Systems and methods for testing with a back-to-back low speed dynamometer

Abstract

Embodiments of the present disclosure provide a dynamometer testing system for testing an engine. The dynamometer testing system may have a platform configured to support a first engine and a second engine mounted side by side so that a first axis of a first output shaft of the first engine is parallel to a second axis of a second output shaft of the second engine. The system may comprise a first torque driveline comprising a first joint configured to be connected to the first output shaft. The system may comprise a second torque driveline comprising a second joint configured to be connected to the second output shaft. The first and second joint may be configured to transfer torque between the respective output shaft and first torque driveline. A pulley system may be configured between the first torque driveline and the second torque driveline.

Description

Agent Ref. 16500-0006-00304SYSTEMS AND METHODS FOR TESTING WITH A BACK-TO-BACK LOW SPEED DYNAMOMETERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present disclosure claims the benefit of priority under the Paris Convention to U.S. Patent Application No. 63 / 640,049, filed April 29, 2024. The aforementioned application is incorporated herein by reference its entirety.TECHNICAL FIELD

[0002] This disclosure relates generally to the field of powered aerial vehicles. More particularly, and without limitation, the present disclosure relates to innovations in aircraft that use electrical propulsion systems. Certain aspects of the present disclosure generally relate to improvements in dynamometer testing systems that may be used in other types of vehicles but provide particular advantages in aerial vehicles.SUMMARY

[0003] Embodiments of the present disclosure provide a dynamometer testing system for testing an engine. The dynamometer testing system may have a platform configured to support a first engine and a second engine mounted side by side so that a first axis of a first output shaft of the first engine is parallel to a second axis of a second output shaft of the second engine. The system may comprise a first torque driveline comprising a first joint configured to be connected to the first output shaft. The first joint may be configured to transfer torque between the first output shaft and the first torque driveline. The system may comprise a second torque driveline comprising a second joint configured to be connected to the second output shaft. The second joint may be configured to transfer torque between the second output shaft and the second torque driveline. A pulley system may be configured between the first torque driveline and the second torque driveline.

[0004] Embodiments of the present disclosure provide a method for testing an engine. The method may comprise supporting a first engine and a second engine mounted side by side on a platform of a dynamometer testing system so that a first axis of a first output shaft of the first engine is parallel to a second axis of a second output shaft of the second engine. The method may comprise connecting a first torque driveline comprising a first joint to the first output shaft. The first joint may be configured to transfer torque between the first output shaft and the first torque driveline. The method may comprise connecting a second torque driveline comprising a second joint to the second output shaft. The first joint may be configured to transfer torque between the first output shaft and the first torque driveline. The first torqueAgent Ref. 16500-0006-00304 driveline and the second torque driveline may be coupled by a pulley system. The method may comprise operating the first engine as a test engine while operating the second engine to provide resistance to the first engine. The method may comprise performing a first measurement of the first engine.

[0005] Embodiments of the present disclosure provide a method for testing an engine using a dynamometer testing system of disclosed embodiments. The method may comprise operating the first engine as a test engine while operating the second engine to provide resistance to the first engine. The method may comprise performing a first measurement of the first engine.

[0006] Embodiments of the present disclosure provide a computer readable medium that stores a set of instructions that is executable by at least one processor to cause a dynamometer testing system to perform operations comprising a method. The method may comprise operating the first engine as a test engine while operating the second engine to provide resistance to the first engine. The method may comprise performing a first measurement of the first engine. In some embodiments, the computer readable medium may comprise a non- transitory computer readable medium.BRIEF DESCRIPTIONS OF FIGURE AND APPENDIX IMAGES

[0007] Fig. 1A schematically illustrates an example VTOL aircraft in a cruise configuration, consistent with some embodiments of the present disclosure.

[0008] Fig. IB schematically illustrates an example VTOL aircraft in a lift configuration, consistent with some embodiments of the present disclosure.

[0009] Figs. 2A-2D schematically illustrate an example back-to-back dynamometer testing system, consistent with some embodiments of the present disclosure.

[0010] Fig. 3A schematically illustrates an example torque driveline of a back-to-back dynamometer testing system, consistent with some embodiments of the present disclosure.

[0011] Fig. 3B schematically illustrates a cross-sectional view of the example torque driveline of Fig. 3A, consistent with some embodiments of the present disclosure.

[0012] Fig. 4A schematically illustrates an example tilter engine pallet system of a back-to- back dynamometer testing system, consistent with some embodiments of the present disclosure.

[0013] Fig. 4B schematically illustrates the tilter engine pallet system of Fig. 4A with the tilter engine rotated counterclockwise about the axis of the output shaft and mounted, consistent with some embodiments of the present disclosure.Agent Ref. 16500-0006-00304

[0014] Fig. 4C schematically illustrates the tilter engine pallet system of Fig. 4A with the tilter engine rotated clockwise about the axis of the output shaft and mounted, consistent with some embodiments of the present disclosure.

[0015] Fig. 5 schematically illustrates an example lifter engine pallet system of a back-to- back dynamometer testing system, consistent with some embodiments of the present disclosure.

[0016] Figs. 6A-6B schematically illustrate an example cooling system for a back-to-back dynamometer testing system, consistent with some embodiments of the present disclosure.

[0017] Fig. 7 is a flow diagram of a method of testing an engine, consistent with embodiments of the present disclosure.DETAILED DESCRIPTION

[0018] The present disclosure addresses components of a dynamometer testing system for engines such as, e.g., vertical takeoff and landing (VTOL) aircraft engines. For example, VTOL aircraft may be intended for frequent (e.g., over 50 flights per workday), short- duration flights (e.g., less than 100 miles per flight) over, into, and out of densely populated regions. Accordingly, components of the VTOL aircraft may be configured and designed to withstand frequent use without excessive wear, generate low heat and vibration, and the aircraft may include mechanisms to effectively control and manage heat or vibration generated by the components. Further, the components of the VTOL aircraft may be configured and designed to generate low levels of noise interior and exterior to the aircraft, and to have a variety of safety and backup mechanisms. These use requirements may place design constraints on aircraft size, weight, operating efficiency (e.g., drag, energy use), which may impact the design and configuration of the aircraft components. Given the focus on safety in passenger transportation, the disclosed embodiments implement new and improved systems for engine testing and qualification that may be implemented in a high-volume manufacturing (HVM) environment. The disclosed embodiments may be used for testing any type of engine in an HVM environment to improve the efficiency and cost-effectiveness of testing engines while better simulating real-world conditions to which the testing engines are expected be exposed.

