Patent Description:
An engine flameout refers to unintended shutdown of an engine due to the extinction of flames in the combustion chamber. In some cases, inclement weather conditions may be responsible for an engine flameout, for example due to ingested ice or water during a rain storm and/or a hail storm. Other causes of engine flameout are also known to exist.

When an engine flameout event occurs during aircraft flight, or in other sensitive circumstances, proper and timely reignition of the engine can be crucial. Traditional approaches require a pilot or other operator to manually command reignition of the engine. In the case of engine flameout during aircraft flight, the pilot may need to concurrently stabilize the aircraft, making manually commanding reignition of the engine a complex operation. In other cases, the pilot may be absent from the cockpit for a period of time (e.g. the aircraft is on autopilot), and thus the engine may be left non-operational for an extended duration.

<CIT> discloses a system and method for starting gas turbine engines.

In accordance with a first aspect of the present invention, there is provided a method for reigniting an engine of an aircraft in accordance with claim <NUM>.

In an embodiment according to the previous embodiment, the method further comprises performing a fuel purge prior to initiating the predetermined ignition sequence while the commanded engine operating state corresponds to the engine on state and when the engine speed is below the predetermined threshold.

In an embodiment according to any one or more of the previous embodiments, performing the fuel purge comprises dry motoring the engine for a predetermined period of time.

In an embodiment according to any one or more of the previous embodiments, the method further comprises, following the predetermined ignition sequence, determining whether the engine was successfully ignited.

In an embodiment according to any one or more of the previous embodiments, the method further comprises, responsive to determining that the engine was not successfully ignited, repeating the predetermined ignition sequence while the commanded engine operating state corresponds to the engine on state and when the engine speed is below the predetermined threshold.

In an embodiment according to any one or more of the previous embodiments, the method further comprises producing an alert indicating that the engine was not successfully ignited.

In an embodiment according to any one or more of the previous embodiments, the method further comprises: detecting a change in the commanded engine operating state from the engine on state to an engine off state; and delaying initiation of the predetermined ignition sequence until a subsequent change in the commanded engine operating state to the engine on state is detected.

In an embodiment according to any one or more of the previous embodiments, the predetermined threshold is a second predetermined threshold, and the method further comprises: comparing the engine speed to a first predetermined threshold greater than the second predetermined threshold; and while the commanded engine operating state corresponds to the engine on state, and when the engine speed is above the first predetermined threshold, performing a predetermined reignition sequence for the engine.

In accordance with a second aspect of the present invention, there is provided a system for reigniting an engine of an aircraft in accordance with claim <NUM>.

In an embodiment according to the previous embodiment, the program instructions are further executable for performing a fuel purge prior to initiating the predetermined ignition sequence while the commanded engine operating state corresponds to the engine on state and when the engine speed is below the predetermined threshold.

In an embodiment according to any one or more of the previous embodiments, the program instructions are further executable for, following the predetermined ignition sequence, determining whether the engine was successfully ignited.

In an embodiment according to any one or more of the previous embodiments, the program instructions are further executable for, responsive to determining that the engine was not successfully ignited, repeating the predetermined ignition sequence while the commanded engine operating state corresponds to the engine on state and when the engine speed is below the predetermined threshold.

In an embodiment according to any one or more of the previous embodiments, the program instructions are further executable for producing an alert indicating that the engine was not successfully ignited.

In an embodiment according to any one or more of the previous embodiments, the program instructions are further executable for: detecting a change in the commanded engine operating state from the engine on state to an engine off state; and delaying initiation of the predetermined ignition sequence until a subsequent change in the commanded engine operating state to the engine on state is detected.

In an embodiment according to any one or more of the previous embodiments, the predetermined threshold is a second predetermined threshold, wherein the program instructions are further executable for: comparing the engine speed to a first predetermined threshold greater than the second predetermined threshold; and while the commanded engine operating state corresponds to the engine on state, and when the engine speed is above the first predetermined threshold, performing a predetermined reignition sequence for the engine.

Features of the systems, devices, and methods described herein may be used in various combinations, in accordance with the embodiments described herein. In particular, any of the above features may be used alone, together in any suitable combination, and/or in a variety of arrangements, as appropriate.

With reference to <FIG>, there is illustrated a gas turbine engine <NUM>. Note that while engine <NUM> is a turbofan engine, the methods and systems described herein may be applicable to turboprop, turboshaft, and other types of gas turbine engines, or combustion engines generally. In addition, the engine <NUM> may be an auxiliary power unit (APU), an auxiliary power supply (APS), a hybrid engine, or any other suitable type of engine. In addition, although the foregoing discussion relates to a singular engine <NUM>, it should be understood that the techniques described herein can be applied substantially concurrently to multiple engines.

