Patent Publication Number: US-2020283124-A1

Title: Propeller Speed Overshoot Preventing Logic

Description:
FIELD 
     The subject matter of the present disclosure is related generally to a control system for an engine operatively coupled with a propeller, and more particularly to a control system for preventing propeller speed overshoot of a propeller operatively coupled with an engine. 
     BACKGROUND 
     Some aerial vehicles include a turboprop engine operatively coupled with a propeller for producing thrust. In some instances, fast acceleration of the turboprop engine can cause the speed of the propeller to overshoot the maximum propeller speed that can be demanded by a pilot, or the maximum demanded propeller speed. For instance, the propeller speed can overshoot the maximum demanded propeller speed during takeoff when the turboprop engine accelerates from an idle engine setting to a take-off power setting. In some cases, the propeller speed can overshoot the maximum demanded propeller speed such that the actual propeller speed reaches or nearly reaches a propeller speed maximum limit. There is typically safety margin between the propeller speed maximum limit and the maximum demanded propeller speed, and when the propeller speed overshoots the maximum demanded propeller speed, the margin can be breached to an unsatisfactory degree. Propeller speed overshoot can negatively affect the turboprop engine and/or propeller life and can limit the number of propellers that can be used with the turboprop engine as propeller speed overshoot can be a limiting factor during propeller selection. Propeller speed overshoot can have other drawbacks as well. 
     Therefore, there is a need for an improved control system for an engine operatively coupled with a propeller and methods for controlling the same that address one or more of the challenges noted above. 
     BRIEF DESCRIPTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one example aspect, the present subject matter is directed to a control system for an engine operatively coupled with a propeller. The control system includes an electric propeller governor having a motor and a flyweight governor spring mechanically coupled with the motor. Further, the control system includes a sensor operable to sense a propeller speed of the propeller. Further, the control system includes one or more control devices communicatively coupled with the motor of the propeller governor and the sensor. The one more control devices are configured to: receive, from the sensor, data indicative of the propeller speed of the propeller; determine whether the propeller speed exceeds a propeller speed threshold; and cause the motor of the electric propeller governor to change a preload on the flyweight governor spring based at least in part on whether the propeller speed exceeds the propeller speed threshold, wherein change of the preload on the flyweight governor spring adjusts a propeller speed set point of the propeller. 
     In another example aspect, the present subject matter is directed to a method for controlling an engine operatively coupled with a propeller. The method includes receiving, by one or more control devices, data indicative of a propeller speed of the propeller. Further, the method includes determining, by the one or more control devices, whether the propeller speed exceeds a propeller speed threshold. Moreover, the method includes adjusting a propeller speed set point to change the propeller speed of the propeller based at least in part on whether the propeller speed exceeds the propeller speed threshold. 
     In another example aspect, the present subject matter is directed to a vehicle. The vehicle includes a gas turbine engine and a propeller operatively coupled with the gas turbine engine. The vehicle also includes a control system. The control system includes a sensor and a controller communicatively coupled with the sensor. The controller is configured to: receive, from the sensor, data indicative of the propeller speed of the propeller; determine whether the propeller speed exceeds a propeller speed threshold; and cause adjustment of a propeller speed set point to change the propeller speed of the propeller based at least in part on whether the propeller speed exceeds the propeller speed threshold. 
     In yet another example aspect, a control system for a drive element operatively coupled with a rotating element is provided. The drive element can drive the rotating element about an axis of rotation. The drive element can be operatively coupled with the rotating element in any suitable manner, such as e.g., by one or more shafts or other mechanical linking members. The driving element can be an electric motor, an engine, a turbine, or some other suitable element for generating useful rotational work. The rotational element can be any suitable rotating element, such as e.g., a propeller, an impeller, blades of a wind turbine, vanes, etc. The control system includes a governor having a motor. Further, the control system includes a sensor operable to sense a rotational speed of the rotating element. Further, the control system includes one or more control devices communicatively coupled with the motor of the governor and the sensor. The one more control devices are configured to: receive, from the sensor, data indicative of the rotational speed of the rotating element; determine whether the rotational speed exceeds a rotational speed threshold; and cause the motor of the governor to adjust the rotational speed of the rotational element if the sensed rotational speed exceeds the rotational speed threshold. 
     In another example aspect, the present subject matter is directed to a method for controlling a system having a driving element operatively coupled with a rotating element. The method includes receiving, by one or more control devices, data indicative of a rotational speed of the rotating element. Further, the method includes determining, by the one or more control devices, whether the rotational speed exceeds a rotational speed threshold. Moreover, the method includes adjusting a rotational speed set point to change the rotational speed of the rotating element based at least in part on whether the rotational speed exceeds the rotational speed threshold. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  provides a schematic top plan view of a vehicle according to an example embodiment of the present subject matter; 
         FIG. 2  provides a side view of a gas turbine engine of the vehicle of  FIG. 1 ; 
         FIG. 3  provides a perspective, cutaway view of the gas turbine engine of  FIG. 2 ; 
         FIG. 4  provides a graph depicting propeller speed of a propeller operatively coupled with an engine versus time according to an example embodiment of the present subject matter; 
         FIG. 5  provides an electronic engine control system according to an example embodiment of the present subject matter; 
         FIG. 6  provides a schematic view of an electric propeller governor of the control system of  FIG. 5 ; 
         FIG. 7  provides a graph depicting propeller speed of a propeller operatively coupled with an engine versus time; 
         FIG. 8  provides a graph that corresponds with the graph of  FIG. 7  and depicts an angle of a single power control lever versus time; 
         FIG. 9  provides a flow diagram of an example method according to an example embodiment of the present subject matter; and 
         FIG. 10  provides an example computing system according to example embodiments of the present subject matter. 
     
    
    
     DETAILED DESCRIPTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Further, as used herein, the terms “axial” or “axially” refer to a dimension along a longitudinal axis of an engine. The term “forward” used in conjunction with “axial” or “axially” refers to a direction toward the engine inlet, or a component being relatively closer to the engine inlet as compared to another component. The term “aft” or “rear” used in conjunction with “axial” or “axially” refers to a direction toward the engine nozzle, or a component being relatively closer to the engine nozzle as compared to another component. The terms “radial” or “radially” refer to a dimension extending between a center longitudinal axis (or centerline) of the engine and an outer engine circumference. Radially inward is toward the longitudinal axis and radially outward is away from the longitudinal axis. 
