AC 33.87-1A

Advisory U.S. Department of Transportation Federal Aviation Circular Administration Subject: Engine Overtorque Test, Calibration Test, Endurance Test, and Teardown Inspection for Turbine Engine Date: 03/09/15 Initiated by: ANE-111 AC No: 33.87-1A Certification (§§ 33.84, 33.85, 33.87,

33.93)

1. Purpose.

a. This advisory circular (AC) provides a method of compliance for the test requirements of Title 14, of the Code of Federal Regulations (14 CFR) 33.84 (engine overtorque test) when the applicant chooses to run that test as part of the endurance test of § 33.87. It also provides information and guidance on the test requirements of § 33.85 (calibration test), § 33.87 (endurance test), and § 33.93 (teardown inspection).

b. This AC applies to part 33 type certification endurance testing of all classes of turbine engines.

2. Applicability.

a. The guidance provided in this AC is directed to engine manufacturers, foreign regulatory authorities, applicants for engine type design approval, and FAA designees.

b. This document is neither mandatory nor regulatory in nature and does not constitute a regulation. It describes an acceptable means, but not the only means, for demonstrating compliance with the applicable regulations. We (the FAA) will consider other methods of demonstrating compliance that an applicant may present. Terms such as “should,” “may,” and “must” are used only in the sense of ensuring applicability of this particular method of compliance when the method of compliance in this AC is used. While these guidelines are not mandatory, we derive them from extensive FAA and industry experience in determining compliance with these regulations.

c. If you choose to use this AC, you should conform to all aspects of the AC. However, we acknowledge that no document can provide guidance that will cover all future engine designs, operating characteristics, or unique certification circumstances. Therefore, if we find that the compliance method(s) defined within this AC do not provide an acceptable means of compliance, we will not be bound to accept the methods in this AC as acceptable.

d. This guidance does not change, create any additional, authorize changes in, or permit deviations from existing regulatory requirements.

3. Cancellation. This AC cancels AC 33.87-1, “Calibration Test, Endurance Test, and Teardown Inspection for Turbine Engine Certification (§§ 33.85, 33.87, 33.93),” April 13, 2006.

4. Explanation of changes. This revision:

a. Adds guidance for the changes made to §§ 33.87 and 33.93 at amendments 25 and 30.

b. Adds guidance for the new § 33.84 regulation introduced by amendment 30.

c. Clarifies and corrects several sections of this AC.

5. Related Regulations and Documents.

a. Related Regulations.

(1) Part 21, §§ 21.31 and 21.33.

(2) Part 33, §§ 33.4, 33.5, 33.7, 33.8, 33.63, 33.82, 33.83, 33.91, and 33.99.

b. Related Documents.

(1) Advisory Circular 33.7-1, “Ratings and Operating Limitations for Turbine Engines (§§ 33.7 and 33.8).”

(2) Advisory Circular 33.87-2, “Comparative Endurance Test Method to Show Durability for Parts Manufacturer Approval of Turbine Engine and Auxiliary Power Unit Parts.”

(3) FAA Order 8110.4C, Type Certification.

6. Discussion.

a. In 1965, we replaced the airworthiness standards of 14 CFR part 13 for the turbine engine calibration test, endurance test, and teardown inspection with those in part 33.

Subsequently, we revised those requirements numerous times over the past four decades. The most significant revisions were in amendments 6 and 10, adopted in 1974 and 1977, respectively.

These amendments upgraded the engine endurance test and teardown inspection requirements to accommodate the increasing complexity of modern turbine engines, and the interface between engines and airframes. See appendix 12 of this AC for a historical background of the changes to the airworthiness standards for the engine calibration test, endurance test, and teardown inspection.

b. In the past, several engine manufacturers have proposed engine testing that is more representative of expected in-service operations in place of the endurance cycle defined in ii

§ 33.87. We accepted some of those proposals; however, we determined that those alternate approaches don't provide an equivalent level of testing. We no longer accept these previously approved methods of compliance to § 33.87. Those previously acceptable alternatives aren't acceptable because the test in § 33.87 does not simulate in-service operation. Rather, compliance to § 33.87 is to demonstrate an accelerated durability test of the engine; to demonstrate a minimum level of engine operability and durability throughout the engine's assigned ratings and operating limitations.

