Code of Federal Regulations

Title 14 - Aeronautics and Space

Volume: 1Date: 2024-01-01Original Date: 2024-01-01Title: Section 33.76 - Bird ingestion.Context: Title 14 - Aeronautics and Space. CHAPTER I - FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION. SUBCHAPTER C - AIRCRAFT. PART 33 - AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES. Subpart E - Design and Construction; Turbine Aircraft Engines.

§ 33.76 Bird ingestion. (a) General. Compliance with paragraphs (b) through (e) of this section shall be in accordance with the following: (1) Except as specified in paragraphs (d) and (e) of this section, all ingestion tests must 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 large single bird, the single largest medium bird which can enter the inlet, and the large flocking bird must be evaluated. Applicants must show that the associated components when struck under the conditions prescribed in paragraphs (b), (c) or (d) of this section, as applicable, will not affect the engine to the extent that the engine cannot comply with the requirements of paragraphs (b)(3), (c)(6) and (d)(4) 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.

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(5) Objects that are accepted by the Administrator may be substituted for birds when conducting the bird ingestion tests required by paragraphs (b) through (e) 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 single bird. 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 result in any condition described in § 33.75(g)(2) of this part. (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)≤A<3.90 (6,045)	2.75 (6.05)
3.90 (6,045)≤A	3.65 (8.03)

(c) Small and medium flocking bird. 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 V 1 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.

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(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. Table 2 to § 33.76—Medium Flocking Bird Weight and Quantity Requirements

Engine Inlet Throat Area (A)— Square-meters (square-inches)	Bird quantity	Bird weight kg. (lb.)
0.05 (77.5)>A	none
0.05 (77.5)≤A <0.10 (155)	1	0.35 (0.77)
0.10 (155)≤A <0.20 (310)	1	0.45 (0.99)
0.20 (310)≤A <0.40 (620)	2	0.45 (0.99)
0.40 (620)≤A <0.60 (930)	2	0.70 (1.54)
0.60 (930)≤A <1.00 (1,550)	3	0.70 (1.54)
1.00 (1,550)≤A <1.35 (2,092)	4	0.70 (1.54)
1.35 (2,092)≤A <1.70 (2,635)	1	1.15 (2.53)
	plus 3	0.70 (1.54)
1.70 (2,635)≤A <2.10 (3,255)	1	1.15 (2.53)
	plus 4	0.70 (1.54)
2.10 (3,255)≤A <2.50 (3,875)	1	1.15 (2.53)
	plus 5	0.70 (1.54)
2.50 (3,875)≤A <3.90 (6045)	1	1.15 (2.53)
	plus 6	0.70 (1.54)
3.90 (6045)≤A <4.50 (6975)	3	1.15 (2.53)
4.50 (6975)≤A	4	1.15 (2.53)

Table 3 to § 33.76—Additional Integrity Assessment

Engine Inlet Throat Area (A)— square-meters (square-inches)	Bird quantity	Bird weight kg. (lb.)
1.35 (2,092)>A	none
1.35 (2,092)≤A <2.90 (4,495)	1	1.15 (2.53)
2.90 (4,495)≤A <3.90 (6,045)	2	1.15 (2.53)
3.90 (6,045)≤A	1	1.15 (2.53)
	plus 6	0.70 (1.54)

(d) Large flocking bird. An engine test will be performed as follows: (1) Large flocking bird engine tests will be performed using the bird mass and weights in Table 4, and ingested at a bird speed of 200 knots. (2) Prior to the ingestion, the engine must be stabilized at no less than the mechanical rotor speed of the first exposed stage or stages that, on a standard day, would produce 90 percent of the sea level static maximum rated takeoff power or thrust.