     The subject matter of the present disclosure is directed generally to a control system for an engine operatively coupled with a propeller, and more particularly, to a control system for preventing propeller speed overshoot of a propeller operatively coupled with an engine. In one example aspect, the control system includes an electronic engine controller and an electric propeller governor. The electric propeller governor includes opposing flyweights operatively coupled with a pilot valve and a flyweight governor spring. Notably, the electric propeller governor includes a motor operatively coupled with the flyweight governor spring. The motor is communicatively coupled with the engine controller. The engine controller is operable to receive data indicative of the speed of the propeller, determine if the measured speed exceeds a propeller speed threshold, and if the threshold is exceeded, the engine controller is configured to change a propeller speed set point. Particularly, the engine controller can cause the motor to change the preload on the flyweight governor spring, which in turn causes adjustment of the propeller speed set point. For example, the propeller speed set point can be adjusted from a minimum demanded propeller speed or set point (Np Min) to a maximum demanded propeller speed or set point (Np Max) when the engine and propeller rapidly accelerate and the propeller speed exceeds the threshold. In this way, the speed of the propeller is prevented from overshooting the demanded propeller speed and is prevented from reaching or obtaining the maximum propeller speed limit (Np Max Limit). Accordingly, the engine and propeller are not subject to the negative impacts associated with propeller speed overshoot. A method for controlling an engine operatively coupled with a propeller is also provided. 
       FIG. 1  provides a schematic top plan view of a vehicle according to an example embodiment of the present subject matter. For this embodiment, the vehicle is a fixed-wing aerial vehicle  50 . In alternative embodiments, the aerial vehicle  50  can be other suitable types of aerial vehicles, such as a rotary aircraft, a vertical take-off and landing aircraft, a tiltrotor aircraft, an airship, an unmanned aerial vehicle, etc. Further, in some embodiments, the vehicle can be other types of vehicles having an engine and a propeller operatively coupled thereto, such as e.g., a marine vehicle or watercraft, a hovercraft, etc. 
     As depicted in  FIG. 1 , the aerial vehicle  50  extends between a first end  52  and a second end  54 , e.g., along a longitudinal axis L. The first end  52  is a forward end of the aerial vehicle  50  and the second end  54  is a rear or aft end of the aerial vehicle  50  in the depicted embodiment of  FIG. 1 . The aerial vehicle  50  includes a fuselage  56  and a pair of wings  58  each extending laterally outward from the fuselage  56 . The aerial vehicle  50  can include various control surfaces for controlling movement of the aerial vehicle  50 . Example control surfaces include elevators, rudders, ailerons, spoilers, flaps, slats, air brakes, or trim devices, etc. Various actuators, servo motors, and other devices can be used to manipulate the various control surfaces and variable geometry components of the aerial vehicle  50 . 
     The aerial vehicle  50  includes an engine  100  mounted to its forward end  52 . The engine  100  can be any suitable aeromechanical torque source. For instance, the engine  100  can be a gas turbine engine. For the depicted embodiment of  FIG. 1 , the engine  100  is configured as a turboprop. However, in alternative embodiments, the engine  100  can be other suitable types of engines operatively coupled with a propeller. For instance, in some alternative embodiments, the engine  100  can be a piston-driven engine. Moreover, in some embodiments, the aerial vehicle  50  can include more than one engine. For example, in some embodiments, the aerial vehicle  50  can include at least one turboprop mounted to each wing  58 . 
     The aerial vehicle  50  also includes a propeller  106  operatively coupled with the engine  100 . For instance, the propeller  106  can be mechanically coupled, e.g., as shown in  FIGS. 2 and 3 . Generally, the propeller  106  is configured to produce thrust when driven by the engine  100 . The propeller  106  includes a plurality of propeller blades  150 . In some embodiments, the blades  150  of the propeller  106  are adjustable in unison through a plurality of blade pitch angles, e.g., by activation of an actuation mechanism. Pitch adjustment of the blades  150  can cause the propeller  106  to produce more or less thrust depending on the blade angle of the blades  150 . 
       FIGS. 2 and 3  provide various views of the engine  100  of the aerial vehicle  50  of  FIG. 1 . Particularly,  FIG. 2  provides a side view of the engine  100  and  FIG. 3  provides a perspective, cutaway view of the engine  100 . For reference, the gas turbine engine  100  defines an axial direction A, a radial direction R, and a circumferential direction C ( FIG. 3 ) extending three hundred sixty degrees (360°) around the axial direction A. The gas turbine engine  100  also defines a longitudinal or axial centerline  102  extending along the axial direction A. The gas turbine engine  100  extends generally along the axial direction A between a first end  103  and a second end  105 , which for this embodiment is the forward and aft end, respectively. Generally, the gas turbine engine  100  includes a gas generator or core turbine engine  104  that is operatively coupled with the propeller  106 . The propeller  106  and various components of the core turbine engine  104  are rotatable about the axial centerline  102 , or more generally, the axial direction A. 
     As shown best in  FIG. 3 , the core turbine engine  104  generally includes, in serial flow arrangement, a compressor section  110 , a combustion section  112 , a turbine section  114 , and an exhaust section  116 . A core air flowpath  118  extends from an annular inlet  120  to one or more exhaust outlets  122  of the exhaust section  116  such that the compressor section  110 , combustion section  112 , turbine section  114 , and exhaust section  116  are in fluid communication. 
     The compressor section  110  can include one or more compressors, such as a high pressure compressor (HPC) and a low pressure compressor (LPC). For this embodiment, the compressor section  110  includes a four-stage axial, single centrifugal compressor. In particular, the compressor includes sequential stages of compressor stator vanes and rotor blades (not labeled), as well as an impeller (not labeled) positioned downstream of the axial stages of stator vanes and rotor blades. The combustion section  112  includes a reverse-flow combustor (not labeled) and one or more fuel nozzles (not shown). The turbine section  114  can define one or more turbines, such as a high pressure turbine (HPT) and a low pressure turbine (LPT). For this embodiment, the turbine section  114  includes a two-stage HPT  126  for driving the compressor of the compressor section  110 . The HPT  126  includes two sequential stages of stator vanes and turbine blades (not labeled). The turbine section  114  also includes a three-stage free or power turbine  128  that drives a propeller gearbox  134 , which in turn drives the propeller assembly  106  ( FIG. 2 ). The exhaust section  116  includes one or more exhaust outlets  122  for routing the combustion products to the ambient air. 
     Referring still to  FIG. 3 , the core turbine engine  104  can include one or more shafts. For this embodiment, the gas turbine engine  100  includes a compressor shaft  130  and a free or power shaft  132 . The compressor shaft  130  drivingly couples the turbine section  114  with the compressor section  110  to drive the rotational components of the compressor. The power shaft  132  drivingly couples the power turbine  128  to drive a gear train  140  of the propeller gearbox  134 , which in turn operatively supplies power and torque to the propeller  106  ( FIG. 2 ) via a torque output or propeller shaft  136  at a reduced RPM. The forward end of the propeller shaft  136  includes a flange  137  that provides a mounting interface for the propeller assembly  106  to be attached to the core turbine engine  104 . 