[0019] Embodiments of the present disclosure provide dynamometer testing stand configurations that may be used to test multiple engines in parallel, with high throughput and a small footprint. For example, some embodiments of the present disclosure may comprise a dynamometer configured to test two engines of, e.g., a distributed electric propulsion system. A dynamometer is a testing device used to measure parameters of the engines, such as outputAgent Ref. 16500-0006-00304 torque or revolutions per minute (RPM), to evaluate their performance. Because a dynamometer according to embodiments of the present disclosure allows two engines to be loaded at once, the setup time required perform engine testing may be reduced and throughput may be increased. In this way, the efficiency and cost-effectiveness of testing engines may be improved. For example, the two engines may be mounted on a common testing stand with their output shafts oriented vertically and the engines arranged side-by- side. The output shafts of the two engines may be mechanically coupled to each other. In this way, the two engines may be alternately employed as a test engine (i.e., the engine under test) and a resistance engine so that, in succession, each may provide resistance to the other as a testing load. For example, in some embodiments a first engine may be used as a test engine to spin a dynamometer shaft while a second engine resists the spin of the dynamometer shaft. This resistance may affect the output torque of the test engine, which may be measured by a sensing system configured to test the first engine. The roles of the first and second engines may then be reversed, and the second engine may be tested in the same manner. This arrangement may be referred to as a back-to-back dynamometer configuration. In some embodiments, the dynamometer may be configured to replicate the real-world operating conditions of VTOL aircraft, such as by controlling, e.g., the temperature, speed, or tilt angle of the engine.

[0020] A dynamometer testing process may involve providing reverse torque to apply force to the engine being tested. For example, a resistance engine may provide a desired amount of resistance to the test engine by, e.g., operating a lower RPM than the test engine, while performance parameters of the test engine are measured. Then the roles of the two engines may be reversed as discussed above. Embodiments disclosed here may eliminate the need for a large external AC engine to operate the dynamometer, thereby lowering costs, decreasing the equipment footprint, and improving throughput.

[0021] In preferred embodiments, the back-to-back dynamometer may include a tilting mechanism configured to replicate flight conditions that are unique to VTOL aircraft, such as transitioning the aircraft from vertical flight to horizontal flight and vice-versa. For example, in some VTOL aircraft, such a transition may be accomplished via a tilt propeller subsystem configured to tilt the propeller and its engine over a range of angles with respect to the aircraft body. The tilt propeller subsystem may redirect thrust between a primarily vertical direction during vertical flight mode to a mostly horizontal direction during forward-flight mode (or horizontal flight mode). Thus, a flight profile may include a full rotation range of the tilt propeller with respect to the aircraft body, as well as an additional tilt range of theAgent Ref. 16500-0006-00304 entire aircraft with respect to gravity. For example, a tilt propeller may be configured to rotate with respect to a longitudinal axis of the aircraft body through a tilting range from, e.g., -10 to 110 degrees. Then, if the entire aircraft itself is designed to pitch up or down by, e.g., an additional + / - 30 degrees during flight, a full flight profile may cover a tilt range with respect to gravity of, e.g., -40 to 140 degrees. In operation, the tilt angle of the tilt propeller engine may affect internal dynamics such as oil flow within the engine or tension / compression vectors in various engine components.

[0022] Therefore, in some embodiments, the tilting mechanism of the dynamometer testing stand may be configured to tilt the engine under test through a full range of tilt angles to simulate a desired flight profile and analyze the engine under any desired tilt angle. For example, the dynamometer may tilt an engine under test from a vertical orientation, during a simulated vertical takeoff phase, to a horizontal orientation during a simulated forward flight phase. During these simulated phases, the test engine may be operated at speeds that it would see during real-world flight. Meanwhile, the resistance engine may provide the degree of resistance that the test engine would be expected to receive during each phase of flight. Thus, an entire flight sequence may be replicated accurately to ensure that the system’s behavior satisfies the requirements of in-flight conditions. In some embodiments, a tilting mechanism of a dynamometer testing stand, e.g., a tilt motor for tilting a platform on which a test engine resides, is configured to cover a range of tilt angles corresponding to or simulating a tilt range of the engine during operation a VTOL aircraft having the engine installed therein.

[0023] As described herein, the tilt angle, torque, RPM, temperature, and other characteristics of electric propulsion systems may vary over a wide range during operation of the aircraft. It is understood that an electrical engine may generate heat during operation and may comprise a heat management system to ensure components of the electrical engine do not fail during operation. In some embodiments, a coolant may be used and circulated throughout some or all components of the engine, such as an inverter, gearbox, or motor to assist with managing the heat generated in the engine. Additional embodiments may include using air cooling methods to cool the electrical engine or may use a mixture of coolant and air to manage the heat generated during operation of the electrical engine. In some embodiments, the coolant being used may be the same liquid that is being used as lubricant throughout the inverter, gearbox, or motor. For example, the inverter, gearbox, and motor may be cooled using a liquid or air. Alternatively, a mixture of air and liquid cooling may be employed. For example, the motor may be cooled using air cooling and the inverter and gearbox may beAgent Ref. 16500-0006-00304 cooled using liquid cooling. Any other combination of air and liquid cooling may be used to cool the inverter, gearbox, and motor or subsets of those components.

[0024] In some embodiments, oil may be used as a lubricant throughout an electrical engine and may also be used as a coolant fluid to assist in managing the heat generated by the engine during operation. As has been disclosed herein, an electrical engine may have different primary functionalities such as being used only for vertical takeoff, hover and landing, and as such only being used in one orientation, or being used during all stages of flight such as vertical takeoff, hover, landing and forward horizontal flight. An engine that is used in all stages of flight may experience various orientations throughout the flight and may comprise more lubricant and coolant than an engine only used in one orientation. As such, all the engines on an aircraft may not include the same amount of lubricant and coolant. For example, a lifting and landing engine may require less than one quart of oil while an engine that operates in all stages of flight may require more than one quart of oil.

[0025] It is understood that by using oil to not only lubricate the electrical engine but also cool the electrical engine rather than another coolant, additional oil will be added to the system, but that such use of oil will obviate the need for traditional components that may be used to cool such an electrical engine. For example, if the electrical engine were cooled by another liquid such as glycol, the engine may comprise separate heat exchangers for both the lubricant fluid and the coolant fluid. As such, in embodiments where a single fluid, such as oil, is being used for both lubrication and cooling, the amount of oil in the engine may be larger than the amount of oil in an engine using both glycol and oil. However, by using a single fluid, only one heat exchanger may be needed to cool the oil, which in turn may help decrease a total weight of the engine. Reduction in the number of heat exchangers may also potentially obviate the need of a number of other components, which in turn may reduce the cross-sectional size of the engine in the direction of flight to reduce drag.

[0026] Disclosed embodiments may reduce the footprint in a factory for testing during HVM, improve the efficiency of such testing, and provide means for testing variables related to operation of engines such as VTOLs. Such testing may include performance and durability testing of components associated with engines according to the disclosed embodiments, or testing of engine temperature or efficiency during changes in orientation such as, in the case of an aircraft, roll, pitch, or yaw which may affect flow of cooling air or oil. The disclosed embodiments may be useful for testing any type of engine, but an exemplary use is in electric engines in which changes in orientation are likely to occur during operation, such as in eVTOLs.Agent Ref. 16500-0006-00304

[0027] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The following descriptions of exemplary embodiments do not represent all implementations consistent with the disclosure. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the subject matter recited in the appended claims.

