100 90 80 ..
QI ~ 70 0 C.
0 60 t;
so 2 f= -i, 40 QI .. "' 30 a::
"o'!.
20 10 0 0 Run-on For Large Flocking Bird Test Ingestion at N1 Equivalent to at Least 90% ISA Day Thrust No Throttle Movement During First Minute ····················•································· . . ........... \ Thrust/Pow er must remain >50% during first minute At Least 50% Rated Thrust/P ower to Suit Appl icant.
Fully Variable .. Dotted line shows notional thrust/throttle variation.
Decrease to Approach: 30-35% Rated Thrust/Power within 30s.
Maintain Setting for 2 min.
Thrust/Power Increase, min 5%,max 10% from Previous Level. Up in lOs, Maintain60
s.
Ground Idle Thrust/Power Decrease, min 5%, max 10% from Previous Level. Down in 10s, Maintain 2 min.
Decrease to Ground Idle.
Downin 10s, Maintain 60 s.
Shutdown 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Time- Minu tes 04/03/2023 AC 33.76-1B F igure 4. Run-On for Large Flocking Bird Ingestion Rule 11 MEDIUM FLOCKING BIRD TEST AT CLIMB CONDITION.
11.1 Test and Measurement Methods.
11.1.1 Climb Flocking Bird Test Rotor Speed Determination.
Calculation of the fan rotor speed associated with the climb phase of flight is dependent on the design and operation of the airplane. For each engine model and installation, the engine manufacturer should collaborate with the airplane manufacturer to determine the engine thrust needed to climb through an altitude of 3,000 feet in ISA standard day conditions (3,000 feet MSL) at 250 knots indicated airspeed (KIAS) (261-knots true airspeed). The associated minimum mechanical fan rotor speed for this condition should be established using engine performance simulations. The minimum speed should be the speed for the lowest rated thrust engine model offered for that aircraft installation. If multiple climb settings are available for a particular aircraft, use the lowest climb setting to determine the core-climb ingestion rotor speed targets. If the airplane manufacturer is unknown or if no coordination on climb settings took place, the engine applicant should include information on the climb settings used during the test in the installation manual.
11.1.2 Climb Rotor Speed Considerations.
Typically, little to no difference exists between takeoff and climb rotor speeds for the smaller turbofan engines installed on business jets. For this reason, the climb conditions for the core-climb ingestion demonstration will often be close to those prescribed for the MFB test of § 33.76(c), where the largest MFB is targeted at the engine core at full rated takeoff condition. For those engines, the most significant difference between the 13
§ 33.76(c) medium flocking bird test and the § 33.76(e) climb flockin g bird test is the bird speed. An applicant may combine the 250 KI AS (261-knots true airspeed) climb flocking bird test with the existing MFB test if the c limb fan rotor spee d is within 3 percent of the rotor speed associated with rated takeoff thrust. The climb flocking bird test requirements may be satisfied by a single combined bird ingestion test using all of the following criteria:
• Engine operating at rated takeoff thrust.
• Largest MFB fired at the 261-knots true airspeed at the engine core.
• Remaining bird velocities, targeting, and run-on in accordance with the § 33.76(c) MFB crit eria. The remaining birds would be fired at the velocity associate d with § 33.76(c), which represents aircraft normal flight velocity up to 1,500 feet AGL, but not less than V1 minimum.
• All birds to be fired within the 1-second requirement of § 33.76(c)(7)(i).
The goal is to show the c ore ingestion demonstration is as rigorous at the current MFB fan speed condition, as it would be at the (air plane) recommended climb fan speed condition. Use of this approach could eliminate a redundant test.
11.1.3 Core In gestion Prediction Analysis.
Some engine configurations may include features that reject all bird material from the core intake at the takeoff and climb conditions. Such engines would be exempt from the recommended climb flocking bird test, but subject to the approach flocking bird test.
The applicant may run the approach flocking bird test if an analysis shows that no bird material will enter the core during the climb flocking bird test. The applicant should validate the analysis using data derived from rig testing, engine testing, and field experience. The applicant should perform the core ingestion prediction analysis before running the § 33.76(c) MFB test. If any amount of bird material (including a single feather or tissue fluorescence under ultraviolet light illumination) is found in the core after the standard § 33.76(c) MFB core demonstration test, then the applicant must perform the climb flocking bird test. Figure 5 shows when an applicant may use the approach flocking bird test instead of the climb flocking bird test.
