Title 14: Aeronautics and Space
PART 33—AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES
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Subpart E—Design and Construction; Turbine Aircraft Engines
§ 33.61 Applicability.
This subpart prescribes additional design and construction requirements for turbine aircraft engines.
§ 33.62 Stress analysis.
A stress analysis must be performed on each turbine engine showing the design safety margin of each turbine engine rotor, spacer, and rotor shaft.
[Amdt. 33–6, 39 FR 35466, Oct. 1, 1974]
§ 33.63 Vibration.
Each engine must be designed and constructed to function throughout its declared flight envelope and operating range of rotational speeds and power/thrust, without inducing excessive stress in any engine part because of vibration and without imparting excessive vibration forces to the aircraft structure.
[Doc. No. 28107, 61 FR 28433, June 4, 1996]
§ 33.65 Surge and stall characteristics.
When the engine is operated in accordance with operating instructions required by §33.5(b), starting, a change of power or thrust, power or thrust augmentation, limiting inlet air distortion, or inlet air temperature may not cause surge or stall to the extent that flameout, structural failure, overtemperature, or failure of the engine to recover power or thrust will occur at any point in the operating envelope.
[Amdt. 33–6, 39 FR 35466, Oct. 1, 1974]
§ 33.66 Bleed air system.
The engine must supply bleed air without adverse effect on the engine, excluding reduced thrust or power output, at all conditions up to the discharge flow conditions established as a limitation under §33.7(c)(11). If bleed air used for engine anti-icing can be controlled, provision must be made for a means to indicate the functioning of the engine ice protection system.
[Amdt. 33–10, 49 FR 6851, Feb. 23, 1984]
§ 33.67 Fuel system.
(a) With fuel supplied to the engine at the flow and pressure specified by the applicant, the engine must function properly under each operating condition required by this part. Each fuel control adjusting means that may not be manipulated while the fuel control device is mounted on the engine must be secured by a locking device and sealed, or otherwise be inaccessible. All other fuel control adjusting means must be accessible and marked to indicate the function of the adjustment unless the function is obvious.
(b) There must be a fuel strainer or filter between the engine fuel inlet opening and the inlet of either the fuel metering device or the engine-driven positive displacement pump whichever is nearer the engine fuel inlet. In addition, the following provisions apply to each strainer or filter required by this paragraph (b):
(1) It must be accessible for draining and cleaning and must incorporate a screen or element that is easily removable.
(2) It must have a sediment trap and drain except that it need not have a drain if the strainer or filter is easily removable for drain purposes.
(3) It must be mounted so that its weight is not supported by the connecting lines or by the inlet or outlet connections of the strainer or filter, unless adequate strength margins under all loading conditions are provided in the lines and connections.
(4) It must have the type and degree of fuel filtering specified as necessary for protection of the engine fuel system against foreign particles in the fuel. The applicant must show:
(i) That foreign particles passing through the specified filtering means do not impair the engine fuel system functioning; and
(ii) That the fuel system is capable of sustained operation throughout its flow and pressure range with the fuel initially saturated with water at 80 °F (27 °C) and having 0.025 fluid ounces per gallon (0.20 milliliters per liter) of free water added and cooled to the most critical condition for icing likely to be encountered in operation. However, this requirement may be met by demonstrating the effectiveness of specified approved fuel anti-icing additives, or that the fuel system incorporates a fuel heater which maintains the fuel temperature at the fuel strainer or fuel inlet above 32 °F (0 °C) under the most critical conditions.
(5) The applicant must demonstrate that the filtering means has the capacity (with respect to engine operating limitations) to ensure that the engine will continue to operate within approved limits, with fuel contaminated to the maximum degree of particle size and density likely to be encountered in service. Operation under these conditions must be demonstrated for a period acceptable to the Administrator, beginning when indication of impending filter blockage is first given by either:
(i) Existing engine instrumentation; or
(ii) Additional means incorporated into the engine fuel system.
