must be at least 10 normal restarts with not longer than 15 minutes since engine shutdown. The remaining starts may be made after completing the 150 hours of endurance testing.
(C) Rotorcraft engines for which a 30-minute OEI power rating is desired. For each rotorcraft engine for which a 30-minute OEI power rating is desired the applicant must conduct the following series of tests:
(1) Takeoff and idling. One hour of alternate 5- minute periods at rated takeoff power and at idling power.
The developed powers at takeoff and idling conditions and their corresponding rotor speed and gas temperature conditions must be as established by the power control in accordance with the schedule established by the manufacturer. During any one period the rotor speed and power may be controlled manually while taking data to check performance. For engines with augmented takeoff power ratings that involve increases in turbine inlet temperature, rotor speed, or shaft power, this period of running at rated takeoff power must be at the augmented power rating. In changing the power setting after each period, the power-control lever must be moved in the manner prescribed in subparagraph (c)(5) of this paragraph.
Rated 30-minute OEI power. Thirty minutes at rated 30-minute OEI power.
(3) Rated maximum continuous power. Two hours at rated maximum continuous power.
(4) Incremental cruise power. Two hours at the successive power-lever positions corresponding with not less than 12 approximately equal speed and time increments between maximum continuous engine rotational speed and ground or minimum idle rotational speed. For engines operating at constant speed, power may be varied in place of speed. If there are significant peak vibrations anywhere between ground idle and maximum continuous conditions, the number of increments chosen must be changed to increase the amount of running conducted while being subjected to the peak vibrations up to not more than 50 percent of the total time spent in incremental running.
Acceleration and deceleration runs. Thirty minutes of accelerations and decelerations, consisting of 6 cycles from idling power to rated takeoff power and maintained at the takeoff power lever position for 30 seconds and at the idling power-lever position for approximately 4-1/2 minutes. In complying with this subparagraph, the power-control lever must be moved from one extreme position to the other in nor more than 1 second, except that, if different regimes of control operations are incorporated necessitating scheduling of the power-control lever motion in going from one extreme Chap 3 Par 58 87
position to the other, a longer period of time is acceptable, but not more than 2 seconds.
(6) Starts. One hundred starts, of which 25 starts must be preceded by at least a 2-hour engine shutdown.
There must be at least 10 false engine starts, pausing for the applicant's specified minimum fuel drainage time, before attempting a normal start. There must be at least 10 normal restarts with not longer than 15 minutes since engine shutdown. The remaining starts may be made after completing the 150 hours of endurance testing.
Rotorcraft engines for which a continuous OEI rating is desired. For each rotorcraft engine for which a continuous OEI power rating is desired, the applicant must conduct the following series of tests:
(1) Takeoff and idling. One hour of alternate 5- minute periods at rated takeoff power and at idling power.
The developed powers at takeoff and at idling conditions and their corresponding rotor speed and gas temperature conditions must be as established by the power control in accordance with the schedule established by the manufacturer. During any one period the rotor speed and power may be controlled manually while taking data to check performance. For engines with augmented takeoff power ratings that involve increases in turbine inlet temperature, rotor speed, or shaft power, this period of running at rated takeoff power must be at the augmented power rating. In changing the power setting after each period, the power control lever must be moved in the prescribed in paragraph (c)(5) of this section.
Rated maximum continuous and takeoff power.
Thirty minutes at-
(i) Rated maximum continuous power during fifteen of the twenty-five 6-hour endurance test cycies; and Rated takeoff power during ten of the twentyfive 6-hour endurance test cycles.
(3) Rated continuous OEI power. One hour at rated continuous OEI power.
(4) Rated maximum continuous power. One hour at rated maximum continuous power.
Incremental cruise power. Two hours at the successive power lever positions corresponding with not less than approximately 12 equal speed and time increments between maximum continuous engine rotational speed and ground or minimum idle rotational speed. For engines operating at constant speed, power may be varied in place of speed. If there are significant peak vibrations anywhere between ground idle and maximum continuous conditions, the number of increments chosen must be changed to increase the amount of running conducted while being subjected to the peak vibrations up to not more than 50 percent of the total time spent in'incremental running.
Chap 3 88 Par 58
Acceleration and deceleration runs. Thirty minutes of accelerations and decelerations, consisting of six cycles from idling power to rated takeoff power and maintained at the takeoff power lever position for 30 seconds and at the idling power lever position for approximately 4-1/2 minutes. In complying with this paragraph, the power control lever must be moved from one extreme position to the other in not more than 1 second, except that if different regimes of control operations are incorporated necessitating scheduling of the power control lever motion in going from one extreme to the other, a longer period of time is acceptable, but not more than 2 seconds.