     The propeller gearbox  134  is enclosed within a gearbox housing  138 . For this embodiment, the housing  138  encloses the epicyclical gear train  140  that includes a star gear  142  and a plurality of planet gears  144  disposed about the star gear  142 . The planetary gears  144  are configured to revolve around the star gear  142 . An annular gear  146  is positioned axially forward of the star and planetary gears  142 ,  144 . As the planetary gears  144  rotate about the star gear  142 , torque and power are transmitted to the annular gear  146 . As shown, the annular gear  146  is operatively coupled to or otherwise integral with the propeller shaft  136 . In some embodiments, the gear train  140  may further include additional planetary gears disposed radially between the plurality of planet gears  144  and the star gear  142  or between the plurality of planet gears  144  and the annular gear  146 . In addition, the gear train  140  may further include additional annular gears. 
     As noted above, the core turbine engine  104  transmits power and torque to the propeller gearbox  134  via the power shaft  132 . The power shaft  132  drives the star gear  142 , which in turn drives the planetary gears  144  about the star gear  142 . The planetary gears  144  in turn drive the annular gear  146 , which is operatively coupled with the propeller shaft  136 . In this way, the energy extracted from the power turbine  128  supports operation of the propeller shaft  136 , and through the power gear train  140 , the relatively high RPM of the power shaft  132  is reduced to a more suitable RPM for the propeller  106 . 
     With reference to  FIG. 2 , during operation of the gas turbine engine  100 , a volume of air indicated by arrow  148  passes across the plurality of propeller blades  150  circumferentially spaced apart from one another along the circumferential direction C and disposed about the axial direction A, and more particularly for this embodiment, the axial centerline  102 . The propeller assembly  106  includes a spinner  163  aerodynamically contoured to facilitate an airflow through the plurality of propeller blades  150 . The spinner  163  is rotatable with the propeller blades  150  about the axial direction A and encloses various components of the propeller assembly  106 , such as e.g., the hub, propeller pitch actuator, piston/cylinder actuation mechanisms, etc. A first portion of air indicated by arrow  152  is directed or routed outside of the core turbine engine  104  to provide propulsion. A second portion of air indicated by arrow  154  is directed or routed through the annular inlet  120  of the gas turbine engine  100 . 
     As shown in  FIG. 3 , the second portion of air  154  enters through the annular inlet  120  and flows downstream to the compressor section  110 , which is a forward direction along the axial direction A in this embodiment. The second portion of air  154  is progressively compressed as it flows through the compressor section  110  downstream toward the combustion section  112 . 
     The compressed air indicated by arrow  156  flows into the combustion section  112  where fuel is introduced, mixed with at least a portion of the compressed air  156 , and ignited to form combustion gases  158 . The combustion gases  158  flow downstream into the turbine section  114 , causing rotary members of the turbine section  114  to rotate, which in turn supports operation of respectively coupled rotary members in the compressor section  110  and propeller assembly  106 . In particular, the HPT  126  extracts energy from the combustion gases  158 , causing the turbine blades to rotate. The rotation of the turbine blades of the HPT  126  causes the compressor shaft  130  to rotate, and as a result, the rotary components of the compressor are rotated about the axial direction A. In a similar fashion, the power turbine  128  extracts energy from the combustion gases  158 , which causes the blades of the power turbine  128  to rotate about the axial direction A. The rotation of the turbine blades of the power turbine  128  causes the power shaft  132  to rotate, which in turn drives the power gear train  140  of the propeller gearbox  134 . 
     The propeller gearbox  134  in turn transmits the power provided by the power shaft  132  to the propeller shaft  136  at a reduced RPM and desired amount of torque. The propeller shaft  136  in turn drives the propeller assembly  106  such that the propeller blades  150  rotate about the axial direction A, and more particularly for this embodiment, the axial centerline  102  of the gas turbine engine  100 . The exhaust gases, denoted by  160 , exit the core turbine engine  104  through the exhaust outlets  122  to the ambient air. 
     It should be appreciated that the example gas turbine engine  100  described herein is provided by way of example only. For example, in other example embodiments, the engine may include any suitable number or types of compressors, turbines, shafts, stages, etc. Additionally, in some example embodiments, the gas turbine engine may include any suitable type of combustor, and may not include the example reverse-flow combustor depicted. It will further be appreciated that the engine can be configured as any suitable type of engine operatively coupled with a propeller. For instance, in some embodiments, the engine can be configured as a reciprocating or piston engine. In addition, it will be appreciated that the present subject matter can be applied to or employed with any suitable type of propeller or fan configuration, including, for example, tractor and pusher configurations. 
     Returning to  FIG. 1 , as shown, the aerial vehicle  50  of  FIG. 1  is equipped with an electronic engine control system (EECS)  200 . As will be detailed herein, the control system  200  includes propeller speed overshoot preventing logic that, in conjunction with other features of the control system  200 , prevent or reduce propeller speed overshoot during fast acceleration or deceleration of the engine  100 . For instance, when the engine  100  accelerates from idle to full power during takeoff of the aerial vehicle  50 , the control system  200  prevents the speed of the propeller from overshooting the demanded maximum propeller speed. In this way, the life of the engine can be increased or extended. For instance, with use of the control system  200  described herein, propeller speed overshoot was decreased by two percent (2%), and consequently, the life of the engine can be increased by a minimum of fifteen percent (15%). Further, with use of the control system  200  described herein, the safety margin of the engine can be increased, the number of propellers that can be selected for use with the engine can be increased as propeller speed overshoot is typically a limiting factor for selecting a suitable propeller for the engine, a wider range for adjustment of the minimum flight pitch angle can be achieved, and a wider range for adjustment of the maximum propeller speed can be achieved due to the greater margin between the maximum propeller speed and minimum propeller speed, among other benefits and advantages. 
       FIG. 4  graphically depicts the advantages of the control system  200  of the present disclosure. Particularly, the graph of  FIG. 4  depicts the propeller speed of a propeller operatively coupled with an engine controlled by the control system  200  of the present disclosure (labeled as Np 1 ) versus time and the propeller speed of a propeller operatively coupled with an engine controlled by a conventional control system (labeled as Np 2 ) versus time. As shown, during fast acceleration of the engine, the propeller speed Np 2  of the propeller controlled by the conventional control system (i.e., a control system without overshoot preventing logic) accelerates rapidly from under 1,200 rpm to about 2,000 rpm in about five seconds (5 s). Notably, the propeller speed Np 2  overshoots the maximum demanded propeller speed (labeled as Np Max) set at 1,900 rpm and increases to about the propeller speed maximum limit (labeled as Np Max Limit), which is 2,000 rpm in this example (103% of Np Max). The propeller speed Np 2  eventually settles within a predetermined range of steady state (e.g., within plus or minus five percent (5%) of a steady state value) at about 1,900 rpm after about ten seconds (10 s). As noted above, overshooting the maximum demanded propeller speed (Np Max) can negatively affect the life of the engine and/or the propeller in a significant way and can limit the selection of propellers available for use with the engine, among other drawbacks. Overshooting the maximum demanded propeller speed (Np Max) and reaching or obtaining the propeller speed maximum limit (Np Max Limit) on the first overshoot as shown in  FIG. 4  especially impacts the life cycle of the engine and propeller. 
