METHODS AND APPARATUS TO CONTROL PROPELLER PITCH IN DUAL ACTING PROPELLERS

Methods, apparatus, systems, and articles of manufacture are disclosed to control propeller pitch in dual acting propellers. An example propeller control system comprising: a piston including a piston rod; a first valve connected to the piston rod via a first piston line and a second piston line, wherein the first valve selectively allows, based on an input signal, hydraulic fluid to transfer to the piston via the first piston line and the second piston line, wherein in the first valve is a three-state valve; and an independent valve connected to the piston rod via a third piston line, wherein the independent valve selectively allows, based on an input signal, hydraulic fluid to transfer to the piston via the third piston line and wherein the independent valve operates independently of the first valve.

CROSS-REFERENCE TO RELATED APPLICATION

This patent claims benefit to Italian Patent Application No. 102023000008460, which was filed on Apr. 28, 2023, and which is hereby incorporated herein by reference in its entirety. Priority to Italian Patent Application No. 102023000008460 filed with the Ministry of Enterprises and Made in Italy on Apr. 28, 2023, is hereby claimed.

FIELD OF THE DISCLOSURE

This disclosure relates generally to propeller control units and, more particularly, to controlling propeller pitch in dual acting propellers.

BACKGROUND

In dual acting propeller aircraft, variable pitch propeller assemblies are operatively configured to adjust propeller blades. Typically, to adjust propeller blade angle, propeller pitch of propeller blades, or a combination of both propeller assemblies include a propeller control unit. Some propeller control units can include a pitch control valve or governor. Based on one or more input signals, the pitch control valve selectively allows an amount of hydraulic fluid to flow to or drain from a pitch actuation assembly positioned within the propeller assembly. The blade angle of the propeller blades can be set to the desired pitch by adjusting the amount of hydraulic fluid in the pitch actuation assembly. Certain variable pitch propeller assemblies include ground beta or reverse mode functionality. For instance, some propeller assemblies include a ground beta enable solenoid and a ground beta enable valve that effectively enable the propeller blades to move from a feather position to a reverse pitch position (e.g., for taxiing on the ground, a reverse angle, for reverse and braking, etc.). These conventional solenoids and valves can increase the weight of the engine.

DETAILED DESCRIPTION

In a dual acting propeller application, the variable pitch propeller assembly includes a plurality of propeller blades rotatable about the axial direction and spaced apart along the circumferential direction. Each propeller blade is rotatable through a plurality of blade angles about respective pitch axes each extending in the radial direction. The variable pitch propeller assembly includes a pitch actuation assembly for adjusting the plurality of propeller blades through the plurality of blade angles and includes a propeller dome defining a chamber, and a propeller control unit (PCU). Typically, the PCU supplies hydraulic fluid to a coarse chamber of a piston to push a cylinder actuator towards a feather position (e.g., a coarse direction). As used herein, the coarse chamber is a cavity located on a first side of the piston in which hydraulic fluid may be supplied or removed to move the piston along an axial direction, which, consequently, moves the propeller blades towards a feather position. As used herein, a fine chamber is a cavity located on a second side of the piston in which hydraulic fluid may be supplied or returned to move the piston along the axial direction, which, consequently, moves the propeller blades towards a reverse position. The feather position, as used herein, is a position at which the propeller blades are approximately parallel to the on-coming airflow. In other words, the propeller blades position with maximum possible pitch angle. As used herein, the coarse direction is the pitch angle increasing. The reverse position, as used herein, is a position at which the propeller blades are approximately perpendicular to the ground level. In other words, the propeller blades position with the minimum possible pitch angle. As used herein, the fine direction is the pitch angle decreasing. The coarse chamber and the fine chamber are separated by a seal. However, a failure of the seal (referred to herein as an actuator seal failure condition) can allow hydraulic fluid to flow from a fine chamber to the coarse chamber within the piston.

Failure of the actuator seal that connects the fine chamber to the coarse chamber within a piston can lead to hazardous events, such as uncontrolled pitch fining. As used herein, pitch fining indicates that the propeller blades are in a vertical position with respect to ground level, which is ideal for take-off and taxiing but not for mid-flight. In some circumstances, uncontrolled pitch fining means feather functionality is ineffective because hydraulic fluid is leaking through the actuator seal from the coarse chamber into the fine chamber. Feathering, as used herein, is the blade pitch angle increasing to the point that the chord line of the blade is approximately parallel to the on-coming airflow. Prior configurations which attempt to enable feathering of the blade even during seal failure conditions include use of counterweights or springs to push the propellers towards a feather position. In prior configurations, the springs are located within a chamber of the propeller dome. In other prior configurations, the counterweights may be located on each blade of the propeller or on the propeller dome. Examples disclosed herein guarantee feather functionality despite the seal failure in counterweight-less applications. Unfortunately, counterweights and springs add extra weight to the aircraft and increase fuel consumption, which reduces efficiency. Examples disclosed herein include an improved PCU with a capability to block hydraulic fluid flow from/to the fine chamber and pressurize the coarse chamber simultaneously. Examples disclosed herein are used in a counterweight-less application, meaning the examples are embedded in a lightweight, compact PCU design, which has a decreased number of internal components and electrical interfaces than prior configurations. Having less internal components increases the mean-time between failure. For example, an additional valve is incorporated in the improved PCU design to control hydraulic fluid flow which reduces pressure drops. Examples disclosed herein provide an improved engine configuration which minimizes or otherwise reduces weight, removes electrical interfaces, and improves associated control logic algorithms.

