tion. The corrected temperatures determined in this manner shall not exceed the maximum established safe values. The fuel used during the cooling tests shall be of the minimum octane number approved for the engines involved, and the mixture settings shall be those used in normal operation. The test procedures shall be as outlined in §§ 4b.452 through 4b.454.

(b) Maximum anticipated air temperature. The maximum anticipated air temperature (hot day condition) shall be 100° F. at sea level, decreasing from this value at the rate of 3.6° F. per thousand feet of altitude above sea level until a temperature of -67° F. is reached above which altitude the temperature shall be constant at -67° F.

(c) Correction factor for cylinder head, oil inlet, and carburetor air temperatures. The cylinder head, oil inlet, and carburetor air temperatures shall be corrected by adding the difference between the maximum anticipated air temperature and the temperature of the ambient air at the time of the first occurrence of maximum head, oil, or air temperature recorded during the cooling test, unless a more rational correction is shown to be applicable.

(d) Correction factor for cylinder barrel temperatures. Cylinder barrel temperatures shall be corrected by adding 0.7 of the difference between the maximum anticipated air temperature 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, unless a more rational correction is shown to be applicable.

[15 F. R. 3543, June 8, 1950, as amended by Amdt. 4b-3, 21 F. R. 994, Feb. 11, 1956] § 4b.452 Climb cooling test procedure. (a) The climb cooling test shall be conducted with the critical engine inoperative and its propeller feathered.

(b) All remaining engines shall be operated at their maximum continuous power or at full throttle when above the critical altitude.

(c) After stabilizing temperatures in flight, the climb shall be started at or below the lower of the two following altitudes and shall be continued until at least 5 minutes after the occurrence of the highest temperature recorded, or until the maximum altitude is reached for which certification is desired:

(1) 1,000 feet below the engine critical altitude,

(2) 1,000 feet below the maximum altitude at which the rate of climb is equal to that established in accordance with § 4b.120 (c).

(d) The climb shall be conducted at an air speed which does not exceed the speed used in establishing the rate of climb required in § 4b.120 (c). It shall be acceptable to conduct the climb cooling test in conjunction with the take-off cooling test of § 4b.453.

§ 4b.452-1 Procedure for demonstrating cooling climb (FAA policies which apply to § 4b.452).

(a) Cylinder heads and bases. If the applicant is not able to provide data for the location of the engine having the hottest cylinder heads and bases, the following procedure should be accomplished. The cylinder heads and bases on one engine should be fully instrumented for the purpose of determining the location of the hottest cylinder head and base to be checked during the cooling climb. Thermocouples should be installed on one head of each of the remaining engines at the location shown to be critical on the fully instrumented engine. The hottest of the critical cylinder heads may be determined by measuring the temperatures of each of the engines under simulated climb conditions. The engine having the hottest cylinder head should be chosen as the engine to be tested for the cooling demonstration. Instruments for determining the oil inlet and cylinder base temperatures should be installed on this engine. The cooler operating outboard engine should be considered to be the critical inoperative engine unless there is reason to believe that another engine is more critical. The cooling tests should be conducted in an atmosphere which is free of any visible moisture.

(b) Configuration. This test should be conducted in the configuration that follows:

Weight-Maximum take-off.

C. G. position-Optional.
Wing flaps Optional.
Landing gear-Optional.

Operating engine(s)—Maximum continuous
power, mixture setting the same as used
in normal operation and cooling controls
in CAA hot day cooling position.
Critical inoperative engine-Throttle closed
on cooler operating outboard engine,
propeller feathered and cowl flaps closed.

(c) Test procedure and required data. (1) Prior to commencing the cooling climb, the engine temperatures should be stabilized in level flight at the lower of the two altitudes specified in § 4b.452 (c). During level flight the cooling climb conditions should be simulated by adjusting the airplane configuration to that shown in paragraph (b) of this section and maintaining the necessary power on the operating engine(s) to obtain the speed specified in § 4b.452 (d).