     In comparison, during fast acceleration of the engine, the propeller speed Np 1  of the propeller controlled by the control system  200  accelerates rapidly from under 1,200 rpm to about 1,900 rpm in about five seconds (5 s). Advantageously, as depicted, during rapid acceleration of the engine, the propeller speed Np 1  rapidly accelerates and has a very minimal, if any, overshoot of the maximum demanded propeller speed (Np Max), which is 1900 rpm in this example as noted above. The propeller speed Np 1  eventually settles within a predetermined range of steady state (e.g., within plus or minus five percent (5%) of a steady state value) at about 1,900 rpm after about ten seconds (10 s). Accordingly, as the propeller speed Np 1  does not or only minimally overshoots the maximum demanded propeller speed (Np Max), the engine and propeller are not negatively impacted in the same manner as the propeller controlled by the conventional control system. The control system  200  that prevents propeller speed overshoot and provides the advantages and benefits described above will be described in detail below. 
       FIG. 5  provides a schematic view of control system  200  according to an example embodiment of the present subject matter. The control system  200  can be an electronic engine control system (EECS), for example. As shown, the control system  200  can include one or more control devices for controlling the engine  100  and the propeller  106 . Particularly, for the depicted embodiment of  FIG. 5 , the one or more control devices include an electronic engine controller (EEC)  210  configured to control the gas turbine engine  100  and the propeller  106 . The controller  210  can operate as the central control unit for the control system  200 , which as noted above, can be an EECS. In some embodiments, the controller  210  can be an analog electronic box. In other embodiments, the controller  210  can be a computing device. 
     Further, in some alternative embodiments, the control system  200  can be a Full Authority Digital Engine and Propeller Control (FADEPC) system operable to provide full digital control of the core turbine engine  104  of the gas turbine engine  100  and the propeller  106 . The controller  210  can operate as the central control unit of the FADEC system. In yet other embodiments, the one or more control devices of the control system  200  can include more than one controller for controlling the core turbine engine  104  and the propeller  106 . For example, in some example embodiments, the control system  200  can include an EEC equipped with Full Authority Digital Engine Control (FADEC) and a propeller controller equipped with Full Authority Digital Propeller Control (FADPC). In such embodiments, the EEC and the propeller controller are communicatively coupled, e.g., via a suitable wired or wireless communication link. 
     The controller  210  depicted in the illustrated embodiment of  FIG. 5  can control various aspects of the core turbine engine  104  and the propeller  106  as noted above. For instance, for this embodiment, the controller  210  includes propeller speed overshoot preventing logic  212  that, in conjunction with other features of the control system  200 , reduce the propeller speed overshoot during fast acceleration or deceleration of the engine  100 . The propeller speed overshoot preventing logic  212  includes propeller speed selector logic  214  (denoted as Np selector logic  214  in  FIG. 5 ) and a motor drive  216  operable to drive a motor (e.g., a stepper motor) as will be explained below. 
     Moreover, the controller  210  can be communicatively coupled with various sensors. For instance, as shown in  FIG. 5 , the controller  210  is communicatively coupled with a sensor  220 , e.g., via a wired or wireless communication link. For this embodiment, the sensor  220  is a propeller speed sensor operable to sense the speed of the propeller  106  as it rotates about its axis of rotation. The controller  210  can receive the data indicative of the propeller speed from the sensor  220 . In some control schemes, the data can be routed to the propeller speed overshoot preventing logic  212  so that the engine  100  and the propeller  106  can be controlled based at least in part on the measured propeller speed. 
     The control system  200  also includes a fuel metering unit (FMU)  230  for metering fuel to the engine  100 , e.g., from a fuel tank onboard the aerial vehicle  50  ( FIG. 1 ). The fuel metering unit  230  is communicatively coupled with the controller  210 , e.g., via a suitable wired or wireless communication link. The controller  210  can control the FMU  230  to selectively allow a volume of fuel to engine  100 , e.g., based on an engine speed set point and/or other control aspects. 
     Further, the control system  200  includes an electric propeller governor  250 . The electric propeller governor  250  can be mounted to the engine  100 , e.g., within or to housing  138  ( FIG. 3 ). Generally, the electric propeller governor  250  is operable to control or govern the speed of the propeller  106 . The electric propeller governor  250  can be any suitable hydromechanical propeller governor. For instance, the electric propeller governor  250  can be a constant speed propeller governor operable to respond to a change in engine speed by directing oil under pressure to a propeller hydraulic cylinder or by releasing oil from the hydraulic cylinder, e.g., to move a piston disposed within the cylinder, to ultimately change the pitch angle of the propeller blades  150  ( FIG. 2 ) of the propeller  106  such that the engine speed can be maintained at a set engine speed. The electric propeller governor  250  can be set to a specific speed set point (rpm) via a propeller speed selector device  240 . The selector device  240  can be any suitable device operable to switch or adjust the speed of the propeller  106 . For instance, the selector device  240  can be a switch located in a cockpit of the aircraft to which the engine  100  and propeller  106  are mounted. In other embodiments, the selector device  240  can be a lever or some other manually adjustable device. 
       FIG. 6  provides a schematic view of the electric propeller governor  250  according to an example embodiment of the present subject matter. As depicted, the electric propeller governor  250  includes a pilot valve  252  controlled by flyweights  254  to control the flow of oil (not shown) to or from a propeller pitch control unit (not shown) of the propeller  106 , which ultimately increases or decreases the propeller speed by changing the pitch of the propeller blades  150 . The electric propeller governor  250  includes a flyweight governor spring  256 , also referred to as a speeder spring, that is mechanically coupled with a spring adjustment mechanism  260  (e.g., a vertical adjusting worm or other suitable adjustment mechanism), which is in turn mechanically coupled with a motor as explained below. The flyweight governor spring  256  opposes the ability of the flyweights  254  to move outward from the flyweight governor spring  256 . The preload (e.g., tension or compression) on the flyweight governor spring  256  can be adjusted manually by user manipulation of the selector device  240  (located within the cockpit of the aerial vehicle  50  ( FIG. 1 )), in response to movement of the flyweights  254  to maintain an onspeed condition, or automatically via control system  200  as will be explained herein. The preload on the flyweight governor spring  256  ultimately controls the speed of the engine  100 . 
