eproof materials or components must shown as follows:

(1) The flame to which the materials components are subjected must be 000+50° F.

(2) Sheet materials approximately 10 aches square must be subjected to the Fame from a suitable burner.

(3) The flame must be large enough o maintain the required test temperaure over an area approximately five nches square.

(g) Firewall materials and fittings must resist flame penetration for at least 15 minutes.

(h) The following materials may be ased in firewalls or shrouds without being tested as required by this section:

(1) Stainless steel sheet, 0.015 inch thick.

(2) Mild steel sheet (coated with aluminum or otherwise protected against corrosion) 0.018 inch thick.

(3) Terne plate, 0.018 inch thick. (4) Monel metal, 0.018 inch thick. (5) Steel or copper base alloy firewall fittings. §23.1193

Cowling.

(a) Each cowling must be constructed and supported so that it can resist any vibration, inertia, and air loads to which It may be subjected in operation.

(b) There must be means for rapid and complete drainage of each part of the cowling in the normal ground and flight attitudes. No drain may discharge where it will cause a fire hazard.

(c) Cowling must be at least fire resistant.

(d) Each part behind an opening in the engine compartment cowling must be at least fire resistant for a distance of at least 24 inches aft of the opening.

(e) Each part of the cowling subjected to high temperatures due to its nearness to exhaust system ports or exhaust gas impingement, must be fire proof.

Subpart F-Equipment

(3) Be installed according to limitations prescribed for that equipment and in compliance with § 23.1431; and

(4) Function properly when installed. (b) Whenever necessary, additional equipment that is installed as prescribed in the operating rules of this chapter, must meet the requirements of this section.

[Docket No. 4080, 29 F.R. 17955, Dec. 18, 1964, as amended by Amdt. No. 23-7, 34 F.R. 13096, Aug. 13, 1969]

§ 23.1303 Flight and navigation instru

ments.

The following are required flight and navigational instruments:

(a) An airspeed indicator. (b) An altimeter.

(c) A magnetic direction indicator. § 23.1305 Powerplant instruments.

The following are required powerplant instruments:

(a) A fuel quantity indicator for each fuel tank.

(b) An oil pressure indicator for each engine and for each turbosupercharger oil system that is separate from other oil systems.

(c) An oil temperature indicator for each engine and for each turbosupercharger oil system that is separate from other oil systems.

(d) A tachometer for each reciprocating engine.

(e) A tachometer (to indicate the speed of the rotors with established limiting speeds) for each turbine engine.

(f) A cylinder head temperature indicator for each air cooled engine with cowl flaps, and for each airplane for which compliance with § 23.1041 is shown at a speed higher than Vy.

(g) A fuel pressure indicator pump-fed engines.

for

(h) A manifold pressure indicator for each altitude engine.

(i) An oil quantity indicator for each oil tank,

(j) A gas temperature indicator for each turbine engine.

(k) A fuel flowmeter for each turbine engine or fuel tank, if pilot action is required to maintain fuel flow within limits.

(1) An indicator to indicate engine thrust or to indicate a gas stream pressure that can be related to thrust, for each turbojet engine, including a free air temperature indicator if needed for this purpose.

(m) A torque indicator for each turbopropeller engine.

(n) A position indicating means to indicate to the flight crew when the propeller blade angle is below the flight low pitch position, for each turbopropeller engine propeller. The source of indication must directly sense the blade position.

(0) A position indicating means to indicate to the flight crew when the thrust reverser is in the reverse thrust position for each turbojet engine.

(p) For turbosupercharger installations, if limitations are established for either carburetor air inlet temperature or exhaust gas temperature, indicators must be furnished for each temperature for which the limitation is established unless it is shown that the limitation will not be exceeded in all intended operations.

[Amdt. No. 23-7, 34 F.R. 13096, Aug. 13, 1969] § 23.1307 Miscellaneous equipment.

(a) There must be an approved safety belt for each occupant.

miscellaneous

(b) The following equipment is required as prescribed in this subpart:

(1) A master switch arrangement. (2) An adequate source of electrical energy.