[0028] Figs. 1A-1B illustrate a VTOL aircraft 100 in a cruise configuration and a vertical take-off, landing, and hover configuration (also referred to herein as a “lift” configuration), respectively, consistent with embodiments of the present disclosure. The aircraft 100 may include fuselage 102, wings 104 mounted to fuselage 102, tail 105, and one or more rear stabilizers 106 mounted to tail 105 or the rear of fuselage 102. A plurality of lift propellers 112 may be mounted to wings 104 and configured to provide lift for vertical take-off, landing, and hover operations of aircraft 100. A plurality of tilt propellers 114 may be mounted to wings 104 and may be tiltable between a cruise configuration in which they provide forward thrust to aircraft 100 for horizontal flight, as shown in Fig. 1A, and the lift configuration in which they provide a portion of the lift required for vertical take-off, landing, and hovering, as shown in Fig. IB. As used herein, a lift configuration may refer to a tilt propeller orientation in which the tilt propeller thrust is providing primarily vertical thrust to the aircraft. A cruise configuration may refer to a tilt propeller orientation in which the tilt propeller thrust is providing primarily horizontal thrust to the aircraft. Alternatively, a cruise configuration may refer to a configuration in which a lift propeller is stowed.

[0029] In some embodiments, lift propellers 112 may be configured for providing lift only, with all propulsion being provided by the tilt propellers. Accordingly, lift propellers 112 may be in fixed positions and may only generate thrust during take-off, landing and hover. Meanwhile, tilt propellers 114 may be tilted to lift configurations in which their thrust is directed vertically for providing additional lift.

[0030] Lift propellers 112 may each have two blades 120 that may be locked for cruising (e.g., horizontal or forward flight) in minimum drag positions in which one blade is directly in front of the other blade as illustrated in Fig. 1A. In some embodiments, lift propellers 112 have more than two blades. In some embodiments, tilt propellers 114 include more blades 118 than lift propellers 112. For example, as illustrated in Figs. 1A-1B, lift propellers 112 may each include, e.g., two blades and tilt propellers 114 may each include, e.g., five blades. In some embodiments, tilt propellers 114 may have, e.g., from 2 to 5 blades.Agent Ref. 16500-0006-00304

[0031] In some embodiments, the aircraft may include only one wing 104 on each side of fuselage 102 (or a single wing that extends across the entire aircraft) and at least a portion of lift propellers 112 may be located rearward of wings 104 and at least a portion of tilt propellers 114 may be located forward of wings 104. In some embodiments, all of lift propellers 112 may be located rearward of wings 104 and all of tilt propellers 114 may be located forward of wings 104. According to some embodiments, all lift propellers 112 and tilt propellers 114 may be mounted to the wings — i.e., no lift propellers or tilt propellers may be mounted to the fuselage. In some embodiments, lift propellers 112 may be all located rearwardly of wings 104 and tilt propellers 114 may be all located forward of wings 104. According to some embodiments, all lift propellers 112 and tilt propellers 114 may be positioned inwardly of the wing tips 109.

[0032] In some embodiments, lift propellers 112 and tilt propellers 114 may be mounted to wings 104 by booms 122. Booms 122 may be mounted beneath wings 104, on top of the wings, and / or may be integrated into the wing profile. In some embodiments, one lift propeller 112 and one tilt propeller 114 may be mounted to each boom 122. Lift propeller 112 may be mounted at a rear end of boom 122 and tilt propeller 114 may be mounted at a front end of boom 122. In some embodiments, lift propeller 112 may be mounted in a fixed position on boom 122. In some embodiments, tilt propeller 114 may be mounted to a front end of boom 122 via a hinge. Tilt propeller 114 may be mounted to boom 122 such that tilt propeller 114 is aligned with the body of boom 122 when in the cruise configuration, forming a continuous extension of the front end of boom 122 that minimizes drag for forward flight.

[0033] According to some embodiments, the at least one wing 104 is a high wing mounted to an upper side of fuselage 102. According to some embodiments, the wings include control surfaces, such as flaps, ailerons or flaperons. According to some embodiments, the wings may have curved wing tips 109 for reduced drag during forward flight. The wing(s) may have any suitable design. For example, the wings have a tapering leading edge or a tapering trailing edge. In some embodiments, the wings may have a substantially straight leading edge in the central section of wings 104. In some embodiments, rear stabilizers 106 include control surfaces, such as one or more rudders, one or more elevators, and / or one or more combined rudder-elevators.

[0034] Aircraft 100 may include at least one door 110 for passenger entry and exit. In some embodiments, door 110 may be located beneath and forward of wings 104 as seen in Figs. 1A-1B.Agent Ref. 16500-0006-00304

[0035] Further discussion of VTOL aircraft may be found in U.S. Patent Publication No. 2021 / 0362849, which is incorporated by reference in its entirety.

[0036] Figs. 2A-2D schematically illustrate an example back-to-back dynamometer testing system 230 for testing engines 231, such as first engine 231a and second engine 23 lb, consistent with some embodiments of the present disclosure. For example, as seen in Fig. 2A, engines 231 may comprise electrical propeller engines for a distributed electric propulsion aircraft, such as VTOL aircraft 100 of Figs. 1A-1B. Testing system 230 may comprise external aluminum extruded cage 233 with front access door 234 for protecting operators from potential hazards during operation. Platform 235 may be configured to support a plurality of engines 231 via quick-change pallet system 236 such that they are mounted side- by-side. Engines 231 may be mounted in various orientations along various axes. For example, a first axis of a first output shaft of first engine 231a may be parallel to a second axis of a second output shaft of second engine 231b. In some embodiments, platform 235 may be tiltable relative to stand 232 about a horizontal (third) axis that is perpendicular to the first axis and the second axis via one or more tilt motors 250. For example, tilt motor 250 may comprise any rotary, linear, or other actuator configured to tilt platform 235 about one or more axes. For example, platform 235 may further be rotatable about a fourth axis that is perpendicular to the first, second, and third axes.

[0037] The output shafts of engines 231 may be coupled to each other by torque drivelines 237 (one such torque driveline 237 being illustrated by cutaway of protective shroud 247) connected to shaft flange 242 of each engine 231 at shaft flange adapter 241. Torque drivelines 237 may in turn be coupled to each other by, e.g., pulley system 238. As further discussed below, torque drivelines 237 may comprise various components configured to transfer torque between first and second engines 23 la-b while allowing shaking, vibration, or other movement of engines 231 within axial and radial degrees of freedom with respect to torque drivelines 237. Each torque driveline 237 may be covered in protective shroud 247. Pulley system 238 may couple torque drivelines 237 such that first engine 231a and second engine 23 lb are configured to rotate in the same direction simultaneously during a testing sequence. Pulley system 238 may include a gear system such as a one-to-one gear drive, a belt and pulley, actuators, hydraulics, fixed pulley, movable pulley, or compound pulley. In contrast, for example, a conventional back-to-back arrangement may be achieved by laying two engines on their sides and coupling their respective shaft flanges directly to each other. However, this arrangement would result in one of the two engines turning in reverse compared to its designed direction of rotation. The upright back-to-back arrangementAgent Ref. 16500-0006-00304 according to embodiments of the present disclosure allows both engines to be rotated in their designed direction while alternately using one of the two engines as a test engine and the other of the two engines as a resistance engine. For example, in a first portion of the testing sequence, first engine 231a may be driven as a test engine while second engine 23 lb provides back torque. The back torque provided by second engine 23 lb may be transferred through torque drivelines 237 and pulley system 238 to resist first engine 231a while the first engine is monitored by various sensors such as, e.g., torque or speed transducers, infrared temperature sensors, engine-mounted accelerometers, or high or low voltage current sensors. For example, torque or speed transducers or other sensing systems may be coupled in-line with torque drivelines 237. In a second portion of the testing sequence, the roles may be reversed by simply alternating control of the engines without requiring any manual adjustments by an operator. The upright back-to-back arrangement allows rapid switching between the first and second portions of the testing sequence and eliminates the time required to unload one test engine and load another. Thus the back-to-back arrangement may save time to enable high throughput testing of engines in a high-volume manufacturing environment.

