Patent Publication Number: US-2007108342-A1

Title: Reconfigurable flight control surface actuation system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims the benefit of U.S. Provisional Application No. 60/736,823 filed Nov. 14, 2005. 
    
    
     TECHNICAL FIELD  
      The present invention relates to flight surface actuation and, more particularly, to an automatically reconfigurable electric flight control surface actuation system.  
     BACKGROUND  
      Aircraft typically include a plurality of flight control surfaces that, when controllably positioned, guide the movement of the aircraft from one destination to another. The number and type of flight control surfaces included in an aircraft may vary, but typically include both primary flight control surfaces and secondary flight control surfaces. The primary flight control surfaces are those that are used to control aircraft movement in the pitch, yaw, and roll axes, and the secondary flight control surfaces are those that are used to influence the lift or drag (or both) of the aircraft. Although some aircraft may include additional control surfaces, the primary flight control surfaces typically include a pair of elevators, a rudder, and a pair of ailerons, and the secondary flight control surfaces typically include a plurality of flaps and slats.  
      The positions of the aircraft flight control surfaces are typically controlled using a flight control surface actuation system. The flight control surface actuation system, in response to position commands that originate from either the flight crew or an aircraft autopilot, moves the aircraft flight control surfaces to the commanded positions. In most instances, this movement is effected via actuators that are coupled to the flight control surfaces. Though unlikely, it is postulated that a flight control surface actuator could become inoperable. Thus, some flight control surface actuation systems are implemented with a plurality of actuators coupled to a single flight control surface.  
      In many flight control surface actuation systems, some of the actuators are hydraulically powered. Some flight control surface actuation systems have been implemented, however, with other types of actuators, including pneumatic and electromechanical actuators. Additionally, in some flight control surface actuation systems, a portion of the actuators, such as those that are used to drive the flaps and slats, are driven via one or more central drive units and mechanical drive trains. These central drive units are typically hydraulically or electrically powered devices.  
      Although the flight control surface actuation systems that include hydraulically powered or pneumatically powered actuators are generally safe, reliable, and robust, these systems do suffer certain drawbacks. Namely, these systems can be relatively complex, can involve the use of numerous parts, can be relatively heavy, and may not be easily implemented to provide sufficient redundancy, fault isolation, and/or system monitoring. The flight control surface actuation systems that include electromechanical actuators also suffer certain drawbacks. For example, many of these systems also do not provide sufficient redundancy, fault isolation, and/or system monitoring. The lack of sufficient redundancy, fault isolation, and/or system monitoring can lead to undesired operational configurations in the event of an inoperable flight control surface. For example, if a single flight control surface becomes inoperable, the remaining surfaces may become inoperable or an asymmetric flight control surface deploy situation may occur.  
      Hence, there is a need for a flight control surface actuation system and method that provides sufficient redundancy, fault isolation, and/or system monitoring to prevent undesired operational configurations, such as an asymmetric flight control surface deploy situation, in the event of an inoperable flight control surface. The present invention addresses one or more of these needs.  
     BRIEF SUMMARY  
      The present invention provides a system and method for preventing undesired operational configurations, such as an asymmetric flight control surface deploy situation, in the event of an inoperable flight control surface. The present invention addresses one or more of these needs.  
      In one embodiment, and by way of example only, a flight control surface actuation system includes a plurality of flight control surface actuators, and a control unit. Each flight control surface actuator is configured to be coupled to a secondary flight control surface on either a first aircraft wing or a second aircraft wing. Each flight control surface actuator is coupled to receive power and is operable, upon receipt thereof, to move its associated secondary flight control surface to a commanded position. The control unit is coupled to receive one or more signals representative of operability of each of the secondary flight control surfaces and is operable, in response thereto, to determine operability of each of the flight control surfaces and upon determining that a flight control surface on one of the first or second aircraft wings is inoperable, to automatically selectively supply or inhibit power to one or more of the flight control surface actuators that are adapted to be coupled to a secondary flight control surface on one of the second or first aircraft wings, respectively, to prevent an asymmetric flight control surface deploy condition.  