Starts. One hundred starts, of which 25 starts must be preceded by at least a 2-hour engine shutdown.
There must be at least 10 false engine starts, pausing for the applicant's specified minimum fuel drainage time, efore attempting a normal start. There must be at least 10 normal restarts with not longer 15 minutes since engine shutdown. The remaining starts may be made after completing the 150 hours of endurance testing.
(e) Rotorcraft engines for which a 2-1/2 minute OEI power rating is desired. For each rotorcraft engine for which a 2-1/2 minute OEI power rating is desired the applicant must conduct the following series of tests:
(1) Takeoff, 2-1/2 Minute OEI, and idling. One hour of alternate 5-minute periods at rated takeoff power and at idling power except that, during the third and sixth takeoff power periods, only 2-1/2 minutes need be conducted at rated takeoff power and the remaining 2-1/2 minutes must be conducted at rated 2-1/2 minute OEI power.
The developed powers at takeoff, 2-1/2 minute OEI, and idling conditions and their corresponding rotor speed and gas temperature conditions must be as established by the power control in accordance with the schedule established by the manufacturer. The applicant may, during any one period, control manually the rotor speed and power while taking data to check performance. For engines with augmented takeoff power ratings that involve increases in turbine inlet temperature, rotor speed, or shait power, this period of running at rated takeoff power must be at the augmented rating. In changing the power setting after or during each period, the power control lever must be moved in the manner prescribed in paragraph (d) (6) of this section.
(2) The tests required in paragraphs (b)(2) through
(b)(6), or (c)(2) through (c)(6), or (a)(2) through (a) (7) of this section, as applicable, except that in one of the 6-hour test sequences, the last 5 minutes of the 30 minutes at takeoff power test period of paragraph (b) (2) of this section, or of the 30 minutes at 30-minute OEI power test period of paragraph (c)(2) of this section, or Chap 3 Par 58 89
of the 1-hour at Continuous OEI power test period of paragraph (d) (3) of this section, must be run at 2-1/2 minute OEI power.
(f) Supersonic aircraft engines. For each engine type certificated for use on supersonic aircraft, the applicant must conduct the following:
(1) Subsonic test under sea level ambient atmospheric conditions. Thirty runs of 1 hour each must be made, consisting of--
(i) Two periods of 5 minutes at rated takeoff augmented thrust each followed by 5 minutes at idle thrusti) One period of 5 minutes at rated takeoff thrust followed by 5 minutes at not more than 15 percent of rated takeoff thrust;
(iii) One period of 10 minutes at rated takeoff augmented thrust followed by 2 minutes at idle thrust, except that if rated maximum continuous augmented thrust ls lower than rated takeoff augmented thrust, 5 of the 10- ninute periods must be at rated maximum continuous augmented thrust; and
(iv) Six periods of 1 minute at rated takeoff augmented thrust each followed by 2 minutes, including acceleration and deceleration time, at idle thrust.
(L) Simulated supersonic test. Each run of the simulated supersonic test must be preceded by changing the inlet air temperature and pressure from that attained at subsonic condition to the temperature and pressure attained at supersonic velocity, and must be followed by a return to the temperature attained at subsonic condition.
Thirty runs of 4 hours each must be made, consisting of--
(i) One period of 30 minutes at the thrust obtained with the power control lever set at the position for rated maximum continuous augmented thrust followed by 10 minutes at the thrust obtained with the power control lever set at the position for 90 percent of rated maximum continuous augmented thrust. The end of this period in the first 5 runs must be made with the induction air temperature at the limiting condition of transient overtemperature, but need not be repeated during the periods specified in subdivisions (ii)through (iv) of this subparagraph;
One period repeating the run specified in subdivision (i) of this subparagraph, except that it must be followed by 10 minutes at the thrust obtained with the power control lever set at the position for 8 percent of
(lii) One period repeating the run specified in subdivision (i) of this subparagraph, except that it must be followed by 10 minutes at the thrust obtained with the power control lever set at the position for 60 percent of rated maximum continuous augmented thrust and then 10 Chap 3 90 Par 58
minutes at not more than 15 percent of rated takeoff thrust;
(iv) One period repeating the runs specified in subdivisions (i) and (ii) of this subparagraph; and
(v) One period of 30 minutes with 25 of the runs made at the thrust obtained with the power control lever set at the position for rated maximum continuous augmented remaining 5 runs at the thrust obtained with the power control lever set at the position for rated maximum continuous augmented thrust for 25 minutes each, followed by subsonic operation at not more than 15 percent of rated takeoff thrust and accelerated to rated takeoff thrust for 5 minutes using hot fuel.
