Patent Description:
The disclosure relates generally to aircraft, and more particularly to improving a stall margin of an aircraft.

The accumulation of ice on an aircraft wing can change the shape of the wing and alter the performance characteristics of the wing. For example, an ice build-up can be accompanied with increased drag, reduced lift, and a reduced angle-of-attack at which the wing enters a stall condition. For this reason, airplanes are often equipped with ice protection systems designed to prevent ice from accumulating on aircraft wings. Ice protection systems can either prevent the formation of ice on the surface(s) altogether or facilitate shedding of the ice before it can accumulate to a dangerous thickness.

The pilot workload during take-off can be relatively high and in the event where the pilot would either forget to activate the ice-protection system of the aircraft or not activate the ice protection system early enough, some ice could potentially form on the wings of the aircraft under appropriate atmospheric conditions and affect the performance characteristics of the wings.

In one aspect, the disclosure describes a method for improving a stall margin of an aircraft during a climb phase of flight according to the disclosure of claim <NUM>.

The climb phase of flight may include an initial climb phase.

The method may comprise automatically commanding the deployment of the leading edge slats when the following condition is also true: the aircraft has exited an initial climb phase of flight.

The method may comprise automatically commanding the deployment of the leading edge slats when the following condition is also true: the aircraft is in an en route phase of flight.

The method may comprise automatically commanding the deployment of the leading edge slats when the following condition is also true: an altitude of the aircraft equals or exceeds about 400ft (<NUM>).

The method may comprise automatically commanding the deployment of the leading edge slats when the following condition is also true: an or the altitude of the aircraft equals or is less than about <NUM>,000ft (<NUM>).

The method may comprise automatically commanding the deployment of the leading edge slats when the following condition is also true: a slat control input device indicates a fully retracted position of the leading edge slats.

The method may comprise automatically commanding the deployment of the leading edge slats when the following condition is also true: a speed of the aircraft equals or is below a predetermined deployment speed threshold value.

The method may comprise, after the automatically commanded deployment of the leading edge slats, automatically commanding a retraction of the leading edge slats when the following condition is true: a speed of the aircraft exceeds the predetermined deployment speed threshold value.

The method may comprise, after automatically commanding deployment of the leading edge slats, automatically commanding a retraction of the leading edge slats when the following condition is true: the angle-of-attack equals or is below a predefined retraction angle-of-attack threshold value.

The automatically commanded retraction of the leading edge slats may be a full retraction of the leading edge slats.

The leading edge slats may include both inboard and outboard leading edge slats on a same wing.

The method may comprise automatically commanding the deployment of the leading edge slats during a degraded level of operation of an actuation system of the leading edge slats.

Embodiments can include combinations of the above features.

In another aspect, the disclosure describes a system for improving a stall margin of an aircraft during a climb phase of flight according to the disclosure of claim <NUM>.

The controller may be configured to automatically command the deployment of the leading edge slats when the following condition is also true: the aircraft has exited an initial climb phase of flight.

The controller may be configured to automatically command the deployment of the leading edge slats when the following condition is also true: the aircraft is in an en route phase of flight.

The controller may be configured to automatically command the deployment of the leading edge slats when the following condition is also true: an altitude of the aircraft equals or exceeds about 400ft (<NUM>).

The controller may be configured to automatically command the deployment of the leading edge slats when the following condition is also true: an or the altitude of the aircraft equals or is less than about <NUM>,000ft (<NUM>).

The controller may be configured to automatically command the deployment of the leading edge slats when the following condition is also true: a slat control input device indicates a fully retracted position of the leading edge slats.

The controller may be configured to automatically command the deployment of the leading edge slats when the following condition is also true: a speed of the aircraft equals or is below a predetermined deployment speed threshold value.

The controller may be configured to, after the automatically commanded deployment of the leading edge slats, automatically command a retraction of the leading edge slats when the following condition is true: a speed of the aircraft exceeds the predetermined deployment speed threshold value.

The controller may be configured to, after the automatically commanded deployment of the leading edge slats, automatically command a retraction of the leading edge slats when the following condition is true: the angle-of-attack equals or is below a predefined retraction angle-of-attack threshold value.