(6) Any strainer or filter bypass must be designed and constructed so that the release of collected contaminants is minimized by appropriate location of the bypass to ensure that collected contaminants are not in the bypass flow path.
(c) If provided as part of the engine, the applicant must show for each fluid injection (other than fuel) system and its controls that the flow of the injected fluid is adequately controlled.
(d) Engines having a 30-second OEI rating must incorporate means for automatic availability and automatic control of a 30-second OEI power.
[Amdt. 33–6, 39 FR 35466, Oct. 1, 1974, as amended by Amdt. 33–10, 49 FR 6851, Feb. 23, 1984; Amdt. 33–18, 61 FR 31328, June 19, 1996]
§ 33.68 Induction system icing.
Each engine, with all icing protection systems operating, must—
(a) Operate throughout its flight power range (including idling) without the accumulation of ice on the engine components that adversely affects engine operation or that causes a serious loss of power or thrust in continuous maximum and intermittent maximum icing conditions as defined in appendix C of Part 25 of this chapter; and
(b) Idle for 30 minutes on the ground, with the available air bleed for icing protection at its critical condition, without adverse effect, in an atmosphere that is at a temperature between 15° and 30 °F (between −9° and −1 °C) and has a liquid water content not less than 0.3 grams per cubic meter in the form of drops having a mean effective diameter not less than 20 microns, followed by a momentary operation at takeoff power or thrust. During the 30 minutes of idle operation the engine may be run up periodically to a moderate power or thrust setting in a manner acceptable to the Administrator.
[Amdt. 33–6, 39 FR 35466, Oct. 1, 1974, as amended by Amdt. 33–10, 49 FR 6852, Feb. 23, 1984]
§ 33.69 Ignitions system.
Each engine must be equipped with an ignition system for starting the engine on the ground and in flight. An electric ignition system must have at least two igniters and two separate secondary electric circuits, except that only one igniter is required for fuel burning augmentation systems.
[Amdt. 33–6, 39 FR 35466, Oct. 1, 1974]
§ 33.71 Lubrication system.
(a) General. Each lubrication system must function properly in the flight attitudes and atmospheric conditions in which an aircraft is expected to operate.
(b) Oil strainer or filter. There must be an oil strainer or filter through which all of the engine oil flows. In addition:
(1) Each strainer or filter required by this paragraph that has a bypass must be constructed and installed so that oil will flow at the normal rate through the rest of the system with the strainer or filter element completely blocked.
(2) The type and degree of filtering necessary for protection of the engine oil system against foreign particles in the oil must be specified. The applicant must demonstrate that foreign particles passing through the specified filtering means do not impair engine oil system functioning.
(3) Each strainer or filter required by this paragraph must have the capacity (with respect to operating limitations established for the engine) to ensure that engine oil system functioning is not impaired with the oil contaminated to a degree (with respect to particle size and density) that is greater than that established for the engine in paragraph (b)(2) of this section.
(4) For each strainer or filter required by this paragraph, except the strainer or filter at the oil tank outlet, there must be means to indicate contamination before it reaches the capacity established in accordance with paragraph (b)(3) of this section.
(5) Any filter bypass must be designed and constructed so that the release of collected contaminants is minimized by appropriate location of the bypass to ensure that the collected contaminants are not in the bypass flow path.
(6) Each strainer or filter required by this paragraph that has no bypass, except the strainer or filter at an oil tank outlet or for a scavenge pump, must have provisions for connection with a warning means to warn the pilot of the occurence of contamination of the screen before it reaches the capacity established in accordance with paragraph (b)(3) of this section.
(7) Each strainer or filter required by this paragraph must be accessible for draining and cleaning.
(c) Oil tanks. (1) Each oil tank must have an expansion space of not less than 10 percent of the tank capacity.
(2) It must be impossible to inadvertently fill the oil tank expansion space.
(3) Each recessed oil tank filler connection that can retain any appreciable quantity of oil must have provision for fitting a drain.
(4) Each oil tank cap must provide an oil-tight seal.