      In yet another exemplary embodiment, in an aircraft having at least first and second aircraft wings, wherein the first aircraft wing has a plurality of secondary flight control surfaces that are each symmetric to a secondary flight control surface on the second wing, and each flight control surface on the first and second aircraft wings has one or more flight control surface actuators coupled thereto, a method of preventing an asymmetric flight control surface deploy condition includes determining operability of each of the plurality of secondary flight control surfaces. If it is determined that a secondary flight control surface on one of the first or second aircraft wings is inoperable, one or more of the symmetric secondary flight control surface on one of the second or first aircraft wings, respectively, is selectively moved, or inhibited from moving, to thereby prevent the asymmetric flight control surface deploy condition.  
      Other independent features and advantages of the preferred flight control system and method will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic diagram of a portion of an exemplary embodiment of an aircraft depicting an exemplary flight control surface actuation system according one embodiment of the present invention; and  
       FIG. 2  is a flowchart depicting an exemplary methodology implemented by the exemplary system of  FIG. 1 , according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT  
      The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.  
      Turning first to  FIG. 1 , a schematic diagram of a portion of an exemplary aircraft and a portion of an exemplary flight control surface actuation system is shown. In the illustrated embodiment, the aircraft  100  includes first and second aircraft wings  101 - 1  and  101 - 2 , respectively, a pair of elevators  102 , a rudder  104 , and a pair of ailerons  106 , which are the primary flight control surfaces, and a plurality of flaps  108 , slats  112 , and spoilers  114 , which are the secondary flight control surfaces. The primary flight control surfaces  102 - 106  control aircraft movements about the aircraft pitch, yaw, and roll axes. Specifically, the elevators  102  are used to control aircraft movement about the pitch axis, the rudder  104  is used to control aircraft movement about the yaw axis, and the ailerons  106  control aircraft movement about the roll axis. It is noted, however, that aircraft movement about the yaw axis can also be achieved either by varying the thrust levels from the engines on opposing sides of the aircraft  100 . It will additionally be appreciated that the aircraft  100  could include horizontal stabilizers (not shown).  
      The secondary control surfaces  108 - 114 , which are all disposed on the first and second aircraft wings  101 - 1 ,  101 - 2 , influence the lift and drag of the aircraft  100 . For example, during aircraft take-off and landing operations, when increased lift is desirable, the flaps  108  and slats  112  may be moved from retracted positions to extended positions. In the extended position, the flaps  108  increase both lift and drag, and enable the aircraft  100  to descend more steeply for a given airspeed, and also enable the aircraft  100  get airborne over a shorter distance. The slats  112 , in the extended position, increase lift, and are typically used in conjunction with the flaps  108 . The spoilers  114 , on the other hand, reduce lift and when moved from retracted positions to extended positions, which is typically done during aircraft landing operations, may be used as air brakes to assist in slowing the aircraft  100 .  
      The flight control surfaces  102 - 114  are moved to deployed positions via a flight control surface actuation system  120 . The flight control surface actuation system  120  includes one or more actuator control units  121 , a plurality of primary flight control surface actuators, which include elevator actuators  122 , rudder actuators  124 , and aileron actuators  126 , and a plurality of secondary control surface actuators, which include flap actuators  128 , slat actuators  132 , and spoiler actuators  134 . It will be appreciated that the number of actuator control units  121  may vary. However, in the depicted embodiment, the flight control surface actuation system  120  includes two multi-channel actuator control units  121  ( 121 - 1 ,  121 - 2 ).  