(3) Electrical protective devices.

INSTRUMENTS: INSTALLATION

§ 23.1321 Arrangement and visibility.

(a) Each flight, navigation, and powerplant instrument for use by any pilot must be easily visible to him.

(b) For each multiengine airplane, identical powerplant instruments must be located so as to prevent confusion as to which engine each instrument relates.

(c) Instrument panel vibration may not damage, or impair the accuracy of, any instrument.

§ 23.1323 Airspeed indicating system.

(a) Except for an allowable installational error of plus or minus three percent of the calibrated airspeed, or five knots, whichever is greater, each airspeed indicating system must indicate true airspeed at sea level with a standard atmosphere

(1) At speeds from Vo to 1.3 Vs1' flaps up; and

with

[Docket No. 4080, 29 F.R. 17955, Dec. 18, 196 as amended by Amdt. No. 23-7, 34 F.R. 1309 Aug. 13, 1969]

§ 23.1325 Static pressure system.

(a) Each instrument provided wit static pressure case connections must so vented that the influence of airpla speed, the opening and closing of wir dows, airflow variations, moisture, other foreign matter will least affect th accuracy of the instruments except noted in paragraph (b) (3) of th section.

(b) If a static pressure system is ne essary for the functioning of instrument systems, or devices, it must comply wit the provisions of subparagraphs (1 through (3) of this paragraph.

(1) The design and installation of static pressure system must be suc that

(i) Positive drainage of moisture provided;

(ii) Chafing of the tubing, and exces sive distortion or restriction at bends i the tubing, is avoided; and

(iii) The materials used are durable suitable for the purpose intended, and protected against corrosion.

(2) A proof test must be conducted to demonstrate the integrity of the static pressure system in the following manner:

(i) Unpressurized airplanes. Evacuate the static pressure system to a pressure differential of approximately 1 inch murcury or to a reading on the altimeter 1,000 feet above the aircraft elevation at the time of the test. Without addi tional pumping for a period of 1 minute the loss of indicated altitude must no exceed 100 feet on the altimeter.

(ii) Pressurized airplanes. Evacuate the static pressure system until a pres sure differential equivalent to the maxi mum cabin pressure differential for which the airplane is type certificated is achieved. Without additional pumping for a period of 1 minute, the loss of indicated altitude must not exceed 2 percent of the equivalent altitude of the maximum cabin differential pressure or 100 feet, whichever is greater.

(3) If a static pressure system is provided for any instrument, device, or system required by the operating rules of

s chapter, each static pressure port st be designed or located in such a nner that the correlation between air essure in the static pressure system d true ambient atmospheric static essure is not altered when the airplane counters icing conditions. An anting means or an alternate source of atic pressure may be used in showing mpliance with this requirement. If the ading of the altimeter, when on the ernate static pressure system differs om the reading of the altimeter when the primary static system by more an 50 feet, a correction card must be ovided for the alternate static sysm.

mdt. 23–1, 30 F.R. 8261, June 29, 1965, as mended by Amdt. 23-6, 32 F.R. 7586, May 1967; 32 F.R. 13505, Sept. 27, 1967; 32 F.R. 714, Sept. 30, 1967]

23.1327 Magnetic direction indicator. (a) Each magnetic direction indicator ust be installed so that its accuracy not excessively affected by the airane's vibration or magnetic fields. (b) The compensated installation may ot have a deviation, in level flight, eater than ten degrees on any head-g.

23.1329 Automatic pilot system.

If an automatic pilot system is intalled, it must meet the following: (a) Each system must be designed so at the automatic pilot can

(1) Be quickly and positively disenged by the pilots to prevent it from terfering with their control of the airane; or

(2) Be sufficiently overpowered by one lot to let him control the airplane.

(b) Unless there is automatic synronization, each system must have a eans to readily indicate to the pilot e alignment of the actuating device relation to the control system it opates.

(c) Each manually operated control r the system operation must be readaccessible to the pilot. Each control ust operate in the same plane and nse of motion as specified in § 23.779 r cockpit controls. The direction of lotion must be plainly indicated on or ear each control.