The engine <NUM> generally comprises in serial flow communication: a fan <NUM> through which ambient air is propelled, a compressor section <NUM> for pressurizing the air, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section <NUM> for extracting energy from the combustion gases. Axis <NUM> defines an axial direction of the engine <NUM>. In some embodiments, a low pressure spool is composed of a low pressure shaft and a low pressure turbine. The low pressure shaft drives the propeller <NUM>. A high pressure spool is composed of a high pressure turbine attached to a high pressure shaft, which is connected to the compressor section <NUM>. It should be noted that other configurations for the engine <NUM> are also considered.

Control of the operation of the engine <NUM> can be effected by one or more control systems, for example an engine controller <NUM>. The engine controller <NUM> can modulate a fuel flow rate provided to the engine <NUM>, the position and/or orientation of variable geometry mechanisms within the engine <NUM>, a bleed level of the engine <NUM>, and the like.

In the course of normal operation, it can occur that the engine <NUM> experiences a flameout event: that is to say, that an unintended shutdown of the engine <NUM> can occur due to the extinction of flames in the combustor <NUM>. The flameout event can occur despite various countermeasures taken to prevent or reduce the risk of the flameout event occurring. In response to the flameout event occurring, it may be desirable for a controller of the engine <NUM> to initiate a procedure for reignition of the engine <NUM> without operator input, for instance to reduce the number of tasks required of the operator of the engine <NUM>. As used herein, the terms "reignite", "reigniting", or "reignition" refer to procedures for starting an engine from a low speed and/or substantially stopped condition, and to procedures for renewing the flames in the combustor <NUM> of the engine <NUM> while the engine <NUM> is still at a high speed condition; that is to say, when one or more elements of the engine <NUM> are rotating at a high speed.

With reference to <FIG>, there is shown a system <NUM> for reigniting an engine of an aircraft, for example the engine <NUM>. The system <NUM> is composed of the engine controller <NUM>, an ignition system <NUM>, and optionally a high-speed reignition system <NUM>. The system <NUM> is communicatively coupled to the engine <NUM> for obtaining information about the operating conditions of the engine <NUM>, for instance from one or more sensors incorporated within the engine <NUM>, or coupled thereto. Additionally, the ignition system <NUM> and the high-speed reignition system <NUM> are coupled to the engine <NUM> for respectively causing ignition and high speed reignition of the engine <NUM>. For example, the ignition system <NUM> is used to ignite the engine <NUM> when the engine is off or at a low speed condition. In instances in which the engine <NUM> is part of an aircraft, the ignition system <NUM> is used by the engine controller <NUM> to cause ignition of the engine <NUM>, for instance when the aircraft is on the ground, or at low speed during flight. The high-speed reignition system <NUM> can be used by the engine controller <NUM> to reignite the engine when the engine is flamed out and remains at a high speed condition, for instance during flight, when the aircraft is already airborne and travelling at some speed.

The system <NUM> is also communicatively coupled to operator input <NUM>, which can include buttons, switches, dials, or other discrete-type input mechanisms, touchscreens or other electronic input devices, and the like. For example, the engine controller <NUM> can be communicatively coupled to the operator input <NUM> for obtaining various commands from an operator of the engine <NUM>. For example, the operator input <NUM> includes an activation switch for the engine <NUM> which sets a commanded operating state for the engine <NUM>. The commanded operating state can be an "off" state, an "on" state, a "start" state, and the like, each associated with respective positions for the activation switch. The "off" position is used to command the engine <NUM> to shut down when in operation, and to remain shut down. The "on" position is used to command the engine <NUM> to remain in operation. The "start" position, which can be a momentary switch position, is used to command the engine to begin operation when in a shutdown state; that is to say, to cause the engine <NUM> to transition from the "off" state to the "on" state. It should be noted that other embodiments are considered: the operator input <NUM> can include other types of devices for commanding the engine <NUM> to operate in one or more states. Additionally, other states for the engine <NUM> are also considered: for instance, a separate "shut down" state can be used to cause the engine <NUM> to transition from the "on" state to the "off" state, and the like.

The engine controller <NUM> can be any suitable type of engine controller, including a full-authority digital engine controller (FADEC) or similar device. In some embodiments, the engine controller <NUM> is used in the context of an aircraft. The engine controller is configured for controlling operation of more than one engine <NUM> substantially concurrently. The engine controller <NUM> is also configured for logging various information about aircraft usage and operating conditions, including engine speed, engine operating state, and the like, and to log the occurrence of certain events, for example engine flameout events. To this end, the engine controller <NUM> can be provided with, or be coupled to, a variety of sensors to allow the engine controller <NUM> to monitor operating conditions of the engine.