[0038] Back-to-back dynamometer testing system 230 may comprise controller 260 configured to control various elements of the testing system such as, e.g., actuators, sensors, thermal and other environmental controls, etc., to perform the operations disclosed herein. For example, controller 260 may comprise one or more processors and memory storing instructions that, when executed by the one or more processors, perform processes disclosed herein, in part or in their entirety. The processor may include one or more processors and may perform handling of any controlled testing system associated with controller 260. The processor may include various types of processing devices. For example, the processor may include one or more of microprocessors, preprocessors, a central processing unit (CPU), support circuits, digital signal processors, integrated circuits, memory, or any other types of devices suitable for running applications. A memory may receive data and / or instructions from the processor. The memory may include one or more of random-access memory (RAM), read-only memory (ROM), flash memory, disk drives, optical storage, tape storage, removable storage, and / or any other types of storage.

[0039] Further, as seen in Figs. 2B-2D, in some embodiments, platform 235 may be tiltable by, e.g., tilt motor 250 to simulate various flight modes of a VTOL or other aircraft. For example, the x-direction shown in Fig. 2B may correspond to a horizontal flight direction, and the y-direction may correspond to a vertical direction. Tilting engines 231 as shown inAgent Ref. 16500-0006-00304Fig. 2B may simulate the gravitational characteristics of, e.g., a lift configuration in which a tilt propeller is oriented at, e.g., 110 degrees from the +x-direction. Under these conditions, the engine performance may be tested under conditions that replicate the real-world internal dynamics of engine 231 under test, such as oil flow characteristics or stress / strain distribution. Similarly, as seen in Fig. 2C, engines 231 may be tilted sideways to simulate a cruise configuration, a dive orientation, etc. As shown in Fig. 2D, in some embodiments the engines may be arranged at a directly vertical orientation, such as to simulate another lift configuration, to simulate the orientation of a lift propeller, to isolate the engine characteristics from tilt effects, or for any desired reason. In some embodiments, platform 235 may be tilted over a range of, e.g., tilt range of -40 to 140 degrees relative to the +x- direction, or any desired range. For example, as used herein, any angle (e.g., tilt angle) may be made with respect to a reference axis that is fixed with respect to a stationary part or surface of the dynamometer system or platform.

[0040] By controlling a tilt angle of platform 235 along with other parameters such as engine speed or temperature of the test engine, or a load applied by the resistance engine, the dynamometer may be capable of replicating the conditions that the test engine may experience during a desired flight mode. Different tilt angles may be used during a test to simulate a full flight operation. For example, a test operation may begin with the engine shafts pointing in the +y-direction while ramping up the test engine RPM to simulate a takeoff operation. This may be followed by a tilt of platform 235 to point in, e.g., the +x- direction to simulate the transition to forward flight, followed by a corresponding transition back to vertical to simulate a landing. In some embodiments, the specific resistance load that is applied by a test engine may account for simulated wind, weather, or other flight conditions. In some embodiments, a flight mode may comprise a failure scenario such as “motor out,” in which an aircraft experiences a failure of at least one engine such that the other engines must be used to compensate. In this case, for example, the test engine RPM or other characteristics may be pushed beyond what is expected during normal operation to simulate the failure mode operations or conditions.

[0041] Fig. 3A schematically illustrates torque driveline 337 of a back-to-back dynamometer testing system, consistent with some embodiments of the present disclosure. Fig. 3B schematically illustrates a cross-section of torque driveline 337 of Fig. 3A along cutline A- A’ . Torque driveline 337 may correspond to, e.g., torque drivelines 237 of Figs. 2A-2D. Shaft flange adapter 341 may be coupled to a shaft flange (not pictured) of an engine, such as first or second engines 231a-b of Fig. 2A. In some embodiments, shaft flange adapter 341Agent Ref. 16500-0006-00304 may be coupled to further components of torque driveline 337 and pulley system 338, such sensors 347 and brake 349, by joint 346. For example joint 346 may be a universal joint or similar joint capable of transferring torque between the engine and torque driveline 337 while isolating, minimizing, reducing, or dampening the effects of misalignment or vibrations in the system. Joint 346 may include a universal joint, universal coupling, knuckle joint, Oldham coupling, slip yoke drive shaft, etc.

[0042] In some embodiments, brake 349 may function as a safety feature to stop the engine as soon as possible if an error occurs. In some embodiments, brake 349 may be configured as a testing element to simulate an engine seizing event. For example, brake 349 may abruptly halt the spinning shaft to test, e.g., the shear strength of engine components.

[0043] Joint 346 may comprise any coupling that is configured to allow relative motion between shaft flange adapter 341 and the further components of the dynamometer testing system (such as sensors 347, pulley system 338, and brake 349) along axial and radial directions of torque driveline 337, while transmitting torque about the axial direction. For example, in a VTOL aircraft, the electric engines may be mounted in a floating manner that allows them to shake along at least one degree of freedom. Joint 346 may be used to isolate vibrations in the engine’s torque driveline to allow this same type of movement during testing, thus allowing the engines to be tested under conditions that resemble the dynamics they experience in actual flight. In some cases, joint 346 may have the effect of reducing, dampening, or minimizing transfer of the effect of misalignment, vibrations or other motions through torque driveline 337. For examplejoint 346 may be configured to allow relative movement between components of the torque driveline and an engine under test, in directions perpendicular to a rotation axis of torque driveline 337. Despite such misalignment or relative motionjoint 346 may continue to transfer the torque between the engine, the output shaft, torque driveline 337, and pulley system 338. The degrees of freedom allowed by joint 346 may have the effect of reducing the vibrations transferred along torque driveline 337. For example, these vibrations may originate from an engine or other part of the testing apparatus. For example Joints such as joint 346 may be commonly used in aircrafts to prevent damaging effects of vibrations from traveling through the aircraft. The effects of joint 346 on transferring the effects of misalignment or vibrations to other parts may be tested by the disclosed embodiments. One or more sensors 347, such as torque or speed transducers, may be coupled in-line with torque driveline 337 to measure, e.g., the torque or RPM of the engines.Agent Ref. 16500-0006-00304

[0044] Fig. 4A schematically illustrates an example pallet 436 for engine 431, consistent with some embodiments of the present disclosure. Figs. 4B-4C illustrate pallet 436 and engine 431 with engine 431 rotated in different configurations for testing. Pallet 436 may be configured to mount a specific engine design onto a table or platform (such as platform 235 in Fig. 2A). For example, pallet 436 may be configured to simulate the mounting condition of a tilter engine in back-to-back dynamometer testing system. For example, pallet 436 may be designed to mount a tilter engine of VTOL aircraft 100 of Figs. 1A-1B in a back-to-back dynamometer testing system using the same mounting designs and mounting locations that are used on the actual VTOL aircraft. For example, as seen in Fig. 4A, engine 431 may be mounted to pallet 436 at a bottom surface of engine 431 in the same way that it would be mounted to a mounting frame (not shown) in VTOL aircraft 100. Pallet 436 may comprise, e.g., drop-in ball locks 440 configured to slide into guides or slots (not shown) in a table or platform, such as platform 235 of Figs. 2A-D. This may allow rapid changeover of one pallet-mounted engine for another. By providing removeable pallets, a quick-change system may be achieved which reduces downtime of a back-to-back dynamometer testing system. Pallet 436 may be configured to be integrated with multiple cooling systems of a dynamometer testing stand. For example, as further discussed below, pallet 436 may allow coolant line connections into oil sump 443 or other portion of an internal oil or coolant system of engine 431. Further, pallet 436 may allow air duct connections, such as air outlet duct connection 445 at an outlet side of air-coolant heat exchanger 444 of engine 431.