(2) When the temperatures have stabilized, i. e., the rate of temperature change is less than 2° F. per minute, the propeller on the inoperative engine should be feathered and the cooling climb commenced at maximum continuous power and at the specified configuration and speed. The climb should be continued for five minutes after occurrence of the highest temperature or until the maximum altitude desired for certification is reached.

(3) The above procedure should be repeated when demonstrating engine cooling for high blower except that temperatures should be stabilized in level flight with simulated climb conditions at an altitude of 1,000 feet below the critical altitude established for the high blower. The weight of the airplane should be such that it will permit a rate of climb equal to that specified in § 4b.120 (c).

(4) The following data should be recorded at no greater than one minute intervals:

(a) The take-off cooling test shall be commenced by stabilizing temperatures during level flight with all engines operating at 75 percent of maximum continuous power with the appropriate cowl flap and shutter settings.

(b) After all temperatures have stabilized, the climb shall be started at the lowest practicable altitude and shall be conducted with one engine inoperative and its propeller feathered.

(c) The remaining engines shall be operated at take-off rpm and power (or at full throttle when above the take-off critical altitude) for the same time interval as take-off power is used during determination of the take-off flight path (see § 4b.116).

(d) At the end of the time interval prescribed in paragraph (c) of this section the power shall be reduced to the maximum continuous power and the climb continued until at least 5 minutes after the occurrence of the highest temperature recorded.

(e) The speed used during take-off power operation (paragraph (c) of this section) shall not exceed the speed used during determination of the take-off flight path (see § 4b.116).

[15 F. R. 3543, June 8, 1950, as amended by Amdt. 4b-8, 18 F. R. 2215, Apr. 18, 1953]

§ 4b.453-1 Procedure for demonstrating take-off cooling (FAA policies which apply to § 4b.453).

(a) Configuration. This test should be conducted in the configuration that follows:

Weight-Maximum take-off.

C. G. position-Optional.

Wing flaps-Take-off position.
Landing gear-Optional.

Operating engine (s)-Take-off rpm or full throttle, mixture setting at take-off and cooling controls in take-off position. Critical inoperative engine-Throttle closed on cooler operating outboard engine (see § 4b.452-1 (a)), propeller feathered and cowl flaps in optional position.

(b) Test procedure and required data. The temperature should be permitted to stabilize during level flight at the lowest practical altitude using 75 percent maximum continuous power on all engines and normal take-off cowl flap or coolant door setting. After the temperatures have stabilized, the configuration of the airplane should be adjusted as specified in paragraph (a) of this section and the climb commenced at the speed and con

tinued for the same time interval as take-off power is used during determination of the take-off flight path (§ 4b.116). At the end of the take-off power time limit, the power should be reduced to maximum continuous. After power has been reduced, the configuration may be adjusted to the enroute condition specified in § 4b.452-1 (b) and the airplane accelerated to the enroute climb speed specified in § 4b.452 (d). The cooling climb should be continued for five minutes after the occurrence of the highest temperature. The same data as outlined in § 4b.452-1 (c) (4) and (5) should be recorded.

[Supp. 24, 19 F. R. 4465, July 20, 1954] § 4b.454 Cooling test procedure for flying boat operation.

In the case of flying boats, cooling shall be demonstrated during taxiing downwind for 10 minutes at 5 mph above the step speed.

§ 4b.454-1 Procedure for demonstrating cooling for seaplanes during water taxiing operations (FAA policies which apply to § 4b.454).

(a) Conditions under which tests are to be made. The cooling test for seaplanes should be conducted while taxiing on water. The tank system should contain fuel of the minimum grade approved for the engines installed. Cylinder and oil inlet temperatures should be permitted to stabilize in flight or by taxiing at reduced speed. The test should be conducted in an atmosphere which is free of visible moisture.

(a) The engine air induction system shall permit supplying the proper quantity of air to the engine under all conditions of operation.

(b) The induction system shall provide air for proper fuel metering and mixture distribution with the induction system valves in any position.

(c) Each reciprocating engine shall be provided with an alternate air source.

(d) Air intakes shall not open within the cowling, unless that portion of the cowling is isolated from the engine accessory section by means of a fireproof diaphragm, or unless provision is made to prevent the emergence of backfire flames.