(d) Each system must be designed and djusted so that, within the range of adstment available to the pilot, it cannot

produce hazardous loads on the airplane or create hazardous deviations in the flight path, under any flight condition appropriate to its use, either during normal operation or in the event of a malfunction, assuming that corrective action begins within a reasonable period of time.

(e) Each system must be designed so that a single malfunction will not produce a hardover signal in more than one control axis. If the automatic pilot integrates signals from auxiliary controls or furnishes signals for operation of other equipment, positive interlocks and sequencing of engagement to prevent improper operation are required.

(f) There must be protection against adverse interaction of integrated components, resulting from a malfunction. § 23.1331 Instruments using a power

supply.

(a) For each airplane—

(1) Each gyroscopic instrument must derive its energy from power sources adequate to maintain its required accuracy at any speed above the best rateof-climb speed;

(2) Each gyroscopic instrument must be installed so as to prevent malfunction due to rain, oil, and other detrimental elements; and

(3) There must be a means to indicate the adequacy of the power being supplied to the instruments.

(b) For each multiengine airplane(1) There must be at least two independent sources of power (not driven by the same engine), a manual or an automatic means to select each power source, and a means to indicate the adequacy of the power being supplied by each source; and

(2) The installation and power supply systems must be designed so that—

(i) The failure of one instrument will not interfere with the proper supply of energy to the remaining instruments; and

(ii) The failure of the energy supply from one source will not interfere with the proper supply of energy from any other source.

§ 23.1335 Flight director instrument.

(a) The flight director instrument, if installed, may not affect the performance and accuracy of the required instruments.

(b) There must be a means to disconnect the flight director instrument from the required instruments or their installations.

§ 23.1337 Powerplant instruments.

(a) Instrument lines. Each powerplant instrument line must meet the requirements of § 23.993. Each line carrying flammable fluids or gases under pressure must have restricting orifices or other safety devices at the source of pressure to prevent escape of excessive fluid or gas if the line fails.

(b) Fuel quantity indicator. There must be a means to indicate to the flight crewmembers the quantity of fuel in each tank during flight. An indicator, calibrated in either gallons or pounds, and clearly marked to indicate which scale is being used, may be used. In addition

(1) Each fuel quantity indicator must be calibrated to read "zero" during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply determined under § 23.959;

(2) Each exposed sight gauge used as a fuel quantity indicator must be protected against damage;

(3) Each sight gauge that forms a trap in which water can collect and freeze must have means to allow drainage on the ground;

(4) Tanks with interconnected outlets and airspaces may be considered as one tank and need not have separate indicators; and

(5) No fuel quantity indicator is required for a small auxiliary tank that is used only to transfer fuel to other tanks if the relative size of the tank, the rate of fuel transfer, and operating instructions are adequate to

(1) Guard against overflow; and

(ii) Give the flight crewmembers prompt warning if transfer is not proceeding as planned.

(c) Fuel flowmeter system. If a fuel flowmeter system is installed, each metering component must have a means to by-pass the fuel supply if malfunctioning of that component severely restricts fuel flow.

(d) Oil quantity indicator. There must be a means to indicate the quantity of oil in each tank

(1) On the ground (such as by a stick gauge); and

(2) In flight, to the flight crew mem

bers, if there is an oil transfer syster a reserve oil supply system.

[Docket No. 4080, 29 F.R. 17955, Dec. 18, 1 as amended by Amdt. No. 23-7, 34 F.R. 13 Aug. 13, 1969]

ELECTRICAL SYSTEMS AND EQUIPMEN § 23.1351 General.

(a) Electrical system capacity. E electrical system must be adequate the intended use. In addition

(1) Electric power sources, th transmission cables, and their associa control and protective devices, must able to furnish the required power at proper voltage to each load circuit sential for safe operation; and

(2) Compliance with subparagra (1) of this paragraph must be shown an electrical load analysis, or by el trical measurements, that account the electrical loads applied to the el trical system in probable combinati and for probable durations.