c. Engine endurance testing is covered by several regulations, not just § 33.87. The test requirements are specified in § 33.82, the calibration tests in § 33.85, the teardown inspection in § 33.93, and the block tests in § 33.99. For engine components and systems that cannot be adequately verified by endurance testing in accordance with the provisions of § 33.87, the applicant must conduct the testing required by § 33.91 to establish that these components are able to function reliably in all certificated operating conditions.

d. Chapters 2, 3, and 4 of this AC correspond to the requirements in §§ 33.85, 33.87, and

33.93, respectively. We arranged the contents of each chapter of this AC in accordance with the order of the paragraphs in the regulation. The general testing requirements contained in §§ 33.82 and 33.99 are included in these chapters wherever applicable. The appendices define documentation requirements for the calibration, endurance tests, teardown inspection, define testing requirements for special applications, and provide background information for the guidance material.

e. The guidance in this AC is derived from extensive FAA and industry experience in determining the basis of compliance to §§ 33.85, 33.87, and 33.93. If, however, we determine that testing performed in accordance with the guidance in this AC would still not result in complete compliance with these regulations, we may require additional supporting data.

If you have any suggestions for improvements or changes, you may use the template provided at the end of this AC.

Collen M D'alessanclu fOr Ann C. Mollica Acting Manager, Engine and Propeller Directorate Aircraft Certification Service 111

Table of Contents

Chapter 1. General1

1-1. Definitions1

Chapter 2. Calibration Tests2

2-1. Power Characteristics2

2-2. General Requirements, § 33.85(a), § 33.85(b), and § 33.85(c)2

2-3. Provisions for 30-second and 2- minute OEI Ratings, § 33.85(d)3

Chapter 3. Endurance Test4

3-1. General Requirements in § 33.87(a)4

a. The endurance test4

b. Endurance test plan requirements6

c. Test engine configuration6

d. Engine component and test equipment calibrations7

e. Engine vibration signature8

f. Servicing and repairs during the endurance test8

g. Endurance test report requirements9

3-2. Specific Requirements in § 33.87(a)(1) Through (a)(9)10

a. Test sequence, § 33.87(a)(1)10

b. Automatic control of the engine, § 33.87(a)(2)10

c. Endurance test at redline conditions, § 33.87(a)(3)10

d. Fuel and lubricating oil for endurance test, § 33.87(a)(4)11

e. Maximum air bleed testing, § 33.87(a)(5)12

f. Accessory drive and mounting attachment loads, § 33.87(a)(6)13

g. Redline gas temperature or oil temperature exclusion, and fuel, oil, and

hydraulic fluid tests, § 33.87(a)(7)14

h. Transient, overspeed, overtemperature, and overtorque demonstrations for a

maximum period of 30 seconds, § 33.87(a)(8)15

i. Additional test requirements for supersonic aircraft engines, § 33.87(a)(9)16

3-3. Special Topics16

a. Endurance test cycles for major design changes, parts manufacturer approvals

(PMAs), repairs, and alterations16

b. Endurance test for multiple engine testing17

3-4. Endurance Test Schedule, § 33.87(b), for Engines Other Than Certain Rotorcraft

Engines17

iv

a. Explanation……17

b. Guidance………18

3-5. Endurance Test Schedule, § 33.87(c), for Rotorcraft Engines for which a

30-minute OEI Power Rating is Desired23

a. Guidance………23

b. Section 33.87(c)(1), Takeoff and idling23

c. Section 33.87(c)(2), Rated maximum continuous and takeoff power23

d. Section 33.87(c)(3) Rated maximum continuous power24

e. Section 33.87(c)(4), Rated 30-minute OEI power24

f. Sections 33.87(c)(5), Incremental cruise power or thrust; 33.87(c)(6)

Acceleration and deceleration runs; and 33.87(c)(7), Starts24

3-6. Endurance Test Schedule, § 33.87(d), for Rotorcraft Engines for which a

Continuous OEI Rating is Desired24

a. Guidance24

b. Section 33.87(d)(1), Takeoff and idling, and § 33.87(d)(2), Rated maximum

continuous and takeoff power25

c. Section 33.87(d)(3), Rated continuous OEI power25

d. Section 33.87(d)(4), Rated maximum continuous power25

e. Section 33.87(d)(5), Incremental cruise power, § 33.87(d)(6), Acceleration, and

deceleration runs, and § 33.87(d)(7), Starts25

3-7. Endurance Test Schedule, § 33.87(e), for Rotorcraft Engines for which a 2½-minute

OEI Power Rating is Desired26

a. Explanation26

b. Guidance26

3-8. Endurance Test Schedule, § 33.87(f), for Rotorcraft Engines for which 30-second

