Figure 11. § 33.87(e), 150-Hour Endurance Test Cycles 16-25 for Rotorcraft 03/09/15 Engine with Rated 2½ Minute and Continuous OEI Power Rating 2 ½-min. OEI - *-2 min *- - 5 min.* Continuous OEI - Takeoff - * 1 hr. *9 applications at Continuous OEI One last application in 25 cycles Maximum - continuous A1-12 1/2 min.→ -4 1/2 min.
Idle - * *-5 min.
1 112 21/2 31/2 5 1/2 AC 33.87-1A Time ~ Hours
Figure 12. § 33.87(f), 2-Hour Supplemental Endurance Test, Cycle 1 of 4 for Rotorcraft Engine with 30-Second and 2-Minute OEI Power Ratings A1-13 Pow er 1 min.
2 min.
30 sec.
2 min.
30 sec.
Idle Takeoff 50% Takeoff 30 Second OEI 2 Minute OEI 30-min OEI * Greatest of * Continuous OEI, or Max Continuous 30 min. 35 min.
* When the rated 30-min OEI is not the greatest, the entire 65 minute period must be run at the greatest of rated continuous OEI or maximum continuous power 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Time ~ Minute 03/09/15 AC 33.87-1A
Figure 13. § 33.87(f), 2-Hour Supplemental Endurance Test, Cycles 2-4 for Rotorcraft Engine with 30-Second and 2-Minute OEI Power Ratings 30 Second OEI 2 Minute OEI Takeoff 50% Takeoff Idle Pow er Greatest of 30-min OEI, or Continuous OEI, or Maximum Continuous 1 min.
30 sec.
2 min.2 min.
30 sec.
5 min.
0 5 10 15 Time ~ Minute 03/09/15 AC 33.87-1A
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Appendix 2. Endurance Test Plan Requirements
1. The applicant must prepare a test plan for the endurance test that thoroughly defines the test objective, test engine, germane or primary test hardware, test facility, test procedures, and the pass or fail criteria. Submit the test plan early enough to allow us sufficient amount of time to review and approve the plan prior to the start of the test.
2. The following paragraphs describe types of information included in a test plan for the calibration test, endurance test, and teardown inspection. We intend this information as a guide to preparing the plan and is not all-inclusive or mandatory.
a. Description of the Test Objective. The applicant should list the part 33 paragraphs for which the tests are intended to show compliance. Provide a brief description of how each quoted regulation will be complied with by the test(s).
b. Test engine configuration. The applicant should identify the test engine configuration.
The configuration of the test engine must substantially conform to the final type design, however, non-type design hardware, components, and software may be used in the test engine to achieve certain test conditions when approved by us. For example, the applicant may need to modify test equipment, engine configurations, and test sequences in order to run the test at simultaneous triple redline conditions. In this case, the applicant should identify, in the test plan, the parts and components in the test engine that are non-type design. The applicant should also validate that the non-type design parts and components will not adversely affect the test outcome or the test integrity.
c. Facility test equipment. The applicant should list all facility test equipment necessary to conduct the test, configuration of slave hardware, bleed configuration, and oil system modification(s) to achieve maximum oil temperature, etc. The applicant should also identify the calibration means for the test equipment.
d. Conformity. The applicant should identify the germane hardware of the test engine in a user friendly format for easy identification. The applicant should also list the components that require pre- and post-endurance test bench calibration, and the required conformities of the test engine. Appendix 5 of this AC provides additional information on conformity inspections.
e. Test procedure. T he test procedure should provide sufficient details to describe the method of compliance. These may include:
(1) discussions of pre- and post-endurance calibration tests,
(2) test cycles or hours,
(3) test sequences if they differ from those prescribed in §§ 33.87(b) through (g),
(4) fuel, oil, and hydraulic fluid to be used and sampling intervals, A2-1
(5) oil consumption, and
(6) other component testing requirements, as applicable.
f. Post-test. Applicants should detail the inspection requirements for the engine “ dirty” and “clean” inspections done at the end of the endurance test and following the complete engine disassembly.
g. Success Criteria. Applicants should describe the pass or fail criteria that determine how engine performance characteristics, or condition of parts and components, or both, meet their regulatory requirements under §§ 33.85 and 33.93.