(3) Starts. One hundred starts must be made, of which 25 starts must be preceded by an engine shutdown of at least 2 hours. There must be at least 10 false engine starts, pausing for the applicant's specified minimum fuel drainage time before attempting a normal start. At least 10 starts must be normal restarts, each made no later than 15 minutes after engine shutdown. The starts may be made at any time, including the period of endurance testing.
*** Guidance. The INTENT of this section is to demonstrate a minimum level of operability of the complete engine, within its to be approved ratings, limitations, inspection, and maintenance Incorporations: AC 20-18A, Qualification Testing of Turbojet Engine Thrust Reversers," dated March 16, 1966.
References: None.
This practice would provide additional operating data/information on which to assess engine-to-propeller compatibility.
b. Approval of transient limitations of measured gas temperature, speeds, torques, engine pressure ratios, oil temperature, etc., should be based on those transient excursions (parameter level and time) consistently demonstrated during the limitations should not be approved for times greater than approximately 30 seconds for transients associated with the Maximum Continuous, Takeoff, Continuous OEI, and 30-Minute OEI ratings. Transients associated with the 2-1/2-Minute OEI rating a to very briet perioday should be limited to very brief periods, on the order of 5 to 10 seconds maximum.
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C• Approvals of turboprop and turboshaft engine limits of torque and output shaft speed, as with other limits, are based on those limits having been demonstrated during the engine block tests, particularly the endurance test. Further, approval of simultaneous usage of both the torque and the output shaft speed limits should be based on demonstration of simultaneous excursions of both parameters. for exampie, each required acceleration to the Takeoff, 30-Minute OEI, Continuous OEI, and 2-1/2 Minute OEI power ratings of the appropriate endurance test schedule should be conducted to the respective torque and output shaft speed limits (value and time) to be requested for approval.
In all cases, approval should be granted only to the extent demonstrated. Of principal concern is that approved individual limits of overtorque and overspeed, if applied together, could, for some engine designs, result in a shaft horsepower level which would not have been evaluated during the engine IC process and, thus, may be an unairworthy condition.
e. Under certain ambient conditions, it may not be possible to simultaneously exercise, to its respective speed limitation, each rotor of a multiple rotor engine during endurance test running. During such a case, and if approved by the cognizant FAA project manager or engineer, the required substantiation may be shown by test replication as necessary, and/or by valid analysis.
59. Section 33.88, Engine Overtemperature Test.
Section 33.88 Engine overtemperature test.
Each engine must be run for 5 minutes at maximum permissible r.p.m. and with the gas temperature at least 75 °F (42 °C) higher than the maximum operating limit.
Following this run, the turbine assembly must be within serviceable limits.
*** Guidance. The INTENT of this section is to demonstrate a minimum overtemperature capability of the engine.
Incorporations: AC 33-3, Turbine and Compressor Rotors Type Certification Procedures, dated September 1968.
References: None.
a. This rule requires the test to be demonstrated on a complete engine, not a rig. The test should be set up on an engine without mismatching component flow capacities, if possible.
For example, the maximum rpm and maximum gas path temperature could be set up on the engine by means of an inlet heater. Then, chaP 58 3 92 Par
by modulating compressor bleed, the 75 °F (42 °C) overtemperature (above the maximum rating steady-state limit) would be obtained, under circumstances close to what couid be experienced in service.
Note that "maximum permissible r.p.m." means the highest rotor speed for power-on engine operation (non-windmill, nonautorotative), whether steady-state or transient, which will be specified on the engine type certificate data sheet (TCDS). Also, note that the critical parameter is turbine inlet gas temperature, not exhaust gas temperature.
The overtemperature test condition should be based on the engine's maximum steady-state operating temperature limit. For example, if an engine's maximum steady-state gas temperature for the takeoff rating is 850 °C, the test should be run at 892 °C;
however, if this same engine also has a 2-1/2-Minute OEI rating with a steady-state temperature of 900 °C, then this test should be conducted at 942 °C.