OEI and 2-minute OEI Ratings are Desired27

a. The 30-second OEI and 2-minute OEI power ratings27

b. Endurance test for 30-second and 2- minute OEI ratings28

c. Test conduct28

d. Test sequences28

e. Test time29

f. Air bleed during test31

g. Accessory drives and mounting attachments31

h. Engine operating limitations32

3-9. Endurance Test Schedule, § 33.87(g), Supersonic A ircraft Engines32

v

3-10. Endurance Test Schedule, § 33.84, Engine Overtorque T est32

a. Maximum engine overtorque test, § 33.8432

b. Maximum engine overtorque32

c. Test conditions32

d Post-test engine inspection33

Chapter 4. Teardown Inspection34

4-1. General Requirements for All Endurance Tests (Except for Engines with

30-second OEI and 2-minute OEI Ratings), § 33.93(a)34

a. Section 33.93(a)(1)34

b. Section 33.93(a)(2)34

4-2. Teardown Inspection Requirements for Engines with 30-second OEI and ....................

2-minute OEI Ratings, § 33.93(b) and (c)36

Appendix 1. Graphic Profiles of Endurance Test SchedulesA1-1

1. Engines other than certain rotorcraft engines, § 33.87(b)A1-1

2. Rotorcraft engines with a 30-minute OEI power rating, § 33.87(c)A1-1

3. Rotorcraft engines with a continuous OEI rating, § 33.87(d)A1-1

4. Rotorcraft engines with a 2½ OEI rating, § 33.87(e)A1-1

a. § 33.87(b) and § 33.87(e)A1-1

b. § 33.87(c) and § 33.87(e)A1-1

c. § 33.87(d) and § 33.87(e)A1-1

5. Rotorcraft engines with a 30-second and 2-minute OEI ratings, § 33.87(f)A1-1

Appendix 2. Endurance Test Plan RequirementsA2-1

Appendix 3. Endurance Test Cycle for Multiple Engine TestsA3-1

1. Regulatory basis for multiple engine testsA3-1

2. Example of multiple engine testsA3-1

Appendix 4. Engine Configuration Modifications in Endurance TestA4-1

Appendix 5. Endurance Test Conformity Inspections and Type Inspection

AuthorizationA5-1

Appendix 6. Test Reports RequirementsA6-1

Appendix 7. Endurance Testing for a Two-Minute Transient Overtemperature Limit

ApprovalA7-1

vi

1. ExplanationA7-1

2. GuidanceA7-1

Appendix 8. Endurance Test for Engine Certification and Showing of Compliance for

Engineering ChangesA8-1

Appendix 9. Rotorcraft Operation with OEI Ratings and Endurance TestA9-1

1. Endurance Test for 30-second OEI and 2-minute OEI RatingsA9-1

2. Endurance Test for 2½-minute OEI RatingA9-1

3. The Difference Between the OEI RatingsA9-2

Appendix 10. Accumulated Endurance Testing Times for §33.87(e)A10-1

Appendix 11. Teardown Inspection Requirements—Dirty Inspection and Clean

InspectionA11-1

Appendix 12. Historical Background for the Calibration Tests, Endurance Tests, and

Teardown Inspection RequirementsA12-1

1. GeneralA12-1

2. Civil Air Regulation (CAR) 14 CFR, part 13 – Aircraft Engine Airworthiness. A12-1

a. CAR part 13, effective March 5, 1952A12-1

b. CAR part 13, amendment 13-1, effective August 8, 1957A12-1

c. CAR part 13, amendment 13-2, effective May 17, 1958A12-2

d. CAR part 13, amendment 13-5, effective February 12, 1963A12-2

e. CAR part 13, amendment 13-6, effective April 22, 1964A12-2

3. 14 CFR, part 33 – Airworthiness Standards: Aircraft EnginesA12-3

a. Part 33, effective February 2, 1965A12-3

b. Part 33, amendment 6, effective October 31, 1974A12-3

c. Part 33, amendment 10, effective March 26, 1984A12-4

d. Part 33, amendment 12, effective October 3, 1988A12-4

e. Part 33, amendment 18, effective August 19, 1996A12-4

f. Part 33, amendment 25, effective October 17, 2008A12-5

g. Part 33, amendment 30, effective November 2, 2009A12-5

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Chapter 1. General

1-1. Definitions. The following definitions apply to the terms used in this AC.

a. Engine component. Systems and accessories that are part of the engine type design.

