Abstract:
A method for controlling an aircraft power system having a plurality of generators includes determining a load set for controlling aircraft power as a function of a number of generators providing power and as a function of a health status of a load to be included in said load set.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Aircraft are complex and use a vast array of electrical devices such as sensors, weapon systems (for military aircraft) and cockpit displays. Other devices include environmental systems, flight controls, galley equipment, communication gear, weather radar, in-flight entertainment systems, external lighting, etc. Typically, DC power supplies, such as batteries, are insufficient to meet the demands for electricity in operating these devices. 
         [0002]    Aircraft are equipped with a number of power generation systems including primary and redundant backup systems to supply power to equipment in an emergency. Primary power is usually provided by AC generators directly connected to the gas turbine engines. Commercial aircraft and many military aircraft are equipped with auxiliary power units (APU), essentially smaller gas turbine engines, which provide an additional power source. The APU supplements the primary power system or replaces it in case of engine failure. If the APU fails, many aircraft carry a ram air turbine (RAT) that can be deployed when needed to provide emergency power to keep critical systems operating long enough to land safely. Some aircraft may also have battery backups. 
       SUMMARY OF THE INVENTION 
       [0003]    According to an example provided herein, a method for controlling an aircraft power system having a plurality of generators includes determining a load set for controlling aircraft power as a function of a number of generators providing power and as a function of a health status of a load to be included in said load set. An apparatus for controlling an aircraft power system having a plurality of electrical power sources, said apparatus comprising: 
         [0004]    According to a further example provided herein an apparatus includes a load panel that determines a load set for controlling aircraft power as a function of a number of functioning power sources and as a function of a health status of a load to be included in the load set. The load panel provides power to loads within the load set. 
         [0005]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  shows an illustrative electrical system for an aircraft. 
           [0007]      FIG. 2  shows a method of power distribution to load sets. 
           [0008]      FIG. 3  shows a method of power distribution from aircraft power sources 
           [0009]      FIG. 4  shows a method of picking loads during a reduction in power in an aircraft. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0010]      FIG. 1  shows an electrical power system  10  for an aircraft (not shown). The system  10  includes first and second primary power panels  12  and  14 , which provide primary power distribution to the aircraft. The first primary power panel  12  includes a first ac generator bus  16 , which includes conductors such as copper wires (not shown) embedded in a hull of an aircraft (not shown) and buried under panels (not shown) in an aircraft cabin (not shown). The first ac generator bus  16  receives ac power at variable frequencies and supplies the variable frequency ac power to frequency insensitive galley equipment  18  such as galley ovens and chillers. The first ac generator bus  16  also supplies variable frequency ac power to a first transformer-rectifier unit (“TRU”)  20 , which steps down the ac power and converts the stepped down power to dc power. A first static inverter  22  converts dc power from the first TRU  20  into fixed frequency ac power. The fixed frequency ac power from the inverter  22 , the dc power from the first TRU  20  and the variable frequency ac power from the first ac generator bus  16  are supplied to a first power management panel  24 . The first power management panel  24  includes a plurality of power relays that can be controlled manually or automatically to provide secondary power distribution to the aircraft. The first power management panel  24  distributes fixed frequency ac power to loads such as hydraulic pumps, fuel pumps, environmental controls, recirculation fans and galley fans. Further, the first power management panel  24  distributes dc power to loads such as communication and navigation equipment and dc instrumentation and electronics. Still further, the first power management panel  24  distributes variable frequency ac power to loads such as ac lighting, gasper fans, and ice and rain protection equipment. The first power management panel  24  also includes a plurality of circuit breakers for line and load fault protection. 
         [0011]    The second primary power panel  14  includes a second ac generator bus  26 , which provides variable frequency ac power to additional galley equipment  28 , a second TRU  30  and second power management panel  34 . A second static inverter  32  converts dc power from the second TRU  30  into fixed frequency ac power. The second power management panel  34  provides secondary power distribution of variable frequency ac power from second ac generator bus  26 , dc power from the second TRU  30  and fixed frequency ac power from the second inverter  32 . The second primary power panel  14 , the second TRU  30 , the second inverter  32  and the second power management panel  34  can provide system redundancy, which increases reliability of the system  10 . 