[0045] Performance of tilt engines such as engine 431 may be affected by orientation of the tilt engine about multiple axes. For example, during flight, tilt engines may experience roll, pitch, and yaw of the aircraft. In a back-to-back dynamometer testing system such as that shown in Figs. 2A-2D, the flow of cooling oil at various angles may be tested by mounting engine 431 in pallet 436 in different orientations with respect to the output shaft axis. For example, by configuring engine 431 in different orientations about the output shaft axis AX, the effects on aircraft engine performance of aircraft motions in multiple axes, such as roll in combination with tilt, may be tested. For example, in Fig. 4A, engine 431 may be mounted at a nominal orientation of 9 = 0 degrees about the output shaft axis AX. For example, an angle of 0 degrees may correspond to the front (as viewed in a lift configuration) or bottom (as viewed in cruise configuration) of engine 431 being aligned with the rotational plane x-y of platform 235 as seen in Figs. 2B-2D.

[0046] Fig. 4B schematically illustrates the tilter engine pallet system of Fig. 4A with engine 431 rotated counterclockwise about the output shaft axis AX, as viewed from above (forAgent Ref. 16500-0006-00304 example, by approximately +20 degrees) and mounted. For example, pallet 436 may be configured with any mounting structure such as multiple mounting holes, brackets, or other structures to allow engine 431 to be mounted as various angles 9 about the output shaft axis AX. Alternatively or additionally, pallet 431 may comprise multiple exchangeable mounting surfaces. In some embodiments, the mounting surface of pallet 431 may be configured as rotatable. For example, the mounting surface may be manually adjustable or may comprise one or more actuators configured to rotate engine 431 about the output shaft axis AX. Providing actuators in pallet 431 allows the engine orientation to be changed without removing the engine or pallets from the testing system, thus improving throughput by reducing downtime between different testing phases. Further, they add additional degrees of freedom to a test recipe by allowing the engine orientation to be changed in real time during the test itself.

[0047] Fig. 4C schematically illustrates the tilter engine pallet system of Fig. 4A with engine 431 rotated clockwise about the output shaft axis AX (by approximately -20 degrees) and mounted, consistent with some embodiments of the present disclosure. While Figs. 4B and 4C illustrate the engine being rotated by + / - 20 degrees, these are only examples and embodiments of the present disclosure are not limited to this. In some embodiments, the pallet may be configured to mount engine 431 at other angles such as, e.g., 5, 10, 15, 25, or 30 degrees, etc. Furthermore, in some embodiments the pallets may be configured to mount engine 431 at multiple discrete orientations or over a continuous range of orientations. Furthermore, in some embodiments, rotation about multiple axes may be achieved by actuating pallet 436 or by mounting pallet 436 in a tilted orientation with respect to, e.g., platform 235 of Figs. 2A-D. For example, pallet 436 may be actuated to move engine 431 from one orientation to another orientation during testing. Alternatively or additionally, platform 235 itself may be configured to tilt about multiple axes using the one or more tilt motors 250.

[0048] Fig. 5 illustrates a further pallet 536 for electrical engine 531, consistent with some embodiments of the present disclosure. For example, pallet 536 may be designed to mount a lifter engine of VTOL aircraft 100 of Figs. 1A-1B in a back-to-back dynamometer testing system in similar manner to pallet 436 of Figs. 4A-4C. For example, pallet 536 may comprise lifter mounts 550 which replicate the mounts found on VTOL aircraft 100. Pallet 536 may comprise, e.g., drop-in ball locks 540 configured to slide into guides or slots (not shown) in a table or platform, such as platform 235 of Figs. 2A-2D. Pallet 536 may be configured to allow air duct connections, such as air outlet duct connection 545, to an air-coolant heatAgent Ref. 16500-0006-00304 exchanger 544. The various connections and ball locks 540 of pallet 536 may be designed to be compatible with pallet 436 of Figs. 4A-4C so that they may both be mounted to a same table or platform, such as platform 235 of Figs. 2A-2D. In this way, a single testing stand may be configured to test multiple different engine designs with a simple quick-change system.

[0049] In some embodiments, pallet 536 may be configured to mount electrical engine 531 at multiple orientations in similar manner as discussed above. In this way, electrical engine 531 may be tested in a manner similar to that discussed above with respect to Figs. 4A-4C. For example, electrical engine 531 may be rotated about the axis of the output shaft and mounted in pallet 536. In some embodiments, pallet 536 may comprise lifter mounts 550 for each orientation. For example, lifter mounts 550 may comprise multiple mounting positions, they may be adjustable or exchangeable to accommodate multiple mounting positions.

[0050] Figs. 6A-6B schematically illustrate example cooling system 600 for use with a back- to-back dynamometer testing system, consistent with some embodiments of the present disclosure. During engine testing, it may be desirable to test the engines under multiple thermal scenarios. For example, a first thermal scenario may comprise cooling the engine by channeling an air flow through heat exchangers of the engines (such as heat exchanger 544 of engine 531). The first thermal scenario may be designed to cool the engine in the same way that it is cooled during an actual flight. A second thermal scenario may instead comprise cooling the engine with a temperature-controlled liquid coolant in thermal contact with an oil flow path in the engine. The second thermal scenario may be designed to provide maximum control over thermal characteristics in order to, e.g., replicate a desired thermal condition or simply remove engine overheating or other thermal phenomena as a variable during testing.

[0051] For example, during real-world operation, an engine of, e.g., VTOL aircraft 100 of Figs. 1A-1B may be cooled by circulating oil or another coolant liquid through an air-coolant heat exchanger, such as air-coolant heat exchanger 444 of Figs. 4A-4C or 544 of Fig. 5. Therefore, a first mode of the dual-mode thermal control system, schematically illustrated in Fig. 6A, may be designed to control the temperature of the oil by motor oil cooling system circuit 600. For example, motor oil cooling system circuit 600 may comprise a chiller configured to circulate a further external temperature-controlled coolant, such as glycol, into thermal contact with the oil of the engines mounted in the dynamometer testing system. For example, in some embodiments, an air-coolant heat exchanger as seen in Figs. 4A-4C and 5 may be replaced for testing purposes with, e.g., a plate heat exchanger as seen in Fig. 6. The plate heat exchangers may be formed of a highly thermally conductive material and mayAgent Ref. 16500-0006-00304 comprise, e.g., a first channel for engine oil and a second channel for the coolant. By flowing the engine oil and coolant in proximity to each other through the thermally conductive material, heat may be exchanged between them to thermally couple the glycol to the motor oil. Flow and temperature of the coolant may be monitored by, e.g., clamp-on flow sensors and temperature sensors. By controlling the temperature of the coolant in cooling system circuit 600, the temperature characteristics of the engines may be precisely controlled in order to achieve a highly controlled testing environment.