(e) Alternate air intakes shall be so located as to preclude the entrance of rain, ice, or any other foreign matter.

(f) For turbine-engine-powered airplanes, provisions shall be made to prevent hazardous quantities of fuel leakage or overflow from drains, vents, or other components of flammable fluid systems to enter the engine intake system.

(g) For turbine engines, the air inlet ducts shall be so located or protected as to minimize the ingestion of foreign matter during take-off, landing, or taxiing.

[15 F. R. 3543, June 8, 1950, as amended by Amdt. 4b-2, 20 F.R. 5306, July 26, 1955; Amdt. 4b-6, 22 F.R. 5565, July 16. 19571

§ 4b.461 Induction system de-icing and anti-icing provisions.

(a) General. The engine air induction system shall incorporate means for the prevention and elimination of ice accumulations.

(b) Heat rise. Unless it is demonstrated that other means will accomplish the intent of paragraph (a) of this section, compliance with the following heat-rise provisions shall be demonstrated in air free of visible moisture at a temperature of 30° F.

(1) Airplanes equipped with altitude engines employing conventional venturi carburetors shall have a preheater capable of providing a heat rise of 120° F. when the engine is operating at 60 percent of its maximum continuous power.

(2) Airplanes equipped with altitude engines employing carburetors which embody features tending to reduce the possibility of ice formation shall have a preheater capable of providing a heat rise of 100° F. when the engine is operating at 60 percent of its maximum continuous power.

Turbine

(c) Turbine powerplants. powered airplanes shall be capable of operation throughout the flight power range without accumulation of ice in the air induction system such as to adversely affect engine operation or cause a serious loss of power and/or thrust in the continuous maximum and intermittent maximum icing conditions as defined in § 4b.1 (b) (7) and (8). Means to indicate the functioning of the powerplant ice protection system shall be provided.

[15 F.R. 3543, June 8, 1950, as amended by Amdt. 4b-6, 22 F.R. 5565, July 16, 1957; Amdt. 4b-11, 24 F.R. 7070, Sept. 1, 1959]

§ 4b.461-1 Procedure for demonstrating carburetor air heat rise (FAA policies which apply to § 4b.461 (b)).

(a) Conditions for tests. The carburetor air temperature should be measured by a minimum of three thermocouples so arranged as to give an average air temperature. This indicator should be calibrated prior to the test. The tests should be conducted at an altitude where the free air temperature is 30° F. or at two altitudes of different temperatures, one of which is near 30° F.

(b) Configuration. This test should be conducted in the configuration that follows:

Weight-Optional.

C. G. position-Optional.
Wing flaps Optional.

Landing gear-Optional.
Engines

60 percent maximum continuous

power. Cowl flaps-Appropriate for flight condition. Mixture setting-Normal cruising position.

(c) Test procedure and required data. (1) After all temperatures have been stabilized (i. e., when the rate of temperature change is less than 2° F. per minute) and with the airplane in level flight and full cold carburetor at 60 per

cent maximum continuous power, the following data should be recorded:

Pressure altitude.

Ambient air temperature.
Indicated air speed.

Carburetor air temperature.

Engines, rpm and manifold pressure.
Torque pressure.
Mixture setting.
Cowl flap setting.

(2) Preheat should then be applied slowly (power may be restored to 60 percent maximum continuous at the applicant's option) and the above data recorded again after the carburetor air temperature has stabilized. The carburetor heat rise should be determined from the results of the data.

[Supp. 24, 19 F.R. 4465, July 20, 1954, as amended by Supp. 34, 22 FR. 6963, Aug. 29, 1957]

§ 4b.462 Carburetor air preheater design.

Carburetor air preheaters shall incorporate the following provisions.

(a) Means shall be provided to assure ventilation of the preheater when the engine is being operated with cold air.

(b) The preheater shall be constructed to permit inspection of exhaust manifold parts which it surrounds and also to permit inspection of critical portions of the preheater itself.

§ 4b.463 Induction system ducts.