In operation, the engine controller <NUM> can monitor the operating state of the engine <NUM> and compare with the commanded operating state for the engine <NUM>, as provided via the operator input <NUM>. In the event of an engine flameout event, the engine controller <NUM> is configured for initiating a procedure to attempt to reignite the engine <NUM>, if the commanded operating state remains unchanged. Put differently, following an engine flameout event, the engine controller <NUM> verifies whether an operator has requested a change in the operating state of the engine <NUM>, via the operator input <NUM>. If the commanded operating state is still the "on" state, the engine controller <NUM> attempts to reignite the engine <NUM>; that is to say, the engine controller <NUM> attempts reignition without any specific input from the operator of the engine <NUM>.

The detection of a flameout event within the engine <NUM> can be done in any suitable fashion. In some embodiments, the engine controller <NUM> can determine the occurrence of a flameout event due to a drop in speed or power of the engine <NUM>, which was not commanded by an operator via the operator input <NUM>. In other embodiments, the engine controller <NUM> can determine the occurrence of a flameout event due to a change in temperature within the engine <NUM>, or within a particular portion thereof. Other approaches for detecting the flameout event are considered.

Following detection of a flameout event, the engine controller <NUM> is configured for attempting to reignite the engine <NUM> using the ignition system <NUM> or, optionally, the high-speed reignition system <NUM>, depending on the operating conditions of the engine <NUM>. In some embodiments, the engine controller <NUM> determines, based on a speed of the engine <NUM>, whether reignition of the engine should be performed by the ignition system <NUM> or by the high-speed reignition system <NUM>. The speed of the engine can be determined in any suitable fashion, using any suitable sensors and/or algorithms. For example, when the speed of the engine <NUM> is above a first threshold, the engine controller <NUM> commands the high-speed reignition system <NUM> to attempt to reignite the engine <NUM>. When the speed of the engine <NUM> is below a second threshold, the engine controller <NUM> instead commands the ignition system <NUM> to reignite the engine <NUM>. The ignition system <NUM> can perform a predetermined ignition sequence for the engine <NUM>, which may also be used when cold starting the engine <NUM> on the ground, or the like. When the speed of the engine is between the first and second thresholds, the engine controller <NUM> can be configured to not attempt reignition, unless manually commanded by an operator.

The particular speed thresholds used by the engine controller <NUM> when deciding whether to reignite the engine <NUM> can vary based on implementation, engine type, engine operating conditions, safety standards, and the like. For example, the first threshold can be set at <NUM>% of a maximum speed for the engine <NUM>, at <NUM>% of a maximum speed for the engine <NUM>, or at any other suitable fraction of the maximum speed for the engine <NUM>. The second threshold can be set at <NUM>% of the maximum speed for the engine <NUM>, <NUM>% of the maximum speed for the engine <NUM>, or any other suitable fraction of the maximum speed for the engine <NUM>. In instances where the engine <NUM> operates in the context of an aircraft, the maximum speed for the engine <NUM> can be a cruising speed, a maximum takeoff speed, or any other suitable speed. Other thresholds can be set based on other values, depending on the operating context of the engine <NUM>.

In addition, it should be understood that other factors may be used by the engine controller <NUM> when determining whether to use the high-speed reignition system <NUM> or the ignition system <NUM>. For instance, the altitude of the aircraft, the air pressure in the vicinity of the engine <NUM>, the operating temperature of the engine, and the like, can factor into the decision of the engine controller <NUM>. Other factors can also be considered.

In some embodiments, the engine controller <NUM> substantially continuously monitors the commanded operating state for the engine <NUM> following the occurrence of the flameout event. If, at any point, the commanded operating state is changed, the engine controller <NUM> cancels the reigniting procedures initiated by the engine controller <NUM>, and waits for the operator of the engine <NUM> to manually request reignition of the engine <NUM>, for example by setting the commanded operating state to "start". Alternatively, if the commanded operating state is changed, the engine controller <NUM> can delay the reigniting procedure initiated by the engine controller <NUM> until the commanded operating state is changed once again. For example, if the commanded operating state is returned to the "on" position, the engine controller <NUM> can resume the reignition procedure. In some other embodiments, the engine controller <NUM> substantially continuously monitors the speed of the engine <NUM>: if the speed of the engine <NUM> is suitable for attempting a reignition procedure, the engine controller <NUM> then determines whether the commanded operating state is the "on" state, and if so, attempts reignition, as appropriate. Other embodiments are also considered.