      The flight control surface actuation system  120  may be implemented using various numbers and types of flight control surface actuators  122 - 134 . In addition, the nunber and type of flight control surface actuators  122 - 134  per flight control surface  102 - 114  may be varied. In the depicted embodiment, however, the system  120  is implemented such that two primary flight control surface actuators  122 - 126  are coupled to each primary flight control surface  102 - 16 , and two secondary control surface actuators  128 - 134  are coupled to each secondary control surface  108 - 114 . Moreover, each of the primary surface actuators  122 - 126 , each of the flap actuators  128 , and each of the spoiler actuators  134  are preferably a linear-type actuator, such as, for example, a ballscrew actuator, and each of the slat actuators  132  are preferably a rotary-type actuator. It will be appreciated that this number and type of flight control surface actuators  122 - 134  are merely exemplary of a particular embodiment, and that other numbers and types of actuators  122 - 134  could also be used.  
      The flight control surface actuation system  120  additionally includes a plurality of control surface position sensors  125 . The control surface position sensors  125  sense the positions of the flight control surfaces  102 - 114  and supply control surface position feedback signals representative thereof. It will be appreciated that the control surface position sensors  125  may be implemented using any one of numerous types of sensors including, for example, linear variable differential transformers (LVDTs), rotary variable differential transformers (RVDTs), Hall effect sensors, resolvers, or potentiometers, just to name a few. In the depicted embodiment, a pair of control surface position sensors  125  is coupled to each of the flight control surfaces  102 - 114 . It will be appreciated, however, that this is merely exemplary of a particular embodiment and that more or less than two position sensors  125  could be coupled to each flight control surface  102 - 114 . Moreover, in other embodiments, the flight control surface actuation system  120  could be implemented without some, or all, of the control surface position sensors  125 .  
      The flight control surface actuators  122 - 134  are each driven by one or more non-illustrated motors. Although the motors may be either electric, pneumatic, or hydraulic motors, in a particular preferred embodiment the motors are electric motors. Moreover, although various numbers of motors could be associated with each actuator, preferably two motors are associated with each flight control surface actuator  122 - 134  such that either, or both, actuator motors can drive the associated actuator  122 - 134 . The actuator motors are selectively energized and, upon being energized, rotate in one direction or another, to thereby supply a drive force to the associated actuator  122 - 134 . The actuators  122 - 134  are each coupled to receive the drive force supplied from its associated actuator motors and, depending on the direction in which the actuator motors rotate, move to commanded positions, to thereby move the primary and secondary flight control surfaces  102 - 114 . It will be appreciated that the actuator motors may be implemented as any one of numerous types of AC or DC motors, but in a preferred embodiment the actuator motors are preferably implemented as DC motors, and most preferably brushless DC motors.  
      The system  120  and actuator control units  121 - 1 ,  121 - 2  may be implemented according to any one of numerous operational configurations. For example, the system  120  could be configured such that one of the control units  121 - 1  ( 121 - 2 ) is an active control unit, while the other control unit  121 - 2  ( 121 - 1 ) is in an inactive (or standby) mode. Alternatively, the system  120  could be configured such that both control units  121 - 1 ,  121 - 2  are active and controlling all, or selected ones, of the flight control surface actuator assemblies  122 - 134 . No matter the specific configuration, each control unit  121 - 1 ,  121 - 2 , when active, receives flight control surface position commands from one or more non-illustrated external systems, such as one or more flight control computers or pilot controls. In response to the flight control surface position commands, the active control units  121 - 1 ,  121 - 2  energize the appropriate flight control surface actuator assemblies  122 - 134 . The flight control surface actuator assemblies  122 - 134 , in response to being energized, move the appropriate flight control surfaces  102 - 114  to the commanded flight control surface position.  