Post test acceptance criteria is that the engine turbine assembly, which includes blades, discs, drums, spacers, shafts, seals, stators, nozzles, and support structure, must be within serviceable limits. Serviceable limits, including dimensional limits, are determined during the type certification process and as published per 'Appendix A to Part 33 -- Instructions for Continued Airworthinessi (See Section 33.4, Instructions for Continued Airworthiness).
60. Section 33.89, Operation Test.
Section 33.89 Operation test.
(a) The operation test must include testing found necessary by the Administrator to demonstrate-- ignition, functioning of the propeller (if the engine (1) Starting, idling, acceleration, overspeeding'is designated to operate with a propeller);
(2) Compliance with the engine response requirements of Section 33.73; and
(3) The minimum power or thrust response time to 95 percent rated takeoff power or thrust, from power lever positions representative of minimum idle and of minimum flight idle, starting from stabilized idle operation, under the following engine load conditions:
(i) No bleed air and power extraction for aircraft use.
(ii) Maximum allowable bleed air and power extraction for aircraft use.
(iii) An intermediate value for bleed air and power extraction representative of that which might be used as a maximum for aircrait during approach to a landing.
(4) If testing facilities are not available, the determination of power extraction required in paragraph Chap 3 Par 59 93
(a)(3) (ii) and (iii) of this section may be accomplished through appropriate analytical means.
(b) The operation test must include all testinq found necessary by the Administrator to demonstrate that the engine has safe operating characteristics throughout its specified operating envelope.
Guidance. The INTENT of this section is to demonstrate safe operating characteristics and a minimum standard of power/thrust response characteristics.
Incorporations: AC 33.65-1, "Surge and Stall Characteristics of Aircraft Turbine Engines," dated December 6, 1985.
References: None.
Note: Although the incorporation applies to large high bypass ratio turbofan engines, the guidance material therein may also be useful for other engine applications.
This section addresses the block test requirements covering surge and stall characteristics. The correlating design and construction requirements are addressed in Section 33.65, "Surge and stall characteristics."
b. Engine transient characteristics at altitude should be defined by testing. However, steady state testing in an altitude test facility, in addition to component and engine analysis, is acceptable, when facility limitations preclude altitude transient testing, if accomplished as follows:
(1) Qualitatively determine, by sea level testing, the transient operating characteristics, including acceleration, deceleration, surge, stall, and flameout.
(2) Considering the limitations of the available altitude test facility, perform a quantitative analysis of the operating characteristics, identified by the above testing, over the complete operating range of the engine.
(3) Select, on the basis of the analysis, those critical conditions which may provide a problem in projected aircraft usage; and demonstrate quantitatively, on a quasi-steady basis, the validity of the analysis in the altitude test facility.
"Quasi-steady" means that disturbances of short duration will be applied to the engine when operating on the steady-state operating line, such that the effect of the transient on the engine is determined before the test facility conditions are disturbed.
Chap 3 94 Par 60
(4) As a part of the sea level demonstration, the ability of the engine to withstand takeoff surge, without damage, should be shown.
(5) The testing and analysis should show that margins are adequate to tolerate likely variations in fuel schedule, variable geometry schedule, anticipated installations and environmental (temperature, pressure, humidity) effects.
C. The operation test should also include:
(1) Low temperature and high temperature tests (fluids and carcass) for starting and operating the engine.
(2) Substantiation of the ignition system design duty cycle.
(3) Substantiation of the propeller parking brake, if the engine is so equipped.
(4) Substantiation of the engine ground and, where feasible, the in-flight starting envelopes. This substantiation should address all possible combinations of ignition system operation and power sources to be approved, and should result in defined acceptable start times, from initiation of the starting sequence to stabilized idle conditions.
(5) Substantiation of the propeller parking brake, if the engine is so equipped.
(6) Substantiation of all engine operating attitudes, and additionally, for powered-lift engines rotationally displaceable along their longitudinal axis, slue angles, and rates.
61. Section 33.90, Initial Maintenance Inspection.
Section 33.90 Initial maintenance inspection.
Each engine, except engines being type certificated through amendment of an existing type certificate or through supplemental type certification procedures, must undergo an approved test run that simulates the conditions in which the engine is expected to operate in service, including start-stop cycles, to establish when the initial maintenance inspection is required. The test run must be accomplished on an engine which substantially conforms to the final type design.
*** Guidance. The INTENT of this section is to demonstrate the ability of new type certificate engines to operate in a simulation Chap 3 Par 60 95
of expected service conditions, for a specified number of cycles and/or hours before requiring maintenance inspection.