[0052] However, it may also be desirable to monitor the engines under real-world temperature conditions. Therefore, a second mode of the dual-mode thermal control system, schematically illustrated in Fig. 6B, may be designed to control the temperature of the oil by air-cooling system circuit 601. For example, air cooling system circuit 601 may comprise a plurality of fans coupled to the engine heat exchangers by a duct system. The duct system and fans may configured to circulate air to and from an external environment, such as the room in which the dynamometer testing system is located, or to a further air chiller or other temperature control device. The fan speed and flow rate may be adjusted to simulate the propeller speed, environmental conditions, etc. By circulating an air flow through the heat exchangers, it may be possible to monitor the engines under the thermal conditions that would be expected during real-world flight.

[0053] Fig. 7 shows diagrammatically dynamometer testing method 700 for testing a first engine and a second engine, consistent with embodiments of the present disclosure. Method 700 includes step 702 of supporting a first engine and a second engine (such as first and second engine 231a and 23 lb of Figs. 2A-D) mounted side by side on a table or platform of a dynamometer testing system (such as dynamometer testing system 230 of Figs. 2A-D) so that a first axis of a first output shaft of the first engine is parallel to a second axis of a second output shaft of the second engine. Method 700 includes step 704 of connecting a first torque driveline comprising a first joint to the first output shaft and connecting a second torque driveline comprising a second joint to the second output shaft, wherein the first driveline and the second driveline are coupled by a pulley system. The first joint or the second joint may be configured to transfer torque between an output shaft and a respective torque driveline.Method 700 includes step 706 of operating the first engine as a test engine while operating the second engine to provide resistance to the first engine. Method 700 includes step 708 of performing a first measurement of the first engine. In some embodiments, method 700 further includes a step 710 of operating the second engine as a test engine while operating the first engine to provide resistance to the second engine, and a step 712 of performing a secondAgent Ref. 16500-0006-00304 measurement of the second engine. For example, operation of the dynamometer testing system may be reversed depending on which engine or components are to be tested.

[0054] A computer-readable medium, for example a non-transitory computer-readable medium, may be provided that stores instructions for one or more processors of a controller (such as, e.g., controller 260 of Fig. 2A) for performing methods according to embodiments of the present disclosure. For example, the instructions stored in the non-transitory computer- readable medium may be executed by the circuitry of the controller for performing any of the above disclosed processes in part or in entirety. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, hard disk, solid-state drive, magnetic tape, or any other magnetic data storage medium, a Compact Disc Read-Only Memory (CD- ROM), any other optical data storage medium, any physical medium with patterns of holes, a Random Access Memory (RAM), a Programmable Read-Only Memory (PROM), and Erasable Programmable Read-Only Memory (EPROM), a FLASH-EPROM or any other flash memory, Non-Volatile Random Access Memory (NVRAM), a cache, a register, any other memory chip or cartridge, and networked versions of the same. The one or more processors can include any combination of any number of a central processing unit (CPU), a graphics processing unit (GPU), a neural processing unit (NPU), a microcontroller unit (MCU), an optical processor, a programmable logic controller, a microcontroller, a microprocessor, a digital signal processor, an intellectual property (IP) core, a Programmable Logic Array (PLA), a Programmable Array Logic (PAL), a Generic Array Logic (GAL), a Complex Programmable Logic Device (CPLD), a Field-Programmable Gate Array (FPGA), a System On Chip (SoC), an Application-Specific Integrated Circuit (ASIC), or the like. In some embodiments, the one or more processors can also be a set of processors grouped as a single logical component.