The controller may be configured to automatically command the deployment of both inboard and outboard leading edge slats on a same wing when the conditions are true.

The controller may be configured to automatically command the deployment of the leading edge slats during a degraded level of operation of an actuation system of the leading edge slats and also during a normal level of operation of the actuation system.

In a further aspect, the disclosure describes an aircraft comprising a system as disclosed herein.

The following disclosure relates to systems and methods for improving a stall margin of an aircraft during a climb phase of flight. In some embodiments, the systems and methods disclosed herein can serve to accommodate a delayed turn-on ice (DTO) situation where an ice protection system of the aircraft is not activated early enough to prevent at least some ice contamination of the (e.g., leading edges of the) wings of the aircraft. A DTO situation could, for example, potentially occur during a phase of flight (e.g., take-off) where the pilot workload is relatively high. The ice contamination during a DTO situation may not necessarily be excessive and the wings may not become visibly contaminated but such ice formation could nevertheless have some effect on the aerodynamic performance of the wings.

The accumulation of ice on aircraft wings can, for example, affect the lift-producing characteristics of some wings and hence reduce the stall margin (i.e., the margin between a level flight angle-of-attack and a stall angle-of-attack). As referenced herein, the angle-of-attack (sometimes called "alpha" or referenced using the Greek letter "α") is intended to encompass the angle between a reference line on a body, such as the chord line of an airfoil (e.g., aircraft wing) or the fuselage centerline (i.e., longitudinal axis) of the aircraft, and a flight path vector representing the relative motion between the body and the fluid (e.g., air) through which the body is moving. During climb, the angle-of-attack can be higher than during other phases of flight so it can be important to have an adequate stall margin during this phase of flight. The systems and methods disclosed herein can make use of automatic slat deployment to increase the lift produced by the wings during a condition of relatively high angle-of-attack during climb in order to improve the stall margin during this phase of flight.

Ultra-long range business jets can have wings that are designed for low drag and high speed performance and such wings can be sensitive to ice contamination. Designing such wings that are also stable in multiple phases of flight and conditions can be challenging. In some cases, such wings can exhibit unusual flight characteristics in some conditions with or without ice contamination. The use of automatic slat deployment to improve stall margin at such high angle-of-attack as disclosed herein could improve the operation of ultra-long range business jets in some situations. For example, it was observed that a wing designed for low drag and high speed performance could, in a relatively high angle-of-attack situation, exhibit flight (e.g., pitch) characteristics that may be undesirable to pilots. It was found that automatic slat deployment could, in some situations, eliminate or mitigate such undesirable flight characteristics for a wing designed for low drag and high speed performance.

<FIG> is a top plan view of an exemplary aircraft <NUM> which may comprise auto-slat system <NUM> as described herein for improving a stall margin of aircraft <NUM>. Aircraft <NUM> may be any type of aircraft such as corporate (e.g., business jet), private, commercial and passenger aircraft suitable for civil aviation. For example, aircraft <NUM> may be a narrow-body, twin-engine jet airliner or may be an ultra-long range business jet. Aircraft <NUM> may be a fixed-wing aircraft.

Aircraft <NUM> may comprise one or more wings <NUM>, fuselage <NUM>, one or more engines <NUM> and empennage <NUM>. One or more of engines <NUM> may be mounted to fuselage <NUM>. Alternatively, or in addition, one or more of engines <NUM> may be mounted to wings <NUM>. Wings <NUM> may each include one or more flight control surfaces such as aileron(s) <NUM>, leading edge slat(s) <NUM>, spoiler(s) <NUM> and trailing edge flap(s) <NUM>. Leading edge slats <NUM> and trailing edge flaps <NUM> may be considered "high-lift" flight control surfaces that may be deployed to increase the amount of lift generated by wings <NUM> during phase(s) of flight requiring increased lift. In some embodiments, wings <NUM> may be designed for low drag and high speed performance for use on an ultra-long range business jet for example.

