), as amended in Amendment 23-43, would be 
revised by deleting the last sentence which reads: ``The engine must 
accelerate and decelerate safely following stabilized operations under 
these rain conditions.'' This requirement is already provided for in 
the first sentence of paragraph (d)(2), which states that the turbine 
engine must be constructed and arranged to provide ``continued safe 
operation.''
    Paragraph (e) of this section would be revised by adding the word 
``powerplant'' in front of ``installation'' to make clear that it 
pertains to all powerplant installations.
    Current paragraph (e)(1) would be reformatted to accommodate the 
added provisions of new paragraph (e)(1)(ii). The current paragraph 
(e)(1) would be divided into paragraphs (e)(1), (e)(1)(i), and 
(e)(1)(ii). Paragraph (e)(1) would be revised by adding the word 
``installation'' in front of ``instruction'' to make clear which 
instructions are applicable. Proposed paragraph (e)(1) would end after 
the word ``under--,'' and paragraphs (e)(1)(i) and (e)(1)(ii) would 
continue the paragraph.
    Proposed paragraph (e)(1)(i) would contain the requirement with 
respect to the engine type certificate currently set forth in paragraph 
(e)(1). Proposed paragraph (e)(1)(ii) would continue the current 
requirement with respect to the propeller type certificate, but also 
would permit the alternative of meeting the requirements of another 
approved procedure that would provide an equivalent level of safety. 
This revision is proposed to be consistent with the proposed revisions 
to Sec. 23.905, Propellers, which are discussed below.

Section 23.903  Engines

    This proposal would revise paragraphs (c) and (g) by adding the 
headings ``Engine isolation'' and ``Restart capability,'' respectively. 
Current Sec. 23.903 includes headings for paragraphs (a), (b), (d), (e) 
and (f) that identify the subject of each paragraph. This revision will 
provide this same identification for paragraphs (c) and (g).
    The heading of paragraph (f) would be changed from ``Restart 
capability'' to ``Restart envelope'' since the paragraph addresses the 
altitude and airspeed envelope for restarting the engines in flight.

Section 23.905  Propellers

    Section 23.905(a), which requires each propeller to have a type 
certificate, would be revised to require the propeller to either be 
type certificated or meet the requirements of another approved 
procedure that provides an equivalent level of safety. This would allow 
a propeller to be installed and approved on a U.S. type certificated 
airplane if that propeller is approved by a procedure that provides a 
level of safety equivalent to that provided by the FAA type 
certificate. For example, some foreign propellers, approved as part of 
the airplane and not having a separate type certificate, could be 
approved without requiring an exemption to part 23 or obtaining a U.S. 
type certificate; but the ``equivalent procedure'' is not intended to 
be limited to a procedure of a foreign authority.
    This proposal would provide an alternative approval process for 
propellers without reducing safety.

Section 23.906  Propeller Vibration

    Current Sec. 23.907(a) requires that each ``propeller with metal 
blades or highly stressed metal components must be shown to have 
vibration stresses, in normal operating conditions, that do not exceed 
values'' that are ``safe for continuous operation.'' The proposed 
revision to paragraph (a) would change the applicability to propellers 
``other than a conventional fixed-pitch wooden propeller.'' This change 
is necessary because all metal and most composite propeller blades are 
highly stressed and need to be evaluated for vibration. Only propellers 
with fixed-pitch wooden blades would be exempt from the vibration 
requirements.

Section 23.925  Propeller Clearance

    Current Sec. 23.925 requires that propeller clearance must be 
evaluated with the airplane at maximum weight, with the most adverse 
center of gravity and with the propeller in the most adverse pitch 
position. To make the requirement consistent with current certification 
practice, paragraph (a) would be revised to read that propeller 
clearance must be evaluated with the airplane at the most adverse 
combination of weight and center of gravity, and with the propeller in 
the most adverse pitch position.
    Interested persons should additionally note that the FAA is also 
proposing a change to Sec. 23.925(b). In the Airframe Harmonization 
notice, the FAA proposes to move the requirements in Sec. 23.925(b) for 
tail wheels, bumpers, and energy absorption devices to Sec. 23.497(c), 
Supplementary conditions for tail wheels, where the structural designer 
would expect to find such a requirement.

Section 23.929  Engine Installation Ice Protection

    This proposal would replace the word ``power'' in Sec. 23.929 in 
the phrase ``without appreciable loss of power'' with the word 
``thrust.'' The word ``thrust'' is more descriptive of the loss 
experienced when ice forms on a propeller.

Section 23.933  Reversing Systems

    This proposal would revise Sec. 23.933(a)(1) to agree with the 
corresponding turbojet and turbofan reversing system airworthiness 
standards of part 25. The purpose of thrust reversing systems for part 
23 airplanes is the same as that for part 25 airplanes. While there is 
no technical change, in the interest of harmonization part 23 would be 
changed to read the same as part 25. Also, this proposal would delete 
the word ``forward'' from paragraph (a)(3) since this word is not 
necessary. It would correct the typographical error in paragraph (b)(2) 
to read ``(b)(1)'' instead of ``(a)(1).''

Section 23.955  Fuel Flow

    Section 23.955(a) would be revised by deleting the word ``and'' 
where it occurs between paragraphs (1), (2), (3) and (4). This is a 
nonsubstantive editorial change. All four paragraphs are independent of 
each other and equally subordinate to paragraph (a).
    Section 23.955(a)(3) would be revised by adding the word 
``probable'' so that the requirement would read as follows: ``If there 
is a flow meter without a bypass, it must not have any probable failure 
mode * * * '' This addition of the word ``probable'' would clarify the 
intent of the requirement that only probable failures need be analyzed.