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(3) The bird must be targeted on the first exposed rotating stage or stages at a blade airfoil height of not less than 50 percent measured at the leading edge. (4) Ingestion of a large flocking bird under the conditions prescribed in this paragraph must not cause any of the following: (i) A sustained reduction of power or thrust to less than 50 percent of maximum rated takeoff power or thrust during the run-on segment specified under paragraph (d)(5)(i) of this section. (ii) Engine shutdown during the required run-on demonstration specified in paragraph (d)(5) of this section. (iii) The conditions specified in paragraph (b)(3) of this section. (5) The following test schedule must be used: (i) Ingestion followed by 1 minute without power lever movement. (ii) Followed by 13 minutes at not less than 50 percent of maximum rated takeoff power or thrust. (iii) Followed by 2 minutes between 30 and 35 percent of maximum rated takeoff power or thrust. (iv) Followed by 1 minute with power or thrust increased from that set in paragraph (d)(5)(iii) of this section, by between 5 and 10 percent of maximum rated takeoff power or thrust. (v) Followed by 2 minutes with power or thrust reduced from that set in paragraph (d)(5)(iv) of this section, by between 5 and 10 percent of maximum rated takeoff power or thrust. (vi) Followed by a minimum of 1 minute at ground idle then engine shutdown. The durations specified are times at the defined conditions. Power lever movement between each condition will be 10 seconds or less, except that power lever movements allowed within paragraph (d)(5)(ii) of this section are not limited, and for setting power under paragraph (d)(5)(iii) of this section will be 30 seconds or less. (6) Compliance with the large flocking bird ingestion requirements of this paragraph (d) may also be demonstrated by: (i) Incorporating the requirements of paragraph (d)(4) and (d)(5) of this section, into the large single bird test demonstration specified in paragraph (b)(1) of this section; or (ii) Use of an engine subassembly test at the ingestion conditions specified in paragraph (b)(1) of this section if: (A) All components critical to complying with the requirements of paragraph (d) of this section are included in the subassembly test; (B) The components of paragraph (d)(6)(ii)(A) of this section are installed in a representative engine for a run-on demonstration in accordance with paragraphs (d)(4) and (d)(5) of this section; except that section (d)(5)(i) is deleted and section (d)(5)(ii) must be 14 minutes in duration after the engine is started and stabilized; and (C) The dynamic effects that would have been experienced during a full engine ingestion test can be shown to be negligible with respect to meeting the requirements of paragraphs (d)(4) and (d)(5) of this section. (7) Applicants must show that an unsafe condition will not result if any engine operating limit is exceeded during the run-on period. Table 4 to § 33.76—Large Flocking Bird Mass and Weight

Engine inlet throat area (square meters/square inches)	Bird quantity	Bird mass and weight (kg (lbs))
A <2.50 (3875)	none
2.50 (3875) ≤A <3.50 (5425)	1	1.85 (4.08)
3.50 (5425) ≤A <3.90 (6045)	1	2.10 (4.63)
3.90 (6045) ≤A	1	2.50 (5.51)

(e) Core flocking bird test. Except as provided in paragraph (e)(4) of this section, for turbofan engines, an engine test must be performed in accordance with either paragraph (e)(1) or (2) of this section. The test specified in paragraph (e)(2) must be conducted if testing or validated analysis shows that no bird material will be ingested into the engine core during the test under the conditions specified in paragraph (e)(1). (1) Climb flocking bird test. (i) Test requirements are as follows: (A) Before ingestion, the engine must be stabilized at the mechanical rotor speed of the first exposed stage or stages that produce the lowest expected power or thrust required during climb through 3,000 feet above mean sea level (MSL) at standard day conditions.