(b) Function. For each electri system, the following apply:

(1) Each system, when installed, m be

(1) Free from hazards in itself, in method of operation, and in its effe on other parts of the airplane; and

(ii) Protected from fuel, oil, wate other detrimental substances, and m chanical damage.

(2) Electric power sources must fur tion properly when connected in co bination or independently, except th alternators may depend on a battery initial excitation or for stabilization.

(3) No failure or malfunction of a electric power source may impair ability of any remaining source to sup load circuits essential for safe operati except that the operation of an alter tor that depends on a battery for init excitation or for stabilization may stopped by failure of that battery.

(4) Each electric power source c trol must allow the independent ope tion of each source, except that contr associated with alternators that depe on a battery for initial excitation or stabilization need not break the conne tion between the alternator and battery.

(c) Generating system. There m be at least one generator if the electri system supplies power to load circu essential for safe operation. In ad tion

1) Each generator must be able to ver its continuous rated power;

2) Generator voltage control equipnt must be able to dependably regue the generator output within rated its; and

3) Each generator must have a rese current cutout designed to disconet the generator from the battery and m the other generators when enough erse current exists to damage that erator.

(d) Instruments. There must be a ans to indicate to appropriate flight wmembers the electric power system antities essential for safe operation. r direct current systems, an ammeter at can be switched into each generator der may be used and if there is only e generator, the ammeter may be in e battery feeder.

Docket No. 4080, 29 F.R. 17955, Dec. 18, 1964, amended by Amdt. No. 23–7, 34 F.R. 13096, g. 13, 1969]

23.1353 Storage battery design and installation.

(a) Each storage battery must be degned and installed as prescribed in this ction.

(b) Safe cell temperatures and presares must be maintained during any robable charging and discharging conition. No uncontrolled increase in cell emperature may result when the battery $ recharged (after previous complete scharge).

(1) At maximum regulated voltage; (2) During a flight of maximum duraon; and

(3) Under the most adverse cooling ndition likely to occur in service. (c) Compliance with paragraph (b) this section must be shown by tests aless experience with similar batteries ad installations has shown that mainining safe cell temperatures and prestres presents no problem. (d) No explosive or toxic gases mitted by any battery in normal opration, or as the result of any probable alfunction in the charging system or attery installation, may accumulate in azardous quantities within the airplane. (e) No corrosive fluids or gases that may escape from the battery may damage Surrounding structures or adjacent essential equipment.

23.1357 Circuit protective devices. (a) Protective devices, such as fuses or

circuit breakers, must be installed in all electrical circuits other than

(1) The main circuits of starter motors; and

(2) Circuits in which no hazard is presented by their omission.

(b) No protective device may protect more than one circuit essential to flight safety.

(c) Each resettable circuit protective device ("trip free" device in which the tripping mechanism cannot be overridden by the operating control) must be designed so that

(1) A manual operation is required to restore service after tripping; and

(2) If an overload or circuit fault exists, the device will open the circuit regardless of the position of the operating control.

(d) If the ability to reset a circuit breaker or replace a fuse is essential to safety in flight, that circuit breaker or fuse must be so located and identified that it can be readily reset or replaced in flight.

(e) If fuses are used, there must be one spare of each rating, or 50 percent spare fuses of each rating, whichever is greater. § 23.1361 Master switch arrangement.

(a) There must be a master switch arrangement to allow ready disconnection of electric power sources from the main bus. The point of disconnection must be adjacent to the sources controlled by the switch.

(b) Load circuits may be connected so that they remain energized after the switch is opened, if they are protected by circuit protective devices, rated at five amperes or less, adjacent to the electric power source.

(c) The master switch or its controls must be so installed that the switch is easily discernible and accessible to a crewmember in flight.

§ 23.1365 Electric cables.

(a) Each electric connecting cable must be of adequate capacity.

(b) Each cable that would overheat in the event of circuit overload or fault must be at least flame resistant and may not emit dangerous quantities of toxic fumes.