FIGS.1and2provide various views of an example gas turbine engine100in which one or more examples shown and described herein can be implemented. Particularly,FIG.1provides a side view of the gas turbine engine100, andFIG.2provides a perspective, cutaway view of the gas turbine engine100ofFIG.1. As shown inFIG.1, the gas turbine engine100is, more specifically, a turboprop engine. The gas turbine engine100defines an axial direction A, a radial direction R, and a circumferential direction C (FIG.2) extending three hundred sixty degrees (360°) around the axial direction A. The gas turbine engine100also defines a longitudinal or axial centerline102extending along the axial direction A. The gas turbine engine100extends generally along the axial direction A between a first end103and a second end105, which is the forward and aft end, respectively. Generally, the gas turbine engine100includes a gas generator or core turbine engine104and a propeller assembly106rotatable about the axial centerline102, or more generally, the axial direction A.

As shown inFIG.2, the core turbine engine104generally includes, in serial flow arrangement, a compressor section110, a combustion section112, a turbine section114, and an exhaust section116. A core air flow path118extends from an annular inlet120to one or more exhaust outlets122of the exhaust section116such that the compressor section110, combustion section112, turbine section114, and exhaust section116are in fluid communication.

The compressor section110can include one or more compressors, such as a high pressure compressor (HPC) and a low pressure compressor (LPC). For this example, the compressor section110includes 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 section112includes a reverse-flow combustor (not labeled) and one or more fuel nozzles (not shown). The turbine section114can define one or more turbines, such as a high pressure turbine (HPT) and a low pressure turbine (LPT). For this example, the turbine section114includes a two-stage HPT126for driving the compressor of the compressor section110. The HPT126includes two sequential stages of stator vanes and turbine blades (not labeled). The turbine section114also includes a three-stage free or power turbine128that drives a propeller gearbox134, which in turn drives the propeller assembly106(FIG.1). The exhaust section116includes one or more exhaust outlets122for routing the combustion products to the ambient air.

Referring still toFIG.2, the core turbine engine104can include one or more shafts. In this example, the gas turbine engine100includes a compressor shaft130and a free or power shaft132. The compressor shaft130drivingly couples the turbine section114with the compressor section110to drive the rotational components of the compressor. The power shaft132drivingly couples the power turbine128to drive a gear train140of the propeller gearbox134, which in turn operatively supplies power and torque to the propeller assembly106(FIG.1) via a torque output or propeller shaft136at a reduced RPM. The forward end of the propeller shaft136includes a flange137that provides a mounting interface for the propeller assembly106to be attached to the core turbine engine104.

The propeller gearbox134is enclosed within a gearbox housing138. For this example, the gearbox housing138encloses the gear train140that includes a star gear142and a plurality of planet gears144disposed about the star gear142. The planetary gears144are configured to revolve around the star gear142. An annular gear146is positioned axially forward of the star gear142and planetary gears144. As the planetary gears144rotate about the star gear142, torque and power are transmitted to the annular gear146. As shown, the annular gear146is operatively coupled to or otherwise integral with the propeller shaft136. In some examples, the gear train140may further include additional planetary gears disposed radially between the plurality of planet gears144and the star gear142or between the plurality of planet gears144and the annular gear146. In addition, the gear train140may further include additional annular gears.

As noted above, the core turbine engine104transmits power and torque to the propeller gearbox134via the power shaft132. The power shaft132drives the star gear142, which in turn drives the planetary gears144about the star gear142. The planetary gears144in turn drive the annular gear146, which is operatively coupled with the propeller shaft136. In this way, the energy extracted from the power turbine128supports operation of the propeller shaft136, and through the gear train140, the relatively high RPM of the power shaft132is reduced to a more suitable RPM for the propeller assembly106.

In addition, the gas turbine engine100includes one or more controllers280that control the core turbine engine104and the propeller assembly106. For this example, the controller280is a single unit control device for a Full Authority Digital Engine (FADEC) system operable to provide full digital control of the core turbine engine104, and in some examples, the propeller assembly106. The controller280depicted in the illustrated example ofFIGS.1and2can control various aspects of the core turbine engine104and the propeller assembly106. For example, the controller280can receive one or more signals from sensory or data collection devices and can determine the blade angle of a plurality of propeller blades150(FIG.1) about their respective pitch axes, as well as their rotational speed about the axial direction A based at least in part on the received signals. The controller280can in turn control one or more components of the gas turbine engine100based on such signals. For example, based at least in part on one or more speed or blade pitch signals (or both), the controller280can be operatively configured to control one or more valves such that an amount of hydraulic fluid can be delivered or returned from a pitch actuation assembly of the gas turbine engine100as will be described in greater detail herein. With reference toFIG.1, the gas turbine engine100includes a sensor162positioned on a spinner163and a flange137. In some examples, the sensor162is a beta sensor to detect the plurality of propeller blades150rotational position or the propeller speed. By rotating the plurality of propeller blades150, a sensor handle positioned on the spinner163will rotate so when it passes under a tip of the sensor positioned on the flange137, and depending on the angle of the blade, a different phase shifting to the electrical signal that is translated and sent to the controller280.

With reference toFIG.1, during operation of the gas turbine engine100, a volume of air indicated by arrow148passes across the plurality of propeller blades150circumferentially spaced apart from one another along the circumferential direction C and disposed about the axial direction A, and more particularly for this example, the axial centerline102. The propeller assembly106includes a spinner163aerodynamically contoured to facilitate an airflow through the plurality of propeller blades150. The spinner163is rotatable with the plurality of propeller blades150about the axial direction A and encloses various components of the propeller assembly106, such as e.g., the hub, propeller pitch actuator, piston/cylinder actuation mechanisms, etc. A first portion of air indicated by arrow152is directed or routed outside of the core turbine engine104to provide propulsion. A second portion of air154is directed or routed through the annular inlet120of the gas turbine engine100. The flow of the second portion of air154is denoted by an arrow.