(5) Each oil tank filler must be marked with the word “oil.”
(6) Each oil tank must be vented from the top part of the expansion space, with the vent so arranged that condensed water vapor that might freeze and obstruct the line cannot accumulate at any point.
(7) There must be means to prevent entrance into the oil tank or into any oil tank outlet, of any object that might obstruct the flow of oil through the system.
(8) There must be a shutoff valve at the outlet of each oil tank, unless the external portion of the oil system (including oil tank supports) is fireproof.
(9) Each unpressurized oil tank may not leak when subjected to a maximum operating temperature and an internal pressure of 5 p.s.i., and each pressurized oil tank may not leak when subjected to maximum operating temperature and an internal pressure that is not less than 5 p.s.i. plus the maximum operating pressure of the tank.
(10) Leaked or spilled oil may not accumulate between the tank and the remainder of the engine.
(11) Each oil tank must have an oil quantity indicator or provisions for one.
(12) If the propeller feathering system depends on engine oil—
(i) There must be means to trap an amount of oil in the tank if the supply becomes depleted due to failure of any part of the lubricating system other than the tank itself;
(ii) The amount of trapped oil must be enough to accomplish the feathering opeation and must be available only to the feathering pump; and
(iii) Provision must be made to prevent sludge or other foreign matter from affecting the safe operation of the propeller feathering system.
(d) Oil drains. A drain (or drains) must be provided to allow safe drainage of the oil system. Each drain must—
(1) Be accessible; and
(2) Have manual or automatic means for positive locking in the closed position.
(e) Oil radiators. Each oil radiator must withstand, without failure, any vibration, inertia, and oil pressure load to which it is subjected during the block tests.
[Amdt. 33–6, 39 FR 35466, Oct. 1, 1974, as amended by Amdt. 33–10, 49 FR 6852, Feb. 23, 1984]
§ 33.72 Hydraulic actuating systems.
Each hydraulic actuating system must function properly under all conditions in which the engine is expected to operate. Each filter or screen must be accessible for servicing and each tank must meet the design criteria of §33.71.
[Amdt. 33–6, 39 FR 35467, Oct. 1, 1974]
§ 33.73 Power or thrust response.
The design and construction of the engine must enable an increase—
(a) From minimum to rated takeoff power or thrust with the maximum bleed air and power extraction to be permitted in an aircraft, without overtemperature, surge, stall, or other detrimental factors occurring to the engine whenever the power control lever is moved from the minimum to the maximum position in not more than 1 second, except that the Administrator may allow additional time increments for different regimes of control operation requiring control scheduling; and
(b) From the fixed minimum flight idle power lever position when provided, or if not provided, from not more than 15 percent of the rated takeoff power or thrust available to 95 percent rated takeoff power or thrust in not over 5 seconds. The 5-second power or thrust response must occur from a stabilized static condition using only the bleed air and accessories loads necessary to run the engine. This takeoff rating is specified by the applicant and need not include thrust augmentation.
[Amdt. 33–1, 36 FR 5493, Mar. 24, 1971]
§ 33.74 Continued rotation.
If any of the engine main rotating systems will continue to rotate after the engine is shutdown for any reason while in flight, and where means to prevent that continued rotation are not provided; then any continued rotation during the maximum period of flight, and in the flight conditions expected to occur with that engine inoperative, must not result in any condition described in §33.75 (a) through (c).
[Doc. No. 28107, 61 FR 28433, June 4, 1996]
§ 33.75 Safety analysis.
It must be shown by analysis that any probable malfunction or any probable single or multiple failure, or any probable improper operation of the engine will not cause the engine to—
(a) Catch fire;
(b) Burst (release hazardous fragments through the engine case);
(c) Generate loads greater than those ultimate loads specified in §33.23(a); or
(d) Lose the capability of being shut down.
[Amdt. 33–6, 39 FR 35467, Oct. 1, 1974, as amended by Amdt. 33–10, 49 FR 6852, Feb. 23, 1984]
§ 33.76 Bird ingestion.