b. Endurance test cycle. The series of runs or sequences prescribed in each §§ 33.87(b) through (g).

c. Germane or primary hardware. The hardware used in the certification test that is affected by, or directly affects the outcome of the certification test and the pass or fail criteria for the given test objectives.

d. Redline conditions. The highest physical rotor speed, gas temperature, or output shaft torque, including transients, which may not be exceeded during operation at any applicable rating. The type certificate data sheet (TCDS) prescribes the limitations for each approved engine rating.

e. Test hardware. The parts and components assembled on the engine and to be tested, or, if not mounted on the engine, are part of the engine type design. The test hardware may deviate from the type design if it remains representative of the type design and the applicant justifies the differences in the test plan. This justification is frequently referred to as “reconciliation.”

f. Triple redline test condition. The engine operation at simultaneous redline rotor speeds, redline gas temperature, and full rated thrust or torque, as required by § 33.87(a)(3). For example, for a two-shaft system engine, the engine operation at simultaneous redlines of the two rotor speeds (e.g. low pressure and high pressure rotor systems) and redline gas temperature, in addition to full rated thrust or torque.

Chapter 2. Calibration Tests

2-1. Power Characteristics.

a. The power characteristics should be established based on the endurance test of the engine that represents the type design and is in the following configuration:

(1) No air bleed for aircraft services, and

(2) With only those accessories installed that are essential for engine functioning, except when the TCDS defines other conditions that are used to determine the engine ratings.

b. The test data is then referenced to the standard atmosphere conditions for which the engine rating is defined.

2-2. General Requirements in §§ 33.85(a), 33.85(b), and 33.85(c).

a. The pre- and post-endurance calibration tests required by § 33.85, establish the engine’s power characteristics in the type design configuration over its entire operating range of speeds, pressures, and temperatures. These tests provide the means for measuring the engine deterioration caused by the endurance test.

b. To identify the changes in engine power characteristics that may occur during the engine endurance test of § 33.87, applicants must compare the engine’s power characteristics established before and after the endurance test, except as provided by § 33.85(d) for the 30­ second and 2-minute OEI ratings. This exception is further discussed in paragraph 2-3 of this AC.

c. Applicants should run the calibration tests with a clean inlet and exhaust, and without special test equipment, such as inlet screen, pre-swirler, mixer screen, or non-type design exhaust nozzles. In addition, the facility hardware must be similar to a production test cell (e.g., engine cowling, bell mouth, and normal engine control schedules). When special test equipment is necessary to obtain simultaneous redline conditions during the endurance test, applicants must address the engine configuration changes. See paragraph 3-1.c. and appendix 4 of this AC for further guidance. The power settings should include the highest power or thrust rating capability of the engine during the initial and final power calibrations. See paragraphs 3-4.a.(2)(a) and

(2)(b) of this AC for power or thrust setting adjustments and permitted power or thrust shortfalls.

d. The calibration test data should show that following completion of the endurance test, the engine is capable of producing its rated power or thrust without exceeding any speed, gas temperature, or operating limit(s) specified in the TCDS.

e. The applicant should record the calibration test measurements only after the engine operating condition stabilizes at each rating condition. The only exception is the recording of data at the 30-second and 2-minute OEI rating conditions described in § 33.85(d), during which the gas temperature need not be stabilized at the end of the rating time limit.

2-3. Provisions for 30-second and 2-minute OEI Ratings, § 33.85(d). The extended engine operation at the 30-second OEI and 2-minute OEI ratings during calibration testing could increase hardware deterioration beyond what the endurance test would demonstrate for the ratings alone. Therefore, the data recorded during the OEI power segments in § 33.87(f) may be used toward compliance with the calibration test requirements of these two ratings. However, the applicant should record this data during the first and last test cycle to properly represent the pretest and post-test performance capability of the engine. The following paragraphs in this section provide guidance on how the data from § 33.87 may be used to support compliance with § 33.85.

a. The applicant should determine the engine’s power characteristics at the 30-second and 2-minute OEI rating conditions. These power characteristics should include deterioration determined from the pretest calibration prior to the endurance test of § 33.87(f), up to and including the third test sequence of the 30-second rated power. The power deterioration through the third test sequence should be the best indicator of the worst-case power deterioration that could occur during actual usage at the rating. This data must be included in the installation manual to define performance characteristics of the engine.

b. If power deterioration exceeds 10 percent at the 30-second rating over the course of the 2-hour test in § 33.87(f), and even if the engine still produces rated power at the end of the test, the applicant should evaluate the mode of deterioration to ensure that the availability of 30­ second rated power in service will not be compromised by deterioration variability.

c. In addition to the calibration data from § 33.85(d), any available information from tests in §§ 33.88 and 33.90 should also be used to establish the engine characteristics throughout the engine operating envelope.