As shown inFIG.2, the second portion of air154enters through the annular inlet120and flows downstream to the compressor section110, which is a forward direction along the axial direction A in this example. The second portion of air154is progressively compressed as it flows through the compressor section110downstream toward the combustion section112.

The compressed air156, with flow indicated by an arrow, flows into the combustion section112where fuel is introduced, mixed with at least a portion of the compressed air156, and ignited to form combustion gases158. The combustion gases158flow downstream into the turbine section114, causing rotary members of the turbine section114to rotate, which in turn supports operation of respectively coupled rotary members in the compressor section110and propeller assembly106. In particular, the HPT126extracts energy from the combustion gases158, causing the turbine blades to rotate. The rotation of the turbine blades of the HPT126causes the compressor shaft130to rotate, and as a result, the rotary components of the compressor are rotated about the axial direction A. In a similar fashion, the power turbine128extracts energy from the combustion gases158, causing the blades of the power turbine128to rotate about the axial direction A. The rotation of the turbine blades of the power turbine128causes the power shaft132to rotate, which in turn drives the gear train140of the propeller gearbox134.

The propeller gearbox134in turn transmits the power provided by the power shaft132to the propeller shaft136at a reduced RPM and desired amount of torque. The propeller shaft136in turn drives the propeller assembly106such that the plurality of propeller blades150rotate about the axial direction A, and more particularly for this example, the axial centerline102of the gas turbine engine100. The exhaust gases, denoted by160, exit the core turbine engine104through the exhaust outlets122to the ambient air.

It should be appreciated that the example gas turbine engine100described herein is provided by way of example only. For example, the engine may include another number and/or type of compressors (such as e.g., reverse flow and/or axial compressors), turbines, shafts, stages, etc. Additionally, in some examples, 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 gas turbine engine, including, for example, turboshaft, turbojets, etc. Moreover, in yet other examples, 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.

Furthermore, although the gas turbine engine100described above is an aeronautical gas turbine engine for propulsion of a fixed-wing aircraft, the gas turbine engine may be configured as any suitable type of gas turbine engine for use in any number of applications, such as marine applications. Furthermore, the innovation could be used on other devices with variable pitch blades such as windmills. The propeller assembly106may rotate due to passing of a fluid, such as air or water, across the plurality of propeller blades150of the propeller assembly106.

FIG.3Ais a schematic view of an example propeller control system300for controlling the propeller assembly106of the gas turbine engine100ofFIGS.1and2. As depicted inFIGS.1and2, the propeller assembly106is driven by the core turbine engine104(FIG.2) by the propeller shaft136. The propeller shaft136(FIG.2) in turn drives a hub from which the plurality of propeller blades150extend outwardly from in the radial direction R. As the propeller shaft136rotates about the axial direction A, the hub in turn rotates the plurality of propeller blades150about the axial direction A. The propeller control system300includes features for controlling the rotational speed of the plurality of propeller blades150about the axial direction A and the pitch of the propeller blades150, as well as features for protecting the components of the propeller assembly106. As shown inFIG.3A, the propeller control system300includes a pitch actuation assembly302and a propeller control unit (PCU)304.

Generally, the pitch actuation assembly302is operatively configured to adjust the plurality of propeller blades150through a plurality of blade angles. Stated differently, the pitch actuation assembly302is operatively configured to rotate each propeller blade150about respective pitch axes P extending in the radial direction R (each pitch axis P is relative to a corresponding propeller blade150). For the example ofFIG.3A, the pitch actuation assembly302is operatively configured to rotate the plurality of propeller blades150between high or coarse pitch blade angles, including a fully feathered blade angle to low or fine pitch blade angles. In this example, the pitch axis P is shown approximately vertical. As used herein, approximately vertical means within 5 degrees of vertical (e.g., perpendicular to the ground). However, in some examples the pitch axis is positioned 10-30 degrees from vertical. As shown inFIG.3A, the plurality of propeller blades150are in a typical flight position (e.g., at an angle approximately 60 degrees from the pitch axis P). Moreover, for this example, the pitch actuation assembly302is additionally operatively configured to rotate the plurality of propeller blades150through reverse pitch angles, which can be useful for ground or taxiing operations, particularly where an aircraft includes multiple engines. In some examples, the reverse position is defined as the plurality of propeller blades150at an angle −20 to −5 degrees from vertical. In this regard, the example propeller assembly106depicted inFIG.3Ais a variable pitch, full feathering, and reverse enabled propeller assembly, and more particularly still, the propeller assembly is configured as a variable pitch constant-speed, full feathering, reverse enabled propeller assembly. In some examples, the propeller control system300includes a sensor342to detect a displacement of the piston. In some examples, the sensor342is a linear variable differential transformer (LVDT) sensor.