     Generally, the electric propeller governor  250  can operate in an onspeed condition, an overspeed condition, and an underspeed condition. When the engine  100  is operating above the engine speed set point, the electric propeller governor  250  operates in an overspeed condition. When this occurs, the flyweights  254  overcome the tension of the flyweight governor spring  256  and move outward from the flyweight governor spring  256 , e.g., as shown in  FIG. 6 . The outward movement of the flyweights  254  moves the pilot valve  252  (e.g., vertically upward) to move oil to or from the propeller pitch control unit (not shown) so that the pitch of the blades  150  can be increased. The increased pitch of the blades  150  increases the load on the engine  100 , and consequently, the engine speed decreases so that the set speed of the engine is maintained. On the other hand, when the engine  100  is operating below the engine speed set point, the electric propeller governor  250  operates in an underspeed condition. When this occurs, the flyweights  254  move or tilt inward due to the lack of centrifugal force on the flyweights  254  to overcome the force of the flyweight governor spring  256 . The pilot valve  252  is moved by the flyweight governor spring  256  (e.g., vertically downward) and the pilot valve  252  meters oil flow to the propeller pitch control unit so that the pitch of the blades  150  can be decreased, which consequently raises the speed of the engine  100 . Oil can be metered to and from the propeller pitch control unit until an onspeed condition is met, e.g., when the force on the flyweights  254  and the tension on the flyweight governor spring  256  are balanced, or stated alternatively, when the speed of the engine matches the engine speed set by the pilot. The balance of forces can be disturbed by the aircraft changing attitude (climb or dive), the pilot changing the tension on the flyweight governor spring  256  utilizing the selector device  240  (e.g., by user manipulation of a switch), or automatically by control system  200  if certain conditions are met during rapid acceleration or deceleration of the engine  100 . 
     With reference now to  FIGS. 5 and 6 , as shown, the electric propeller governor  250  includes a motor  262  mechanically coupled with the flyweight governor spring  256 . For instance, the output shaft  264  of the motor  262  can be mechanically coupled with the flyweight governor spring  256  via spring adjustment mechanism  260  as shown in  FIG. 6 . The motor  262  can be a stepper motor, for example. When certain conditions are met during rapid acceleration or deceleration of the engine  100 , the controller  210  can cause the motor  262  of the electric propeller governor  250  to change the preload on the flyweight governor spring  256 , e.g., by applying a torque on spring adjustment mechanism  260  via output shaft  264 , which in turns adjusts the tension of flyweight governor spring  256 . More particularly, if certain conditions are met during rapid acceleration or deceleration of the engine  100 , the motor drive  216  of the controller  210  can send one or more command signals  272  (e.g., one or more pulses) to the motor  262  such that the output shaft  264  of the motor  262  is rotated the desired number of steps. In this way, the motor  262  can accurately and precisely control the preload on the flyweight governor spring  256 . In other example embodiments, the motor  262  can be mechanically coupled with the flyweight governor spring  256  in other example manners. Further, the selector device  240  can be communicatively coupled (e.g., electrically connected) with the motor  262 . For instance, as shown best in  FIG. 5 , the selector device  240  can be directly electrically connected with the propeller speed selector logic  214  of controller  210 , which is electrically connected with and controls the motor drive  216 , which in turn is electrically connected with and controls the motor  262 . In this way, a pilot can manipulate the selector device  240  within the cockpit, and in turn, the motor  262  can turn its output shaft  264  to ultimately change the preload on the flyweight governor spring  256 . Thus, the pilot can use the selector device  240  to change or adjust the propeller speed via selector device  240 . In yet other embodiments, the selector device  240  can be mechanically coupled (e.g., one or more linkages) to spring adjustment mechanism  260 , and in such embodiments, manual manipulation of selector device  240  (e.g., a lever) can cause adjustment of the preload on flyweight governor spring  256 . 
     With reference now to  FIGS. 5, 7, and 8 , an example manner in which the control system  200  can reduce or prevent propeller speed overshoot is provided.  FIG. 7  provides a graph depicting propeller speed of the propeller  106  operatively coupled with the engine  100  versus time and  FIG. 8  provides a graph that corresponds with the graph of  FIG. 7  and depicts the angle of a single power control lever (SPCL), which is representative of the demanded engine power, versus time. 
     During operation of the engine  100 , or more particularly the engine  100  and propeller  106  operatively coupled thereto, the controller  210  receives data  270  ( FIG. 5 ) indicative of the propeller speed (denoted as “Np” in  FIG. 5 ) of the propeller  106 . The controller  210  can receive the data  270  from the sensor  220  communicatively coupled thereto, e.g., via a wired or wireless communication link. The controller  210  can continuously receive data  270  during operation of the engine  100  or can receive data  270  at predetermined intervals, e.g., every ten milliseconds (10 ms). In this way, the speed of the propeller  106  can continuously or nearly continuously be monitored during operation of the engine  100 . Once the controller  210  receives the data  270  indicative of the propeller speed of the propeller  106 , the controller  210  is configured to determine whether the measured propeller speed exceeds a propeller speed threshold. 
     For instance, when the SPCL ( FIG. 5 ) is moved from an angle of zero degrees (0°) to an angle of about thirty-three degrees (33°) as shown in  FIG. 8 , the engine  100  ( FIG. 5 ) accelerates rapidly from idle to full power, and consequently, the propeller speed of the propeller  106  rapidly accelerates as well as shown in  FIG. 7 . Particularly, as depicted in  FIG. 7 , the propeller speed Np of the propeller  106  accelerates from under 1,200 rpm to about 1,900 rpm in about five seconds (5 s). For this embodiment, the propeller speed threshold is set at 1,675 rpm as shown in  FIG. 7 . As the propeller speed is accelerating (i.e., increasing in speed over time), the propeller speed threshold is an acceleration propeller speed threshold. The propeller speed overshoot preventing logic  212  of the controller  210  can determine whether the measured propeller speed (as determined from the data  270 ) exceeds the propeller speed threshold. As shown in  FIG. 7 , for this embodiment, the propeller speed Np of the propeller  106  exceeds the acceleration propeller speed threshold of 1,675 rpm at about four seconds (4 s). 
     As depicted in  FIG. 7 , the propeller can be set at different propeller speed set points, e.g., a first set point and a second set point. The set point of the propeller speed corresponds to a demanded propeller speed (Np demanded). The first set point can correspond to a minimum propeller speed demanded (Np Min) and the second set point can correspond to a maximum propeller speed demanded (Np Max). In some embodiments, the propeller speed set point of the propeller  106  is only switchable between a first set point and a second set point. For instance, for this embodiment, the propeller speed set point of the propeller  106  is only switchable between a minimum propeller speed demanded (Np Min) and a maximum propeller speed demanded (Np Max). Stated differently, the pilot can demand either a minimum propeller speed (Np Min) or a maximum propeller speed (Np Max). 