If 33.76{c) test shows core ingestion, then climb flocking bird test must be run MCL: Fan spee d and thru st needed to climb throu gh an altit ude of 3,000feet in ISA standard day conditions at 250 KIAS(261knots true) NO Run Approach flocking bird test YEs· YES
VALIDATED ANALYSIS?
NO NO Run Climb flocking bird test TEST
SHOWS CORE INGESTION ?
YES ~711 OSlF 04/03/2023 AC 33.76-1B F igure 5. Core Ingestion Prediction Analyses for Climb Flocking Bird Test 15
11.2 T arget Selection.
The optimum target location varies with engine design. The span-wise location depends on the geometric features of the front of the engine. Determine the target location that maximizes the amount of bird material ingested into the core for the given test condition. The optimum target location ensures the test properly challenges the core during engine demonstration. When determining the target location, use analysis based on component test, dynamic simulation verified by test, and experience with similar designs.
11.3 Engine Operation Requirements.
After ingestion, a power or thrust decrease below the required value of each segment, or when setting power between segments, is acceptable provided the time below the required value is no longer than 3 seconds. A power or thrust loss greater than 3 seconds duration is considered a sustained power loss.
11.4 Run-On Sequence Requirements.
All steps in the test sequence must be completed for showing compliance with § 33.76(e)(1)(iii) or 33.76(e)(2)(iii). Requirements are specified in terms of maximum rated takeoff power or thrust in this paragraph. The rotor speed to attain the specified power setting will vary with test day conditions. These power settings are a percentage of maximum rated takeoff power or thrust, not a percentage of the actual test day preingestion power or thrust specified in § 33.76(d)(2).
For the climb flocking bird test, the applicant must demonstrate the entire run-on sequence for showing compliance with § 33.76(e)(1)(iii). The total engine run-on sequence test duration may exceed 20 minutes, due to the time used for accelerations and decelerations.
For the approach flocking bird test, the applicant must demonstrate the entire run-on sequence for showing compliance with § 33.76(e)(2)(iii). The total engine run-on sequence test duration may exceed 7 minutes, due to the time used for accelerations and decelerations. The applicant must not move the throttle for 1 minute after bird ingestion as required by § 33.76(e)(2)(iii)(B). The thrust or power level may go below flight idle power or thrust for any amount of time in the first minute after bird ingestion, but the engine must not flame out or go sub-idle as required by 33.76(e)(2)(ii). If thrust or power is below 50 percent at the end of 1 minute, the throttle must be increased until thrust or power is between 30 and 35 percent maximum rated takeoff power or thrust.
The remaining run-on for the approach flocking bird test is 6 minutes long as defined in § 33.76(e)(2)(iii). Figure 6 shows a graph of § 33.76(d)(5) run-on requirements.
100 90 80 ..
QI ~ 70 a. .. 60 0 ti so 2 ~ 40 "i, QI ..
~ 30 °' ~ 20 10 0 0 Run-On for Climb Flocking Bird Test Ingestion at Nl Equivalent to minimum climb thrust Nl@ 3,000ft above No Throttle Movement During First Minute __ L_ + + + ----i~ __ ,"' ~ ~ - -_ ... ~ _ --..----- ----' I I At Least 50% Rated Thrust/Power to Suit App licant. Fully Variable. (Dotted line is notional example of thrust/throttle variation) If thrust drops below 50%, move throttle to raise to at least 50% after 1 minute.
+ Decrease to Approach: 30-35% Rated Thrust/Power with in 30s.
Maintain Setting for 2 min.
+ + Thrust/Power Increase, min 5%, max 10% from Previous Level. Up in 10s, Ma intain 60s.
I for 1 min after ingestion;
tjen run-on final 6 minutes Thrust/Power Decrease, min 5%, max 10% from Previous Level. Downin 10s, Maintain 2 min.
Decrease to Ground Idle.
Down in 10s, Maintain 60s.
Shutdow n 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Time- Minutes 12 04/03/2023 AC 33.76-1B Figure 6. Run-On for Climb Flocking Bird Test SUGGESTIONS FOR IMPROVING THIS AC.
If you have suggestions for improving this AC, you may use the Advisory Circular Feedback Form at the end of this AC.
Digitally signed by DANIEL DANIEL J. J. ELGAS FORDate: 2023.04.03 09:48:43 ELGAS -04'00' Victor Wicklund Acting Director, Policy & Innovation Division Aircraft Certification Service 17
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