Abstract:
An avionics system for providing information to pilots provides a communications bus, allowing each instrument in communication with the bus to access information from a plurality of sensors. Software based instrumentation and the ability to remove and insert computation units in communication with the bus provide the ability to change instrumentation. Interchangeable display units provide additional redundancy in the event of display unit failure.

Description:
FIELD OF THE INVENTION 
     The invention concerns the field of avionics, specifically the providing of information to a pilot or flight crew and, potentially, to ground-based communications regarding the status of an aircraft. 
     BACKGROUND OF THE INVENTION 
     Avionics devices generally available in modern aircraft range from instruments which had their technological origins in the first half of the twentieth century to more advanced, electronic- and computer-operated units. Regardless of their level of technological advancement, avionics devices characteristically accept information or data from a source and provide that information to the pilot either visually in raw form or in a translated (e.g., graphical) format that is more readily meaningful, or via a combination of visual and audio information. 
     These devices have historically been single-function units. That is, an avionics device will usually provide a single major piece of information. For example, a directional gyro indicates magnetic course, and tells the pilot nothing about airspeed, engine rpm, or oil temperature. Multi-function avionics devices were historically limited to a small set of functions, for example, a turn-and-bank coordinator provides a turn indicator and a slip-and-skid indicator. 
     One of the historical purposes served by an array of discrete devices is redundancy and, thus, overall systems reliability. For example, if the gyro in an artificial horizon failed in flight, that failure would not affect the operation of the airspeed indicator, the turn-and-bank coordinator, or the directional gyro, thus leaving the pilot without the artificial horizon but with an adequate instrument panel. 
     A further purpose in such discrete devices has been compensating for the variations in instruments needed for various airplanes. For example, the airspeed indicator for an aircraft may bear markings to indicate maximum flap extension speed, maneuvering speed, and never exceed speed. Because these speeds vary for different aircraft, combining other expensive instruments with the airspeed indicator would require manufacturing a variety of different models of the instrument package just to provide varied airspeed indications needed for various aircraft. Thus the cost of manufacturing and keeping inventory would rise, as would the cost to the aircraft owner to replace a device when only one component had failed. 
     The advent of reliable microelectronics and computers, as well as solid-state “gyroscopes” has changed the available instrumentation options. Electronic flight information systems, or “EFIS,” now combine a group of flight data displays into one or more displays for the pilot. These systems often combine information such as an artificial horizon display, directional gyro display, airspeed indicator, and vertical speed indicator into a single graphical display. Because they use electronic processors, these units can provide programmable indicators, such as for airspeed limitations, and can thus be programmed for use in a wide variety of airplanes. 
     However, EFIS does not eliminate the need for some redundancy for the purpose of safety. In a single-display EFIS, the failure of one critical component, such as a power-supply connection to the display, can eliminate all of the information the EFIS normally displays. Thus, safety concerns dictate that the airplane be equipped with some redundant, discrete instrumentation, which is expensive, or that the EFIS be manufactured to extreme reliability standards, which is also expensive. Costs for high-quality, FAA-approved EFIS units can be on the order of $50,000, and beyond the financial reach of many small airplane pilots. Indeed, the cost of such a unit exceeds the total value of many small airplanes. 
     Avionics devices also must be connected to an airplane to be of use. Depending on the avionics device, such connections may include: (1) condition inputs, such as ram- or static-air pressure, outside air temperature, oil pressure, and the like; (2) signal inputs, such as antenna feeds for communications and navigation radios; and (3) controls from the pilot, such as frequency changes or changes to trim settings. Further, a device may require additional connections, supplying such needs as power to operate, power to operate built-in lighting (usually from a dimmer circuit), or a source of positive or negative (vacuum) air pressure. Power connections must often be routed through switches and circuit breakers. Thus, the “behind-the-panel” wiring and connections for an airplanes avionics is complicated, often messy in appearance, and expensive to repair or replace. 
     Further, avionics devices cannot always be flexibly arranged on an aircraft panel. Once the original holes are set in the panel, instrument positions are somewhat fixed. Even though many devices conform to “standard” sizes, a 3½-inch device cannot be moved into a 2¼-inch instrument hole, even if wiring and other connections could be moved. Similarly, radio widths and heights follow “standards” which change with function, the manufacturer, and the ever-advancing level of technology, which allows smaller devices to do more than their predecessors. 
     Accordingly, it is desirable to provide an avionics system which simultaneously overcomes many of the limitations of the current state of the art. It is an object of the present invention to provide a device and method for providing avionics information to a pilot which is reliable, allows continued operation in the event of the failure of one, or even multiple, components, reduces interconnection complexity, allows easy replacement or upgrade of individual components, and allows for flexibility in display arrangement. 
     It is a further object of this invention to reduce manufacturing costs, and thus retail costs, for avionics devices, and to allow greater flexibility in selecting avionics components for installation in a particular airplane. 
     SUMMARY OF THE INVENTION 
     The present invention comprises an information bus, which is intended to provide a set or subset of sensor information to each avionics device. For purposes of this invention, “sensor” includes all forms of devices intended to collect information from the environment, or from the airplane itself. Thus, “sensor,” as used herein, includes, but is not limited to: pilot tubes; static air pressure sensors; fuel gauges; oil pressure sensors; oil temperature sensors; water pressure sensors; water temperature sensors fuel pressure sensors; fuel, water, or oil flow sensors; thermocouples; cylinder head temperature sensors; exhaust gas temperature sensors; engine rotation rate sensors; electrical voltage sensors; electrical current sensors; trim position sensors; antennas, such as communication, navigation, and transponder antennas; air or vacuum pressure sensors; and gyroscopic or rotational position sensors. As those of skill in the art will recognize, not all of these sensors will exist on every airplane. Further, it may be desirable to provide redundancy for some sensors, such as gyroscopes, so that all flight instruments which depend on gyroscopic information from the bus will not become non-functional as the result of failure of a single gyroscope. 