Section 23.959  Unusable Fuel Supply

    Current Sec. 23.959 requires that the unusable fuel supply for each 
tank be established and states certain parameters for establishing the 
unusable supply. The current text of Sec. 23.959 would be redesignated 
as paragraph (a); a proposed new paragraph (b) would require that the 
effect of any fuel pump failure on the unusable fuel supply also be 
established.
    It has been industry practice to include in the Airplane Flight 
Manual an entry describing any additional unusable fuel quantity that 
results from a fuel pump failure. This proposal would not require any 
change in the fuel quantity indicator marking required by Sec. 23.1553.

Section 23.963  Fuel Tanks: General

    Current Sec. 23.963(b), which requires that each flexible fuel tank 
liner must be of an acceptable kind, would be revised by replacing the 
phrase ``must be of an acceptable kind'' with the phrase ``must be 
shown to be suitable for the particular application.'' The word 
``acceptable'' is inexact since all components of a type certificated 
airplane must be acceptable. This is a clarifying, nonsubstantive 
change. Also the reference to Sec. 23.959 would be revised by changing 
it to Sec. 23.959(a) to coincide with the proposed revision of 
Sec. 23.959 discussed above.

Section 23.965  Fuel Tank Tests

    Section Sec. 23.965(b)(3)(i) would be revised by changing the 
phrase ``the test frequency of vibration cycles per minute is obtained 
by * * *'' to ``the test frequency of vibration is the number of cycles 
per minute obtained by * * *''. This would clarify that it is the 
number of cycles per minute that is to be used during testing of a fuel 
tank. The frequency of vibration to be used during testing of a fuel 
tank on a non-propeller driven airplane has received differing 
interpretations during certification procedures.

Section 23.973  Fuel Tank Filler Connection

    Current Sec. 23.973(f) specifies a minimum diameter of the fuel 
filler opening for airplanes with turbine engines that are not equipped 
with pressure fueling systems. The proposed paragraph (f) would remove 
the provision related to pressure fueling systems to make the 
regulation apply to all airplanes with turbine engines, including 
turbine engines that are equipped with pressure fueling systems. The 
need to restrict the fuel opening diameter on the top side of the fuel 
tank is not related to a function of whether or not the airplane is 
equipped with pressure refueling.

Section 23.975  Fuel Tank Vents and Carburetor Vents

    Current 23.975(a)(5), as amended in Amendment 23-43, requires that 
there be no undrainable points in any vent lines where moisture can 
accumulate and that any drain lines installed in the vent lines must 
discharge clear of that airplane and be accessible for drainage. This 
paragraph would be revised to clarify that there may be no points in 
any vent line where moisture can accumulate unless drainage is 
provided. The intent is to allow low spots in the fuel tank vent system 
if a drain is provided for each low spot.

Section 23.979  Pressure Fueling System

    Section 23.979(b) would be revised to add a requirement for 
commuter category airplanes that an automatic shutoff means must 
provide indication at each fueling station of failure of the shutoff 
means to stop fuel flow at the maximum level. This revision makes the 
commuter category automatic shutoff means requirements similar to the 
requirements for transport category airplanes in Sec. 25.979.

Section 23.1001  Fuel Jettisoning System

    This proposal would revise Sec. 23.1001(b)(2) to redefine the speed 
at which the fuel jettisoning system tests should be conducted. In a 
separate notice, as identified in the background section of this 
document, the FAA determined that the best rate-of-climb speed no 
longer need be determined under part 23, and has proposed that it be 
eliminated from Sec. 23.69(b). Accordingly, this proposal would 
redefine the climb speed as stated in Sec. 23.1001(b)(2) to reference 
Sec. 23.69(b) as proposed.

Section 23.1013  Oil Tanks

    This proposal would delete the word ``crankcase'' in 
Sec. 23.1013(d)(1), making this paragraph applicable to all engine 
installations.

Section 23.1041  General

    Current Sec. 23.1041 under the cooling heading requires that 
powerplant and auxiliary power unit cooling provisions must maintain 
the temperature of powerplant components and engine fluids within the 
limits established for those components and fluids to the maximum 
altitude for which approval is requested. This section would be revised 
to state ``to the maximum altitude and maximum ambient atmospheric 
temperature conditions for which approval is requested.''
    For reciprocating engine powered airplanes, it has been the 
practice to correct the cooling temperatures to 100  deg.F ambient 
temperature. In practice, turbine engine powered airplanes have been 
corrected to the maximum temperature for which approval is requested. 
The standard would be revised to require all airplanes, regardless of 
engine type, to demonstrate adequate cooling at one maximum ambient 
atmosphere temperature for which approval is requested.

