Patent Description:
Aircraft wings typically include a set of actuable control surface elements. These control surface elements define control surfaces (also known as auxiliary aerofoils) which are moveable relative to the fixed wing structure in order to alter the aerodynamic characteristics of the wing. Such control surface elements include leading edge devices such as slats, and trailing edge devices such as flaps.

Typically, control surface elements are actuated at either span-wise end by two separate actuators. It is conceivable that if either of these actuators malfunctions, inconsistent actuation and skew or loss of the relevant control surface could occur. It is important that if skew or loss is detected, the relevant systems are shut down and the pilot of the aircraft is notified.

Various methods have been proposed in the prior art for providing detection of skew and/or loss of control surface elements. One such system described in <CIT> provides a cable or lanyard which is coupled to each of a series of control surface elements. The cable is put in tension in the event of skew or loss. A movement detector with a proximity sensor is provided coupled to the cable such that any movement of the cable resulting from skew and/or loss can be detected. This detector is mounted on the endmost flap or slat. It is coupled to the flap/slat electronics unit (FSEU) in the aircraft fuselage via electric cables running from the moveable control surface element through the fixed wing structure to the fuselage and to the FSEU.

A challenge in designing such systems is that relatively small deflections or movements, that are caused by wing structural deflections, dynamics of the aircraft or temperature changes, may confuse the detection system. Such spurious movements do not cause problems in the extension or retraction of the surface elements, but the confusion to the detection may result in the system unnecessarily responding to minor misalignments.

The apparatus of <CIT> allows serious displacement, or misalignment, of one or more adjacent surface elements to be detected during their extension or retraction, while ignoring the smaller, spurious, movements.

A problem with each of these prior art systems is that neither system enables the detection of a seized cable, or in some cases, an undetected failure of the sensor(s).

In the event of failure of the detection system, for example cable seizure, or seizure of any other component of the detection system, skew or loss can no longer be detected, which compromises the safety of the system. A check is therefore required at regular intervals to verify the cable is not seized. This is a manual operation which adds maintenance time, cost and administration effort. Aircraft regulations, particularly for commercial aircraft, are also making certification more difficult for systems which have undetected failures.

The present invention provides an aircraft control surface skew and/or loss detection system and a method for operating an aircraft as set out in the appended independent claims.

According to an aspect of the present invention there is an aircraft control surface skew and/or loss detection system as set out in claim <NUM>.

The first and second sensors may be configured to detect a third relative position of the first and second parts indicative of skew and/or loss of one of the control surface elements.

The first and second sensors may be configured to detect a fourth relative position of the first and second parts indicative of a loss of a tensile force in the cable.

The sensor includes a first sensor configured to detect when the first and second parts are within a first range of relative positions.

The first sensor may be incapable of detecting the relative positions of the first and second parts when the first and second parts are outside of the first range.

The sensor includes a second sensor configured to detect when the first and second parts are within a second range of relative positions.

The second sensor may be incapable of detecting the relative positions of the first and second parts when the first and second parts are outside of the second range.

The first range may overlap the second range.

The first range may not overlap the second range.

One of the third relative position and fourth relative position may be outside one of the first and second ranges and inside the other of the first and second ranges. The other of the third and fourth relative positions may be inside said one of the first and second ranges and outside of said other of the first and second ranges. The other of the third and fourth relative positions may be outside of both the first and second ranges.

The at least one sensor may include a continuous sensor.

The continuous sensor may be a linear sensor, for example a linear variable differential transformer.

The continuous sensor may be a rotary sensor, for example a rotary sensor including means to convert linear to rotary motion, such as a rack and pinion.

The continuous sensor may be a sensor that detects the continuous position of a grating.

The aircraft control surface skew and/or loss detection system may be configured such that when the first and/or second sensor detects the first relative position when the wing structure is being supported is indicative of a failure of the detection system.

The aircraft control surface skew and/or loss detection system may be configured such that when the first and/or second sensor detects the second relative position when the wing structure is supporting a load is indicative of a failure of the detection system. The first part may be mounted on one of the control surface elements.