         [0012]    The ac generator buses  16  and  26  handle ac power having a limited range of frequencies. For example, the frequency of the ac power can be between 400 Hz and 800 Hz. Powering certain equipment at variable frequencies and other equipment at a fixed frequency allows the size and weight of the static inverters  22  and  32  to be reduced because the static inverters  22  and  32  do not have to supply ac power to all of the equipment. For certain aircraft, the static inverters  22  and  32  may be reduced in size by as much as 70 percent. 
         [0013]    An Essential and Flight Critical Load Management Panel  36  provides ac and dc power to selected flight instruments and other critical dc or ac loads in the event primary power is lost. The dc power may be supplied by a battery system  38 , and the ac power may be supplied by a combination of the battery system  38  and a third static inverter  40 . The third static inverter  40  converts the dc power from the battery system  38  to fixed frequency ac power. 
         [0014]    Primary power is supplied to either the first or second ac generator bus  16  or  26  by an auxiliary generator  42 . The auxiliary generator may be a generator, an APU, a RAT or similar device or any combination thereof (hereinafter referred to as “ECS”). An ECS generator  42  is operable to provide appropriate power as required by the system  10 . Having a four-pole design and a maximum speed of 24000 rpm, for example, the ECS generator  42  can produce ac power having a frequency between 400 Hz and 800 Hz. The ECS generator  42  is sized to provide full bus loads at all times to either the first or second ac generator bus  16  or  26 . During normal operating conditions, the ECS generator  42  is selectively connected to one of the first and second ac generator buses  16  and  26  by a first power relay  44  and either a second or third power relay  51  or  53 . 
         [0015]    Primary power is supplied to the other of the first and second ac generator buses  16  and  26  by closing either a fourth of fifth power relay  50  or  52  to connect one of the aircraft&#39;s two main engine generators  46  or  48 . When backup power is needed for the ECS generator  42 , the main engine generators  46  and  48  are connected to the first and second generator buses  16  and  26 , respectively, by closing the fourth and fifth power relays  50  and  52  and opening the first power relay  44 . Typically, there will be a main engine generator  46  or  48  corresponding to each main engine of the aircraft, and an ac generator bus  16  or  26  corresponding to each main engine generator  46  or  48 . Each main engine generator  46  and  48  is operable to provide ac power having a limited frequency range. Having a 4-pole design and a maximum speed of 24000 rpm, each main engine generator  46  and  48  can operate between 50% and 100% of maximum speed and produce ac power between 400 Hz and 800 Hz. Though relays are defined herein, other types of switches including contactors and solid state devices etc. are also contemplated herein. 
         [0016]    Such an electrical power system  10  offers increased reliability due to the additional redundancy between the main engine generators  46  and  48  and the ECS generator  42 . Such an electrical power system  10  also reduces aircraft fuel consumption because the ECS generator  42 , not a main engine generator  46  or  48 , is providing primary ac power to one of the ac generator buses  16  or  26 . 
         [0017]    The electrical power system  10  further includes a bus power control unit (“BPCU”)  54  for controlling the power relays  44 ,  50 ,  51 ,  52  and  53  to connect either the ECS generator  42  or one of the main engine generators  46  and  48  to the first and second ac generator buses  16  and  26 . In addition to controlling the power relays  44 ,  50 ,  51 ,  52  and  53 , the BPCU  54  controls the relays in the first and second power management panels  24  and  34  and the Essential and Flight Critical Load Management Panel  36 . The power management panels  24 ,  34  send the appropriate power to redundant transponders  55 ,  56  and other loads  57 ,  58  which may also be redundant. The Essential and Flight Critical Load Management Panel  36  may also have a manual override  59 . 