(a) General. Compliance with paragraphs (b) and (c) of this section shall be in accordance with the following:
(1) All ingestion tests shall be conducted with the engine stabilized at no less than 100-percent takeoff power or thrust, for test day ambient conditions prior to the ingestion. In addition, the demonstration of compliance must account for engine operation at sea level takeoff conditions on the hottest day that a minimum engine can achieve maximum rated takeoff thrust or power.
(2) The engine inlet throat area as used in this section to determine the bird quantity and weights will be established by the applicant and identified as a limitation in the installation instructions required under §33.5.
(3) The impact to the front of the engine from the single large bird and the single largest medium bird which can enter the inlet must be evaluated. It must be shown that the associated components when struck under the conditions prescribed in paragraphs (b) or (c) of this section, as applicable, will not affect the engine to the extent that it cannot comply with the requirements of paragraphs (b)(3) and (c)(6) of this section.
(4) For an engine that incorporates an inlet protection device, compliance with this section shall be established with the device functioning. The engine approval will be endorsed to show that compliance with the requirements has been established with the device functioning.
(5) Objects that are accepted by the Administrator may be substituted for birds when conducting the bird ingestion tests required by paragraphs (b) and (c) of this section.
(6) If compliance with the requirements of this section is not established, the engine type certification documentation will show that the engine shall be limited to aircraft installations in which it is shown that a bird cannot strike the engine, or be ingested into the engine, or adversely restrict airflow into the engine.
(b) Large birds. Compliance with the large bird ingestion requirements shall be in accordance with the following:
(1) The large bird ingestion test shall be conducted using one bird of a weight determined from Table 1 aimed at the most critical exposed location on the first stage rotor blades and ingested at a bird speed of 200-knots for engines to be installed on airplanes, or the maximum airspeed for normal rotorcraft flight operations for engines to be installed on rotorcraft.
(2) Power lever movement is not permitted within 15 seconds following ingestion of the large bird.
(3) Ingestion of a single large bird tested under the conditions prescribed in this section may not cause the engine to:
(i) Catch fire;
(ii) Release hazardous fragments through the engine casing;
(iii) Generate loads greater than those ultimate loads specified under §33.23(a); or
(iv) Lose the ability to be shut down.
(4) Compliance with the large bird ingestion requirements of this paragraph may be shown by demonstrating that the requirements of §33.94(a) constitute a more severe demonstration of blade containment and rotor unbalance than the requirements of this paragraph.
Table 1 to § 33.76_Large Bird Weight Requirements------------------------------------------------------------------------Engine Inlet Throat Area (A)_Square-meters (square-inches) Bird weight kg. (lb.)------------------------------------------------------------------------1.35 (2,092)> A........................ 1.85 (4.07) minimum, unless a smaller bird is determined to be a more severe demonstration.1.35 (2,092)[le] A< 3.90 (6,045)....... 2.75 (6.05)3.90 (6,045)[le] A........................ 3.65 (8.03)------------------------------------------------------------------------
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(c) Small and medium birds. Compliance with the small and medium bird ingestion requirements shall be in accordance with the following:
(1) Analysis or component test, or both, acceptable to the Administrator, shall be conducted to determine the critical ingestion parameters affecting power loss and damage. Critical ingestion parameters shall include, but are not limited to, the effects of bird speed, critical target location, and first stage rotor speed. The critical bird ingestion speed should reflect the most critical condition within the range of airspeeds used for normal flight operations up to 1,500 feet above ground level, but not less than V1 minimum for airplanes.
(2) Medium bird engine tests shall be conducted so as to simulate a flock encounter, and will use the bird weights and quantities specified in Table 2. When only one bird is specified, that bird will be aimed at the engine core primary flow path; the other critical locations on the engine face area must be addressed, as necessary, by appropriate tests or analysis, or both. When two or more birds are specified in Table 2, the largest of those birds must be aimed at the engine core primary flow path, and a second bird must be aimed at the most critical exposed location on the first stage rotor blades. Any remaining birds must be evenly distributed over the engine face area.