Chapter 3. Endurance Test

3-1. General Requirements in § 33.87(a).

a. The endurance test. The endurance test is not a simulation of expected in- service operation, but an accelerated severity test intended to demonstrate a minimum level of engine operability and durability within the approved engine ratings and operating limitations.

(1) The test requirements of §§ 33.87(b), (c), (d), (e), or (g) are to demonstrate that at the end of the test, the engine conforms to its type design and is safe for continued operation.

The requirement for § 33.87(f) is to demonstrate that at the end of the supplemental test, at a minimum, the structural integrity of the engine is maintained. This determination should be based on the inspection and maintenance requirements that are defined in the instructions for continued airworthiness (ICA) that will be submitted in compliance with § 33.4. To demonstrate this minimum level of durability and operability, the engine should:

(a) Continue to produce its rated power or thrust at the end of the test in §§ 33.87(b), (c), (d), (e), or (g) without exceeding any of the operating limitations defined by compliance with §§ 33.4, 33.5, and 33.7 and prescribed in the TCDS.

(b) Demonstrate acceptable operability from minimum to rated takeoff power or thrust without overtemperature, surge, stall, or other detrimental occurrences.

(c) Demonstrate durability while operating up to rated thrust, power, or torque;

redline and transient rotor speeds and gas temperatures; and when applying maximum rated loads on accessory drives and mounting attachments.

(d) Demonstrate the maximum compressor bleed air capability for engine and aircraft use. Paragraph 3-2.e. of this AC provides guidance for maximum compressor bleed air.

(e) Demonstrate acceptable operation at minimum and maximum fuel and hydraulic fluid pressure limit conditions. Advisory Circular 33.7-1 provides information and guidance on the fuel pressure limit locations.

(f) Demonstrate acceptable operation at the minimum and maximum lubrication oil pressure and temperature limit conditions.

(g) Demonstrate starting capability and drainage or expulsion of unwanted fluids or fuel that may accumulate after a false start.

(2) The test engine may also be used for other part 33 engine tests in conjunction with the endurance test runs. In addition, the data and results from the endurance test may also be used to show compliance to other part 33 regulations. These regulations may include:

(a) Engine ratings and operating limitations in § 33.7.

(b) Engine power and thrust settings in § 33.8(b).

(c) Suitability and durability of materials in § 33.15.

(d) Fluid drainage demonstration in § 33.17(f).

(e) Durability in § 33.19(a).

(f) Accessory attachments in § 33.25.

(g) Surge and stall characteristics in § 33.65.

(h) Bleed air systems in § 33.66 and bleed and power extraction in § 33.89.

(i) Ignition system function in § 33.69.

(j) Fuel system in § 33.67(a) and (b).

(k) Lubrication system, § 33.71(a) and (b).

(l) Hydraulic actuating systems, § 33.72.

(m) Power or thrust response, § 33.73, and acceleration time in § 33.89(a).

(n) Engine-propeller system tests for turbopropeller engines in § 33.95.

(o) Thrust reverser test in § 33.97.

(p) Fuel venting emissions in Subpart B of 14 CFR part 34.

(3) The general endurance test requirements specified in § 33.82, the calibration test in § 33.85, the endurance test in § 33.87, the teardown inspection in § 33.93, and the general conduct of block test requirements specified in § 33.99 form integral parts of the engine’s endurance testing. However, some systems or components may not be adequately substantiated by endurance testing alone under the requirements of § 33.87. For these systems or components, applicants should complete additional component level tests under the requirements defined in § 33.91 to establish that the systems, or components, can function reliably in all engine operating and atmospheric conditions that will be certificated. For example, to properly demonstrate its operability and durability characteristics, the main accessory gearbox must be tested at the maximum rated pad loads and power extraction loads that will be certified. If these extreme gearbox load conditions exceed the capability of the applicant’s endurance testing facilities, then the applicant may choose to complete an additional gearbox rig test at these maximum rating conditions.

(4) The endurance test must include at least 150 hours of testing in accordance with the series of test schedules specified in §§ 33.87(b), (c), (d), (e), and (g), depending upon the type 5