     Notably, the controller  210  is configured to adjust the propeller speed set point to change the propeller speed of the propeller based at least in part on whether the propeller speed exceeds the propeller speed threshold. For instance, if the propeller speed exceeds the propeller speed threshold, e.g., as shown in  FIG. 7  at about four seconds (4 s), then the propeller speed set point (i.e., Np demanded) is adjusted from Np Min to Np Max. For instance, as depicted in  FIG. 7 , when the propeller speed exceeds the acceleration propeller speed threshold of 1,675 rpm, the propeller speed selector logic  214  of the propeller speed overshoot preventing logic  212  adjusts the propeller speed set point from Np Min to Np Max. 
     For this embodiment, to adjust the propeller speed set point, the controller  210  causes the motor  262  of the electric propeller governor  250  to change the preload on the flyweight governor spring  256  based at least in part on whether the propeller speed exceeds the acceleration propeller speed threshold. That is, the controller  210  causes the motor  262  of the electric propeller governor  250  to change the preload on the flyweight governor spring  256  if the measured propeller speed exceeds the acceleration propeller speed threshold. For instance, the motor drive  216  of the controller  210  can cause the stepper motor  262  to change the preload on the flyweight governor spring  256  if the propeller speed exceeds the propeller speed threshold. The motor drive  216  can command the motor  262  such that the motor  262  gradually or linearly changes the preload on the flyweight spring  256  at predefined rate of set point change, e.g., as shown in  FIG. 7 . In  FIG. 7 , the motor drive  216  commands the motor  262  to gradually change the preload on the flyweight spring  256  over the course of about two and a half seconds from four seconds (4 s) to about six and on a half seconds (6.5 s). The gradual or linear change of the preload on the flyweight governor spring  256  prevents vibration and jarring of the components of the propeller  106  and engine  100  during engine acceleration. The drive motor  216  can cause the motor  262  to drive its output shaft  264  ( FIG. 6 ) such that the output shaft  264  applies a torque on the spring adjustment mechanism  260  ( FIG. 6 ), which in turn can adjust the tension or preload on the flyweight governor spring  256 . 
     Notably, changing the preload on the flyweight governor spring  256  adjusts the propeller speed set point of the propeller  106 , or in this embodiment, the preload of the flyweight governor spring  256  adjusts the propeller speed set point of the propeller  106  from Np Min to Np Max as shown in  FIG. 7 . By adjusting the propeller speed set point during fast acceleration as described above, advantageously, the propeller speed is prevented from overshooting the demanded propeller speed, or Np Max in this example. Rather, as depicted in  FIG. 7 , the propeller speed reaches the demanded propeller speed or Np Max (1,900 rpm in this example) and then stabilizes after several seconds. The propeller speed does not overshoot Np Max and consequently does not reach at or near the propeller speed maximum limit, or Np Max Limit. Accordingly, as shown, the control system  200  prevents the propeller speed from overshooting Np Max and thus the engine  100  and/or propeller  106  are not impacted by the drawbacks associated with overshooting the maximum demanded propeller speed and prevents the propeller speed from reaching at or near the propeller speed maximum limit (Np Max Limit), e.g., as shown by Np 2  in  FIG. 4  that is controlled by a conventional control system. 
     As further shown in  FIG. 7 , the propeller speed threshold can also correspond to a deceleration propeller speed threshold if the propeller speed is decelerating (i.e., decreasing in speed over time). For instance, when the SPCL ( FIG. 5 ) is moved from an angle of about thirty-three degrees (33°) to an angle of zero degrees (0°) as shown in FIG. Bat about fifteen seconds (15 s), the engine  100  ( FIG. 5 ) decelerates rapidly from full power to idle power, and consequently, the propeller speed of the propeller  106  rapidly decelerates as well as shown in  FIG. 7 . Particularly, as depicted in  FIG. 7 , the propeller speed of the propeller  106  decelerates from about 1,900 rpm to under 1,200 rpm in about ten seconds (10 s). For this embodiment, the deceleration propeller speed threshold is set at 1,650 rpm as shown in  FIG. 7 . The propeller speed overshoot preventing logic  212  of the controller  210  can determine whether the measured propeller speed (as determined from the data  270 ) exceeds the deceleration propeller speed threshold. As shown in  FIG. 7 , for this embodiment, the propeller speed of the propeller  106  exceeds the deceleration propeller speed threshold of 1,650 rpm at about nineteen seconds (19 s). 
     The controller  210  is configured to adjust the propeller speed set point to change the propeller speed of the propeller based at least in part on whether the propeller speed exceeds the propeller speed threshold. For instance, if the propeller speed exceeds the deceleration propeller speed threshold, e.g., as shown in  FIG. 7  at about nineteen seconds (19 s), then the propeller speed set point (i.e., the demanded propeller speed) is adjusted from Np Max to Np Min. As depicted in  FIG. 7 , when the propeller speed exceeds the deceleration propeller speed threshold of 1,650 rpm, the propeller speed selector logic  214  adjusts the propeller speed set point from Np Max to Np Min. 
     For this embodiment, to adjust the propeller speed set point, the controller  210  causes the motor  262  of the electric propeller governor  250  to change the preload on the flyweight governor spring  256  based at least in part on whether the propeller speed exceeds the deceleration propeller speed threshold. That is, the controller  210  causes the motor  262  of the electric propeller governor  250  to change the preload on the flyweight governor spring  256  if the measured propeller speed exceeds the deceleration propeller speed threshold. For instance, the motor drive  216  of the controller  210  can cause the stepper motor  262  to change the preload on the flyweight governor spring  256  if the propeller speed exceeds the deceleration propeller speed threshold. The motor drive  216  can command the motor  262  such that the motor  262  gradually or linearly changes the preload on the flyweight spring  256 , e.g., as shown in  FIG. 7 . In  FIG. 7 , the motor drive  216  commands the motor  262  to gradually or linearly change the preload on the flyweight spring  256  over a predetermined time, or over the course of about two seconds from nineteen seconds (19 s) to about twenty-one seconds (21 s) in this example. The drive motor  216  can cause the motor  262  to drive its output shaft  264  ( FIG. 6 ) such that the output shaft  264  applies a torque on the spring adjustment mechanism  260  ( FIG. 6 ), which in turn can adjust the tension or preload on the flyweight governor spring  256 . Changing the preload on the flyweight governor spring  256  adjusts the propeller speed set point of the propeller  106 , or in this embodiment, the preload on the flyweight governor spring  256  adjusts the propeller speed set point of the propeller  106  from Np Max to Np Min as shown in  FIG. 7 . 