Section 23.1043  Cooling Tests

    Section 23.1043(a)(3) would be revised to shown that the minimum 
grade fuel requirement applies to both turbine and reciprocating 
engines and that the lean mixture requirement applies to reciprocating 
engines only. The introductory text of paragraph (a) would be 
simplified by deleting the requirement that compliance must be shown 
``under critical ground, water, and flight operating conditions to the 
maximum altitude for which approval is requested.'' This requirement is 
already contained in Sec. 23.1041.
    The requirement in the introductory text of paragraph (a), which 
states that, for turbo-charged engines, each turbocharger must be 
operated through the part of the climb profile for which turbo-charger 
operation is requested, would be moved to paragraph (a)(4) to improve 
the organization of the section.
    Paragraph (a)(1) would not be substantively changed. It would be 
revised to be consistent with proposed changes to Sec. 23.1041 and 
changes to the introductory text of paragraph (a) described above.
    Paragraph (a)(2) is reworded without substantive change to make 
this language identical to the JAR.
    Paragraph (a)(3) would be revised to clarify that the requirement 
for mixture settings applies to reciprocating engines and that the 
mixture settings must be the leanest recommended for the climb. While 
this has been the case in practice, it has not been explicitly stated 
in the rule. The ``leanest recommended for climb'' mixture setting is 
considered a normal operating condition.
    Paragraph (a)(5) is removed because water taxi tests are required 
by Sec. 23.1041 as amended by Amendment 23-43.
    Paragraphs (c) and (d) would be revised by adding the requirement 
that cooling correction factors be determined for the appropriate 
altitude. This would codify current certification practice and increase 
safety by ensuring the proper correction factor is determined.

Section 23.1045  Cooling Test Procedures for Turbine Engine Powered 
Airplanes

    Current 23.1045(a)(3) requires that compliance with Sec. 23.1041 
must be shown by certain specified phases of operations: takeoff, 
climb, en route, and landing. It also specifies that the cooling tests 
must be conducted with the airplane in the configuration and under the 
operating conditions that are critical to cooling for each stage of 
flight. It also defines a ``stabilized'' temperature as having a rate 
of change of less than 2  deg.F per minute.
    Current paragraph (a) would be revised to state more generally that 
compliance with Sec. 23.1041 must be shown for all phases of 
operations. Also, the airplane must be flown in the configuration, at 
the speeds, and following the procedures recommended in the Airplane 
Flight Manual for the relative stage of flight that corresponds to the 
applicable performance requirements critical to cooling.
    The purpose of this proposed revision is to clarify the cooling 
test procedures by specifying that all phases of operations, not only 
the four phases of flight, are to be evaluated for proper cooling.

Section 23.1047  Cooling Test Procedures for Reciprocating Engine 
Powered Airplanes

    This proposal would revise the cooling test procedures in 
Sec. 23.1047 for reciprocating engine powered airplanes by deleting the 
specific procedures. Many of the current provisions in Sec. 23.1047 
provide procedures for conducting a cooling test that are inappropriate 
in the regulation. Experience has shown that such detailed procedures 
are not directly applicable to certain engine configurations and 
certain operating conditions. Guidance material is available that 
provides appropriate procedures for testing different types of engine 
configurations and for testing at different operating conditions.

Section 23.1091  Air Induction System

    Current Sec. 23.1091 requires the air induction system design 
protect against ingestion of foreign material located ``on the runway, 
taxiway, or other airport operating surface.'' This proposal would 
require the air induction system design protect against foreign matter, 
from whatever source, ``during takeoff, landing, and taxiing.'' This 
would codify current certification practice and increase safety by 
protecting against universal foreign matter rather than foreign matter 
from a restricted source.

Section 23.1093  Induction System Icing Protection

    Section 23.1093(c) would be revised by adding the heading 
``Reciprocating engines with superchargers.'' This is being done to be 
consistent with paragraphs (a) and (b) of this section, which have 
headings.

Section 23.1105  Induction System Screens

    Current Sec. 23.1105 requires that any induction screens must be 
upstream of the carburetor. This requirement would be revised to 
include fuel injection systems. Some reciprocating engines incorporate 
a fuel injection system, and the same provisions required for a 
carburetor are necessary for a fuel injection system.

Section 23.1107  Induction System Filters

    Current Sec. 23.1107, which was added in Amendment 23-43, applies 
to reciprocating engine installations. The introductory section of this 
paragraph would be revised by deleting the reference to reciprocating 
engine installations to make the section applicable to airplanes with 
either reciprocating or turbine engines. If a filter is installed in 
the induction system of a turbine powered airplane, the same provisions 
that apply to a reciprocating engine are necessary.

Section 23.1121  General

    This proposal would revise Sec. 23.1121(g) by adding standards for 
APU exhaust systems; these were overlooked when APU standards were 
introduced into part 23 by Amendment 23-43. Prior to Amendment 23-43, 
applicants for type certification of part 23 airplanes having APU 
installations were required to comply with special conditions for those 
installations. Amendment 23-43 included a codification, albeit an 
incomplete one, of those special conditions.

Section 23.1141  Powerplant Controls: General

    Current Sec. 23.1141(b) requires that each flexible control be of 
an acceptable kind. This paragraph would be revised to replace the 
phrase ``must be of an acceptable kind'' with the phrase ``must be 
shown to be suitable for the particular application.'' This is a 
clarifying, non-substantive change.

Section 23.1143  Engine Controls

    Current Sec. 23.1143(f) requires that if a power or thrust control 
incorporates a fuel shutoff feature, the control must have a means to 
prevent the inadvertent movement of the control into the shutoff 
position. Paragraph (f) would be revised to add that a fuel control 
(other than a mixture control) must also have such a means.

Section 23.1153  Propeller Feathering Controls

    Current Sec. 23.1153 requires that if there are propeller 
feathering controls, each propeller must have a separate control, and 
each control must have a means to prevent inadvertent operation. This 
section would be revised because it does not matter whether the 
feathering controls are separate from the propeller speed and pitch 
controls as long as it is possible to feather each propeller 
separately.

