Abstract:
A rotor blade fold system for an aircraft includes one or more actuators operably connected to one or more blade components of one or more rotor blades of the aircraft. One or more sensors are located at the one or more rotor blades and are configured to sense operation of the one or more blade components. A fold control system is configured to monitor output from the one or more sensors and is capable of stopping operation of the blade fold system, via communication with the one or more actuators, if the one or more blade components are not operating within predetermined limits.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a nonprovisional application of U.S. Provisional Patent Application No. 61/355,345 filed Jun. 16, 2010, the entire contents of which are incorporated herein by reference. 
     
    
     FEDERAL RESEARCH STATEMENT 
       [0002]    This invention was made with Government support under N00019-06-C-0081 awarded by the Department of the Navy. The Government has certain rights in this invention. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    The subject matter disclosed herein relates to blade fold systems for aircraft. 
         [0004]    Rotor-driven aircraft, for example, helicopters, utilize blade folding systems which fold the blades of a main rotor to reduce the space required for parking and/or storing the aircraft. Such systems are typically activated by an operator and visually monitored. Upon activation, each blade is to individually articulate from a spread position to a folded position. In a blade fold or blade spread, a number of events must happen in the proper sequence, for each blade and also among the blades. During operation, however, any number of faults in the system may prevent the blade folding sequence from occurring as required, and thus operates in an undesired sequence. At such times, it is desired to stop the blade folding sequence before a collision between the blades occurs to prevent costly damage to the blades. Detecting these faults, however, requires human observation and is therefore prone to human error and inattention, and further may be acting at a speed not easily perceptible by humans (either too fast or too slow). 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    According to one aspect of the invention, a rotor blade fold system for an aircraft includes one or more actuators operably connected to one or more blade components of one or more rotor blades of the aircraft. One or more sensors are located at the one or more rotor blades and are configured to sense operation of the one or more blade components. A fold control system is configured to monitor output from the one or more sensors and is capable of stopping operation of the blade fold system, via communication with the one or more actuators, if the one or more blade components are not operating within predetermined limits. 
         [0006]    According to another aspect of the invention, a method of folding one or more rotor blades of an aircraft includes activating one or more actuators operably connected to the one or more rotor blades. The one or more blades are urged toward a folded position via activation of the one or more actuators, and one or more blade components of the one or more rotor blades are monitored via one or more sensors disposed at the one or more rotor blades. A determination is made if the one or more blade components are operating within a predetermined limit, and operation of the blade fold system is stopped if the one or more blade components are not operating within the predetermined limit. 
         [0007]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0009]      FIG. 1  is a plan view of a rotor for an aircraft in an extended configuration; 
           [0010]      FIG. 2  is a schematic view of a single rotor blade; 
           [0011]      FIG. 3  is a plan view of a rotor for an aircraft in a folded condition; 
           [0012]      FIG. 4  is a flow diagram of an embodiment of a blade fold system; and 
           [0013]      FIG. 5  is a flow diagram of another embodiment of a blade fold system. 
       
    
    