<FIG> schematically shows auto-slat system <NUM> superimposed on aircraft <NUM> where auto-slat system <NUM> may be associated with leading edge slats <NUM> movably attached to a port side (i.e., left) wing <NUM> and also with leading edge slats <NUM> movably attached to a starboard side (i.e., right) wing <NUM>. As illustrated in <FIG>, auto-slat system <NUM> may be associated with all of leading edge slats <NUM> of each wing <NUM>. For example, auto-slat system <NUM> may be associated with both inboard and outboard leading edge slats <NUM> of each wing <NUM> relative to fuselage <NUM>. However, it is understood that in some embodiments, auto-slat system <NUM> could be associated with only one or some (e.g., inboard or outboard) slat(s) of each wing <NUM>.

<FIG> is a schematic representation of an exemplary auto-slat system <NUM> for improving a stall margin of aircraft <NUM>. In some embodiments, auto-slat system <NUM> may be used specifically in a climb phase of flight of aircraft <NUM> following a take-off procedure associated with relatively high pilot workload for example. Auto-slat system <NUM> is illustrated in <FIG> together with only two leading edge slats <NUM> of one wing <NUM> for simplicity but it is understood that auto-slat system <NUM> can be associated with some or all leading edge slats <NUM> of both wings <NUM>.

It is understood that aspects of the present disclosure are applicable to slat actuation systems of different configurations than those shown and described herein. In some embodiments, auto-slat system <NUM> may comprise driveline <NUM> for receiving a driving force (e.g., rotary force, torque) from power drive unit <NUM> (hereinafter "PDU <NUM>"). Auto-slat system <NUM> may comprise a plurality of actuators <NUM> operatively coupled between driveline <NUM> and one or more leading edge slats <NUM> associated with wings <NUM> of aircraft <NUM>. Actuators <NUM> may be configured to cause actuation of the one or more leading edge slats <NUM> in response to the driving force received at driveline <NUM>. Driveline <NUM> may be a common driveline configured to drive all of actuators <NUM> for the purpose of deploying and retracting leading edge slats <NUM> (e.g., by way of different directions of rotation of one or more torque tubes of driveline <NUM>).

Actuators <NUM> may each comprise a (e.g., ball) screw type of actuator or any other type of actuator suitable for actuating or transmitting an actuation force from driveline <NUM> to respective leading edge slats <NUM>. Actuators <NUM> may be configured to convert a rotary input motion from driveline <NUM> to output motion suitable for actuating respective leading edge slats <NUM>. PDU <NUM> may comprise a common source of motive power for driving driveline <NUM>. In various embodiments, PDU <NUM> may comprise an electric motor or a hydraulic motor drivingly coupled to driveline <NUM> for example.

Auto-slat system <NUM> may comprise controller <NUM>. Controller <NUM> may be operatively coupled to leading edge slats <NUM> via PDU <NUM> for commanding actuation of leading edge slats <NUM>. Controller <NUM> may also be operatively coupled to other avionics component(s) or otherwise configured to receive commands from a pilot of aircraft <NUM> directly or indirectly, or receive commands from an auto-flight system of aircraft <NUM>. Controller <NUM> may also be operatively coupled to receive data <NUM> directly or indirectly from one or more suitable data sources such as sensors or other avionics components. Controller <NUM> may be operatively coupled to slat control input device <NUM> actuatable by the pilot(s) to command actuation of leading edge slats <NUM>. In some embodiments, slat control input device <NUM> may be a flap/slat control lever for commanding actuation of trailing edge flaps <NUM> and leading edge slats <NUM>. Control input device <NUM> may serve to command different high-lift configuration settings.

Controller <NUM> may comprise one or more data processors and one or more computer-readable memories storing machine-readable instructions executable by the data processor(s) and configured to cause controller <NUM> to perform a series of steps so as to implement a computer-implemented process such that instructions, when executed by such data processor(s) or other programmable apparatus, can cause the functions/acts specified in the methods described herein to be executed. Memory(ies) can comprise any storage means (e.g. devices) suitable for retrievably storing machine-readable instructions executable by the data processor(s) of controller <NUM>.

Various aspects of the present disclosure can be embodied as systems, devices, methods and/or computer program products. Accordingly, aspects of the present disclosure can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, aspects of the present disclosure can take the form of a computer program product embodied in one or more non-transitory computer readable medium(ia) having computer readable program code embodied thereon. The computer program product can, for example, be executed by controller <NUM> to cause the execution of one or more methods disclosed herein in entirety or in part. It is understood that, based on the present disclosure, one skilled in the relevant arts could readily write computer program code for implementing the methods disclosed herein.