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Appendix 3. Endurance Test Cycle for Multiple Engine Tests
1. Regulatory basis for multiple engine tests.
a. Section 33.87(a)(3) allows for multiple tests if all the associated limits to the engine operating condition being demonstrated cannot be held at the 100 percent level simultaneously.
If the applicant selects multiple tests to comply with the endurance test requirement, then the applicant must run the additional test(s) in accordance with the prescribed test sequence under §§ 33.87(b) through (g), applicable to all the engine rating conditions (i.e., takeoff, maximum continuous, OEI, and other ratings) being demonstrated. The applicant must run all of these tests on the same engine hardware the applicant presents for certification.
b. For rotorcraft engines for which the applicant desires 30-second OEI and 2-minute OEI ratings, the applicant must repeat the test sequence defined in § 33.87(f) for not less than 120 minutes. If a second test is required to demonstrate all the limits associated with the engine operating condition, then the total test time at the desired OEI conditions should not be less than 240 minutes.
c. Section 33.87(a)(3) also requires that at least 100 percent of the value of all the engine operating parameters associated with a particular engine operating condition must be maintained during the series of runs specified under §§ 33.87(b) through (g), as applicable. If a parameter limit for a particular engine rating (for example, rotor speed for maximum continuous rating) is not defined, then run the test segments associated with that rating condition to the maximum engine redline condition, as defined in the TCDS.
2. Example of multiple engine tests. The following is an example of an acceptable multiple engine test sequence for a turbofan engine in compliance with § 33.87(b). If during the first test, the applicant demonstrates simultaneous core rotor speed limit and the gas temperature limit, the applicant should demonstrate the second test at the fan rotor speed limit and the gas temperature limit, simultaneously, in accordance with the test sequences defined in §§ 33.87(b)(1), (b)(2)(i),
(b)(2)(ii), (b)(3), and (b)(5). This second demonstration would accumulate an additional 87.5 hours of testing at redline fan speed and gas temperature, resulting in a total time of 237.5 hours on the same engine hardware for this endurance test. The applicant may choose to run the test in two parts (on the same set of engine hardware) as provided in paragraphs a. and b. below.
a. Part One. Run a standard 150-hour endurance test in accordance with § 33.87(b) at the redline core rotor speed, the gas temperature limit, and the rated thrust, simultaneously.
(1) During the takeoff parts of the test, the applicant must maintain:
(a) The fan rotor speed at the level associated with producing the test parameters in 2.a.(1)(b), (c), and (d) of this paragraph,
(b) The core rotor speed at or above the takeoff redline limit,
(c) The gas temperature at or above the takeoff redline limits, and A3-1
(d) The thrust at or above the takeoff rating value.
(2) During the maximum continuous parts of the test, the applicant must maintain:
(a) The fan rotor speed at the level associated with producing the test parameters in 2.a.(2)(b), (c), and (d) of this paragraph,
(b) The core rotor speed at the maximum permissible speed associated with the maximum continuous rating. If a maximum permissible rotor speed is not defined for the maximum continuous rating, then the maximum continuous test segments must be run to the rotor speed redline limit usually associated with the takeoff rating,
(c) The gas temperature at or above the rated maximum continuous limit. If a gas temperature limit is not defined for the maximum continuous rating, then the maximum continuous test segments must be run to the maximum gas temperature redline limit usually associated with the takeoff rating, and
(d) The thrust at or above the rated maximum continuous value.
b. Part Two. Re-run only the takeoff and maximum continuous parts of the cycle under the test sequences defined in §§ 33.87(b)(1), (b)(2)(i), (b)(2)(ii), (b)(3), and (b)(5) at fan rotor speed, gas temperature limits, and rated thrust simultaneously. The run time for Part Two is 87.5 hours, which consists of 18.75 hours at takeoff power, 45 hours at maximum continuous, and
23.75 hours at minimum idle.