       [0014]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Shown in  FIG. 1  is a view of a rotor  10 , for example, a helicopter. The rotor  10  includes a plurality of rotor blades  12  extending from a rotor hub  14 . Each blade  12  includes features that allow for folding and unfolding of the blade  12 . For example, as shown in  FIG. 2 , the blades  12  include a pitch lock  16  located at the hub  14 . The pitch lock  16  is connected to a pitch lock actuator  18 . Further, the blades  12  each include and at least one hinge  20  and hinge lock  22  located along the blade  12  at a desired location. The hinge lock  22  is connected to a hinge lock actuator  26 . A majority length of the airfoil of blade  12  is folded about the hinge  20  by a fold actuator  24 . The actuators provide the forces necessary to move the all of the various components and when operated in the proper sequence allow the blades  12  to fold into a stowed position as shown in  FIG. 3 . The system described herein is a hydraulic system including hydraulic pitch lock actuators  18  and hinge lock actuators  26 , as well as hydraulic control of the hinge  20 . It is to be appreciated, however, that the system may utilize other types of actuators, for example, electric actuators, to control the blade  12  fold and may require additional positioning actuators which move the blades  12  in other planes of motion about or around the hub  14 . 
         [0016]    Referring again to  FIG. 2 , the pitch lock actuators  18 , hinge lock actuators  26 , and fold actuators  24  are connected to a fold control system  28  which controls the sequencing on the actuators  18 ,  26  and the fold actuator  24  during a blade fold and blade spread operation. Sensors  30  are located at each of the actuators  18 ,  26  and the fold actuators  24  to monitor the blade fold operation and are in operable communication with the fold control system  28 . If, during operation of the blade fold system, a sensor  30  indicates an actuator  18 ,  26  and/or  24  is operating outside of a predetermined limit, the fold control system  28  takes appropriate action, which may include holding or aborting the blade fold operation or reversing the sequence to return to the starting configuration. 
         [0017]      FIG. 4  illustrates an example of a blade fold process including a method of fault detection in and control during the blade fold process. The pitch lock actuators  18  are activated in block  40 . For example, in a hydraulic system, this may comprise opening a valve to allow hydraulic fluid to the pitch locks  16 . A sensor  30  is disposed at each pitch lock  16  to determine if the pitch locks  16  are engaged (block  42 ), how far along their stroke the pitch locks  16  have advanced, and/or at what rate the pitch locks  16  are advancing to lock the pitch of the blades  12 . If the sensors indicate that the pitch locks  16  do not begin to engage, or are not fully engaged within predetermined time limits (block  44 ), the fold control system  28  may stop all operation of the blade fold system (block  46 ). 
         [0018]    Once the pitch locks  16  are successfully engaged as indicated by the sensors  30 , the fold control system  28  energizes the hinge lock actuators  26  to retract the hinge locks  22  thereby allowing the blades  12  to be folded (block  48 ). The sensors  30  disposed at the hinge locks  22  monitor the hinge lock  22  retraction to determine that the hinge lock  22  retraction is begun within a predetermined time limit  54  and that all of the hinge locks  22  are moving at the correct rate and also retracted within a time limit (block  52 ). If one of these conditions is not met, the fold control system  28  may take action including slowing or stopping the fold process (block  54 ). In some embodiments, once all of the hinge locks  22  are fully retracted, the fold control system  28  activates the fold actuator  24  at each hinge  20  to begin fold of the blades  12  in a desired sequence (block  56 ). The sensors  30  disposed at the hinges  20  monitor progress and rate (block  58 ) of the folding of each blade  12 , especially relative to adjacent blades  12  to prevent collision of adjacent blades  12  during the fold operation. If the progress of folding an adjacent blade  12  is determined to be slower than desired when compared to a predetermined limit and or the progress of the blade  12 , the fold control system  28  may slow or stop the fold operation (block  60 ). 
         [0019]    In some embodiments, the folding of a particular blade  12  may begin immediately following retraction of the hinge lock  22  of the blade  12 , not necessarily requiring retraction of all of the hinge locks  22  at all of the blades  12 . In such embodiments, the sensors  30  monitor progress of retraction of the hinge locks  22  and/or advancement of the hinges  20  of adjacent blades  12  to determine if the adjacent blades  12  are retracting at the desired rate. If the sensors indicate advancement is delayed or stopped unexpectedly, the fold control system  28  may slow or stop the fold operation. 
         [0020]    Once the sensors  30  indicate that all blades  12  are fully folded (block  62 ), the folding operation is stopped by the fold control system  28  (block  64 ). Utilization of the sensors  30  and the fold control system  28  to monitor and control the fold operation increases the efficiency of the fold operation and increases prevention of collisions of blades  12  during the fold operation due to system faults by early detection of potential faults and immediate, automatic preventative action by the fold control system  28  such as stoppage of the fold operation prior to occurrence of the collision. Use of sensors  30  for monitoring reduces reliance on visual monitoring of the fold process, thereby reducing the potential for human error. 
         [0021]    Sensors  30  may also be utilized to monitor a blade spread process in which the blades  12  spread from the folded position shown in  FIG. 3  to the spread position illustrated in  FIG. 1 , thus forming a rotary wing. A blade spread process is illustrated in  FIG. 5 . In block  66 , the sensors  30  confirm that the hinge locks  22  are fully retracted so the blade spread may begin without the blades  12  colliding with the hinge lock  22  mechanism. Once retraction of the hinge locks  22  is confirmed, the fold control system  28  activates the fold actuator  24  at each hinge  20  to begin spread of the blades  12  in a desired sequence (block  68 ). The sensors  30  disposed at the hinges  20  monitor progress and rate (block  70 ) of the spread of each blade  12 , especially relative to adjacent blades  12  to prevent collision of adjacent blades  12  during the fold operation. If the progress of spreading an adjacent blade  12  is determined to be slower than desired when compared to a predetermined limit and or the progress of the blade  12 , the fold control system  28  may slow or stop the fold operation (block  72 ). 
         [0022]    When the blades  12  reach their fully spread position, as shown for example, in  FIG. 1 , the hinge locks  22  are engaged and engagement is confirmed by the sensors (block  74 ). The pitch locks  16  are retracted (block  76 ) via the pitch lock actuators  18 . The sensors  30  at the pitch locks  16  monitor the pitch lock  16  disengagement, and when disengagement is confirmed by the sensors  30 , the blade spread is complete (block  78 ). 
         [0023]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.