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(B) The climb flocking bird test shall be conducted using one bird of the highest weight specified in table 2 to this section for the engine inlet area. (C) Ingestion must be at 261-knots true airspeed. (D) The bird must be aimed at the first exposed rotating stage or stages, at the blade airfoil height, as measured at the leading edge that will result in maximum bird material ingestion into the engine core. (ii) Ingestion of a flocking bird into the engine core under the conditions prescribed in paragraph (e)(1)(i) of this section must not cause any of the following: (A) Sustained power or thrust reduction to less than 50 percent maximum rated takeoff power or thrust during the run-on segment specified under paragraph (e)(1)(iii)(B) of this section, that cannot be restored only by movement of the power lever. (B) Sustained power or thrust reduction to less than flight idle power or thrust during the run-on segment specified under paragraph (e)(1)(iii)(B) of this section. (C) Engine shutdown during the required run-on demonstration specified in paragraph (e)(1)(iii) of this section. (D) Any condition specified in § 33.75(g)(2). (iii) The following test schedule must be used (power lever movement between conditions must occur within 10 seconds or less, unless otherwise noted): Note 1 to paragraph (e)(1)(iii) introductory text. Durations specified are times at the defined conditions in paragraphs (e)(1)(iii)(A) through (I) of this section. (A) Ingestion. (B) Followed by 1 minute without power lever movement. (C) Followed by power lever movement to increase power or thrust to not less than 50 percent maximum rated takeoff power or thrust, if the initial bird ingestion resulted in a reduction in power or thrust below that level. (D) Followed by 13 minutes at not less than 50 percent maximum rated takeoff power or thrust. Power lever movement in this condition is unlimited. (E) Followed by 2 minutes at 30-35 percent maximum rated takeoff power or thrust. (F) Followed by 1 minute with power or thrust increased from that set in paragraph (e)(1)(iii)(E) of this section, by 5-10 percent maximum rated takeoff power or thrust. (G) Followed by 2 minutes with power or thrust reduced from that set in paragraph (e)(1)(iii)(F) of this section, by 5-10 percent maximum rated takeoff power or thrust. (H) Followed by 1 minute minimum at ground idle. (I) Followed by engine shutdown. (2) Approach flocking bird test. (i) Test requirements are as follows: (A) Before ingestion, the engine must be stabilized at the mechanical rotor speed of the first exposed stage or stages that produce approach idle thrust when descending through 3,000 feet MSL at standard day conditions. (B) The approach flocking bird test shall be conducted using one bird of the highest weight specified in table 2 to this section for the engine inlet area. (C) Ingestion must be at 209-knots true airspeed. (D) The bird must be aimed at the first exposed rotating stage or stages, at the blade airfoil height measured at the leading edge that will result in maximum bird material ingestion into the engine core. (ii) Ingestion of a flocking bird into the engine core under the conditions prescribed in paragraph (e)(2)(i) of this section may not cause any of the following: (A) Power or thrust reduction to less than flight idle power or thrust during the run-on segment specified under paragraph (e)(2)(iii)(B) of this section. (B) Engine shutdown during the required run-on demonstration specified in paragraph (e)(2)(iii) of this section. (C) Any condition specified in § 33.75(g)(2). (iii) The following test schedule must be used (power lever movement between conditions must occur within 10 seconds or less, unless otherwise noted): Note 2 to paragraph (e)(2)(iii) introductory text. Durations specified are times at the defined conditions in paragraphs (e)(2)(iii)(A) through (H) of this section.

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(A) Ingestion. (B) Followed by 1 minute without power lever movement. (C) Followed by 2 minutes at 30-35 percent maximum rated takeoff power or thrust. Power lever movement in this condition is unlimited. (D) Followed by 1 minute with power or thrust increased from that set in paragraph (e)(2)(iii)(C) of this section, by 5-10 percent maximum rated takeoff power or thrust. (E) Followed by 2 minutes with power or thrust reduced from that set in paragraph (e)(2)(iii)(D) of this section, by 5-10 percent maximum rated takeoff power or thrust. (F) Followed by 1 minute minimum at ground idle. (G) Followed by engine shutdown. (H) Power lever movement between each condition must be 10 seconds or less, except that any power lever movements are allowed within the time period of paragraph (e)(2)(iii)(C) of this section. (3) Results of exceeding engine-operating limits. Applicants must show that an unsafe condition will not result if any engine-operating limit is exceeded during the run-on period. (4) Combining tests. The climb flocking bird test of paragraph (e)(1) of this section may be combined with the medium flocking bird test of paragraph (c) of this section, if the climb first stage rotor speed calculated in paragraph (e)(1) of this section is within 3 percent of the first stage rotor speed required by paragraph (c)(1) of this section. As used in this paragraph (e)(4), “combined” means that, instead of separately conducting the tests specified in paragraphs (c) and (e)(1) of this section, the test conducted under paragraph (c) of this section satisfies the requirements of paragraph (e) of this section if the bird aimed at the core of the engine meets the bird ingestion speed criteria of paragraph (e)(1)(i)(C) of this section. [Doc. No. FAA-1998-4815, 65 FR 55854, Sept. 14, 2000, as amended by Amdt. 33-20, 68 FR 75391, Dec. 31, 2003; Amdt. 33-24, 72 FR 50868, Sept. 4, 2007; Amdt. 33-23, 72 FR 58974, Oct. 17, 2007; Amdt. 33-36, 88 FR 19810, Apr. 4, 2023]