Controller <NUM> may be operatively coupled to PDU <NUM> for commanding deployment and retraction of leading edge slats <NUM> in unison by controlling the operation of PDU <NUM> accordingly. In some embodiments, controller <NUM> may be dedicated to the actuation of leading edge slats <NUM> or may be configured to carry out other tasks as well. In some embodiments, controller <NUM> may comprise or be integrated with a dedicated high-lift system controller for example. In some embodiments, controller <NUM> may comprise or be integrated with a flight control computer (FCC) of a fly-by-wire system of aircraft <NUM> for example. Controller <NUM> may be configured to automatically command deployment and retraction of leading edge slats <NUM> based on data <NUM>. In some embodiments, controller <NUM> may also be configured to control the actuation of leading edge slats <NUM> based on commands from a pilot or from an auto-flight system of aircraft <NUM>.

Data <NUM> may comprise information indicative of a current state or operating condition of aircraft <NUM>. Data <NUM> may comprise substantially real-time sensed parameters acquired via suitable sensors, computed/derived parameters and predetermined threshold values for example. In various embodiments, data <NUM> may comprise current angle-of-attack information, speed (e.g., airspeed), phase of flight, altitude, a position of leading edge slats <NUM> and predetermined threshold values (e.g., limits). Some or all of data <NUM> may be received at controller <NUM> in order to permit controller <NUM> to perform the tasks described herein. It is understood that some of data <NUM> could instead be computed/derived by controller <NUM> or could be stored in memory that is accessible by controller <NUM>.

Using data indicative of a phase of flight of aircraft <NUM> and data indicative of angle-of-attack α of aircraft <NUM>, controller <NUM> may automatically command a deployment of leading edge slats <NUM> when the following conditions are true: aircraft <NUM> is in a climb phase of flight; and angle-of-attack α equals or exceeds a predefined deployment angle-of-attack value.

The automatic deployment of leading edge slats <NUM> of wings <NUM> may be used specifically in a climb phase of flight of aircraft <NUM> following a take-off procedure associated with relatively high pilot workload. The take-off phase of flight may be divided into sub-phases of flight or segments and may terminate at the conclusion of an initial climb phase. The climb phase of flight referred herein may comprise an initial climb. The initial climb normally takes place after the aircraft leaves the ground (i.e., the aircraft is in air) and a climb pitch attitude has been established. The initial climb phase can normally be considered complete when the aircraft has reached a safe maneuvering altitude or an en route climb has been established. In some situations, the beginning of the initial climb phase may correspond to a moment when the high-lift surfaces are retracted and a thrust level of engines <NUM> is changed. In some situations, the beginning of the initial climb phase may correspond to an altitude of about 400ft (<NUM>). The initial climb phase may terminate when aircraft <NUM> is in a clean configuration, which may correspond to an altitude of about 1500ft (<NUM>). The climb phase of flight referred herein may also comprise an en route climb phase of flight. The en route climb phase may begin immediately following the initial climb and may terminate when aircraft <NUM> has reached an initial assigned cruise altitude.

In some embodiments, the automatic deployment of leading edge slats <NUM> may be transparent to the pilot(s) of aircraft <NUM>. Alternatively, the automatic deployment of leading edge slats <NUM> may be accompanied by a communication informing the pilot(s) of aircraft <NUM> of the automatic deployment of leading edge slats <NUM>. Such communication can include a text message or other type of visual indication provided on a flight deck of aircraft <NUM>, and/or the communication can include an aural message. In order to avoid distracting the pilot(s) during periods of relatively high pilot workload, it is contemplated that the automatic deployment of leading edge slats <NUM> and the optional accompanying communication would occur only after an initial take-off procedure.