According to an alternative aspect of the present invention there is a method of operating an aircraft including an aircraft control surface skew and/or loss detection system as set out in claim <NUM>.

Detecting failure of the detection system may include:-.

According to an unclaimed example, there is an aircraft control surface skew and/or loss detection system including:.

Advantageously, the provisions of at least two signals indicative of the position of the sensor target relative to the at least one sensor allows the system to detect changes in the position of different parts or regions of the sensor target and, therefore, skew or misalignment of either of the control surface elements, if the cable is broken or detached, as well as if the cable becomes seized.

The aircraft control surface skew and/or loss detection system may further include a sensor that is configured to generate a signal that is indicative of the weight of an aircraft being supported by a wheel of the aircraft.

The signal indicative of the weight of an aircraft being supported by an aircraft wheel, or not, in conjunction with the provision of signals relating to the position of the sensor target relative to the sensor facilitates the assessment of whether or not the cable is seized.

The sensor assembly may be configured to generate a signal that is indicative of movement of the cable in order to determine whether or not the cable is seized.

The sensor assembly may include a first sensor and a second sensor. Each of the first sensor and the second sensor may be associated with a different part or region of the sensor target. The first sensor may, for example, be associated with a first or a second end of the sensor target and the second sensor may, for example, be associated with the other of the first and second ends of the sensor target.

In this way, whether or not the cable is free to move and, therefore, whether the cable is seized can be determined.

The aircraft control surface skew and/or loss detection system may be configured such that when the detection system is in a normal, unloaded, aircraft on ground condition, at least one of the first sensor and the second sensor may overlap the sensor target.

By 'unloaded' condition, we refer to a condition in which the aircraft is on the ground and the weight of the aircraft is supported by the wheels, i.e. that the wings of the aircraft are unloaded. By 'loaded' condition, we refer to a condition in which the aircraft is in the air and the weight of the aircraft is supported by the wings, i.e. that the wings of the aircraft are loaded.

The aircraft control surface skew and/or loss detection system may be configured such that when the detection system is in a normal, unloaded, aircraft on ground condition, each of the first sensor and the second sensor may overlap the sensor target.

The aircraft control surface skew and/or loss detection system may be configured such that when the detection system is in a normal, unloaded aircraft on ground condition, the second sensor overlaps the sensor target and further wherein, when the detection system is in a normal, loaded aircraft in air condition, the second sensor is spaced apart from the sensor target.

The aircraft control surface skew and/or loss detection system may be configured such that when the detection system is in a normal, unloaded aircraft on ground condition, the first sensor overlaps the sensor target and further wherein, when the detection system is in a normal, loaded aircraft in air condition, the first sensor overlaps the sensor target.

The aircraft control surface skew and/or loss detection system may be configured such that when the detection system is in a normal, unloaded aircraft on ground condition, the first sensor is spaced apart from the sensor target and further wherein, when the detection system is in a normal, loaded aircraft in air condition, the first sensor overlaps the sensor target.

The continuous sensor may allow the detection of the position and movement of different parts or regions of the sensor target or armature.

The continuous sensor may be a rotary sensor. The rotary sensor may include means to convert linear to rotary motion, for example a rack and a pinion.

The continuous sensor may be a sensor that detects the continuous position of a grating, for example an electromagnetic sensor or an optical sensor having a grating.

Examples of skew and/or loss detection systems according to the present invention will now be described with reference to the accompanying drawings in which:.

Referring to <FIG> a control surface element skew and/or loss detection system <NUM> is shown schematically. The system <NUM> is shown installed on a wing <NUM> having a fixed wing structure <NUM> having a fixed leading edge <NUM>. A plurality of control surface elements in the form of first slat <NUM>, second slat <NUM>, a third slat <NUM> and a fourth slat <NUM> are independently moveably mounted to the fixed wing structure <NUM>. The method of attachment and actuation of the slats <NUM>, <NUM>, <NUM>, <NUM> is well known in the art and will not be described further here. The overall position of the slat system is indicated by a system movement transducer, typically located at the endmost position of each wing. Under normal conditions, each of the slats <NUM>, <NUM>, <NUM>, <NUM> move together and thus the system movement transduces system does not detect abnormal slat movement.