      The control units  121 - 1 ,  121 - 2  may also be configured receive one or more monitor signals that are representative of secondary flight control surface actuator assembly  108 - 114  operability. The control units  121 - 1 ,  121 - 2 , in response to these monitor signals, determine the operability of the secondary flight control surfaces  108 - 114 . If one or both control units  121 - 1 ,  121 - 2  determines that a secondary flight control surface  108 - 114  is partially or fully inoperable, it automatically compensates the system  120  to prevent an asymmetric deploy configuration. It will be appreciated that a partially or fully inoperable secondary flight control surface may be caused by a jam or other fault associated with the flight control surface  108 - 114  itself, or by one or more partially or fully inoperable secondary flight control surface actuator assemblies  128 - 134 . It will additionally be appreciated that the monitor signals that the control units  121 - 1 ,  121 - 2  receive may be supplied directly from the flight control surfaces actuator assemblies  108 - 114 . In the depicted embodiment, however, the monitor signals are supplied from the secondary flight control surface position sensors  125 .  
      More specifically, at least in the depicted embodiment, the control units  121 , in response to the position signals supplied from the secondary flight control surface position sensors  125 , determines the status and position of each secondary flight control surface  108 - 114 . If one or both of the control units  121 - 1 ,  121 - 2  determines that the system  120  is in, or would be in, an asymmetric deploy condition due to one or more of the secondary flight control surfaces  108 - 114  on one of the aircraft wings  101 - 1  ( 101 - 2 ) becoming inoperable, one or both control units  121 - 1 ,  121 - 1  either supplies actuator position commands to, or inhibits actuator position commands from being supplied to, the symmetric secondary flight control surface actuators  128 - 134  on the other aircraft wing  101 - 2  ( 101 - 1 ). Thus, the symmetric secondary flight control surface  108 - 114  is either moved to, or remains in, the same position as the inoperable secondary flight control surface  108 - 114 .  
      It will be appreciated that the control units  121 - 1 ,  121 - 2  may implement the above-described functionality via hardware, firmware, software, or various combinations thereof. Preferably, however, the control units  121 - 1 ,  121 - 2  implement this functionality via software. It will additionally be appreciated that one or both of the actuator control units  121 - 1 ,  121 - 2  could be formed as an integral part of, and/or one or more of its above-described functions could be implemented as within, the one or more flight control computers. In any case, the process that is implemented by the control units  121 - 1 ,  121 - 2  (either separately or as part of one or more flight control computers) is depicted in flowchart form in  FIG. 2  and, for completeness of explanation, will now be described. In doing so, it should be understood that the parenthetical references in the following description correspond to the reference numerals used in the depicted flowchart.  
      Turning now to  FIG. 2 , it is seen that, upon system  100  initiation ( 201 ), the operable control unit  121  (or control units) determines the operability of each of the secondary flight control surfaces  108 - 114  ( 202 ,  204 ). As noted above, this can be accomplished using any one of numerous techniques, but is preferably accomplished via the position signals received from the secondary flight control surface position sensors  125 . If a secondary flight control surface  108 - 114  is determined to be inoperable, the control unit  121  (or units) then determines the position of the inoperable secondary flight control surface  108 - 114  ( 206 ) and the position of the symmetric secondary flight control surface  108 - 114  on the opposite aircraft wing  101  ( 208 ).  
      After the positions of the inoperable and symmetric secondary flight control surfaces  108 - 114  are determined, a magnitude difference between the two positions is determined ( 210 ), and compared to a predetermined value ( 212 ). If the magnitude difference equals or exceeds the predetermined value, then the symmetric secondary flight control surface  108 - 114  is moved to a position that is at least substantially equal to the position of the inoperable secondary flight control surface  108 - 114  ( 214 ). If, however, the magnitude difference is less than the predetermined value, then the symmetric secondary flight control surface  108 - 114  is already in a position that is at least substantially equal to the position of the inoperable flight control surface  108 - 114 , and need not be moved. In this instance, further movement of the symmetric flight control surface  108 - 114  is inhibited ( 216 ) by, for example, inhibiting the supply of actuator position commands to the associated actuator  128 - 134 . However, the remaining operable secondary flight control surfaces  108 - 134  may be normally operated.  
      This flight control system  100  described herein, and the methodology  200  that is implemented thereby, prevents or at least inhibits an asymmetric deploy condition of the secondary flight control surfaces  108 - 114  without adversely affecting aircraft handling.  
      While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.