In some embodiments, the automatic deployment of leading edge slats <NUM> may be inhibited prior to the initial climb phase of flight. In some embodiments, the automatic deployment of leading edge slats <NUM> may be permitted only after aircraft <NUM> has entered the initial climb phase of flight. In some embodiments, the automatic deployment of leading edge slats <NUM> may be inhibited prior to the en route climb phase of flight. In some embodiments, the automatic deployment of leading edge slats <NUM> may be permitted only after aircraft <NUM> has exited the initial climb phase of flight. In some embodiments, the automatic deployment of leading edge slats <NUM> may be permitted only after aircraft <NUM> has entered an en route phase of flight.

<FIG> is a state diagram for auto-slat system <NUM> and illustrates retracted and deployed states of leading edge slats <NUM> and the applicable deploy and retract triggers that cause the automatic deployment or retraction of leading edge slats <NUM>. The state diagram illustrates the operation of auto-slat system <NUM> when auto-slat system <NUM> is in its armed state (i.e., auto-slat active region) when one or more conditions are met based on one or more parameters from data <NUM>. For example, as explained above, auto-slat system <NUM> may be armed or active only in a climb phase of flight in some embodiments. Additional conditions to be met for causing auto-slat system <NUM> to be armed may include some or all of the following:.

In some embodiments, the use of auto-slat system <NUM> may be used to accommodate or compensate for some potential ice contamination of wings <NUM> due to a DTO situation. Accordingly, auto-slat system <NUM> may be inhibited at higher altitudes where the risk of ice contamination is reduced (e.g., at altitudes above <NUM>,<NUM> feet (<NUM>)).

However, it is understood that auto-slat system <NUM> may be used to mitigate undesirable flight characteristics with or without ice contamination.

One or more deploy triggers may be required to trigger the automatic deployment of leading edge slats <NUM> after auto-slat system <NUM> has been armed. For example, the current angle-of-attack α being equal to or exceeding the predefined deployment angle-of-attack threshold value (e.g., <NUM> degrees) can be a deploy trigger.

Auto-slat system <NUM> may also be configured to, after the automatically commanded deployment of leading edge slats <NUM>, automatically command a retraction of leading edge slats <NUM> when one or more conditions are met. For example, once leading edge slats <NUM> are deployed, leading edge slats <NUM> may be automatically retracted once angle-of-attack α has been reduced and/or a speed of aircraft <NUM> has increased. For example, controller <NUM> may be configured to automatically command the retraction of leading edge slats <NUM> when the following condition is true: the angle-of-attack α equals or is below a predefined retraction angle-of-attack threshold value. Alternatively or in addition, controller <NUM> may be configured to automatically command the retraction of leading edge slats <NUM> when auto-slat system <NUM> exits its armed state (i.e., auto-slat active region). For example, controller <NUM> may be configured to automatically command the retraction of leading edge slats <NUM> when the following condition is true: the speed of the aircraft exceeds the predetermined deployment speed threshold value (e.g., > <NUM> kts (<NUM>/h)).

The automatically commanded retraction of leading edge slats <NUM> may be a full retraction of leading edge slats <NUM> (i.e., back to a <NUM> degree position corresponding to the commanded position indicated by slat control input device <NUM>). In some embodiments, the retraction angle-of-attack threshold value (e.g., <NUM> degrees) may be lower than the deployment angle-of-attack threshold value (e.g., <NUM> degrees).

In some embodiments, auto-slat system <NUM> may be configured to operate during a normal level of operation of the actuation system of leading edge slats <NUM> and also during a degraded level of operation of an actuation system of the leading edge slats <NUM>. In other words, auto-slat system <NUM> may be configured to operate when the actuation system is fully functional and also when the actuation system has a reduced functionality due to a partial failure of part(s) (e.g., PDU <NUM>, actuators <NUM>, driveline <NUM>) of the actuation system for example.

During the normal level of operation, leading edge slats <NUM> may be deployed to a predetermined deployed position at a predetermined deployment speed by auto-slat system <NUM> when the appropriate one or more conditions are met. However, during a degraded level of operation, the actuation system of leading edge slats <NUM> may not be capable of deploying leading edge slats <NUM> to the same deployed position at the same deployment speed due to the air loads acting on leading edge slats <NUM> and to the reduced capacity of the actuation system. Accordingly, it may be acceptable under a degraded level of operation to deploy leading edge slats <NUM> to a lower deployed position and at a lower deployment speed. In some embodiments, a deployed position (e.g., <NUM> degrees) of leading edge slats <NUM> under a degraded level of operation may be about half of a deployed position (e.g., <NUM> degrees) of leading edge slats <NUM> under a normal level of operation of the actuation system. Similarly, a deployment speed of leading edge slats <NUM> under a degraded level of operation may be about half of a deployment speed of leading edge slats <NUM> under a normal level of operation of the actuation system.