Section 23.1181  Designated Fire Zones; Regions Included

    Current Sec. 23.1181, which was added in Amendment 23-43, defines 
designated fire zones for reciprocating engines and turbine engines. 
Proposed new Sec. 23.1181(b)(3) would add to the designated fire zones 
for turbine engines any complete powerplant compartments that do not 
have firewalls between compressor, accessory, combustor, turbine and 
tailpipe sections. The proposal would codify current certification 
practice and increase safety by ensuring that all appropriate regions 
of turbine engines are evaluated as designated fire zones.

Section 23.1183  Lines, Fittings, and Components

    Current Sec. 23.1183(a) includes the requirement that flexible hose 
assemblies must be approved. This requirement in paragraph (a) would be 
revised by replacing the word ``approved'' with the words ``shown to be 
suitable for the particular application.'' The revision clarifies what 
is required.

Section 23.1191  Firewalls

    Current Sec. 23.1191(a) requires that each engine, auxiliary power 
unit, fuel-burning heater, and other combustion equipment intended for 
operation in flight must be isolated ``by fire walls, shrouds, or 
equivalent means.'' Paragraph (b) of the section requires that each 
firewall or shroud must be constructed so that no hazardous quantity of 
liquid, gas, or flame can pass from the engine compartment to other 
parts of the airplane.
    Paragraph (b) would be revised to define isolated compartment and 
to show that the provisions of paragraph (b) would also apply to APU's.

Section 23.1203  Fire Detector System

    Current Sec. 23.1203(e) requires that wiring and other components 
of each fire detector system in an engine compartment must be at least 
fire resistant. For accuracy, proposed Sec. 23.1203(e) would replace 
the words ``engine compartment'' with ``designated fire zone'' to 
correct an oversight in the amendment and to make it consistent with 
Sec. 23.1181.

Section 23.1305  Powerplant Instruments

    Current Sec. 23.1305(b)(3), as amended in Amendment 23-43, 
requires, for reciprocating engine-powered airplanes, a cylinder head 
temperature indicator for each air-cooled engine with cowl flaps; each 
airplane for which compliance with Sec. 23.1041 is shown at a speed 
higher than VY; and each commuter category airplane.
    The proposed revision to paragraph (b)(3) would delete paragraph 
(b)(3)(ii), which refers to compliance with Sec. 23.1041. The flight 
notice referenced above contains a proposal to delete the determination 
of the VY speed and this notice proposes a change that the engine 
cooling test of Sec. 23.1047 be conducted at a speed recommended in the 
Airplane Flight Manual (AFM). Accordingly, other sections referencing 
the VY speed or the engine cooling test would also be amended.
    The proposed revision would retain the requirement that a cylinder 
head temperature indicator is required for commuter category airplanes 
having reciprocating engines and for airplanes having air-cooled 
engines and cowl flaps.

Section 23.1337  Powerplant Instruments

    Under the area of ``Installation,'' the reference in 
Sec. 23.1337(b)(1) to Sec. 23.959 would be changed to Sec. 23.959(a), 
in accordance with the revision to Sec. 23.959 proposed in this notice. 
The revision would redesignate the existing Sec. 23.959 text as 
Sec. 23.959(a); there is no change in the requirement itself.

Regulatory Evaluation, Regulatory Flexibility Determination, and Trade 
Impact Assessment

    Proposed changes to Federal regulations must undergo several 
economic analyses. First, Executive Order 12866 directs that each 
Federal agency shall propose or adopt a regulation only upon a reasoned 
determination that the benefits of the intended regulation justify its 
costs. Second, the Regulatory Flexibility Act of 1980 requires agencies 
to analyze the economic effect of regulatory changes on small entities. 
Third, the Office of Management and Budget directs agencies to assess 
the effects of regulatory changes on international trade. In conducting 
these analyses, the FAA has determined that this rule: (1) Would 
generate benefits that would justify its costs and is not a 
``significant regulatory action'' as defined in the Executive Order; 
(2) is not ``significant'' as defined in DOT's Policies and Procedures; 
(3) would not have a significant impact on a substantial number of 
small entities; and (4) would not constitute a barrier to international 
trade. These analyses, available in the docket, are summarized below.

Regulatory Evaluation Summary

    The FAA has determined that the benefits of the proposed rule, 
though not directly quantifiable, would exceed the expected costs. 
Minor costs, ranging from $240 to $6,000 per certification, are 
projected for four of the provisions in this proposal. No costs are 
attributed to the other thirty-two provisions. The benefits of the 
proposed rule are considered below in four categories: (1) 
harmonization, (2) safety, (3) reduced need for special conditions, and 
(4) clarification.

Harmonization

    The proposed rule, in concert with other rulemaking and policy 
actions, would provide nearly uniform powerplant airworthiness 
standards for airplanes certificated in the United States and the JAA 
member countries. Thirty-four of the thirty-six sections affected by 
the proposed rule would be harmonized. The resulting greater uniformity 
of standards would simplify airworthiness approval for import and 
export purposes and reduce the cost of certification for airplanes 
seeking certification under both sets of regulations.