Incorporations: None.
References: None.
The requirements of this section are separate and distinct from those of Section 33.14, "Start-stop cyclic stress."
up mental test fat Age leant my sundat as from development tests and service experience where applicable and when creditable. The following information should be supplied to permit assessment of the inspection/overhaul period in support of the abbreviated flight cycle:
(1) The design flight cycle for the engine should identity the time history of engine power, or thrust usage including reverse thrust, if applicable, from engine start-up through shutdown, during a typical flight of a representative aircraft which uses the engine.
(2) The design analysis should identify those features of the engine for which initial life limitations will be established, or which will require threshold maintenance inspection; and whether a limitation is based on low cycle fatigue (cycles) or total engine or part-time (hours).
(3) A substantiation of the validity of the limitations and the acceptability of the test procedure as a valid representation of the design flight cycle, with regard to stress, temperature, and vibration (simulating the maximum rotor imbalances to be approved for production acceptance).
b. The initial maintenance inspection test run of engines designed to drive a propeller should be equipped with a propeller representative of the intended application, and include propeller parking brake usage and APU-mode operations, if so equipped.
62. Section 33.91, Engine Component Tests.
Section 33.91 Engine component tests.
(a) For those systems that cannot be adequately substantiated by endurance testing in accordance with the provisions of Section 33.87, additional tests must be made to establish that components are able to function reliably in all normally anticipated flight and atmospheric conditions.
Chap 3 96 Par 61
(b) Temperature limits must be established for those components that require temperature controlling provisions in the aircraft installation to assure satisfactory functioning, reliability, and durability.
Each unpressurized hydraulic fluid tank may not fail or leak when subjected to maximum operating temperature and an internal pressure of 5 p.s.i.' leak when pressurized hydraulic fluid tank may not fail or subjected to maximum operating temperature and an internal pressure not less than 5 p.s.i. plus the maximum operating pressure of the tank.
For an engine type certificated for use in supersonic aircraft, the systems, safety devices, and petite and test that may fail because of operation at maximum and minimum operating temperatures must be identified and tested at maximum and minimum operating temperatures and while temperature and other operating conditions are cycled between maximum and minimum operating values.
*** Guidance. The INTENT of this section is to assure test substantiation of all engine components, functions, and features which would not otherwise have been evaluated by endurance or other testing.
Incorporations: None.
References: None.
Engine component tests may include, but are not limited to, the following:
Fire proof/resistance tests of flammable fluid carrying or holding components.
b. Sea level and altitude pressure conditions testing/calibration of electronic control, fuel, lube, pneumatic, and starting systems.
c. Cold and hot ambient temperature conditions testing/calibration of fuel, lube, pneumatic, and starting systems.
d. Other environmental testing, such as salt spray, humidity, fungus, explosive atmosphere, etc.
e. Electromagnetic compatibility (EMC/HERF) testing.
f. Testing of engine electronic control lightning tolerance, as discussed under Section 33.7 of this AC.
Chap 3 Par 62 97
g. Engine thrust reverser systems tests.
h. Engine mount structure loads tests.
i. Engine ignition systems (duty cycles) tests.
j. Compressor mapping tests.
K. Engine control and monitoring systems software validations; and
1. Tests of electronic control integrity, while operating with various combinations of intended dispatchable control subsystem failures.
63. Section 33.92, Windmilling Tests.
Section 33.92 Windmilling tests.
(a) For engines to be used in supersonic aircraft, unless means are incorporated in the engine to stop rotation of the engine rotors when the engine is shut down in flight, each engine rotor must either seize or be capable of rotation for 3 hours at the limiting windmilling rotational r.p.m. with no oil in the engine system, without the engine--
(1) Catching fire;
(2) Bursting (releasing hazardous uncontained fragments) ; or
(3) Generating loads greater than those ultimate loads specified in Section 33.23(a).
(b) A turbojet or turbofan engine incorporating means to stop rotation of the engine rotors when the engine is shut down in flight must be subjected to 25 operations under the following conditions:
(1) Each engine must be shut down while operating at rated maximum continuous thrust.
(2) For engines certificated for use on supersonic aircraft, the temperature of the induction air and the external surfaces of the engine must be held at the maximum limit during the tests required by this paragraph.
*** Guidance. The INTENT of this section is self-evident.
Incorporations: None.
References: None.
Chap 3 98 Par 62