Induction system ducts shall incorporate the following provisions.

(a) Induction system ducts ahead of the first stage of the supercharger shall be provided with drains to prevent hazardous accumulations of fuel and moisture in the ground attitude. The drains shall not discharge in locations which might cause a fire hazard.

(b) Sufficient strength shall be incorporated in the ducts to prevent induction system failures resulting from normal backfire conditions.

(c) Ducts which are connected to components of the airplane between which relative motion could exist shall incorporate provisions for flexibility.

(d) Induction system ducts within any fire zone for which a fire-extinguishing system is required shall be of fireresistant construction.

[15 F. R. 3543, June 8, 1950, as amended by Amdt. 4b-6, 17 F. R. 1096, Feb. 5, 1952]

§ 4b.464 Induction system screens.

If induction system screens are employed, they shall comply with the following provisions:

(a) Screens shall be located upstream from the carburetor.

(b) Screens shall not be located in portions of the induction system which constitute the only passage through which air can reach the engine, unless the screen is so located that it can be de-iced by heated air.

system

(c) De-icing of induction screens by means of alcohol alone shall not be acceptable.

(d) It shall not be possible for fuel to impinge upon the screens. § 4b.465 Carburetor air cooling.

Installations employing two-stage superchargers shall be provided with means to maintain the air temperature at the inlet to the carburetor at or below the maximum established value. The demonstration of this provision shall be accomplished in accordance with § 4b.451. § 4b.465-1

Procedure for demonstrating carburetor air cooling (FAA policies which apply to § 4b.465). Carburetor air cooling should be demonstrated in conjunction with the tests required by §§ 4b.452 and 4b.453. [Supp. 24, 19 F. R. 4465, July 20, 1954] § 4b.466 Inter-coolers and aftercoolers.

Inter-coolers and after-coolers shall be capable of withstanding without failure all vibration, inertia, and air pressure loads to which they would be subjected in operation.

§ 4b.467 Exhaust system and installation components.

(a) General. (1) The exhaust system shall be constructed and arranged to assure the safe disposal of exhaust gases without the existence of a fire hazard or carbon monoxide contamination of air in personnel compartments.

(2) Unless appropriate precautions are taken, exhaust system parts shall not be located in hazardous proximity to portions of any system carrying flammable fluids or vapors nor shall they be located under portions of such systems where the latter could be subject to leakage.

(3) All airplane components upon which hot exhaust gases might impinge,

or which could be subjected to high temperatures due to proximity to exhaust system parts, shall be constructed of fireproof material. All exhaust system components shall be separated by means of fireproof shields from adjacent portions of the airplane which are outside the engine compartment.

(4) Exhaust gases shall not discharge in a manner to cause a fire hazard with respect to any flammable fluid vent or drain.

(5) Exhaust gases shall not discharge at a location which will cause a glare seriously affecting pilot visibility at night.

(6) All exhaust system components shall be ventilated to prevent the existence of points of excessively high temperature.

(7) Exhaust shrouds shall be ventilated or insulated to avoid during normal operation a temperature sufficiently high to ignite any flammable fluids or vapors external to the shrouds.

(b) Exhaust piping. (1) Exhaust piping shall be constructed of material resistant to heat and corrosion, and shall incorporate provisions to prevent failure due to expansion when heated to operating temperatures.

(2) Exhaust pipe shall be supported to withstand all vibration and inertia loads to which they would be subjected in operation.

(3) Portions of the exhaust piping which are connected to components between which relative motion could exist shall incorporate provisions for flexibility.

(c) Exhaust heat exchangers. (1) Exhaust heat exchangers shall be constructed and installed to assure their ability to withstand without failure all vibration, inertia, and other loads to which they would be subjected in operation.

(2) Heat exchangers shall be constructed of materials which are suitable for continued operation at high temperatures and which are resistant to corrosion due to elements contained in exhaust gases.

(3) Provision shall be made for the inspection of all critical portions of exhaust heat exchangers.

(4) Heat exchangers shall incorporate cooling provisions wherever they are subject to contact with exhaust gases.