Safety

    In addition to the harmonization benefits, five proposed changes 
would provide additional safety benefits. First, the proposed rule 
would revise Sec. 23.933(a)(1) to more closely agree with the 
corresponding turbojet and turbofan reversing system airworthiness 
standards of part 25. The FAA estimates that this provision would 
necessitate an additional 100 hours of failure mode and effects 
analysis at an assumed cost rate of $60 per hour, including labor and 
overhead. The estimated $6,000 cost would apply to each certification. 
The FAA projects that no additional production or operating costs would 
result from this provision.
    The primary potential benefit of the provision is the additional 
safety that could result from analyzing the feasible range of reverser 
system failures, the effects of those failures, and the corresponding 
capabilities necessary to correct the failure or circumvent its 
effects. Such an analysis would reduce the possibility that an 
unanticipated condition with catastrophic potential would remain in the 
system. In addition to the safety benefit, it is expected that some 
operating benefits and manufacturing economies would result from the 
uniformity of standards between parts 23 and 25. The FAA is not able to 
quantify the potential benefits of this provision but has determined 
that the benefits would exceed the expected minor costs.
    Second, the proposed rule would add a new paragraph (b) to 
Sec. 23.959 requiring that the effect of any fuel pump failure on the 
unusable fuel supply be determined. Though not previously required, it 
has been industry practice to include this information in the Airplane 
Flight Manual. The FAA estimates that the nominal cost of making this 
determination would be $240 per certification (4 hours of engineering 
analysis at $60 per hour). In addition, an insignificant cost ($1) 
would be incurred in adding a table entry to the manual for each 
airplane that is produced. The fact that the proposed requirement is 
already standard practice supports the FAA's position that the 
potential benefits of the provision would exceed the minor costs. The 
safety benefits of this provision would be derived from the assurance 
that this vital information would continue to be provided for future 
airplane models.
    Third, under Sec. 23.979, the proposed rule would add the 
requirement for commuter category airplanes that an indication be 
provided at each fueling station in the event of a failure of the 
shutoff means to stop fuel flow at the maximum level. The FAA estimates 
that the proposed required device would necessitate an incremental 
design and development cost of $3000 per certification (50 hours of 
engineering design at $60 per hour) and an additional nominal 
manufacturing cost of $10 per airplane. The benefit of the provision is 
the avoidance of a potentially catastrophic condition whereby excess 
fuel could unknowingly be forced out of the contained fuel system by 
the pressure fueling system. The FAA holds that these potential 
benefits would exceed the minor associated costs.
    Fourth, Sec. 23.1041 would require that the powerplant cooling 
system must be able to maintain the specified operating temperatures of 
the powerplant components and fluids. The ambient temperature for 
testing reciprocating engine airplanes is currently required to be 
corrected to show the capacity of the cooling system at 100  deg.F. 
Under the proposal, this temperature standard would be revised to the 
``maximum ambient temperature conditions for which approval is 
requested.''
    No costs are attributed to this provision. Reciprocating engine 
airplane manufacturers would continue to have the option to request 
approval for operations at the existing 100  deg.F temperature.
    A decision to request approval for a higher temperature would 
necessitate demonstration of the capability of the cooling system at 
that temperature. That choice, however, would be made at the 
manufacturer's discretion and would be based on its decision that any 
associated incremental cooling system costs would be recovered in the 
marketplace. The potential benefit of this provision is the reduced 
likelihood that an inadequate cooling system would be relied on during 
high temperature operations.
    Finally, Sec. 23.1045(a) would be revised to state more generally 
that compliance with the cooling margin requirements of Sec. 23.1041 
must be shown for all phases of operation, as compared to the four 
phases of flight currently listed. In effect, the proposal would add 
the taxi phase of operation.
    The FAA estimates that the specific addition of the taxi phase 
would necessitate an incremental 5 hours of engineering analysis valued 
at $60 per hour, for a total of $300 per certification. The potential 
benefit of this provision is the enhanced safety that would result from 
evaluating the efficacy of the cooling system during the taxi phase of 
operation. In the taxi phase of operation, engine power settings and 
heat production generally may be lower than that experienced during 
flight, but available air circulation might also be lower. The heat 
mechanics of the two phases of operation are distinct and warrant 
separate evaluation. The FAA holds that the potential benefits of this 
provision would exceed the nominal associated costs.

Reduced Need for Special Conditions

    The proposed rule includes five provisions that would replace the 
need for processing certain parts or materials as special conditions 
because they have been considered novel or unusual design features. The 
subjects of these provisions include composite propellers, fuel 
injection systems for reciprocating engines, induction filters on 
turbine engines, fuel shutoff controls other than mixture controls, and 
auxiliary power units. No costs are attributed to these provisions. 
Formalization of the equivalent safety standards and requirements for 
these subjects would obviate the need for special conditions actions 
and would simplify the certification process for manufacturers.

Clarification

    Several unclear provisions of part 23 were revealed during the 
harmonization review. In response to this finding, the proposal 
includes a number of no-cost, editorial revisions that would clarify 
the existing requirements. These changes would benefit manufacturers by 
removing potential confusion about the specific standards and 
requirements necessary for product certification.
    In summary, the FAA holds that each of the provisions, as well as 
the entire proposal, would be cost beneficial.

Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (RFA) was enacted by 
Congress to ensure that small entities are not unnecessarily or 
disproportionately burdened by Government regulations. The RFA requires 
a Regulatory Flexibility Analysis if a proposed rule would have a 
significant economic impact, either detrimental or beneficial, on a 
substantial number of small entities. Based on implementing FAA Order 
2100.14A, Regulatory Flexibility Criteria and Guidance, the FAA has 
determined that the proposed amendments would not have a significant 
economic impact on a substantial number of small entities.

