58. Section 33.87, Endurance Test.
Section 33.87 Endurance test.
(a) General. Each engine must be subjected to an endurance test that includes a total of 150 hours of operation and, depending upon the type and contemplated use of the engine, consists of one of the series oi runs specified in paragraphs (b) through (f) of this section, as applicable. For engines tested under paragraph (b),
(c), (d), or (e) of this section, the prescribed 6-hour test sequence must be conducted 25 times to complete the required 150 hours of operation. The following test requirements apply:
(1) The runs must be made in the order found appropriate by the Administrator for the particular engine being tested.
(2) Any automatic engine control that is part of the engine must control the engine during the endurance test except for operations where automatic control is normally overridden by manual control or where manual control is otherwise specified for a particular test run.
Except as provided in paragraph (a) (5) of this seen de pe engine i at eat 10 percent de the value associated with the particular engine operation being tested. More than one test may be run if all parameters cannot be held at the 100 percent level simultaneously.
The runs must be made using fuel, lubricants and hydraulic fluid which conform to the specifications specified in complying with Section 33.V(c).
(5) Maximum air bleed for engine and aircraft services must be used during at least one-fifth of the runs. However, for these runs, the power or thrust or the rotor shaft rotational speed may be less than 100 percent of the value associated with the particular operation being tested if the Administrator finds that the validity of the endurance test is not compromised.
(6) Each accessory drive and mounting attachment must be loaded. The load imposed by each accessory used only for aircraft service must be the limit load specified by the applicant for the engine drive and attachment point during rated maximum continuous power or thrust and higher output. The endurance test of any accessory drive and mounting attachment under load may be accomplished on a separate rig if the validity of the test is confirmed by an approved analysis.
(7) During the runs at any rated power or thrust the gas temperature and the oil inlet temperature must be maintained at the limiting temperature except where the Chap 3 84 Par 58
test periods are not longer than 5 minutes and do not allow stabilization. At least one run must be made with fuel, oil, and hydraulic fluid at the minimum pressure limit and at least one run must be made with fuel, oil, and hydraulic fluid at the maximum pressure limit with fluid temperature reduced as necessary to allow maximum pressure to be attained.
(8) If the number of occurrences of either transient rotor shaft overspeed or transient gas overtemperature is limited, the number of the accelerations required by paragraphs (b), (c), (d), and (e) of this section must be made at the limiting overspeed or overtemperature. If the number of occurrences is not limited, half the required accelerations must be made at the limiting overspeed or.
overtemperature.
(9) For each engine type certificated for use on supersonic aircraft, the following additional test requirements apply:
(i) To change the thrust setting, the power control lever must be moved from the initial position to the final position in not more than 1 second except for movements into the fuel burning thrust augmenter augmentation position if additional time to confirm ignition is necessary.
During the runs at any rated augmented thrust, the hydraulic fluid temperature must be maintained at the limiting temperature except where the test periods are not long enough to allow stabilization.
(iii) During the simulated supersonic runs, the fuel temperature and induction air temperature may not be less than the limiting temperature.
The endurance test must be conducted with the fuel burning thrust augmenter installed, with the primary and secondary exhaust nozzles installed, and with the variable area exhaust nozzles according to the methods specified in complying with Section 33.5(b).
(v) During the runs at thrust settings for maximum continuous thrust and percentages thereot, the engine must be operated with the inlet air distortion at the limit for those thrust settings.
Engines other than certain rotorcraft engines.
For each engine, except a rotorcraft engine for which a rating is desired under paragraph (c), (d), or (e) of this section, the applicant must conduct the following runs:
(1) Takeoff and idling. One hour of alternate 5- minute periods at rated takeoff power and thrust and at idling power and thrust. The developed powers and thrusts at takeoff and idling conditions and their corresponding rotor speed and gas temperature conditions must be established by the power control in accordance with the schedule established by the manufacturer. The applicant Chap 3 Par 58 85
may, during any one period, manually control the rotor speed, power, and thrust 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 takeoff must be at the augmented rating.
engines that do not materially increase operating severity, the amount of running conducted at the augmented rating is determined by the Administrator. In changing the power setting after each period, the power control lever must be moved in the manner prescribed in
(2) Rated maximum continuous and takeoff power and thrust. Thirty minutes at -
(i) Rated maximum continuous power and thrust during fifteen of the twenty-five 6-hour endurance test cycles;
(ii) Rated takeoff power and thrust during ten of the twenty-five 6-hour endurance test cycles.
(3) Rated maximum continuous power and thrust. One hour and 30 minutes at rated maximum continuous power and thrust.
Incremental cruise power and thrust. Two hours and 30 minutes at the successive power lever positions corresponding to at least 15 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, the thrust and power may be varied in place of speed. If there is significant peak vibration anywhere between ground idle and maximum continuous conditions, the number of increments chosen may be changed to increase the amount of running made while subject to the peak vibrations up to not more than 50 percent of the total time spent in incremental running.
minutes of accelerations and decelerations, consisting of 6 cycles from idling power and thrust to rated takeoff power and thrust and maintained at the takeoff power lever position for approximately 4-1/2 minutes. position for 30 seconds and at the idling power lever subparagraph othe In complying with this subparagraph, 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 scheduling of the power-control lever motion in going from one extreme position to the other, a longer period of time is acceptable, but not more than 2 seconds.
(6) Starts. One hundred starts must be made, 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 Chap 3 86 Par 58
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.
Chap 3 Par 58 91
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