(3) In addition, except for rotorcraft engines, it must also be substantiated by appropriate tests or analysis or both, that when the full fan assembly is subjected to the ingestion of the quantity and weights of bird from Table 3, aimed at the fan assembly's most critical location outboard of the primary core flowpath, and in accordance with the applicable test conditions of this paragraph, that the engine can comply with the acceptance criteria of this paragraph.
(4) A small bird ingestion test is not required if the prescribed number of medium birds pass into the engine rotor blades during the medium bird test.
(5) Small bird ingestion tests shall be conducted so as to simulate a flock encounter using one 85 gram (0.187 lb.) bird for each 0.032 square-meter (49.6 square-inches) of inlet area, or fraction thereof, up to a maximum of 16 birds. The birds will be aimed so as to account for any critical exposed locations on the first stage rotor blades, with any remaining birds evenly distributed over the engine face area.
(6) Ingestion of small and medium birds tested under the conditions prescribed in this paragraph may not cause any of the following:
(i) More than a sustained 25-percent power or thrust loss;
(ii) The engine to be shut down during the required run-on demonstration prescribed in paragraphs (c)(7) or (c)(8) of this section;
(iii) The conditions defined in paragraph (b)(3) of this section.
(iv) Unacceptable deterioration of engine handling characteristics.
(7) Except for rotorcraft engines, the following test schedule shall be used:
(i) Ingestion so as to simulate a flock encounter, with approximately 1 second elapsed time from the moment of the first bird ingestion to the last.
(ii) Followed by 2 minutes without power lever movement after the ingestion.
(iii) Followed by 3 minutes at 75-percent of the test condition.
(iv) Followed by 6 minutes at 60-percent of the test condition.
(v) Followed by 6 minutes at 40-percent of the test condition.
(vi) Followed by 1 minute at approach idle.
(vii) Followed by 2 minutes at 75-percent of the test condition.
(viii) Followed by stabilizing at idle and engine shut down.
(ix) The durations specified are times at the defined conditions with the power being changed between each condition in less than 10 seconds.
(8) For rotorcraft engines, the following test schedule shall be used:
(i) Ingestion so as to simulate a flock encounter within approximately 1 second elapsed time between the first ingestion and the last.
(ii) Followed by 3 minutes at 75-percent of the test condition.
(iii) Followed by 90 seconds at descent flight idle.
(iv) Followed by 30 seconds at 75-percent of the test condition.
(v) Followed by stabilizing at idle and engine shut down.
(vi) The durations specified are times at the defined conditions with the power being changed between each condition in less than 10 seconds.
(9) Engines intended for use in multi-engine rotorcraft are not required to comply with the medium bird ingestion portion of this section, providing that the appropriate type certificate documentation is so endorsed.
(10) If any engine operating limit(s) is exceeded during the initial 2 minutes without power lever movement, as provided by paragraph (c)(7)(ii) of this section, then it shall be established that the limit exceedence will not result in an unsafe condition.