<FIG> is flow diagram illustrating method <NUM> for improving stall performance of aircraft <NUM> during a climb phase of flight. Method <NUM> can be performed using auto-slat system <NUM> as described above or using another suitable system. Method <NUM> may represent a control law (or part thereof) associated with auto-slat system <NUM>. Aspects and functions of auto-slat system <NUM> disclosed herein can also be applicable to method <NUM>. Method <NUM> may comprise:
using data indicative of a phase of flight of aircraft <NUM> and data indicative of angle-of-attack α, automatically commanding a deployment (see block <NUM>) of leading edge slats <NUM> movably attached to wings <NUM> of aircraft <NUM> when at least the following conditions are true:.

At block <NUM>, if the relevant parameter(s) are not indicative of the active region of auto-slat system <NUM> being applicable, the control of leading edge slats <NUM> may revert to being based on pilot input (e.g., via slat control input device <NUM>).

At block <NUM>, if the angle-of-attack α does not equals or exceed the predefined deployment angle-of-attack threshold value, the control of leading edge slats <NUM> may revert to being based on pilot input (e.g., via slat control input device <NUM>).

As explained above, the climb phase of flight may include an initial climb phase of flight and/or an en route climb phase of flight.

Method <NUM> may comprise automatically commanding the deployment (see block <NUM>) of leading edge slats <NUM> when one or more of the following additional conditions in any combination are also true:.

At block <NUM>, if the relevant parameter(s) are not indicative of the active region of auto-slat system <NUM> being applicable, leading edge slats <NUM> may be retracted and the control of leading edge slats <NUM> may revert to being based on pilot input (e.g., via slat control input device <NUM>).

After automatically commanding deployment of leading edge slats <NUM>, method <NUM> may comprise automatically commanding a retraction (see block <NUM>) of leading edge slats <NUM> when the following condition is true: angle-of-attack α equals or is below a predefined retraction angle-of-attack threshold value (see block <NUM>).

Alternatively or in addition, after automatically commanding deployment of leading edge slats <NUM>, method <NUM> may comprise automatically commanding a retraction (see block <NUM>) of leading edge slats <NUM> when auto-slat system <NUM> is no longer in its auto-slat active region (see block <NUM>). For example, method <NUM> may comprise automatically commanding the retraction of leading edge slats <NUM> when the following condition is true: the speed of the aircraft exceeds the predetermined deployment speed threshold value (e.g., > <NUM> kts (<NUM>/h)).

The automatically commanded retraction of leading edge slats <NUM> may be a full retraction of leading edge slats <NUM>. Leading edge slats <NUM> that are automatically deployed and/or retracted may include both inboard and outboard leading edge slats <NUM> on a same wing <NUM>.

As explained above, method <NUM> may be performed during a degraded level of operation of the actuation system of leading edge slats <NUM>, or, during a normal level of operation of the actuation system of leading edge slats <NUM>.

The above description is meant to be exemplary only, and one skilled in the relevant arts will recognize that changes may be made to the embodiments described without departing from the scope of the appended claims.

The present disclosure may be embodied in other specific forms without departing from the subject matter of the claims.

Claim 1:
A method for improving a stall margin of an aircraft (<NUM>) during a climb phase of flight, the method comprising:
using data indicative of a phase of flight of the aircraft (<NUM>) and data indicative of an angle-of-attack of the aircraft, automatically commanding a deployment of leading edge slats (<NUM>) movably attached to wings (<NUM>) of the aircraft when at least the following conditions are true:
the aircraft is in a climb phase of flight following a take-off procedure;
the angle-of-attack equals or exceeds a predefined deployment angle-of-attack threshold value when the aircraft is in the climb phase of flight; and
the leading edge slats are in a fully retracted position.