The system <NUM> includes a cable or lanyard <NUM> and a known skew sensor mechanism (or sensor assembly) <NUM>. The body <NUM> of the sensor mechanism <NUM> is attached to slat <NUM>. The cable <NUM> has a first end <NUM> and a second end <NUM>. The cable <NUM> is attached to the skew sensor mechanism <NUM> at the second end <NUM> and is free to run through each of the slats <NUM>, <NUM>, <NUM>, <NUM> and is earthed at the first end <NUM> to the first slat <NUM>.

Movement of any of the slats relative to the other slats will cause tension or pulling in the cable <NUM>, such tension being detected by the skew sensor mechanism <NUM>.

The known skew sensor mechanism <NUM> is a spring loaded piston-in-cylinder arrangement and will be described in more detail with reference to <FIG>.

With reference to <FIG>, the skew sensor mechanism <NUM> has a sensor target <NUM> that is provided as part of a piston <NUM>, a body <NUM> in the form of a hollow cylinder (also known as a housing) <NUM>, a resilient biasing means in the form of a spring <NUM> and a sensor <NUM>. The piston <NUM> has a first end <NUM> and a second end <NUM>. The cable <NUM> is connected to the second end <NUM> of the piston <NUM>. The cylinder <NUM> has a first end <NUM> and a second end <NUM>. The sensor target <NUM> and the piston <NUM> are moveable within the cylinder <NUM>. The spring <NUM> is positioned between the second end <NUM> of the piston <NUM> and the second end <NUM> of the cylinder <NUM>. The sensor <NUM> is mounted on the outside of the cylinder <NUM>.

The sensor <NUM> is able to detect when the sensor target <NUM> of the piston <NUM> is in a 'target near' or 'activated' or 'ON' position when the sensor target is close to the sensor or is in a 'target far' or 'deactivated' or 'OFF' position when the sensor target is remote from the sensor. Typically, the sensor <NUM> is a proximity sensor and the sensor target <NUM> of the piston <NUM> is a metallic target. The proximity sensor may be an electric coil, the inclusion of which changes with the proximity or remoteness of the metallic target. Alternatively, the sensor <NUM> may be a Hall Effect device with a magnetic target or a switch with a mechanical target. Any suitable sensor and sensor target may be used.

The cable <NUM> passes through a plurality of slats, as shown in <FIG>, and is held in tension by the spring <NUM> such that the sensor target <NUM> is proximal to the sensor <NUM>.

The arrangement of the skew sensor mechanism <NUM> shown in <FIG> is indicative of no panel skew, i.e. the mechanism <NUM> is in a normal state with the wing either in a relaxed, unloaded state wherein the associated aircraft is on the ground or in a loaded state in normal flight. The sensor target <NUM> is in the 'target near' position. In other words, the senor target <NUM> is within the detection range of the sensor <NUM>.

With reference now to <FIG>, the arrangement of the skew sensor mechanism <NUM> is indicative of panel skew (i.e. that one or more of the slats is skewed or misaligned relative to the other slats). The panel skew has caused the cable <NUM> to be pulled to the right, compressing the spring <NUM> at the second end <NUM> of the cylinder <NUM>. The sensor target <NUM> is thus moved away from the sensor <NUM>, which is able to detect that the sensor target <NUM> has moved to a 'target far' position. The 'target far' is an indication that a failure has occurred in this case that panel skew has occurred.

Referring now to <FIG>, the arrangement of the skew sensor mechanism <NUM> is indicative that the cable <NUM> has failed (is broken or disconnected). Following a break <NUM> in the cable <NUM>, the spring <NUM> extends, thereby allowing the sensor target <NUM> to move toward the first end <NUM> of the cylinder <NUM>. The sensor target <NUM> is thus moved away from the sensor <NUM>, which is able to detect that the sensor target <NUM> has moved to a 'target far' position. The 'target far' is an indication that a failure has occurred in this case that cable failure has occurred.