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Table 2 to § 33.76_Medium Flocking Bird Weight and Quantity Requirements------------------------------------------------------------------------ Engine Inlet Throat Area (A)_ Bird weight kg. Square-meters (square-inches) Bird quantity (lb.)------------------------------------------------------------------------0.05 (77.5)> A............... none.............. ..................0.05 (77.5)[le] A <0.10 (155) 1................. 0.35 (0.77)0.10 (155)[le] A <0.20 (310). 1................. 0.45 (0.99)0.20 (310)[le] A <0.40 (620). 2................. 0.45 (0.99)0.40 (620)[le] A <0.60 (930). 2................. 0.70 (1.54)0.60 (930)[le] A <1.00 3................. 0.70 (1.54) (1,550).1.00 (1,550)[le] A <1.35 4................. 0.70 (1.54) (2,092).1.35 (2,092)[le] A <1.70 1................. 1.15 (2.53) (2,635). plus 3............ 0.70 (1.54)1.70 (2,635)[le] A <2.10 1................. 1.15 (2.53) (3,255). plus 4............ 0.70 (1.54)2.10 (3,255)[le] A <2.50 1................. 1.15 (2.53) (3,875). plus 5............ 0.70 (1.54)2.50 (3,875)[le] A <3.90 1................. 1.15 (2.53) (6045). plus 6............ 0.70 (1.54)3.90 (6045)[le] A <4.50 3................. 1.15 (2.53) (6975).4.50 (6975)[le] A............... 4................. 1.15 (2.53)------------------------------------------------------------------------
Table 3 to § 33.76_Additional Integrity Assessment------------------------------------------------------------------------ Engine Inlet Throat Area (A)_ Bird weight kg. square-meters (square-inches) Bird quantity (lb.)------------------------------------------------------------------------1.35 (2,092)> A.............. none.............. ..................1.35 (2,092)[le] A <2.90 1................. 1.15 (2.53) (4,495).2.90 (4,495)[le] A <3.90 2................. 1.15 (2.53) (6,045).3.90 (6,045)[le] A.............. 1................. 1.15 (2.53) plus 6............ 0.70 (1.54)------------------------------------------------------------------------
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[Doc. No. FAA–1998–4815, 65 FR 55854, Sept. 14, 2000, as amended by Amdt. 33–20, 68 FR 75391, Dec. 31, 2003] § 33.77 Foreign object ingestion—ice.
(a)–(b) [Reserved]
(c) Ingestion of ice under the conditions of paragraph (e) of this section may not—
(1) Cause a sustained power or thrust loss; or
(2) Require the engine to be shutdown.
(d) For an engine that incorporates a protection device, compliance with this section need not be demonstrated with respect to foreign objects to be ingested under the conditions prescribed in paragraph (e) of this section if it is shown that—
(1) Such foreign objects are of a size that will not pass through the protective device;
(2) The protective device will withstand the impact of the foreign objects; and
(3) The foreign object, or objects, stopped by the protective device will not obstruct the flow of induction air into the engine with a resultant sustained reduction in power or thrust greater than those values required by paragraph (c) of this section.
(e) Compliance with paragraph (c) of this section must be shown by engine test under the following ingestion conditions:
(1) Ice quantity will be the maximum accumulation on a typical inlet cowl and engine face resulting from a 2-minute delay in actuating the anti-icing system; or a slab of ice which is comparable in weight or thickness for that size engine.
(2) The ingestion velocity will simulate ice being sucked into the engine inlet.
(3) Engine operation will be maximum cruise power or thrust.
(4) The ingestion will simulate a continuous maximum icing encounter at 25 degrees Fahrenheit.
[Doc. No. 16919, 49 FR 6852, Feb. 23, 1984, as amended by Amdt. 33–19, 63 FR 14798, Mar. 26, 1998; 63 FR 53278, Oct. 5, 1998; Amdt. 33–20, 65 FR 55856, Sept. 14, 2000] § 33.78 Rain and hail ingestion.
(a) All engines. (1) The ingestion of large hailstones (0.8 to 0.9 specific gravity) at the maximum true air speed, up to 15,000 feet (4,500 meters), associated with a representative aircraft operating in rough air, with the engine at maximum continuous power, may not cause unacceptable mechanical damage or unacceptable power or thrust loss after the ingestion, or require the engine to be shut down. One-half the number of hailstones shall be aimed randomly over the inlet face area and the other half aimed at the critical inlet face area. The hailstones shall be ingested in a rapid sequence to simulate a hailstone encounter and the number and size of the hailstones shall be determined as follows:
(i) One 1-inch (25 millimeters) diameter hailstone for engines with inlet areas of not more than 100 square inches (0.0645 square meters).
(ii) One 1-inch (25 millimeters) diameter and one 2-inch (50 millimeters) diameter hailstone for each 150 square inches (0.0968 square meters) of inlet area, or fraction thereof, for engines with inlet areas of more than 100 square inches (0.0645 square meters).