     As shown best in  FIG. 7 , the deceleration propeller speed threshold can be offset from the acceleration propeller speed threshold. Particularly, for this embodiment, the acceleration threshold (1,675 rpm) and the deceleration (1,650 rpm) threshold are offset by 25 rpm. In this manner, hysteresis is utilized to prevent undesired switching between Np Max and Np Min, e.g., caused by tolerances and control accuracies. For this embodiment, the acceleration propeller speed threshold is set at a higher rpm than the deceleration propeller speed threshold. 
     Further, in some embodiments, in addition to the propeller speed exceeding either the accelerating or decelerating propeller speed threshold, the speed of the propeller must also be accelerating or decelerating at a predetermined rate in order for the control system  200  to switch the propeller speed set point, e.g., from Np Min to Np Max or vice versa. For instance, in some embodiments, the controller  210  is configured to determine whether the propeller speed is changing at a predetermined rate (i.e., whether the propeller speed is accelerating or decelerating at a predetermined rate) based at least in part on the received data indicative of the propeller speed of the propeller. In such embodiments, if the propeller speed is changing at the predetermined rate and the propeller speed exceeds the propeller speed threshold, then the controller  210  is configured to automatically cause the motor  262  of the electric propeller governor  250  to change the preload on the flyweight governor spring  256 . As a result, the controller  210  automatically changes the propeller speed set point (e.g., from Np Min to Np Max or from Np Max to Np Min). 
     The predetermined rate can correspond to an acceleration predetermined rate or a deceleration predetermined rate depending on whether the propeller speed is increasing or decreasing. For instance, the acceleration predetermined rate can be set to correspond with acceleration of the propeller speed during takeoff of the vehicle  50  ( FIG. 1 ) as shown in  FIG. 7 . For example, the acceleration predetermined rate can correspond to a rate of 600 rpm over a period of eight seconds (8 s). Thus, if the propeller speed increases by or more than 600 rpm over a period of eight seconds (8 s), as it does in  FIG. 7 , the controller  210  can determine that the propeller speed exceeds the acceleration propeller speed threshold and is accelerating at the predetermined rate, and accordingly, the controller  210  can automatically cause adjustment of the propeller speed set point, e.g., from Np Min to Np Max. Further, in some embodiments, the deceleration predetermined rate can be set to correspond with deceleration of the propeller speed during a power down of the engine  100  as shown in  FIG. 7 . For instance, the deceleration predetermined rate can correspond to a rate of 400 rpm over a period of ten seconds (10 s), for example. Thus, if the propeller speed decreases by or more than 400 rpm over a period of ten seconds (10 s), as it does in  FIG. 7 , the controller  210  can determine that the propeller speed exceeds the deceleration propeller speed threshold and is decelerating at the deceleration predetermined rate, and accordingly, the controller  210  can automatically cause adjustment of the propeller speed set point, e.g., from Np Max to Np Min. 
       FIG. 9  provides a flow diagram of an example method ( 300 ) for controlling an engine operatively coupled with a propeller. For instance, the method ( 300 ) can be implemented to control the engine  100  and/or propeller  106  of the vehicle  50  of  FIG. 1 . However, the method ( 300 ) can be implemented to control other engines operatively coupled with a propeller. Some or all of the method ( 300 ) can be implemented by control system  200  disclosed herein. In addition, it will be appreciated that exemplary method ( 300 ) can be modified, adapted, expanded, rearranged and/or omitted in various ways without deviating from the scope of the present subject matter. 
     At ( 302 ), the method ( 300 ) includes receiving, by one or more computing devices, data indicative of a propeller speed of the propeller. For instance, with reference to  FIG. 5 , the controller  210  of the control system  200  can receive data  270  indicative of the speed of the propeller  106  from the sensor  220 . In some implementations, the controller  210  can receive data  270  continuously during operation of the engine  100  and propeller  106 . The data  270  can be routed from sensor  220  to controller  210  the any suitable wired and/or wireless communication link. The data  270  can be analog and/or digital signals. The data  270  indicative of the speed of the propeller  106  can be utilized by controller  210  to control the propeller speed set point of the propeller  106  and can also be used to determine the acceleration or deceleration of the propeller  106 . 
     At ( 304 ), the method ( 300 ) includes determining, by the one or more computing devices, whether the propeller speed exceeds a propeller speed threshold. For instance, with reference to  FIG. 5 , once the controller  210  receives the data  270  indicative of the propeller speed of the propeller  106 , the controller  210  can determine whether the propeller speed exceeds a propeller speed threshold. In some implementations, the method ( 300 ) further includes determining, by the one or more computing devices, whether the propeller speed of the propeller is increasing or decreasing based at least in part on the received data indicative of the propeller speed of the propeller. In such implementations, if the propeller speed of the propeller is increasing over time (i.e., the propeller is accelerating), then the propeller speed threshold is an acceleration propeller speed threshold. Accordingly, the controller  210  determines whether the measured speed of the propeller  106  exceeds the acceleration propeller speed threshold. That is, the controller  210  determines whether the measured propeller speed is greater than the acceleration propeller speed threshold. For example, if the acceleration propeller speed threshold is set at 1,675 rpm (e.g., as shown in  FIG. 7 ), the controller  210  determines whether the measured propeller speed is greater than 1,675 rpm. 
     If, on the other hand, the propeller speed of the propeller is decreasing over time (i.e., the propeller is decelerating), then the propeller speed threshold is a deceleration propeller speed threshold. Accordingly, the controller  210  determines whether the measured speed of the propeller  106  exceeds the deceleration propeller speed threshold. That is, the controller  210  determines whether the measured propeller speed is less than the deceleration propeller speed threshold. For example, if the deceleration propeller speed threshold is set at 1,650 rpm (e.g., as shown in  FIG. 7 ), the controller  210  determines whether the measured propeller speed is less than 1,650 rpm. Notably, in some implementations, the deceleration propeller speed threshold and the acceleration propeller speed threshold are offset from one another. In this way, inadvertent or undesirable switching between propeller speed set points is prevented. 
     At ( 306 ), the method ( 300 ) includes adjusting a propeller speed set point to change the propeller speed of the propeller based at least in part on whether the propeller speed exceeds the propeller speed threshold. For instance, if the measured propeller speed exceeds the propeller speed threshold as determined at ( 304 ), then at ( 306 ) the propeller speed set point can be adjusted. In some implementations, the propeller speed set point is automatically adjusted to adjust propeller speed of the propeller if the propeller speed exceeds a propeller speed threshold. 