Trade Impact Assessment

    The proposed rule would not constitute a barrier to international 
trade, including the export of American airplanes to foreign countries 
and the import of foreign airplanes into the United States. Instead, 
the proposed powerplant airworthiness standards would be harmonized 
with those of foreign aviation authorities and would lessen current 
restraints on trade caused by differences in certification 
requirements.

Federalism Implications

    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.

Conclusion

    The FAA proposes to revise the airworthiness standards to provide 
propulsion standards for normal, utility, acrobatic, and commuter 
category airplanes to harmonize them with the standards that will be 
proposed for the same category airplanes by the Joint Aviation 
Authorities in Europe. If adopted, the proposed revisions would reduce 
the regulatory burden on the United States and European airplane 
manufacturers by relieving them of the need to show compliance with 
different standards each time they seek certification approval of an 
airplane in a different country.
    For the reasons discussed in the preamble, and based on the 
findings in the Regulatory Evaluation, the FAA has determined that this 
proposed regulation is not significant under Executive Order 12866. In 
addition, the FAA certifies that this proposal, if adopted, 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. This proposal is not considered significant 
under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 
1979). An initial regulatory evaluation of the proposal has been placed 
in the docket. A copy may be obtained by contacting the person 
identified under FOR FURTHER INFORMATION CONTACT.

List of Subjects in 14 CFR Part 23

    Aircraft, Aviation safety, Signs and symbols.

The Proposed Amendment

    In consideration of the foregoing, the Federal Aviation 
Administration proposes to amend part 23 of the Federal Aviation 
Regulations (14 CFR part 23) as follows:

PART 23--AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND 
COMMUTER CATEGORY AIRPLANES

    1. The authority citation for part 23 continues to read as follows:

    Authority: 49 U.S.C. app. 1344, 1354(a), 1355, 1421, 1423, 1425, 
1428, 1429, and 1430; 49 U.S.C. 106(g).


Sec. 23.777  [Amended]

    2. Section 23.777(c)(2) is amended by adding the words ``single 
and'' between the words ``for'' and ``tandem'' in the first sentence.
    3. The table in Sec. 23.779(b)(1) is amended by adding a new item 
between the items ``mixture'' and ``carburetor air heat or alternate 
air'' to read as follows:


Sec. 23.779  Motion and effect of cockpit controls.

* * * * *
    (b) * * *

------------------------------------------------------------------------
                                              Motion and effect         
------------------------------------------------------------------------
(1) Powerplant controls:                                                
                                                                        
                                  *****                                 
  Fuel.............................  Forward for open.                  
                                                                        
                                                                        
                                  *****                                 
------------------------------------------------------------------------

    4. Section 23.901 is amended by revising paragraphs (d)(1), (d)(2), 
(e) Introductory text and (e)(1) to read as follows:


Sec. 23.901  Installation.

* * * * *
    (d) * * *
    (1) Result in carcass vibration characteristics that do not exceed 
those established during the type certification of the engine.
    (2) Provide continued safe operation without a hazardous loss of 
power or thrust while being operated in rain for at least three minutes 
with the rate of water ingestion being not less than four percent, by 
weight, of the engine induction airflow rate at the maximum installed 
power or thrust approved for takeoff and at flight idle.
    (e) The powerplant installation must comply with--
    (1) The installation instructions provided under--
    (i) The engine type certificate; and
    (ii) The propeller type certificate or the requirements of another 
approved procedure that provides an equivalent level of safety.
* * * * *
    5. Section 23.903 is amended by adding headings to paragraphs (c) 
and (g), and by revising the heading of paragraph (f) to read as 
follows:


Sec. 23.903  Engines.

* * * * *
    (c)  Engine isolation. * * *
* * * * *
    (f)  Restart envelope. * * *
    (g)  Restart capability. * * *


Sec. 23.905  [Amended]

    6. Section 23.905 is amended by adding the words ``or meet the 
requirements of another approved procedure that provides an equivalent 
level of safety'' to the end of paragraph (a).


Sec. 23.907  [Amended]

    7. Section 23.907(a) introductory text is amended by removing the 
words ``with metal blades or highly stressed metal components'' and 
replacing them with the words ``other than a conventional fixed-pitch 
wooden propeller.''
    8. Section 23.925 is amended by revising the introductory text to 
read as follows:


Sec. 23.925  Propeller clearance.

    Unless smaller clearances are substantiated, propeller clearances, 
with the airplane at the most adverse combination of weight and center 
of gravity, and with the propeller in the most adverse pitch position, 
may not be less than the following:
 * * * * *


Sec. 23.929  [Amended]

    9. Section 23.929 is amended by removing the word ``power'' and 
adding, in its place, the word ``thrust.''
    10. Section 23.933 is amended by removing the word ``forward'' 
where ever it appears in paragraph (a)(3); by revising the reference in 
paragraph (b)(2) that reads ``(a)(1)'' to read ``(b)(1)''; and by 
revising paragraph (a)(1) to read as follows:


Sec. 23.933  Reversing systems.

    (a) * * *
    (1) Each system intended for ground operation only must be designed 
so that, during any reversal in flight, the engine will produce no more 
than flight idle thrust. In addition, it must be shown by analysis or 
test, or both, that--
    (i) Each operable reverser can be restored to the forward thrust 
position; or
    (ii) The airplane is capable of continued safe flight and landing 
under any possible position of the thrust reverser.
 * * * * *
    11. Section 23.955 is amended by revising paragraphs (a)(1) through 
(a)(4) to read as follows:


Sec. 23.955  Fuel flow.