In each of the conditions shown in <FIG>, the sensor <NUM> detects that the sensor target <NUM> is in the 'target far' position. In other words, the system <NUM> is not able to differentiate between skewed panels or cable failure.

The prior art system <NUM> of <FIG> also cannot detect if either failure of the detection system has occurred, for example by seizure of the cable <NUM>, the sensor <NUM>, or other component of the detection system. Also, depending what type of sensor <NUM> is used, it cannot detect if the sensor has failed in the 'target near' state such that when there is a panel skew or cable failure resulting in the target being in a 'target far' position, the sensor still nevertheless indicates 'target near'.

Table <NUM> below shows various conditions, the corresponding actual sensor target position and apparent sensor target position and also when a failure is detected.

As regards conditions <NUM> and <NUM> in Table <NUM>, clearly there is no failure.

As regards conditions <NUM> and <NUM>, it is apparent that the failure is detected immediately.

As regards conditions <NUM> and <NUM>, it is not possible for the sensor system to detect a seized cable and hence separate manual checks must be carried out.

In condition <NUM>, the sensor has failed by permanently providing a "target near" signal even though the target may be near or far. As will be appreciated, it is not possible for the sensor system to detect this failure, and as such separate system checks are required.

In condition <NUM>, the sensor has again failed but in this case the sensor permanently indicates a "target far" condition whether the target is near or far. As will be appreciated, it is immediately apparent that a failure has occurred.

As will also be appreciated, it is not possible to distinguish between any conditions <NUM>, <NUM> and <NUM>.

With reference to <FIG> there is shown a skew sensor mechanism <NUM> according to a first embodiment of the present invention.

The skew sensor mechanism (or sensor assembly) <NUM> has a sensor target <NUM> that is provided as part of a piston (or second part of the assembly) <NUM> a body <NUM> in the form of a hollow cylinder (or housing or first part of the assembly) <NUM>, a resilient biasing means in the form of a spring <NUM>, a first sensor <NUM> and a second sensor <NUM>. The piston <NUM> has a first end <NUM> and a second end <NUM>. The cable <NUM> is connected to the second end <NUM> of the piston <NUM>. The cylinder <NUM> has a first end <NUM> and a second end <NUM>. The sensor target <NUM> and the piston <NUM> are moveable within the cylinder <NUM>. The spring <NUM> is positioned between the second end <NUM> of the piston <NUM> and the second end <NUM> of the cylinder <NUM>. The first and second sensors <NUM>, <NUM> are mounted on the outside of the cylinder <NUM>.

The associated wing <NUM>, leading edge <NUM>, first slat <NUM>, second slat <NUM>, third slat <NUM> and fourth slat <NUM> are all shown schematically in <FIG> only.

The arrangement shown in <FIG> is representative of the associated aircraft (not shown) being on the ground such that the weight of the aircraft is on the wheels (not shown) and the aircraft wing <NUM> is in a relaxed unloaded state. In other words, the wing structure is supported by the wheels.

Each of the first sensor <NUM> and the second sensor <NUM> are in the 'target near' position or state, indicating a normal, non-operational (i.e. non flying) state.

When the aircraft (not shown) takes off and the wing <NUM> bends up due to supporting the weight of the aircraft, it pulls the cable <NUM> as shown in <FIG>. The sensor target <NUM> is pulled to the right such that the spring is compressed between the second end <NUM> of the sensor target <NUM> and the second end <NUM> of the cylinder <NUM>. In this state, the second sensor <NUM> is in the 'target far' position and the first sensor <NUM> is in the 'target near' position. The weight of the aircraft is not on the wheels at this time (i.e. the wing structure is supporting a load). The change in the position of the second sensor <NUM> is indicative that the first and second parts of the assembly have moved from a first relative position indicative that the wing is supported by the aircraft, in particular the wheels of the aircraft to a second relative position indicative that the wing is supporting a load (i.e. the wing is supporting the aircraft) and that the cable (or any other part of the sensor system) of the skew sensor mechanism <NUM> has not seized. Similarly, the change in where the weight of the aircraft is supported (from the wheels to the wing, i.e. not on the wheels) is indicative that the skew sensor mechanism <NUM> has not seized.