Pitch actuation assembly302ofFIG.3Aincludes a housing, cylinder, or propeller dome306that defines an interior chamber and encloses a control piston308that is translatable along the axial direction A within the chamber of the propeller dome306. In particular, the propeller dome306and the outboard side310of the control piston308define a first side of the interior chamber312and the propeller dome306. The inboard side314of the control piston308and the propeller dome306define a second side of the interior chamber316. The control piston308separates the first side of the interior chamber312(e.g., coarse chamber) from the second side of the interior chamber316(e.g., fine chamber) of the chamber along the axial direction A. In some examples, the first side of the interior chamber312(e.g., coarse chamber) actuating area is larger than the second side of the interior chamber316(e.g., fine chamber) actuating area. The control piston308is operatively coupled with a piston rod318that extends along the axial direction A. In particular, the piston rod318extends from the propeller assembly106(where the piston rod318is connected to the control piston308) to the PCU304along the axial direction A. The piston rod318and the control piston308are translatable in unison. The piston rod318encloses three hydraulic fluid transfers or beta tubes that also extend along the axial direction A. The first of the three hydraulic fluid transfers or beta tubes is a fine line320, the second is a coarse line322, and the third is a pitch lock line324. The fine line320transfers hydraulic fluid to the second side316(e.g., fine chamber) and the coarse line322transfers hydraulic fluid to the first side312(e.g., coarse chamber). To control the blade angles of the plurality of propeller blades150, hydraulic fluid (e.g., oil) can be fed through the fine line320and/or the coarse line322to the second side316of the chamber or to the first side312of the chamber in a double-acting system to translate the control piston308along the axial direction A. Depending on the desired blade pitch, hydraulic fluid can enter and exit the fine line320and the coarse line322. Due to use and wear of the control piston308, a gap can occur between the propeller dome306and a seal326causing seal failure. When seal failure occurs, hydraulic fluid supplied to the first side312(e.g., coarse chamber) passes through the seal and is drained from the first side312(e.g., coarse chamber) to the second side316(e.g., fine chamber) of the chamber. External loads overcome the first side312(e.g., coarse chamber) pressure and push an actuator328towards fine pitch, which is a hazardous condition because the plurality of propeller blades150may break during high rotational speeds. When the actuator328pushes towards fine pitch without being commanded, the PCU304engages the pitch lock line324to supply hydraulic fluid to a pitch lock mechanism330(described in more detail inFIG.3B) and prevents the plurality of propeller blades150from pitch fining. In prior methods, counterweights or spring automatically push the propeller towards feather in case of seal failure. The PCU304has the capability to supply hydraulic fluid to the first side312(e.g., coarse chamber) while blocking the second side316(e.g., fine chamber) flow. Additionally, in some examples, the PCU304does this independent of the pitch lock line324capability. Thus, feather capability is guaranteed in the case of failure seals between the first side312(e.g., coarse chamber) to the second side316(e.g., fine chamber) of the chamber independent of counterweights and spring because the first side312is larger than the second side316and the PCU304blockage capability. In return, reducing the weight of the aircraft.

FIG.3Bis a schematic view of the pitch lock mechanism330inFIG.3A. The pitch lock mechanism330locks the plurality of propeller blades150(FIG.1) from moving to the reverse position. When seal failure occurs, hydraulic fluid is supplied through the pitch lock line324(shown inFIG.3A) causing a spring332to compress and plates334to move from a first position336to a second position338. The plates334in the second position338cause a force340on the propeller dome306. In some examples, the force340is a high friction force preventing the piston from moving.

FIG.4is a schematic view of the example propeller control unit (PCU)304ofFIG.3A. The PCU304includes a supply402and a drain404for providing hydraulic fluid to the fine line320, the coarse line322, and the pitch lock line324. In some examples, hydraulic fluid is drained via the fine line320when fine pitch is desired. The supply402and the drain404are controlled by three control valves: a pitch control valve406, a pitch lock valve408, and a mode selection valve410. The pitch control valve406, the pitch lock valve408, and the mode selection valve410are fed hydraulic fluid via a supply line412and drain hydraulic fluid via a drain line (e.g., return line)414. The pitch control valve406selectively allows, based on one or more input signals, hydraulic fluid to flow to the mode selection valve410via a pitch control supply line416. The mode selection valve410is a three-state valve to feed the coarse line322or the fine line320based on one or more input signals. In some examples, the mode selection valve410allows the pitch lock valve408to be independent of both the pitch control valve406and the mode selection valve410.

When the mode selection valve410receives a signal or input signals to pitch the plurality of blades150to increase the propeller blade angle (e.g., feather pitch), the mode selection valve410supplies hydraulic fluid to the coarse line322to create high pressure in the first side312(e.g., coarse chamber). In some examples, this is referred to as a feather command. This pressure forces the control piston308to the right and the actuator328moves the plurality of blades150towards feather. Additionally, hydraulic fluid drains via the fine line320, which returns the hydraulic fluid to the mode selection valve410. The mode selection valve410diverts the hydraulic fluid to the drain line414, which returns the hydraulic fluid to the drain404.

However, if there is a seal failure (e.g., hydraulic fluid leaking from the first side312to the second side316) at seal326, the feather command will be ineffective because the pressure in the first side312(e.g., coarse chamber) is no longer able to overcome the external load on the plurality of propeller blades150. In some examples, the failure is detected by a sensor, and a signal is sent to the pitch lock valve408to engage and supply hydraulic fluid via the pitch lock line324, which locks the plurality of propeller blades150from pitching towards the fine direction (e.g., moving towards parallel with the P-axis). In some examples, a sensor located on the plurality of propeller blades150compared to a control system set point is used to detect failure. In other examples, a sensor located on the propeller dome306compared to the control system set point is used to detect failure. In some examples, sensors on the fine line320and the coarse line322are used to detect failure. In some examples, the sensor may be one of a variable reluctance sensor, a pressure sensor, or a variable differential transducer sensor. To overcome this failure, the mode selection valve410engages a fine line blockage (described in more detail inFIGS.5-7below). The fine line blockage blocks hydraulic fluid from being drained or supplied through the fine line320and the coarse line322is supplied with hydraulic fluid to pressurize the first side312(e.g., coarse chamber). The fine line blockage removes the drainage path on the fine line320, and thus, as the first side312(e.g., coarse chamber) is being pressurized the second side316(e.g., fine chamber) is prevented from draining. Thus, the pressure is increased in both chambers to overcome the seal leakage from the first side312(e.g., coarse chamber) from the second side316(e.g., fine chamber).