    (a) * * *
    (1) The quantity of fuel in the tank may not exceed the amount 
established as the unusable fuel supply for that tank under 
Sec. 23.959(a) plus that necessary to show compliance with this 
section.
    (2) If there is a fuel flowmeter, it must be blocked during the 
flow test and the fuel must flow through the meter or its bypass.
    (3) If there is a flowmeter without a bypass, it must not have any 
probable failure mode that would restrict fuel flow below the level 
required in this fuel demonstration.
    (4) The fuel flow must include that flow needed for vapor return 
flow, jet pump drive flow, and for all other purposes for which fuel is 
used.
 * * * * *
    12. Section 23.959 is amended by designating the text of the 
section as paragraph (a), and by adding a new paragraph (b) to read as 
follows:


Sec. 23.959  Unusable fuel supply.

 * * * * *
    (b) The effect on the unusable fuel quantity as a result of a 
failure of any pump shall be determined.
    13. Section 23.963 is amended by revising the reference in 
paragraph (e) that reads ``Sec. 23.959'' to read ``Sec. 23.959(a)'' and 
by revising paragraph (b) to read as follows:


Sec. 23.963  Fuel tanks: general.

 * * * * *
    (b) Each flexible fuel tank liner must be shown to be suitable for 
the particular application.
 * * * * *
    14. Section 23.965 is amended by revising paragraph (b)(3)(i) to 
read as follows:


Sec. 23.965  Fuel tank tests.

 * * * * *
    (b) * * *
    (3) * * *
    (i) If no frequency of vibration resulting from any r.p.m. within 
the normal operating range of engine or propeller speeds is critical, 
the test frequency of vibration is the number of cycles per minute 
obtained by multiplying the maximum continuous propeller speed in 
r.p.m. by 0.9 for propeller-driven airplanes, except that for non-
propeller driven airplanes the test frequency of vibration is 2,000 
cycles per minute.
 * * * * *
    15. Section 23.973(f) is revised to read as follows:


Sec. 23.973  Fuel tank filler connection.

* * * * *
    (f) For airplanes with turbine engines, the inside diameter of the 
fuel filler opening must be no smaller than 2.95 inches.
    16. Section 23.975(a)(5) is revised to read as follows:


Sec. 23.975  Fuel tank vents and carburetor vapor vents.

    (a) * * *
    (5) There may be no point in any vent line where moisture can 
accumulate with the airplane in either the ground or level flight 
attitudes, unless drainage is provided. Any drain valve installed in 
the vent lines must discharge clear of the airplane and be accessible 
for drainage;
 * * * * *
    17. Section 23.979(b) is revised to read as follows:


Sec. 23.979  Pressure fueling systems.

 * * * * *
    (b) An automatic shutoff means must be provided to prevent the 
quantity of fuel in each tank from exceeding the maximum quantity 
approved for that tank. This means must--
    (1) Allow checking for proper shutoff operation before each fueling 
of the tank; and
    (2) For commuter category airplanes, indicate at each fueling 
station, a failure of the shutoff means to stop the fuel flow at the 
maximum quantity approved for that tank.
* * * * *
    18. Section 23.1001 is amended by revising paragraph (b)(2) to read 
as follows:
* * * * *


Sec. 23.1001  Fuel jettisoning system.

* * * * *
    (b) * * *
    (2) A climb at the speed at which the one engine inoperative 
enroute climb data have been established in accordance with 
Sec. 23.69(b), with the critical engine inoperative and the remaining 
engines at maximum continuous power; and
* * * * *


Sec. 23.1013  [Amended]

    19. Section 23.1013 is amended by removing the word ``crankcase'' 
in paragraph (d)(1).


Sec. 23.1041  [Amended]

    20. Section 23.1041 is amended by adding the phrase ``and maximum 
ambient atmospheric temperature conditions'' between the words 
``maximum altitude'' and ``for which approval''.
    21. Section 23.1043 (a), (c), and (d) are revised to read as 
follows:


Sec. 23.1043  Cooling tests.

    (a) General. Compliance with Sec. 23.1041 must be shown on the 
basis of tests, for which the following apply:
    (1) If the tests are conducted under ambient atmospheric 
temperature conditions deviating from the maximum for which approval is 
requested, the recorded powerplant temperatures must be corrected under 
paragraphs (c) and (d) of this section, unless a more rational 
correction method is applicable.
    (2) No corrected temperature determined under paragraph (a)(1) of 
this section may exceed established limits.
    (3) The fuel used during the cooling tests must be of the minimum 
grade approved for the engine and, for a reciprocating engine, the 
mixture settings must be the leanest recommended for climb.
    (4) For turbocharged engines, such turbocharger must be operated 
through that part of the climb profile for which operation with the 
turbocharger is requested.
    (b) * * *
    (c) Correction factor (except cylinder barrels). Temperatures of 
engine fluids and powerplant components (except cylinder barrels) for 
which temperature limits are established, must be corrected by adding 
to them the difference between the maximum ambient atmospheric 
temperature for the relevant altitude for which approval has been 
requested and the temperature of the ambient air at the time of the 
first occurrence of the maximum fluid or component temperature recorded 
during the cooling test.
    (d) Correction factor for cylinder barrel temperatures. Cylinder 
barrel temperatures must be corrected by adding to them 0.7 times the 
difference between the maximum ambient atmospheric temperature for the 
relevant altitude for which approval has been requested and the 
temperature of the ambient air at the time of the first occurrence of 
the maximum cylinder barrel temperature recorded during the cooling 
test.
    22. Section 23.1045(a) is revised to read as follows:


Sec. 23.1045  Cooling test procedures for turbine engine powered 
airplanes.