In some embodiments, prior to attempting reignition of the engine <NUM>, the engine controller <NUM> can command a fuel purge of the engine <NUM>. The fuel purge can be performed in any suitable way, for instance by dry motoring the engine <NUM>. For example, once the engine controller <NUM> has determined that the speed of the engine <NUM> is below the second threshold, and that the commanded operating state for the engine <NUM> is set to "on" (for instance as set by the operator input <NUM>), the engine controller <NUM> can command dry motoring of the engine <NUM> for a predetermined period of time. Other steps can also be taken prior to reigniting the engine <NUM>.

In some embodiments, the engine controller <NUM> is configured for determining whether the reignition attempt was successfully executed. Techniques similar to those used for detecting the flameout event can be used to determine whether the engine <NUM> was successfully reignited. When the engine <NUM> was not successfully reignited, the engine controller <NUM> can produce an alert, for example for an operator of the engine <NUM>. The alert can be a visual alert, an audible alert, or the like. In addition, the engine controller <NUM> can attempt to reignite the engine <NUM> substantially continuously, if a previous attempt has failed. Once the engine <NUM> is successfully reignited, the engine controller <NUM> can return to normal operation, and can optionally inform the operator that the engine <NUM> is once again operational.

In one example, the engine controller <NUM> detects an engine flameout event, then determines the commanded engine operating state and the engine speed. The operator input <NUM> still indicates a commanded operating state of "on", and the engine speed is above the first threshold. The engine controller <NUM> then attempts to reignite the engine <NUM> via the high-speed reignition system <NUM>. When the engine controller <NUM> detects that the high-speed reignition system <NUM> failed to reignite the engine <NUM>, the engine controller once again determines the commanded engine operating state and the engine speed. At this second time, the engine controller <NUM> determines that the engine speed is now below the second threshold, and that commanded engine operating state is unchanged. The engine controller <NUM> then commands the ignition system <NUM> to attempt reignition of the engine <NUM>. After determining that the engine <NUM> was successfully reignited, the engine controller <NUM> can return to normal operation.

With reference to <FIG>, there is shown a method <NUM> for reigniting an engine of an aircraft, for example the engine <NUM>. As will be described, certain optional steps of the method <NUM> can also serve for reigniting the engine <NUM>. It should also be noted that although the foregoing discussion is focused on embodiments in which the engine <NUM> is used in the context of an aircraft, other implementations are also considered. In some embodiments, the method <NUM> forms part of one or more procedures initiated by a controller of the engine <NUM>, for instance the engine controller <NUM>, for reigniting the engine <NUM> without any specific operator input.

At step <NUM>, the operation of the engine <NUM> is monitored, for example by the engine controller <NUM>, to detect the occurrence of flameout events, such as flameout events during flight. At decision step <NUM>, when a flameout event is detected by the engine controller <NUM>, the method <NUM> moves to step <NUM>. As long as no flameout event is detected, the method returns to step <NUM>.

At step <NUM>, the speed of the engine <NUM> and the commanded operating state for the engine <NUM> are monitored, for example by the engine controller <NUM>. The engine controller <NUM> is configured for interfacing with any suitable type and number of sensors, systems, and the like, for adequately monitoring the speed and commanded operating state of the engine <NUM>.

At decision step <NUM>, a determination is made regarding whether the commanded operating state for the engine <NUM> is set to the on state. For example, the engine controller <NUM> detects the commanded operating state from an operator input, for instance the operator input <NUM>. Optionally, if the commanded operating state is set to off, or any other state different from the on state, the method <NUM> proceeds to step <NUM>, where the reignition procedure initiated by the engine controller <NUM> is halted. Optionally still, the method <NUM> can return to step <NUM>, and continue to monitor the speed and commanded operating state. When the commanded operating state is set to the on state, the method <NUM> proceeds optionally to decision step <NUM>, or to decision step <NUM>.

At optional decision step <NUM>, a determination is made regarding whether the engine speed is above a first threshold. The first threshold can be a fraction of a maximum operating speed of the engine <NUM>, for example <NUM>% of the maximum speed, <NUM>% of the maximum speed, or any other suitable value. When the engine speed is above the first threshold, the method <NUM> moves to optional step <NUM>. When the engine speed is not above the first threshold, the method <NUM> moves to decision step <NUM>. The comparison between the engine speed and the first threshold can be performed in any suitable way, using any suitable calculations or algorithms.