     In some implementations, the propeller speed set point is adjustable between a maximum set point (Np Max) and a minimum set point (Np Min). In some implementations, the propeller speed set point is adjustable only between the maximum set point (Np Max) and the minimum set point (Np Min). In such implementations, if the propeller speed of the propeller is increasing and the propeller speed of the propeller exceeds the acceleration propeller speed threshold, then the propeller speed set point is adjusted from the minimum set point (Np Min) to the maximum set point (Np Max). For example, with reference to  FIG. 7 , the propeller speed is shown rapidly increasing from about one and a half seconds (1.5 s) to about four and a half seconds (4.5 s), and as depicted, the propeller speed exceeds the acceleration propeller speed threshold of 1,675 rpm at about four seconds (4 s). Accordingly, the propeller speed set point or demanded propeller speed is adjusted from the minimum set point (Np Min) to the maximum set point (Np Max). The control system  200  can automatically switch or adjust the propeller speed set point when the propeller speed exceeds the acceleration propeller speed set point. By adjusting the propeller speed set point from Np Min to Np Max during fast acceleration of the engine  100  and propeller  106 , the propeller speed is prevented from overshooting the demanded propeller speed (Np Max) and does not reach or obtain the maximum propeller speed limit (Np Max Limit); thus, the propeller  106  and engine  100  are not subject to the negative impacts associated with propeller speed overshoot. 
     If, on the other hand, the propeller speed of the propeller is decreasing and the propeller speed of the propeller exceeds the deceleration propeller speed threshold, then the propeller speed set point is adjusted from the maximum set point (Np Max) to the minimum set point (Np Min). For example, with reference to  FIG. 7 , the propeller speed is shown rapidly decreasing at about fifteen seconds (15 s). As depicted, the propeller speed exceeds the deceleration propeller speed threshold of 1,650 rpm at about nineteen seconds (19 s). Thus, the propeller speed set point or demanded propeller speed is adjusted from the maximum set point (Np Max) to the minimum set point (Np Min). Notably, the control system  200  can automatically switch or adjust the propeller speed set point when the propeller speed exceeds the deceleration propeller speed set point. 
     In some implementations, adjusting the propeller speed set point based at least in part on whether the propeller speed exceeds the propeller speed threshold at ( 306 ) includes causing, by the one or more computing devices, a motor mechanically coupled with a flyweight governor spring of an electric propeller governor to change a preload on the flyweight governor spring. For instance, with reference to  FIGS. 5 and 6 , once the controller  210  determines that the measured propeller speed exceeds the propeller speed threshold at ( 304 ), the motor drive  216  of the controller  210  can command or pulse the motor  262 . When the motor  262  is pulsed, the output shaft  264  of the motor  262  is rotated or otherwise move about its axis of rotation, which applies a torque on the spring adjustment mechanism  260 . When the torque is applied on the spring adjustment mechanism  260 , the preload on the flyweight governor spring  256  is changed. That is, the spring adjustment mechanism  260  changes the tension on the flyweight governor spring  256 . The adjustment of the preload on the flyweight governor spring  256  adjusts the propeller speed set point, e.g., from Np Min to Np Max or vice versa depending on whether the propeller speed is accelerating or decelerating. 
     In some further implementations, causing, by the one or more computing devices, the motor mechanically coupled with the flyweight governor spring of the electric propeller governor to change the preload on the flyweight governor spring includes commanding, by a motor drive of the one or more computing devices communicatively coupled with the motor, the motor to change the preload on the flyweight governor spring such that the propeller speed set point linearly changes from a first set point to a second set point (e.g., from Np Min to Np Max or vice versa). For instance, as shown in  FIG. 7 , when the propeller speed exceeds the acceleration propeller speed threshold at about four seconds (4 s), the motor drive  216  ( FIG. 5 ) commands the motor  262  ( FIG. 5 ) to change the preload on the flyweight governor spring  256  ( FIG. 5 ) such that the propeller speed set point linearly changes from Np Min to Np Max. This gradual or linear change smooths or eases the propeller into the higher demanded speed, or Np Max. As further depicted in  FIG. 7 , when the propeller speed exceeds the deceleration propeller speed threshold at about nineteen seconds (19 s), the motor drive  216  ( FIG. 5 ) commands the motor  262  ( FIG. 5 ) to change the preload on the flyweight governor spring  256  ( FIG. 5 ) such that the propeller speed set point linearly changes from Np Max to Np Min. This gradual or linear change smooths or eases the propeller into the lower demanded speed, or Np Min and prevents jarring of the engine  100  and the propeller  106  operatively coupled thereto. 
       FIG. 10  provides an example computing system  500  according to example embodiments of the present subject matter. The computing system  500  can include one or more computing device(s)  510 . For instance, one of the computing device(s)  510  can be the controller  210  described herein. The computing device(s)  510  can include one or more processor(s)  510 A and one or more memory device(s)  510 B. The one or more processor(s)  510 A can include any suitable processing device, such as a microprocessor, microcontroller, integrated circuit, logic device, and/or other suitable processing device. The one or more memory device(s)  510 B can include one or more computer-readable media, including, but not limited to, non-transitory computer-readable media, RAM, ROM, hard drives, flash drives, and/or other memory devices. 
     The one or more memory device(s)  510 B can store information accessible by the one or more processor(s)  510 A, including computer-readable instructions  510 C that can be executed by the one or more processor(s)  510 A. The instructions  510 C can be any set of instructions that when executed by the one or more processor(s)  510 A, cause the one or more processor(s)  510 A to perform operations. In some embodiments, the instructions  510 C can be executed by the one or more processor(s)  510 A to cause the one or more processor(s)  510 A to perform operations, such as any of the operations and functions for which the computing system  500  and/or the computing device(s)  510  are configured, such as e.g., operations for controlling the engine  100  ( FIG. 1 ) and/or propeller  106  ( FIG. 1 ) as described herein. Thus, the method ( 300 ) can be implemented at least in part by the one or more computing device(s)  510  of the computing system  500 . The instructions  510 C can be software written in any suitable programming language or can be implemented in hardware. Additionally, and/or alternatively, the instructions  510 C can be executed in logically and/or virtually separate threads on processor(s)  510 A. The memory device(s)  510 B can further store data  510 D that can be accessed by the processor(s)  510 A. For example, the data  510 D can include data indicative of the various propeller speed thresholds, among other potential items or settings described herein. 
     The computing device(s)  510  can also include a network interface  510 E used to communicate, for example, with the other components of system  500  (e.g., via a network). The network interface  510 E can include any suitable components for interfacing with one or more network(s), including for example, transmitters, receivers, ports, controllers, antennas, and/or other suitable components. One or more external devices, such as an external remote control, can be configured to receive one or more commands from the computing device(s)  510  or provide one or more commands to the computing device(s)  510 . 
     The technology discussed herein makes reference to computer-based systems and actions taken by and information sent to and from computer-based systems. It will be appreciated that the inherent flexibility of computer-based systems allows for a great variety of possible configurations, combinations, and divisions of tasks and functionality between and among components. For instance, processes discussed herein can be implemented using a single computing device or multiple computing devices working in combination. Databases, memory, instructions, and applications can be implemented on a single system or distributed across multiple systems. Distributed components can operate sequentially or in parallel. 
     Although specific features of various embodiments may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the present disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.