In some examples, the lack of drainage from the second side316(e.g., fine chamber) causes the hydraulic fluid to leak through the seal failure of the seal326from the second side316(e.g., fine chamber) to the first side312(e.g., coarse chamber). The leakage of fluid from the second side316causes hazardous conditions because the leakage of fluid allows the control piston308to move towards the second side316(e.g., fine chamber). If pitch coarsening or feathering is commanded in the presence of fluid leakage, the command is ineffective due to the leakage. On the other hand, if fine line blockage is commanded, then feathering functionality is restored, as the fine line320is blocked, the oil in the first side312is pressurized, the oil in the second side316is pressurized by the control piston308motion and is pushed out of the second side316through the failed seal, and the control piston308continues to move up to full feather position. Thus, the increased pressure allows the control piston308to overcome the external loads and regain pitch feathering capability.

In some examples, the second side316(e.g., fine chamber) flow is larger than the first side312(e.g., coarse chamber). In some examples, the mode selection valve410operates independently of the pitch lock valve408functionality. In other examples, the pitch lock functionality of the pitch lock valve408is included in the mode selection valve410, and, as a result, one of a fine line blockage state, a nominal state, or a feather state (described further below in connection withFIGS.5A-7) is provided via the mode selection valve410operating as an independent valve. In some examples, the pitch lock valve408is a solenoid valve.

The mode selection valve410has three states that are illustrated inFIGS.5A-7.FIG.5Ais a schematic view of the mode selection valve410depicted in a fine line blockage state500. As described above, the fine line blockage state500, also referred to as a first state, blocks or prevents hydraulic fluid from being drained or supplied through the fine line320and the coarse line322is supplied with hydraulic fluid to pressurize the first side312(e.g., coarse chamber) when seal failure condition is detected. As shown inFIG.5A, the fine line320is blocked to prevent hydraulic fluid from flowing through the fine line320. In the fine line blockage state500, the drain line414is blocked as well to ensure the second side316(e.g., the fine chamber) (FIG.4) is pressured to force the hydraulic fluid within to flow through the seal failure from the second side316(e.g., the fine chamber) to the first side312(e.g., the coarse chamber) (FIG.4), if not at all. The coarse line322is supplied with hydraulic fluid to pressurize the first side312(e.g., coarse chamber). As shown inFIGS.5A-7, the mode selection valve410includes three supply lines: a fine valve line502, a coarse valve line504, and a supply valve line506. As shown in the example ofFIG.5A, the supply valve line506, also referred to as the first valve line, allows the mode selection valve410to supply hydraulic fluid to the coarse line322, also referred to as the first piston line, via a port508during the seal failure condition.

FIG.5Bis an example configuration of the internal valve components of the mode selection valve410. In this example, the mode selection valve410is shown in the fine line blockage state500, also shown inFIG.5A. This example configuration illustrates a translating spool514that includes ports508,510,512. The translating spool514translates, slides, and/or moves within the seal feather valve to align the ports508,510,512with the supply lines, the fine line320, the coarse line322, and/or the drain line414. InFIG.5B, the supply valve line506and the coarse line322are aligned via the port508. This allows the hydraulic fluid to enter the mode selection valve410via the supply valve line506and exit via the coarse line322. Furthermore, the fine valve line502and the coarse valve line504do not align with one of the ports508,510,512. As such, hydraulic fluid is blocked or prevented from transferring via the fine valve line502and the coarse valve line504.

FIG.6is a schematic view of the mode selection valve410depicted in a nominal state600. The nominal state600, also referred to as a second state, is the normal operation mode of the mode selection valve410when a seal failure condition has not occurred. During the nominal state600, hydraulic fluid can flow through the fine valve line502to the fine line320via a port604and the coarse valve line504to the coarse line322via the port512, respectively.

FIG.7is a schematic view of the mode selection valve410depicted in a feather state700, also referred to as a third state. As mentioned previously, feathering refers to movement of the blade pitch angle increasing to the point that the chord line of the blade is approximately parallel to the on-coming airflow, and the feather state700is the state of the mode selection valve410to force the blade to feather pitch angle. The feather state700is the hydraulic flow through the mode selection valve410when the seal failure is not detected. As shown inFIG.7, in the feather state700the supply valve line506allows the hydraulic fluid to flow to the coarse line322via the port508and the fine line320is routed to the drain line414via the port510. This configuration, the feather state700, allows for the first side312(e.g., the coarse chamber) (FIG.3A) to fill with hydraulic fluid, pressuring the first side312(e.g., the coarse chamber), and hydraulic fluid to be returned from the second side316(e.g., fine chamber) to the mode selection valve410via the fine line320and out through the drain line414. The mode selection valve410is commanded to operate in the three states via predetermined valve currents. In other words, each state corresponds to a particular current level.