(1) During the takeoff parts of the test, the applicant must maintain:
(a) The core rotor speed at the level associated with producing the test parameters in 2.b.(1)(b), (c), and (d) of this paragraph,
(b) The fan rotor speed at the takeoff redline limit,
(c) The gas temperature at the takeoff redline limit, and
(d) The thrust at the rated takeoff thrust level.
(2) During the maximum continuous parts of the test, the applicant must maintain:
(a) The core rotor speed at the level associated with producing the test parameters in 2.b.(2)(b), (c), and (d) of this paragraph,
(b) The fan rotor speed at the maximum permissible speed associated with the maximum continuous rating. If a maximum permissible rotor speed is not defined for the maximum continuous rating, then the maximum continuous test segments must be run to the rotor speed redline limit usually associated with the takeoff rating, A3-2
(c) The gas temperature at the maximum continuous redline limit. If a gas temperature limit is not defined for the maximum continuous rating, then the maximum continuous test segments must be run to the maximum gas temperature redline limit usually associated with the takeoff rating, and
(d) The thrust at the maximum continuous rating level.
c. The total run time for the multiple endurance test runs, including Part One and Part Two is 237.5 hours, i.e., 150 hours and 87.5 hours.
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Appendix 4. Engine Configuration Modifications in Endurance Test
1. To run the endurance test at redline conditions simultaneously, i.e., at maximum permissible rotor speeds, gas temperature, and full rated thrust or torque as required by § 33.87(a)(3), the applicant may need to modify the engine configuration or use certain additional facility test equipment. The applicant should include the modifications to the engine configurations and additional facility test equipment in the test plan. See appendix 2, paragraphs 2.b. and 2.c. The following methods are commonly used to match engine speeds and temperatures to achieve the desired test conditions.
a. Change the inlet airflow and condition by:
(1) Changing the inlet nozzle area,
(2) Installing an inlet grid or screen to introduce a pressure drop at the inlet, or
(3) Heating the inlet air.
b. Variable compressor stator vane mis-scheduling.
c. Use of customer bleed from high-pressure compressor or low-pressure compressor, or both.
d. Use of a variable area hot section nozzle.
e. Use of a variable area exhaust nozzle.
2. When one or more of the above methods is chosen, the applicant should provide a technical justification that shows that the tested configuration does not compromise test requirements under § 33.87 or mask stability issues.
3. Operating the engine at triple redline conditions requires some nonstandard adjustments to the engine’s designed control and operating characteristics. These adjustments may result in unintended adverse consequences to some engine design features.
a. For example, attaining redline core rotor speeds simultaneously with redline gas temperatures may require off-design point scheduling of the compressor variable stator vanes and other engine hardware. This in turn may reduce the amount of air that can be bled internally from the compressor for pressurization of bearing sump areas and for cooling various high- and low-pressure turbine components. Section 33.87 does not require that the engine be tested with an engine system, such as these cooling circuits, reduced in capability or effectiveness below the design intent level at which it would operate if the engine remained in a type design configuration.
b. The applicant may propose minor modifications to the engine to mitigate these unintended consequences. For example, the applicant may propose restoring the type design A4-1
cooling by modifying the compressor internal cooling flow circuit and increase the flow regulating orifice diameters.
c. For each proposed modification, the applicant should show in the test plan that the modification doesn’t enhance the capability to withstand the rigors of the intended test conditions for that modified part or for any other part affected by the modified part. For example, for the modification discussed in paragraph b. of this appendix, the applicant should show that:
(1) The modifications to the compressor cooling flow circuit do not improve the capability of the compressor case to withstand the test conditions, and
(2) The increased cooling flow does not improve the capability to withstand the rigors of the test for the hot section parts that are pressurized or cooled by this flow. The reconciliation for any such modified parts (i.e. non-type design) should be included in the reconciliation section of the test plan.
d. The modifications to the test engine configuration should still allow the engine to substantially conform to the final type design. In addition, the test engine, as modified, should be representative of the durability and capability of a typical type design engine to withstand the rigors of the test.