With reference <FIG>, the arrangement of the skew sensor mechanism <NUM> is indicative that panel skew has occurred and that one or more of the slats is skewed or misaligned relative to the other slats. The panel skew has caused the cable <NUM> to be pulled to the right, compressing the spring <NUM> at the second end <NUM> of the cylinder <NUM>. The sensor target <NUM> is thus moved away from the first sensor <NUM> and the second sensor <NUM>, each of which indicates that the sensor target <NUM> has moved to a 'target far' state and hence it is possible to determine that panel skew has occurred. Note there is no overlap between the sensor target <NUM> and either of the sensors <NUM>, <NUM> in this condition.

With reference to <FIG>, the arrangement of the skew sensor mechanism <NUM> is indicative that the cable <NUM> has failed (i.e. is broken or disconnected). Following a break <NUM> in the cable <NUM>, the spring <NUM> expands, thereby causing the sensor target <NUM> to move toward the first end <NUM> of the cylinder <NUM>. The sensor target <NUM> is thus moved away from the first sensor <NUM>, which is able to detect that the sensor target <NUM> has moved to a 'target far' state. The second sensor 13a is able to detect that the sensor target <NUM> is in a 'target near' state and hence it is possible to determine a broken cable.

The arrangement shown in <FIG> allows a differentiation between a panel skew and a broken cable to be made.

The system <NUM> of <FIG> advantageously removes the need for a manual latency failure check in respect of a seized mechanism.

Table <NUM> below shows various conditions with the associated first and second sensor actual target positions and indicated target positions together with when the failure is detected.

As regards conditions <NUM> and <NUM> in table <NUM>, clearly there is no failure.

As regards condition <NUM>, this condition is detected upon take-off since in a fully functioning system upon take-off the second sensor target position should change to far but does not thereby indicating a seized cable.

As regards condition <NUM>, during flight the seized cable is not detected, but upon landing the second sensor actual target position should change to near, but would not, thereby indicating a seized cable.

It is not possible for the sensor system to detect the failure as shown in condition <NUM>, and as such separate system checks are required.

In condition <NUM>, the failure is detected immediately.

In condition <NUM>, the failure is detected upon take-off.

In condition <NUM>, the failure is detected upon landing.

In a further embodiment, if cylinder <NUM> was longer such that piston <NUM> and target <NUM> moved left such that sensor <NUM> also indicated 'target far' state when the cable was broken, the sensor mechanism would still be able to detect panel skew or a broken cable but would not be able to determine which type of failure had occurred.

With reference to <FIG> there is shown a skew sensor mechanism (or sensor assembly) <NUM> according to a second embodiment of the present invention.

The skew sensor mechanism <NUM> has a sensor target <NUM> that is provided as part of a piston (or second part of the mechanism or assembly) <NUM>, a body <NUM> in the form of a hollow cylinder (or a housing or first part of the mechanism or assembly) <NUM>, a resilient biasing means in the form of a spring <NUM>, a first sensor <NUM> and a second sensor <NUM>. The piston <NUM> has a first end <NUM> and a second end <NUM>. The cable <NUM> is connected to the second end <NUM> of the piston <NUM>. The cylinder <NUM> has a first end <NUM> and a second end <NUM>. The sensor target <NUM> and the piston <NUM> are moveable within the cylinder <NUM>. The spring <NUM> is positioned between the second end <NUM> of the piston <NUM> and the second end <NUM> of the cylinder <NUM>. The first and second sensors <NUM>, <NUM> are mounted on the outside of the cylinder <NUM>.