FIG.8is a flowchart representative of example machine readable instructions and/or example operations800that may be executed, instantiated, and/or performed by programmable circuitry to control the PCU304. The example machine-readable instructions and/or the example operations800ofFIG.8begin at block802, at which the one or more sensors detects a propeller pitch angle drift towards fine direction. In some examples, a drift can indicate that the propeller pitch angle is moving to and/or motions toward the fine direction for a period of time. In some examples, the period of time is a range of 0.5 second and 3 seconds. In other examples, drift can be defined as movement or motion of the propeller pitch angle to the fine direction by certain number of degrees. In some examples, the number of degrees is a range of 0.5 degrees and 5 degrees. In some examples, the propeller corresponds to the plurality of propeller blades150inFIGS.1and3-4. At block804, oil and/or hydraulic fluid is increased to flow to the coarse chamber. In some examples, the coarse chamber corresponds to the first side312inFIGS.3and4. At block806, a pitch tracking failure condition is detected. In some instances, pitch tracking failure condition is caused by a seal failure at the seal326between the control piston308(FIG.3A) and the propeller dome306(FIG.3A). At block808, a pitch lock is activated to stop the propeller pitch. In some examples, the pitch lock corresponds to the pitch lock valve408(FIG.4). At block810, a control logic test whether feather pitch is commanded. In some examples, the feather pitch command is a request to pitch the plurality of propeller blades150(FIG.1) to increase the propeller blade angle between the plurality of propeller blades150and the P-axis (FIG.3A). If feather pitch is not commanded, the control logic loops to block808. If feather pitch is commanded, the control logic test if the feather pitch command is effective (block812). If the feather pitch command is effective, the control logic feathers the propeller to desired position (block816). In some examples, if the feather pitch command is effective then the angle of plurality of propeller blades150increases between the plurality of propeller blades150and the P-axis. If the feather pitch command is ineffective, the control logic initiates fine line blockage (block814). In some examples, if the feather pitch command is ineffective then the angle does not increase between the plurality of propeller blades150and the P-axis. In some examples, the fine line blockage corresponds to the fine line blockage state500of the mode selection valve410, shown inFIG.5A. In some instances, the mode selection valve410is actuated, controlled, and/or operated to the fine line blockage state500. Once the fine line blockage is initiated, the propellers are feathered to desired position (block816). Thereafter, the example method ofFIG.8ends and the control of the example PCU304resumes in normal conditions until another command or failure is detected.

FIG.9illustrates a graphic view900of example operations800ofFIG.8to adjust the plurality of propeller blades150(FIG.1) pitch angle when the pitch lock valve408is an independent valve. The x-axis represents time902and the y-axis represents the change in value of propeller pitch angle904and propeller RPM906, thus the change in value over time can be charted for the propeller pitch angle904and the propeller RPM906Prior to point1on the graphic view900, the propeller pitch angle904and the propeller RPM906are constant. At point1, a seal failure is detected. In some examples, the seal failure detection at point1corresponds to block802ofFIG.8. After point1, the propeller pitch angle904begins to decrease at a first pitch slope908and the propeller RPM906begins to increase at a first RPM slope910. At point2, a pitch lock is activated. In some examples, point2corresponds to block808ofFIG.8. Due to the pitch lock activation at point2, the propeller pitch angle904and the propeller RPM906remain constant. At point3, a feather pitch is commanded. At point4, the plurality of propeller blades150are feathered with fine line blockage (described inFIG.5A). In some examples, the hydraulic fluid is increased with the mode selection valve410in the fine line blockage state500described inFIG.5A. After point4, the propeller pitch angle904begins to increase at a second pitch slope912and the propeller RPM906begins to decrease at a first RPM slope914. At point5, the plurality of propeller blades150reach a desired pitch angle. Thus, after point5the propeller pitch angle904and the propeller RPM906remain constant.

FIG.10is a flowchart representative of example machine readable instructions and/or example operations1000that may be executed, instantiated, and/or performed by programmable circuitry to control the PCU304. The example machine-readable instructions and/or the example operations1000ofFIG.10begin at block1002, at which the one or more sensors detects a propeller pitch angle drift towards fine. In some examples, drift is defined as movement or motion of the propeller pitch angle toward the fine direction for a period of time. In some examples, the period of time is a range of 0.5 second and 3 seconds. In other examples, drift can be defined as movement or motion of the propeller pitch angle toward the fine direction by certain number of degrees. In some examples, the number of degrees is a range of 0.5 degrees and 5 degrees. At block1004, oil and/or hydraulic fluid is increased to flow to coarse chamber. In some examples, the hydraulic fluid is increased with the mode selection valve410in the nominal state600as shown and described inFIG.6. At block1006, pitch tracking failure condition is detected. In some instances, pitch tracking failure condition is caused by seal failure between the control piston308(FIG.3A) and the propeller dome306(FIG.3A). At block1008, a pitch lock is activated to stop the propeller pitch. In some examples, the pitch lock corresponds to the pitch lock valve408(FIG.4). At block1010, a control logic tests whether feather pitch is commanded. If feather pitch command is not requested, the control logic loops to block1008. If feather pitch is commanded, the control logic disengages the pitch lock (block1012). At block1014, a control logic test whether the feather pitch command is effective. If the feather pitch command is effective the control logic feathers the propeller to desired position (block1018). In some examples, if the feather pitch command is effective the control logic positions the mode selection valve410in the feather state700as shown and described inFIG.7. If the feather pitch command is ineffective, the controls logic initiates fine line blockage (block1016). In some examples, the fine line blockage corresponds to the fine line blockage state500of the mode selection valve410, shown inFIG.5A. Once the fine line blockage is initiated, the propeller is feathered to desired position (block1018). Thereafter, the example method ofFIG.10ends and the control of the example PCU304resumes in normal conditions until another command or failure is detected.