    (a) Compliance with Sec. 23.1041 must be shown for all phases of 
operation. The airplane must be flown in the configurations, at the 
speeds, and following the procedures recommended in the Airplane Flight 
Manual for the relevant stage of flight, and that correspond to the 
applicable performance requirements that are critical to cooling.
* * * * *
    23. Section 23.1047 is revised to read as follows:


Sec. 23.1047  Cooling test procedures for reciprocating engine powered 
airplanes.

    Compliance with Sec. 23.1041 must be shown for the climb (or, for 
multiengine airplanes with negative one-engine-inoperative rates of 
climb, the descent) stage of flight. The airplane must be flown in the 
configurations, at the speeds and following the procedures recommended 
in the Airplane Flight Manual (AFM), and that correspond to the 
applicable performance requirements that are critical to cooling.
    24. Section 23.1091 is amended by revising paragraph (c)(2) to read 
as follows:


Sec. 23.1091  Air induction system.

* * * * *
    (c) * * *
    (2) The airplane must be designed to prevent water or slush on the 
runway, taxiway, or other airport operating surfaces from being 
directed into the engine or auxiliary power unit air intake ducts in 
hazardous quantities. The air intake ducts must be located or protected 
so as to minimize the ingestion of foreign matter during takeoff, 
landing, and taxiing.


Sec. 23.1093  [Amended]

    25. Section 23.1093 is amended by adding the heading 
``Reciprocating engines with Superchargers'' to paragraph (c).
    26. Section 23.1105 is amended by revising paragraph (a) to read as 
follows:


Sec. 23.1105  Induction system screens.

* * * * *
    (a) Each screen must be upstream of the carburetor or fuel 
injection system.
* * * * *
    27. Section 23.1107 is amended by revising the introductory text to 
read as follows:
* * * * *


Sec. 23.1107  Induction system filters.

    If an air filter is used to protect the engine against foreign 
material particles in the induction air supply--
* * * * *
    28. Section 23.1121(g) is revised to read as follows:


Sec. 23.1121  General.

* * * * *
    (g) If significant traps exist, each turbine engine and auxiliary 
power unit exhaust system must have drains discharging clear of the 
airplane, in any normal ground and flight attitude, to prevent fuel 
accumulation after the failure of an attempted engine or auxiliary 
power unit start.
* * * * *
    29. Section 23.1141(b) is revised to read as follows:


Sec. 23.1141  Powerplant controls: general.

* * * * *
    (b) Each flexible control must be shown to be suitable for the 
particular application.
* * * * *
    30. Section 23.1143(f) is amended by revising the introductory text 
to read as follows:


Sec. 23.1143  Engine controls.

* * * * *
    (f) If a power or thrust control, or a fuel control (other than a 
mixture control) incorporates a fuel shutoff feature, the control must 
have a means to prevent the inadvertent movement of control into the 
off position. The means must--
* * * * *
    31. Section 23.1153 is revised to read as follows:


Sec. 23.1153  Propeller feathering controls.

    If there are propeller feathering controls, whether or not they are 
separate from the propeller speed and pitch controls, it must be 
possible to feather each propeller separately. Each control must have 
means to prevent inadvertent operation.
    32. Section 23.1181 is amended by adding a new paragraph (b)(3) to 
read as follows:


Sec. 23.1181  Designated fire zones; regions included.

* * * * *
    (b) * * *
    (3) Any complete powerplant compartment in which there is no 
isolation between compressor, accessory, combustor, turbine, and 
tailpipe sections.
* * * * *


Sec. 23.1183  [Amended]

    33. Section 23.1183(a) is amended by removing the word ``approved'' 
in the next to the last sentence, and replacing it with the words 
``shown to be suitable for the particular application.''
    34. Section 23.1191 is amended by revising paragraph (b) to read as 
follows:


Sec. 23.1191  Firewalls.

* * * * *
    (b) Each firewall or shroud must be constructed so that no 
hazardous quantity of liquid, gas, or flame can pass from the 
compartment created by the firewall or shroud to other parts of the 
airplane.
* * * * *
    35. Section 23.1203 is amended by revising paragraph (e) to read as 
follows:


Sec. 23.1203  Fire detector system.

* * * * *
    (e) Wiring and other components of each fire detector system in a 
designated fire zone must be at least fire resistant.
* * * * *


Sec. 23.1305  [Amended]

    36. Section 23.1305 is amended by removing paragraph (b)(3)(ii) and 
redesignating paragraph (b)(3)(iii) as paragraph (b)(3)(ii).


Sec. 23.1337  [Amended]

    37. Section 23.1337 is amended by removing the reference to 
``Sec. 23.959'' in paragraph (b)(1) and replacing it with 
``Sec. 23.959(a)''.

    Issued in Washington, DC, on June 22, 1994.
Thomas E. McSweeny,
Director, Aircraft Certification Service.
[FR Doc. 94-15619 Filed 6-29-94; 8:45 am]
BILLING CODE 4910-13-M