The arrangement shown in <FIG> is representative of the associated aircraft (not shown) being on the ground such that the weight of the aircraft is on the wheels (not shown) and the aircraft wing <NUM> is in a relaxed unloaded state. In other words, the wing structure is supported.

In this embodiment, the first sensor <NUM> is in the 'target far' position or state and the second sensor <NUM> is in the 'target near' position or state, indicating normal, non-operational (i.e. non flying), condition.

When the aircraft (not shown) takes off and the wing <NUM> bends up due to supporting the weight of the aircraft, it pulls the cable <NUM> as shown in <FIG>. The sensor target <NUM> is pulled to the right such that the spring is compressed between the second end <NUM> of the sensor target <NUM> and the second end <NUM> of the cylinder <NUM>. In this state, the second sensor <NUM> changes to the 'target far' position and the first sensor <NUM> changes to the 'target near' position. The weight of the aircraft is not on the wheels at this time (i.e. the wing structure is supporting a load). The change in the position of each of the first sensor <NUM> and the second sensor <NUM> is indicative that the first and second parts of the assembly have moved from a first relative position indicative that the wing is supported to a second relative position indicative that the wing is supporting a load and that the cable of the skew sensor mechanism <NUM> has not seized. Similarly, the change in where the weight of the aircraft is supported (from the wheels to the wing, i.e. not on the wheels) is indicative that the skew sensor mechanism <NUM> has not seized.

With reference <FIG>, the arrangement of the skew sensor mechanism <NUM> is indicative that panel skew has occurred and that one or more of the slats is skewed or misaligned relative to the other slats. The panel skew has caused the cable <NUM> to be pulled to the right, compressing the spring <NUM> at the second end <NUM> of the cylinder <NUM>. The sensor target <NUM> is thus moved further away from the first sensor <NUM> moved away from and the second sensor <NUM>, such that each of the first sensor <NUM> and the second sensor <NUM> are able to detect that the sensor target <NUM> has moved to a 'target far' state and hence it is possible to determine a panel skew. Note there is no overlap between the sensor target <NUM> and either of the sensors <NUM>, <NUM> in this condition.

With reference to <FIG>, the arrangement of the skew sensor mechanism <NUM> is indicative that the cable <NUM> has failed (i.e. is broken or disconnected). Following a break <NUM> in the cable <NUM>, the spring <NUM> expands, thereby causing the sensor target <NUM> to move toward the first end <NUM> of the cylinder <NUM>. The sensor target <NUM> is thus moved away from the first sensor <NUM>, which is able to detect that the sensor target <NUM> has moved to a 'target far' state. The second sensor <NUM> is able to detect that the sensor target <NUM> is in a 'target near' state. Hence, during flight it is possible to determine that cable failure has occurred.

The arrangement shown in <FIG> allows differentiation between failure due to panel skew and failure due to a broken cable.

The system <NUM> of <FIG>, therefore, also advantageously removes the need for a manual latency failure check in respect of a seized mechanism.

Furthermore, since in this system both of the first sensor <NUM> and the second sensor <NUM> change state during normal operation (i.e. both change state between the aircraft being on the ground and flying), both mechanical failures (seizure and electrical failures of the sensors) cannot be latent for an interval greater than one flight.

Table <NUM> below shows various conditions together with the first and second sensor actual target position, indicated target position and when the failure is detected.

As can be seen from table <NUM>, all failures are detectable. Condition <NUM>, skew, is detectable both in flight and on the ground. Condition <NUM> cable brake is immediately detectable during flight but if the cable breaks when the aircraft is on the ground this failure is not indicated. The failures shown in conditions <NUM>-<NUM> are all detectable either on take-off or on landing.

In a further embodiment, if cylinder <NUM> was longer such that piston <NUM> and target <NUM> moved left such that sensor <NUM> also indicated 'target far' state when the cable was broken, the sensor mechanism would still be able to detect panel skew or cable failure, but would not be able to determine which type of failure had occurred.