FIG.11illustrates a graphic view1100of example control logic1000ofFIG.10to adjust the plurality of propeller blades150(FIG.1) pitch angle. The x-axis represents time1102and the y-axis represents the value of propeller pitch angle1104and propeller RPM1106. Prior to point1on the graphic view900, the propeller pitch angle1104and the propeller RPM1106are constant. At point1, a seal failure is detected. In some examples, the seal failure detection at point1corresponds to block1002ofFIG.10. In some examples, the hydraulic fluid is increased with the mode selection valve410in the nominal state600as shown and described inFIG.6. After point1, the propeller pitch angle1104begins to decrease at a first pitch slope1108and the propeller RPM1106begin to increase at a first RPM slope1110. At point2, a pitch lock is activated. In some examples, point2corresponds to block1008ofFIG.10. Due to the pitch lock activation at point2, the propeller pitch angle904and the propeller RPM906remain constant. At point3, a feather pitch is commanded, and the pitch lock is disengaged. Due to the pitch lock functionality not included in an independent valve, the pitch lock needs to be disengaged before initiating feathering. In some examples, point3corresponds to blocks1010and1012ofFIG.10. At point4, the pitch lock is re-engaged. In some examples, the pitch lock is re-engaged because pitch tracking failure is detected again. At point5, the plurality of propeller blades150are feathered with fine line blockage (described inFIG.5A). In some examples, the hydraulic fluid is increased with the mode selection valve410in the fine line blockage state500described inFIG.5A. After point5, the propeller pitch angle1104begins to increase at a second pitch slope1112and the propeller RPM1106begins to decrease at a second RPM slope1114. At point6, the plurality of propeller blades150reach a desired pitch angle. Thus, after point6the propeller pitch angle1104and the propeller RPM1106remain constant. Due to the pitch lock functionality not being an independent valve (e.g., pitch lock is not independent from feather functionality), the propeller pitch angle1104continues to increase and the propeller RPM1106continues to decrease between points2to5. In contrast, the propeller pitch angle904and the propeller RPM906are constant between points2to4, as shown in the graphic view900ofFIG.9where the pitch lock valve408is an independent valve.

FIG.12is a block diagram of an example programmable circuitry platform1200structured to execute and/or instantiate the example machine-readable instructions and/or the example operations ofFIGS.8and10. The programmable circuitry platform1200can be, for example, a server, a personal computer, a workstation, a self-learning machine (e.g., a neural network), a mobile device (e.g., a cell phone, a smart phone, a tablet such as an iPad™), etc.) or other wearable device, or any other type of computing and/or electronic device.

The programmable circuitry platform1200of the illustrated example includes programmable circuitry1212. The programmable circuitry1212of the illustrated example is hardware. For example, the programmable circuitry1212can be implemented by one or more integrated circuits, logic circuits, FPGAs, microprocessors, CPUs, GPUs, DSPs, and/or microcontrollers from any desired family or manufacturer. The programmable circuitry1212may be implemented by one or more semiconductor based (e.g., silicon based) devices.

The programmable circuitry1212of the illustrated example includes a local memory1213(e.g., a cache, registers, etc.). The programmable circuitry1212of the illustrated example is in communication with main memory1214,1216, which includes a volatile memory1214and a non-volatile memory1216, by a bus1218. The volatile memory1214may be implemented by Synchronous Dynamic Random Access Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS® Dynamic Random Access Memory (RDRAM®), and/or any other type of RAM device. The non-volatile memory1216may be implemented by flash memory and/or any other desired type of memory device. Access to the main memory1214,1216of the illustrated example is controlled by a memory controller1217. In some examples, the memory controller1217may be implemented by one or more integrated circuits, logic circuits, microcontrollers from any desired family or manufacturer, or any other type of circuitry to manage the flow of data going to and from the main memory1214,1216.

The programmable circuitry platform1200of the illustrated example also includes interface circuitry1220. The interface circuitry1220may be implemented by hardware in accordance with any type of interface standard, such as an Ethernet interface, a universal serial bus (USB) interface, a Bluetooth® interface, a near field communication (NFC) interface, a Peripheral Component Interconnect (PCI) interface, and/or a Peripheral Component Interconnect Express (PCIe) interface.

In the illustrated example, one or more input devices1222are connected to the interface circuitry1220. The input device(s)1222permit(s) a user (e.g., a human user, a machine user, etc.) to enter data and/or commands into the programmable circuitry1212.

One or more output devices1224are also connected to the interface circuitry1220of the illustrated example. The interface circuitry1220of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip, and/or graphics processor circuitry such as a GPU.

The programmable circuitry platform1200of the illustrated example also includes one or more mass storage discs or devices1228to store firmware, software, and/or data. Examples of such mass storage discs or devices1228include magnetic storage devices (e.g., floppy disk, drives, HDDs, etc.), optical storage devices (e.g., Blu-ray disks, CDs, DVDs, etc.), RAID systems, and/or solid-state storage discs or devices such as flash memory devices and/or SSDs.

The machine readable instructions1232, which may be implemented by the machine readable instructions ofFIGS.8and10, may be stored in the mass storage device1228, in the volatile memory1214, in the non-volatile memory1216, and/or on at least one non-transitory computer readable storage medium such as a CD or DVD which may be removable.

From the foregoing, it will be appreciated that example systems, apparatus, articles of manufacture, and methods have been disclosed that allow dual acting propellers to feather propeller blades when seal failure occurs with less weight added to the aircraft and minimizing dedicated control logic. Disclosed systems, apparatus, articles of manufacture, and methods improve the efficiency of aircraft by reducing weight added to the propeller control system. Additionally, the apparatus and methods disclosed herein allow for pitch fining under seal failure conditions and minimize dedicated control logic by removing seal failure identification algorithm. Disclosed systems, apparatus, articles of manufacture, and methods are accordingly directed to one or more improvement(s) in the operation of a machine such as a computer or other electronic and/or mechanical device.

Example methods, apparatus, systems, and articles of manufacture to control propeller pitch in dual acting propellers are disclosed herein. Further aspects of the present disclosure are provided by the subject matter of the following clauses.