(2) In addition to complying with paragraph (a)(1) of this section and except as provided in paragraph (b) of this section, it must be shown that each engine is capable of acceptable operation throughout its specified operating envelope when subjected to sudden encounters with the certification standard concentrations of rain and hail, as defined in appendix B to this part. Acceptable engine operation precludes flameout, run down, continued or non-recoverable surge or stall, or loss of acceleration and deceleration capability, during any three minute continuous period in rain and during any 30 second continuous period in hail. It must also be shown after the ingestion that there is no unacceptable mechanical damage, unacceptable power or thrust loss, or other adverse engine anomalies.
(b) Engines for rotorcraft. As an alternative to the requirements specified in paragraph (a)(2) of this section, for rotorcraft turbine engines only, it must be shown that each engine is capable of acceptable operation during and after the ingestion of rain with an overall ratio of water droplet flow to airflow, by weight, with a uniform distribution at the inlet plane, of at least four percent. Acceptable engine operation precludes flameout, run down, continued or non-recoverable surge or stall, or loss of acceleration and deceleration capability. It must also be shown after the ingestion that there is no unacceptable mechanical damage, unacceptable power loss, or other adverse engine anomalies. The rain ingestion must occur under the following static ground level conditions:
(1) A normal stabilization period at take-off power without rain ingestion, followed immediately by the suddenly commencing ingestion of rain for three minutes at takeoff power, then
(2) Continuation of the rain ingestion during subsequent rapid deceleration to minimum idle, then
(3) Continuation of the rain ingestion during three minutes at minimum idle power to be certified for flight operation, then
(4) Continuation of the rain ingestion during subsequent rapid acceleration to takeoff power.
(c) Engines for supersonic airplanes. In addition to complying with paragraphs (a)(1) and (a)(2) of this section, a separate test for supersonic airplane engines only, shall be conducted with three hailstones ingested at supersonic cruise velocity. These hailstones shall be aimed at the engine's critical face area, and their ingestion must not cause unacceptable mechanical damage or unacceptable power or thrust loss after the ingestion or require the engine to be shut down. The size of these hailstones shall be determined from the linear variation in diameter from 1-inch (25 millimeters) at 35,000 feet (10,500 meters) to 1/4-inch (6 millimeters) at 60,000 feet (18,000 meters) using the diameter corresponding to the lowest expected supersonic cruise altitude. Alternatively, three larger hailstones may be ingested at subsonic velocities such that the kinetic energy of these larger hailstones is equivalent to the applicable supersonic ingestion conditions.
(d) For an engine that incorporates or requires the use of a protection device, demonstration of the rain and hail ingestion capabilities of the engine, as required in paragraphs (a), (b), and (c) of this section, may be waived wholly or in part by the Administrator if the applicant shows that:
(1) The subject rain and hail constituents are of a size that will not pass through the protection device;
(2) The protection device will withstand the impact of the subject rain and hail constituents; and
(3) The subject of rain and hail constituents, stopped by the protection device, will not obstruct the flow of induction air into the engine, resulting in damage, power or thrust loss, or other adverse engine anomalies in excess of what would be accepted in paragraphs (a), (b), and (c) of this section.
[Doc. No. 28652, 63 FR 14799, Mar. 26, 1998] § 33.79 Fuel burning thrust augmentor.
Each fuel burning thrust augmentor, including the nozzle, must—
(a) Provide cutoff of the fuel burning thrust augmentor;
(b) Permit on-off cycling;
(c) Be controllable within the intended range of operation;
(d) Upon a failure or malfunction of augmentor combustion, not cause the engine to lose thrust other than that provided by the augmentor; and
(e) Have controls that function compatibly with the other engine controls and automatically shut off augmentor fuel flow if the engine rotor speed drops below the minimum rotational speed at which the augmentor is intended to function.
[Amdt. 33–6, 39 FR 35468, Oct. 1, 1974]
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