The skew sensor mechanisms <NUM>, <NUM> of <FIG> and <FIG> are particularly advantageous as the components can be made relatively simple, robust and tolerant of the harsh environment within the aircraft surface.

Referring to <FIG> there is an unclaimed example of a skew sensor mechanism (or sensor assembly) <NUM>. The skew sensor mechanism <NUM> has a sensor target (or second part) in the form of an armature <NUM>, a hollow cylinder (or housing or first part) <NUM>, a resilient biasing means in the form of a spring <NUM>, and a continuous, linear sensor in the form of a Linear Variable Differential Transformer (LVDT) <NUM>. Other continuous linear sensors could also be used. The armature <NUM> has a first end <NUM> and a second end <NUM>. The cable <NUM> is connected to the second end <NUM> of the armature <NUM>. The cylinder <NUM> has a first end <NUM> and a second end <NUM>. The armature <NUM> is moveable within the cylinder <NUM>. The spring <NUM> is positioned between the second end <NUM> of the armature <NUM> and the second end <NUM> of the cylinder <NUM>. The sensor <NUM> is mounted on the outside of the cylinder <NUM>.

With reference to <FIG> there is a further unclaimed example of a skew sensor mechanism (or sensor assembly) <NUM>. The skew sensor mechanism <NUM> has a sensor target (or second part) in the form of a rack <NUM>, a hollow cylinder (or housing or first part) <NUM>, a resilient biasing means in the form of a spring <NUM>, a pinion <NUM> and a continuous, rotary sensor <NUM>. Other means to convert linear to rotary sensor motion could be used. The rack <NUM> has a first end <NUM> and a second end <NUM>. The cable <NUM> is connected to the second end <NUM> of the rack <NUM>. The cylinder <NUM> has a first end <NUM> and a second end <NUM>. The rack <NUM> is moveable within the cylinder <NUM>. The spring <NUM> is positioned between the second end <NUM> of the rack <NUM> and the second end <NUM> of the cylinder <NUM>. The rotary sensor <NUM> is mounted on the outside of the cylinder <NUM>.

With reference to <FIG> there is a yet further unclaimed example of a skew sensor mechanism (or sensory assembly) <NUM>. The skew sensor mechanism <NUM> has a sensor target (or second part) in the form of a grating style target <NUM>, a hollow cylinder (or housing or first part) <NUM>, a resilient biasing means in the form of a spring <NUM> and a detector <NUM>. The target <NUM> has a first end <NUM> and a second end <NUM>. The cable <NUM> is connected to the second end <NUM> of the target <NUM>. The cylinder <NUM> has a first end <NUM> and a second end <NUM>. The target <NUM> is moveable within the cylinder <NUM>. The spring <NUM> is positioned between the second end <NUM> of the target <NUM> and the second end <NUM> of the cylinder <NUM>. The detector <NUM> is mounted on the outside of the cylinder <NUM>. In this embodiment, the sensor could be an optical sensor or an electromagnetic sensor. Other continuous grating style sensors could be used.

Each of the sensor assemblies <NUM>, <NUM> and <NUM> are attached to the wing in a manner similar to that shown in <FIG>.

With reference to <FIG> there is shown a further embodiment of a skew sensor mechanism <NUM> in which components which fulfil the same or substantially the same function as those of skew sensor mechanism <NUM> are labelled <NUM> greater.

In this example the housing <NUM> is attached to the second slat <NUM>. Cable <NUM> is attached at one end to first sensor target <NUM> and at an opposite end to first slat <NUM>. A stop <NUM> prevents the first sensor target <NUM> moving further left than as shown in <FIG>.

The sensor assembly <NUM> also includes a second sensor target <NUM>' and a third sensor <NUM>'. A second cable <NUM>' is attached at one end to the second sensor target <NUM>' and at an opposite end to the fourth slat <NUM>. The stop <NUM> prevents the second sensor target <NUM>' moving further to the right than as shown in <FIG>.

<FIG> shows the relative position of the component when the associated aircraft is on the ground. All three sensors indicate target near.