At step <NUM>, a predetermined reigniting sequence for the engine <NUM> is initiated, for example by the engine controller <NUM>. The reigniting sequence can be implemented by any suitable device or system, including the high speed reignition system <NUM>. In this fashion, an attempt at reigniting the engine is performed when the commanded operating state is the on state, and when the engine speed is above the first predetermined threshold. Optionally, after step <NUM>, the method <NUM> can move to decision step <NUM>.

At decision step <NUM>, a determination is made regarding whether the engine speed is below a second threshold, which is distinct from the first threshold. The second threshold can be a fraction of a maximum operating speed of the engine <NUM>, for example <NUM>% of the maximum speed, <NUM>% of the maximum speed, or any other suitable value. When the engine speed is below the second threshold, the method <NUM> moves to step <NUM>. When the engine speed is not below the second threshold, the method <NUM> can return to some previous step, for instance step <NUM>, and continue to monitor the speed and commanded operating state of the engine <NUM>. The comparison between the engine speed and the second threshold can be performed in any suitable way, using any suitable calculations or algorithms.

At step <NUM>, a predetermined ignition sequence for the engine <NUM> is initiated, for example by the engine controller <NUM>. The ignition sequence can be implemented by any suitable device or system, including the ignition system <NUM>. In this fashion, an attempt at reigniting the engine is performed when the commanded operating state is the on state, and when the engine speed is below the second predetermined threshold. In some embodiments, the ignition sequence implemented by the ignition system <NUM> is the same ignition sequence as would be used to start the engine <NUM> from a shutdown state, for instance a cold start ignition sequence. In other embodiments, the ignition sequence may be a different ignition sequence. Optionally, after step <NUM>, the method <NUM> can move to decision step <NUM>.

At decision step <NUM>, optionally a determination is made regarding whether an engine reignition is detected. For example, the engine controller <NUM> is configured for monitoring the operating conditions of the engine <NUM> to detect a reignition of the engine <NUM>, following steps <NUM> or <NUM>, respectively. If the engine <NUM> was successfully reignited, the method <NUM> can optionally move to step <NUM>. If the engine <NUM> was not successfully reignited, the method <NUM> can return to some previous step, for instance step <NUM>, to reattempt reigniting the engine <NUM>. Optionally still, if the engine <NUM> was not successfully reignited, an alert can be produced for the operator of the engine <NUM>, for instance by the engine controller <NUM>.

At step <NUM>, following successful reignition of the engine <NUM>, or following a determination that the commanded operating state has changed, or is no longer set to the "on" state, the reignition procedure initiated by the engine controller <NUM> can be deactivated. In some embodiments, once the controller-initiated procedure is deactivated, the engine controller <NUM> requires a manual input from an operator to reignite the engine.

In some embodiments, a fuel purge of the engine <NUM> is performed as part of either or both of the predetermined reigniting sequence at high speed and the predetermined ignition sequence. Other variations are also considered, as appropriate.

With reference to <FIG>, the method of <FIG> may be implemented by a computing device <NUM> as an embodiment of the engine controller <NUM>. The processing unit <NUM> may comprise any suitable devices configured to implement the functionality of the engine controller <NUM> such that instructions <NUM>, when executed by the computing device <NUM> or other programmable apparatus, may cause the functions/acts/steps performed by the engine controller <NUM> as part of the method <NUM> and as described herein to be executed. The processing unit <NUM> may comprise, for example, any type of general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, a central processing unit (CPU), an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, other suitably programmed or programmable logic circuits, custom-designed analog and/or digital circuits, or any combination thereof.

It should be noted that the computing device <NUM> may be implemented as part of a FADEC or other similar device, including electronic engine control (EEC), engine control unit (EUC), engine electronic control system (EECS), and the like. In addition, it should be noted that the techniques described herein can be performed by the engine controller <NUM> substantially in real-time.

Claim 1:
A method (<NUM>) for reigniting an engine (<NUM>) of an aircraft, comprising:
obtaining a commanded engine operating state from an operator input (<NUM>) settable to an engine off state, to an engine start state, and to an engine on state, wherein:
the engine off state commands the engine (<NUM>) to shut down when in operation and to remain shut down;
the engine start state commands the engine (<NUM>) to begin operation when shut down; and
the engine on state commands the engine (<NUM>) to remain in operation after beginning the operation;
detecting an engine flameout event during aircraft flight;
responsive to detecting the engine flameout event, monitoring an engine speed and the commanded engine operating state;
comparing the engine speed to a predetermined threshold;
determining whether the commanded engine operating state corresponds to the engine on state following the detection of the engine flameout event; and
while the commanded engine operating state corresponds to the engine on state, and when the engine speed is below the predetermined threshold, initiating a predetermined ignition sequence for the engine (<NUM>).