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Appendix 5. Endurance Test Conformity Inspections and Type Inspection Authorization
1. The calibration and endurance test engine(s) must substantially conform to the final type design configuration, except for non-type design hardware approved by us. The applicant should make all inspections necessary to determine that the parts and components of the engine adequately conform to the drawings and specifications of the type design, and the engine is built to the assembly procedures specified in the type design. Our manufacturing inspectors or an FAA designee will conduct pre- and post- test conformity inspections. The applicant should also disclose any deviations (referred to as “nonconformances”) of hardware, software, and components from the type design, and should provide acceptable evidence that these non-type design characteristics will not adversely affect the outcome or the integrity of the test. Finally, the applicant should report the data generated in pretest conformity inspections to us for our review. For reporting, the applicant should use the applicable reporting format. Refer to FAA Order 8110.4C for the type certification procedures related to conformity inspections.
2. Certain test hardware should be subject to preassembly conformity inspections by either our manufacturing inspector or the FAA-designated inspector. The inspectors should give particular attention to critical characteristics of critical and major parts that are subject to significant temperatures, distortion, cracking, fatigue, creep, and wear. This conformity inspection may vary, depending upon circumstances, and is based on a conformity inspection plan. Our pretest review of applicant's quality control procedures, inspection personnel experience, and inspection facilities capability will help to determine the extent of the required conformity inspections prior to the endurance test. Refer to FAA Order 8110.4C for conformity inspection requirements.
3. The type inspection authorization (TIA) is normally prepared by our certifying office upon the applicant’s request, and is used to authorize conformity inspections to ensure that the test engine hardware conforms to the approved type design for certification. The TIA should identify the test engine configuration, including germane hardware for the test, the FAA-approved nontype design hardware, and the parts that are subject to preassembly inspection. We may also issue a TIA requiring special inspections on either the test engine or the test facilities when we find it necessary. For more information on the request for conformity inspection, TIA, statement of conformity, type inspection report, and related instructions, see chapter 5 of FAA Order 8110.4C, Type Certification.
4. The following example shows hardware that is germane to a demonstration under § 33.87 required by a redesigned annular combustor. Assume the combustor redesign alters the actual discharge gas temperature profile relative to the gas temperature measured by the turbine temperature assembly. This factor then changes the operating envir onment of all parts that are affected by a change in the gas temperature characteristics. The objective of the endurance test is to demonstrate that the core engine hardware affected by changes to the gas path environment will satisfactorily pass a 150-hour endurance test at the maximum permissible gas temperature.
In this example, the germane hardware is the:
a. Diffuser case,
b. Combustor section, which includes:
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(1) Fuel nozzles;
(2) Inner and outer liners, inner and outer cowls, and domes;
(3) Inner and outer support rings; and
(4) Combustion case.
c. High-pressure turbine (HPT) section, which includes:
(1) Disks, vanes, blades, and side plates;
(2) Air seals and shrouds;
(3) Inner and outer supports, and outer case; and
(4) Cooling air manifold.
d. HPT to low-pressure turbine (LPT) transition duct,
e. LPT section, which includes:
(1) Disks, blades, and vanes;
(2) Air seals and shrouds; and
(3) Inner and outer supports, and outer case.
f. Exhaust section, which includes:
(1) Turbine exhaust case,
(2) Tailpipe, and
(3) Gas temperature probe assembly.
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