A propeller control system comprising a piston including a piston rod, a first valve connected to the piston rod via a first piston line and a second piston line, wherein the first valve selectively allows, based on an input signal, hydraulic fluid to transfer to the piston via the first piston line and the second piston line, wherein in the first valve is a three-state valve, and an independent valve connected to the piston rod via a third piston line, wherein the independent valve selectively allows, based on an input signal, hydraulic fluid to transfer to the piston via the third piston line and wherein the independent valve operates independently of the first valve.

The propeller control system of any preceding clause, further includes a propeller dome to house the piston wherein a first side of the piston defines a coarse chamber and a second side of the piston defines a fine chamber, and wherein the coarse chamber is larger than the fine chamber, and the fine chamber is separated from the coarse chamber with a seal.

The propeller control system of any preceding clause, wherein in the first valve includes a first state, the first state is a first valve line connected to the first piston line of the piston rod via a first port to transfer hydraulic fluid to a first side of the piston, and a second valve line disconnected from the second piston line of the piston rod.

The propeller control system of any preceding clause, wherein in the first valve includes a second state, the second state is a second valve line connected to the first piston line of the piston rod via a second port to transfer hydraulic fluid to a first side of the piston, and a third valve line connected to the second piston line of the piston rod via a third port to transfer hydraulic fluid to a second side of the piston.

The propeller control system of any preceding clause, wherein in the first valve includes a third state, the third state is a first valve line connected to the first piston line of the piston rod via a first port to transfer hydraulic fluid to a first side of the piston, and the second piston line of the piston connected to a drain line via a third port to transfer hydraulic fluid from a second side of the piston.

The propeller control system of any preceding clause, further including a second valve to selectively allow, based on a signal, hydraulic fluid transfer to the first valve.

The propeller control system of any preceding clause, wherein the independent valve is connected to the third piston line of the piston rod to transfer hydraulic fluid, wherein the hydraulic fluid is transferred with respect to a pitch lock mechanism to prevent a plurality of blades from moving towards fine direction.

The propeller control system of any preceding clause, wherein a controller sends a signal to the first valve to operate in a first state, a second state, or a third state.

A variable pitch propeller assembly comprising a plurality of blades rotatable about an axial direction, a piston including a piston rod, and a propeller control system including a first valve to selectively, based on an input signal, transfer hydraulic fluid to a first piston line and a second piston line of the piston rod via the first piston line and the second piston line, wherein in the first valve is a three-state valve, and an independent valve to transfer hydraulic fluid to a third line of the piston rod, wherein the independent valve operates independently of the first valve.

The variable pitch propeller assembly of any preceding clause, wherein in the first valve includes a first state, the first state is a first valve line connected to the first piston line of the piston rod via a first port to transfer hydraulic fluid to a first side of the piston, and a second valve line disconnected from the second piston line of the piston rod.

The variable pitch propeller assembly of any preceding clause, wherein in the first valve includes a second state, the second state is a second valve line connected to the first piston line of the piston rod via a second port to transfer hydraulic fluid to a first side of the piston, and a third valve line connected to the second piston line of the piston rod via a third port to transfer hydraulic fluid to a second side of the piston.

The variable pitch propeller assembly of any preceding clause, wherein in the first valve includes a third state, the third state is a first valve line connected to the first piston line of the piston rod via a first port to transfer hydraulic fluid to a first side of the piston, and the second piston line of the piston connected to a drain line via a third port to transfer hydraulic fluid from a second side of the piston.

The variable pitch propeller assembly of any preceding clause, wherein a second valve is to selectively allow, based on a signal, hydraulic fluid transfer to the first valve.

The variable pitch propeller assembly of any preceding clause, further includes a propeller dome to house the piston wherein a first side of the piston defines a coarse chamber and a second side of the piston defines a fine chamber, wherein the coarse chamber is larger than the fine chamber, and the fine chamber is separated from the coarse chamber with a seal.

The variable pitch propeller assembly of any preceding clause, wherein the independent valve transfers hydraulic fluid with respect to the third line of the piston rod to a pitch lock mechanism to prevent the plurality of blades from moving towards fine direction.

The variable pitch propeller assembly of any preceding clause, a controller sends a signal to the first valve to operate in a first state, a second state, or a third state.

A method to control propeller pitch in dual acting propellers, the method comprising detecting a drift in a pitch angle of a blade towards fine direction, defining a pitch tracking failure condition, supplying, in response to detecting the drift, hydraulic fluid to a first side of a piston defining a coarse chamber, actuating, based on detection of the pitch tracking failure condition, a first valve in a first state, the first state is a first valve line connected to the first piston line of a piston rod via a first port to transfer hydraulic fluid to a first side of the piston, and a second valve line disconnected from a second piston line of the piston rod, and feathering a plurality of blades to a desired position.

The method of any preceding clause, further including activating an independent valve to transfers hydraulic fluid to a third piston line of the piston rod to a pitch lock mechanism to prevent the plurality of blades from moving towards fine direction.

The method of any preceding clause, wherein in the first valve includes a second state, the second state is a second valve line connected to the first piston line of the piston rod via a second port to transfer hydraulic fluid to a first side of the piston, and a third valve line connected to the second piston line of the piston rod via a third port to transfer hydraulic fluid to a second side of the piston.

The method of any preceding clause, wherein in the first valve includes a third state, the third state is a first valve line connected to the first piston line of the piston rod via a first port to transfer hydraulic fluid to a first side of the piston, and the second piston line of the piston connected to a drain line via a third port to transfer hydraulic fluid from a second side of the piston.