[0055] Embodiments of the present disclosure may further be described by the following clauses:1. A dynamometer testing system for an engine, the system comprising: a platform configured to support a first engine and a second engine mounted side by side so that a first axis of a first output shaft of the first engine is parallel to a second axis of a second output shaft of the second engine; a first torque driveline comprising a first joint configured to be connected to the first output shaft, the first joint configured to transfer torque between the first output shaft and the first torque driveline;Agent Ref. 16500-0006-00304 a second torque driveline comprising a second joint configured to be connected to the second output shaft, the second joint configured to transfer torque between the second output shaft and the second torque driveline; and a pulley system between the first torque driveline and the second torque driveline.2. The system of clause 1, further comprising an engine cooling system configured to circulate coolant fluid to the first engine or the second engine.3. The system of clause 2, wherein the coolant fluid comprises motor oil of the first engine or the second engine.4. The system of any of clauses 1 to 3, further comprising a first pallet configured to support the first engine on the platform.5. The system of clause 4, wherein at least one of the platform and the first pallet comprises a vibration isolation fixture configured to isolate vibrations of the first engine from the platform.6. The system of clause 4 or 5, wherein the first pallet is configured to mount the first engine at a plurality of orientations about the first axis.7. The system of any of clauses 4 to 6, wherein the first pallet comprises an adjustable mounting surface configured to rotate the first engine about the first axis.8. The system of clause 7, wherein the first pallet comprises an actuator configured to rotate the adjustable mounting surface about the first axis.9. The system of any of clauses 4 to 8, further comprising a second pallet configured to support the second engine on the platform.10. The system of any of clauses 1 to 9, wherein the first or second torque driveline further comprises a brake configured to stop rotation of the first or second torque driveline.11. The system of any of clauses 1 to 10, wherein the platform comprises a first tilt motor configured to tilt the platform about a third axis that is oriented perpendicular to the first axis.12. The system of clause 11, wherein the first tilt motor is configured to tilt the platform over a range of tilt angles corresponding to or simulating a tilt range of the first engine or the second engine, the tilt range being a tilt range of the first engine and / or the second engine during operation of a VTOL aircraft having the first engine and / or the second engine respectively installed therein.13. The system of clause 11 or 12, wherein the first tilt motor is configured to tilt the platform over a range from at least -10 degrees to at least 100 degrees with respect to a reference axis that is fixed with respect to a stationary surface of the platform.Agent Ref. 16500-0006-0030414. The system of any of clauses 11 to 13, wherein the platform comprises a second tilt motor configured to tilt the platform about a fourth axis that is oriented perpendicular to both the first axis and the third axis.15. The system of any of clauses 1 to 14, further comprising an external protective housing configured to enclose the platform for safety.16. The system of any of clauses 1 to 15, further comprising a first sensor configured to measure a first parameter of the first engine.17. The system of clause 16, wherein the first sensor is comprised in the first torque driveline.18. The system of clause 16 or 17, wherein the first sensor comprises a torque transducer, a speed transducer, a temperature sensor, an accelerometer, or a current sensor.19. The system of any of clauses 16 to 18, further comprising a second sensor configured to measure a second parameter of the second engine.20. The system of clause 19, wherein the second sensor is comprised in the second torque driveline.21. The system of clause 19 or 20, wherein the second sensor comprises a torque transducer, a speed transducer, a temperature sensor, an accelerometer, or a current sensor.22. The system of any preceding clause, wherein the first joint and / or the second joint is further configured to dampen and / or isolate misalignment and / or vibration in a direction perpendicular to the first axis or the second axis.23. The system of clause 22, wherein one of the first joint or the second joint comprise a universal joint.24. The system of any preceding clause, wherein the first engine or the second engine comprises an electric engine.25. The system of any preceding clause, wherein the first engine or the second engine comprises an aircraft engine.26. The system of any preceding clause, wherein the first engine or the second engine comprises a vertical takeoff and landing (VTOL) aircraft engine.27. The system of any preceding clause, wherein the first engine or the second engine comprises an automobile engine.28. A method for testing an engine, the method comprising: supporting a first engine and a second engine mounted side by side on a platform of a dynamometer testing system so that a first axis of a first output shaft of the first engine is parallel to a second axis of a second output shaft of the second engine;Agent Ref. 16500-0006-00304 connecting a first torque driveline comprising a first joint to the first output shaft, the first joint configured to transfer torque between the first output shaft and the first torque driveline; connecting a second torque driveline comprising a second joint to the second output shaft, the first joint configured to transfer torque between the first output shaft and the first torque driveline, wherein the first torque driveline and the second torque driveline are coupled by a pulley system; operating the first engine as a test engine while operating the second engine to provide resistance to the first engine; and performing a first measurement of the first engine.29. The method of clause 28, wherein performing the first measurement comprises performing a measurement with a torque transducer, a speed transducer, a temperature sensor, an accelerometer, or a current sensor.30. The method of clause 28 or 29, further comprising circulating, by an engine cooling system, coolant fluid to the first engine or the second engine.31. The method of clause 30, wherein the wherein the coolant fluid comprises motor oil of the first engine or the second engine.32. The method of any of clauses 28 to 31, further comprising isolating vibrations of the first engine from the platform via a vibration isolation fixture on at least one of the first pallet or the platform.33. The method of any of clauses 28 to 32, further comprising: changing an orientation of the first engine about the first axis from a first orientation to a second orientation; and performing a second measurement of the first engine.34. The method of clause 33, wherein changing the orientation of the first engine about the first axis comprises mounting the first engine in the second orientation.35. The method of clause 33, wherein changing the orientation of the first engine about the first axis comprises adjusting an orientation of a mounting surface of the first engine.36. The method of clause 33 or 35, wherein changing the orientation of the first engine about the first axis comprises actuating movement of the first engine from the first orientation to the second orientation.37. The method of any of clauses 28 to 36, further comprising braking the first engine.38. The method of any of clauses 28 to 37, further comprising tilting the platform, via a first tilt motor, about a third axis that is perpendicular to the first axis.Agent Ref. 16500-0006-0030439. The method of clause 38, wherein tilting the platform about the third axis comprises tilting the platform over a range of tilt angles corresponding to a tilt range corresponding to or simulating a tilt range of the first engine and / or the second engine during operation of a VTOL aircraft having the first engine and / or the second engine respectively installed therein.40. The method of clause 38 or 40, wherein tilting the platform about the third axis comprises tilting the platform over a range from at least -10 degrees to at least 100 degrees with respect to a reference axis that is fixed with respect to a stationary part of the dynamometer testing system.41. The method of any of clauses 38 to 40, further comprising tilting the platform, via a second tilt motor, about a fourth axis that is oriented perpendicular to both the first axis and the second axis.42. A method for testing an engine using the dynamometer testing system of any of clauses 1 to 27, the method comprising: operating the first engine as a test engine while operating the second engine to provide resistance to the first engine; and performing a first measurement of the first engine.43. The method of clause 42, wherein performing the first measurement comprises performing a measurement with a torque transducer, a speed transducer, a temperature sensor, an accelerometer, or a current sensor.44. The method of clause 42 or 43, further comprising causing an engine cooling system to circulate coolant fluid to the first engine or the second engine.45. The method of clause 44, wherein the coolant fluid comprises motor oil of the first engine or the second engine.46. The method of any of clauses 42 to 45, further comprising operating a vibration isolation fixture located on at least one of the platform or a first pallet supporting the first engine on the platform, to isolate vibrations of the first engine from the platform.47. The method of any of clauses 42 to 46, further comprising: changing an orientation of the first engine about the first axis from a first orientation to a second orientation; and performing a second measurement of the first engine.48. The method of clause 47, wherein changing the orientation of the first engine about the first axis comprises adjusting an orientation of a mounting surface of the first engine.Agent Ref. 16500-0006-0030449. The method of clause 47 or 48, wherein changing the orientation of the first engine about the first axis comprises actuating movement of the first engine from the first orientation to the second orientation.50. The method of any of clauses 42 to 49, further comprising causing the first engine to brake.51. The method of any of clauses 42 to 50, further comprising operating a first tilt motor to tilt the platform about a third axis perpendicular to the first axis.52. The method of clause 51 , wherein tilting the platform about the third axis comprises tilting the platform over a range of tilt angles simulating a tilt range of the first engine and / or the second engine during operation of a VTOL aircraft having the first engine and / or the second engine respectively installed therein.53. The method of clause 51 or 52, wherein tilting the platform about the third axis comprises tilting the platform over a range from at least -10 degrees to at least 100 degrees with respect to a reference axis that is fixed with respect to a stationary part of the dynamometer testing system.54. The method of any of clauses 40 to 42, further comprising operating a second tilt motor to tilt the platform about a fourth axis that is oriented perpendicular to both the first axis and the second axis.55. A computer readable medium that stores a set of instructions that is executable by at least one processor to cause a dynamometer testing system to perform operations comprising the method of any of clauses 42 to 54.

[0056] The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the inventions disclosed herein. Embodiments of the present disclosure are further illustrated with reference to the attached appendix.

Claims

Agent Ref. 16500-0006-00304CLAIMS:

1. A dynamometer testing system for an engine, the system comprising: a platform configured to support a first engine and a second engine mounted side by side so that a first axis of a first output shaft of the first engine is parallel to a second axis of a second output shaft of the second engine; a first torque driveline comprising a first joint configured to be connected to the first output shaft, the first joint configured to transfer torque between the first output shaft and the first torque driveline; a second torque driveline comprising a second joint configured to be connected to the second output shaft, the second joint configured to transfer torque between the second output shaft and the second torque driveline; and a pulley system between the first torque driveline and the second torque driveline.

2. The system of claim 1, further comprising an engine cooling system configured to circulate coolant fluid to the first engine or the second engine.

3. The system of claim 2, wherein the coolant fluid comprises motor oil of the first engine or the second engine.

4. The system of any of claims 1 to 3, further comprising a first pallet configured to support the first engine on the platform.

5. The system of claim 4, wherein at least one of the platform and the first pallet comprises a vibration isolation fixture configured to isolate vibrations of the first engine from the platform.

6. The system of claim 4 or 5, wherein the first pallet is configured to mount the first engine at a plurality of orientations about the first axis.

7. The system of any of claims 4 to 6, wherein the first pallet comprises an adjustable mounting surface configured to rotate the first engine about the first axis.

8. The system of claim 7, wherein the first pallet comprises an actuator configured to rotate the adjustable mounting surface about the first axis.

9. The system of any of claims 4 to 8, further comprising a second pallet configured to support the second engine on the platform.