<FIG> shows the relative position of the components with the associated aircraft in flight. In this case the first sensor <NUM> and second sensor <NUM>' both indicate target near whereas the second sensor <NUM> indicates target far. <FIG> shows the normal flight condition.

<FIG> shows a condition where skew of first slat <NUM> has occurred. Under these circumstances the first sensor <NUM> indicates target far.

<FIG> shows the position of the components when skew of fourth slat <NUM> or third slat <NUM> has occurred. Under these circumstances the third sensor <NUM>' indicates target far.

As shown in <FIG>, all three sensors indicate target far showing either skew of the second slat <NUM> or skew of both the first slat <NUM> and one or both of the third and fourth slats.

<FIG> shows failure of cable <NUM> during flight. Thus all sensors are indicating target near.

Longer wings tend to flex more during normal operation and the difference between the wing flex which pulls the cable during normal operation and the amount of pull during a true skew event can overlap. The embodiment shown in <FIG> overcomes this problem by adding further skew sensors. In this case there are two targets and three sensors. Sensor <NUM> acts as a proximity sensor in respect of both the first sensor target <NUM> and the second sensor target <NUM>'.

<FIG> show respective side and plan views of a skew sensor mechanism (or sensor assembly) <NUM> in which components that fulfil the same or substantially the same function as those of skew sensor mechanism <NUM> are labelled <NUM> greater. Skew sensor mechanism <NUM> does not have an equivalent to stop <NUM> but, as can be seen from <FIG>, the targets are allowed to overlap each other thereby ensuring the cable <NUM> and <NUM>' are always under tension.

Each of the sensor assemblies <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are configured to detect a first relative position of the first and second parts that is indicative of the wing structure supporting a load and a second relative position of the first and second parts that is indicative that the wing structure is supported. Each of the sensor assemblies <NUM>, <NUM> and <NUM> is configured to detect the relative position of a first and second part that is indicative of skew. Each of the sensor assemblies <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are configured to detect a relative position of a first and second part that is indicative of a failure of the respective cable <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

Variations fall within the scope of the present invention.

Skew and/or loss of one of any number of surfaces can be detected with the aforementioned invention.

The skew sensor mechanism can be positioned in any of the surfaces within the control surface element skew and/or loss detection system. As shown in <FIG> and <FIG>, the appropriate skew sensor mechanism is associated with four control surface elements (in these cases four slats) though in further embodiments these skew sensor mechanisms can be associated with more or less than four control surfaces.

Claim 1:
An aircraft control surface (<NUM>) skew and/or loss detection system (<NUM>) including:
an aircraft wing structure having a fixed part (<NUM>) and at least two control surface elements (<NUM>,<NUM>,<NUM>,<NUM>) wherein the at least two control surface elements (<NUM>,<NUM>,<NUM>,<NUM>) are configured to be moveable relative to the fixed part (<NUM>),
a cable (<NUM>) operably connected to each of the at least two control surface elements (<NUM>,<NUM>,<NUM>,<NUM>) such that a tensile force is applied to the cable (<NUM>) upon skew and/or loss of one of the control surface elements (<NUM>,<NUM>,<NUM>,<NUM>), and
a sensor assembly (<NUM>) having a first part and a second part, wherein one of the first and second parts has a first sensor and a second sensor (<NUM>,<NUM>) and wherein the cable (<NUM>) is coupled to the other of the first and second part such that skew and/or loss of one of the control surface elements (<NUM>,<NUM>,<NUM>,<NUM>) causes movement of the second part relative to the first part, wherein:
the first and second sensors (<NUM>,<NUM>) are configured to detect a first relative position of the first and second parts indicative of the wing structure (<NUM>) supporting a load whilst in flight, characterized in that
the first and second sensors are configured to detect a second relative position of the first and second parts indicative of the wing structure (<NUM>) being supported whilst on the ground,
and in that the first sensor (<NUM>) is configured to detect when the first and second parts are within a first range of relative positions, and
the second sensor (<NUM>) is configured to detect when the first and second parts are within a second range of relative positions.