         [0018]    A central maintenance controller (“CMC”)  60 , which may be a part of the BPCU  54 , communicates with the dc loads, fixed frequency (ff) ac loads, the variable frequency (vf) ac loads, transponders  55 ,  56  and other loads  57 ,  58  via signal lines  61  and communicates with the Essential and Flight Critical Load Management Panel  36  via signal line  62  as will be discussed herein. 
         [0019]    Referring now to  FIG. 2 , operation of the Essential and Flight Critical Load Management Panel  36  are described. If there is a normal power situation (e.g., all power sources are operating properly) (see step  200 ), a full load is available for use by the crew (see step  210 ). If normal power is not available, the Essential and Flight Critical Load Management Panel  36  includes a processor  37  to run an instruction set to determine a required load set based on available power step (see step  220 ), then trade redundancy within the load set (step  230 ). For instance, if the Essential and Flight Critical Load Management Panel  36  includes an electrical load such as a transponder  55  (there is usually only one on the Essential and Flight Critical Load Management Panel  36 ) that is on standby power if an emergency occurs, the Essential and Flight Critical Load Management Panel  36  sheds powering the transponder  55  by turning off power thereto in the panel and maintains powering and communicating with the powered transponder  56 . 
         [0020]      FIG. 3  illustrates an example process for performing step  220  of  FIG. 2 . The Essential and Flight Critical Load Management Panel  36  includes a processor  37  to run an instruction set that determines available power (step  300 ). The Essential and Flight Critical Load Management Panel  36  determines how many generators (e.g., main engine generators  46 ,  48  and ECS generator(s)  42  are on-line (step  310 ) and creates a given load set (step  320 ) for the number of generators still on-line. For instance, if two of the three generators  42 ,  46 ,  48  are on line, a load set for that generator may include flight controls, cockpit displays, environmental systems, flight controls, galley equipment, communication gear, weather radar, and external lighting. The selection criteria is based on a weighting of criticality versus power required by load. If the ECS generator  42  is on-line (step  330 ) the load set may be determined by Essential and Flight Critical Load Management Panel  36  (step  340 ) to include flight controls, communication gear, weather radar, and external lighting. If there are no generators on-line (step  350 ), the Essential and Flight Critical Load Management Panel  36  determines a battery-only load set which may include flight controls and communication gear. Power is then distributed by Essential and Flight Critical Load Management Panel  36  with the load sets that have been determined. 
         [0021]      FIG. 4  illustrates an example process for performing step  230  of  FIG. 2 . After redundancy has been shed (step  400 ), the Essential and Flight Critical Load Management Panel  36  gathers reported equipment health information (step  410 ) from CMC  60 , utilizes known power consumption information for equipment that is functional (step  420 ) and then chooses to run the healthy (e.g., undamaged) equipment with the lowest power draw within the load set (step  430 ). For example, if a load, such as transponder  56  is not functioning (i.e., unhealthy), a health status assessment can be performed by power management panels  24 ,  34 , which communicate with the essential and flight critical load management panel  36  comparing known power consumption of the transponder  56  with actual power consumption or the like from transponder  56 , and a standby transponder  55  may be placed on Essential and Flight Critical Load Management Panel  36  and powered while the transponder  56  that is not healthy is removed from Essential and Flight Critical Load Management Panel  36  and not powered. Similarly, unhealthy flight instrumentation may be shed and back-up flight instrumentation may be integrated into a primary flight display. The equipment health assessment may either be internally generated, i.e., the component being powered has reported a health problem to the CMC  60 , or externally generated, i.e., the component being powered is not acting normally. For example, the component may be using too much power, too little power, is not responding as instructed, or can&#39;t be “heard” (i.e., not detected) by the CMC  60 . 
         [0022]    The Essential and Flight Critical Load Management Panel  36  may be manually overridden by manual overrides  59  if functionality is needed. For instance, if emergency power to control flaps (not shown) to safely land the aircraft is required, any load set not including flap control may be overridden to enable power to be provided for flap control. 
         [0023]    Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. 
         [0024]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.