10. The system of any of claims 1 to 9, wherein the first or second torque driveline further comprises a brake configured to stop rotation of the first or second torque driveline.Agent Ref. 16500-0006-0030411. The system of any of claims 1 to 10, wherein the platform comprises a first tilt motor configured to tilt the platform about a third axis that is oriented perpendicular to the first axis.

12. The system of claim 11, wherein the first tilt motor is configured to tilt the platform over a range of tilt angles simulating a tilt range of the first engine and / or the second engine installed in a VTOL aircraft during operation of the VTOL aircraft.

13. The system of claim 11 or 12, wherein the first tilt motor is configured to tilt the platform over a range from at least -10 degrees to at least 100 degrees with respect to a reference axis that is fixed with respect to a stationary surface of the platform.

14. The system of any of claims 11 to 13, wherein the platform comprises a second tilt motor configured to tilt the platform about a fourth axis that is oriented perpendicular to both the first axis and the third axis.

15. The system of any of claims 1 to 14, further comprising an external protective housing configured to enclose the platform for safety.

16. The system of any of claims 1 to 15, further comprising a first sensor configured to measure a first parameter of the first engine.

17. The system of claim 16, wherein the first sensor is comprised in the first torque driveline.

18. The system of claim 16 or 17, wherein the first sensor comprises a torque transducer, a speed transducer, a temperature sensor, an accelerometer, or a current sensor.

19. The system of any of claims 16 to 18, further comprising a second sensor configured to measure a second parameter of the second engine.

20. The system of claim 19, wherein the second sensor is comprised in the second torque driveline.

21. The system of claim 19 or 20, wherein the second sensor comprises a torque transducer, a speed transducer, a temperature sensor, an accelerometer, or a current sensor.

22. The system of any preceding claim, wherein the first joint and / or the second joint is further configured to dampen and / or isolate misalignment and / or vibration in a direction perpendicular to the first axis or the second axis.

23. The system of claim 22, wherein one of the first joint or the second joint comprise a universal joint.

24. The system of any preceding claim, wherein the first engine or the second engine comprises an electric engine.Agent Ref. 16500-0006-0030425. The system of any preceding claim, wherein the first engine or the second engine comprises an aircraft engine.

26. The system of any preceding claim, wherein the first engine or the second engine comprises a vertical takeoff and landing (VTOL) aircraft engine.

27. The system of any preceding claim, wherein the first engine or the second engine comprises an automobile engine.

28. A method for testing an engine, the method comprising: supporting a first engine and a second engine mounted side by side on a platform of a dynamometer testing system so that a first axis of a first output shaft of the first engine is parallel to a second axis of a second output shaft of the second engine; connecting a first torque driveline comprising a first joint to the first output shaft, the first joint configured to transfer torque between the first output shaft and the first torque driveline; connecting a second torque driveline comprising a second joint to the second output shaft, the first joint configured to transfer torque between the first output shaft and the first torque driveline, wherein the first torque driveline and the second torque driveline are coupled by a pulley system; operating the first engine as a test engine while operating the second engine to provide resistance to the first engine; and performing a first measurement of the first engine.

29. The method of claim 28, wherein performing the first measurement comprises performing a measurement with a torque transducer, a speed transducer, a temperature sensor, an accelerometer, or a current sensor.

30. The method of claim 28 or 29, further comprising circulating, by an engine cooling system, coolant fluid to the first engine or the second engine.

31. The method of claim 30, wherein the coolant fluid comprises motor oil of the first engine or the second engine.

32. The method of any of claims 28 to 31, further comprising isolating vibrations of the first engine from the platform via a vibration isolation fixture on at least one of the platform or a first pallet supporting the first engine on the platform.

33. The method of any of claims 28 to 32, further comprising: changing an orientation of the first engine about the first axis from a first orientation to a second orientation; andAgent Ref. 16500-0006-00304 performing a second measurement of the first engine.

34. The method of claim 33, wherein changing the orientation of the first engine about the first axis comprises mounting the first engine in the second orientation.

35. The method of claim 33, wherein changing the orientation of the first engine about the first axis comprises adjusting an orientation of a mounting surface of the first engine.

36. The method of claim 33 or 35, wherein changing the orientation of the first engine about the first axis comprises actuating movement of the first engine from the first orientation to the second orientation.

37. The method of any of claims 28 to 36, further comprising braking the first engine.

38. The method of any of claims 28 to 37, further comprising tilting the platform, via a first tilt motor, about a third axis that is perpendicular to the first axis.

39. The method of claim 38, wherein tilting the platform about the third axis comprises tilting the platform over a range of tilt angles simulating a tilt range of the first engine and / or the second engine during operation of a VTOL aircraft having the first engine and / or the second engine respectively installed therein.

40. The method of claim 38 or 39, wherein tilting the platform about the third axis comprises tilting the platform over a range from at least -10 degrees to at least 100 degrees with respect to a reference axis that is fixed with respect to a stationary part of the dynamometer testing system.

41. The method of any of claims 38 to 40, further comprising tilting the platform, via a second tilt motor, about a fourth axis that is oriented perpendicular to both the first axis and the second axis.

42. A method for testing an engine using the dynamometer testing system of any of claims 1 to 27, the method comprising: operating the first engine as a test engine while operating the second engine to provide resistance to the first engine; and performing a first measurement of the first engine.

43. The method of claim 42, wherein performing the first measurement comprises performing a measurement with a torque transducer, a speed transducer, a temperature sensor, an accelerometer, or a current sensor.

44. The method of claim 42 or 43, further comprising causing an engine cooling system to circulate coolant fluid to the first engine or the second engine.Agent Ref. 16500-0006-0030445. The method of claim 44, wherein the wherein the coolant fluid comprises motor oil of the first engine or the second engine.

46. The method of any of claims 42 to 45, further comprising operating a vibration isolation fixture located on at least one of the platform or a first pallet supporting the first engine on the platform to isolate vibrations of the first engine from the platform.

47. The method of any of claims 42 to 46, further comprising: changing an orientation of the first engine about the first axis from a first orientation to a second orientation; and performing a second measurement of the first engine.

48. The method of claim 47, wherein changing the orientation of the first engine about the first axis comprises adjusting an orientation of a mounting surface of the first engine.

49. The method of claim 47 or 48, wherein changing the orientation of the first engine about the first axis comprises actuating movement of the first engine from the first orientation to the second orientation.

50. The method of any of claims 42 to 49, further comprising causing the first engine to brake.

51. The method of any of claims 42 to 50, further comprising operating a first tilt motor to tilt the platform about a third axis perpendicular to the first axis.

52. The method of claim 51, wherein tilting the platform about the third axis comprises tilting the platform over a range of tilt angles simulating a tilt range of the first engine and / or the second engine during operation of a VTOL aircraft having the first engine and / or the second engine respectively installed therein.

53. The method of claim 51 or 52, wherein tilting the platform about the third axis comprises tilting the platform over a range from at least -10 degrees to at least 100 degrees with respect to a reference axis that is fixed with respect to a stationary part of the dynamometer testing system.

54. The method of any of claims 40 to 42, further comprising operating a second tilt motor to tilt the platform about a fourth axis that is oriented perpendicular to both the first axis and the second axis.

55. A computer readable medium that stores a set of instructions that is executable by at least one processor to cause a dynamometer testing system to perform operations comprising the method of any of claims 42 to 54.

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