     In many applications it will be desirable to digitize information which is collected in analog form by a sensor, and making the digitized information available on the bus. For example, it may be desirable to use a pressure transducer to create an electronic signal corresponding to the ram air pressure, and providing the electronic signal to the bus. However, doing so is not critical, although digitizing such information will likely be the most cost-efficient approach. 
     Further, separate information lines are not required on the bus for every sensor output; such signals may be multiplexed if desired. Moreover, not all of the sensor information needs to be available at every location on the bus. For example, it may be desirable to separate one section of the bus carrying radio signals from another section, to prevent interference with radio operations from other devices, or vice versa. Alternatively, antenna feeds may be removed from the bus altogether, and directed solely to computation devices which perform appropriate communication or navigation radio functions. 
     Computation devices are interconnectable with the bus in a manner which allows information to pass from the bus to each computation device, and vice versa. Each computation device generates secondary information corresponding to one or more avionics functions. Thus, as used herein, “computation device” means a device which performs an avionics function based on an available piece or set of information. Accordingly, as used herein, computation devices include devices which perform the function of attitude instruments, engine instruments, communications and navigation radios, or other instruments and indicators, and which provide information to the pilot or flight crew or allow or assist the pilot or flight crew to perform their functions. 
     Those of skill in the art will recognize that multiple avionics functions can be performed by a single computation device. Although some functions will doubtlessly be so combined in various instantiations of this invention to allow for more efficient displays, this invention also provides for multiple individual instruments, allowing greater flexibility in the event of failure, lower repair cost, and greater flexibility for the aircraft owner in selecting which avionics instruments to install in his airplane. 
     The computation devices comprise printed circuit boards, similar to those found in desktop computers. Accordingly, each printed circuit board can be connected to the information bus by inserting a tabbed edge into a socket connected to the information bus, thereby allowing individual computation devices to be quickly installed, replaced, or removed from the airplane. Thus, new avionics devices can be quickly added, failed components replaced, or upgraded devices quickly installed. Those of skill in the art will recognize that it is desirable to mount the information bus in a rack or similar unit, to allow the use of edge guides and locking devices to insure that the printed circuit boards are correctly positioned, secured in place, and protected from damage due to vibration or other movement of the aircraft. 
     In the preferred embodiment, a secondary bus will comprise power supply circuitry, and the printed circuit boards will comprise edge connectors configured to attach the boards to the appropriate power circuit. In this way, switching circuitry, such as that used to turn power on or off to devices attached to the avionics master power switch, can be greatly simplified. 
     The secondary information generated by the computation devices is presented to the pilot or flight deck crew by electronically generating a visual display on a display device in analog, digital, or a combined analog-digital format. The generation of the visual display information is preferably transmitted to the display device via a standardized cable. As used herein, a “standardized cable” is one which has the same pin-out specification as other such cables in the avionics system. Thus, if a display unit for a more critical flight instrument fails, the standardized cables can be exchanged between the failed display unit and a display unit which is being used for a less critical flight instrument, thus salvaging the function of the more needed flight instrument. 
     The display units will preferably be liquid crystal displays, and will also preferably be TFT displays or of equal or better resolution and clarity. Such displays provide low power usage, clarity, visibility in direct sunlight conditions, and can also provide color capability. However, other display types can suffice for use as display units as contemplated in this invention. 
     As with any avionics system, there will be some variation in actual display sizes used. For example, radio functions are more likely to be displayed on a rectangular display, with the longer axis disposed horizontally, if only to mimic the current radio faceplates to which most pilots are accustomed. Conversely, standard flight instruments such as an artificial horizon or directional gyro are more likely to be displayed on a square or rectangular display which mimics a standard 3½-inch device. Flight instruments for which information can be displayed on a smaller scale, such as fuel gauges or trim tab position indicators, could be displayed on a square or rectangular display which mimics a 2¼-inch device, to save valuable panel space. However, the use of standardized cables means that information which is displayable at 2¼-inches is also displayable at 3½-inches, and, within readability limits, vice versa. Further, those of skill in the art will recognize that, because the display units can transmit information via the standardized cable as well as receiving it, information regarding the display size can be provided automatically, and the display generator can adjust under software control to the actual display size in use. Even if three sizes of display units are used, this invention allows the efficient replacement of any one display unit, in the event of failure, by maintaining a stock of only three spares, one for each size in use. 
     Because the display units involved will be relatively flat and lightweight, they can be readily positioned on the avionics panel by means of set screws. Thus, a matrix of threaded holes set into an avionics panel can allow rapid and easy repositioning of any display unit, so that the pilot or flight crew will no longer be locked in to whatever panel layout was initially drilled. Further, the addition or removal of any avionics device will no longer require the creation of a new hole in the panel or open gap therein. Given sufficiently strong adhesives to secure the appropriate tape, the display units can alternatively be affixed to the avionics panel with a tape adhesive, such as VELCRO®, allowing the rapid repositioning of any display unit. 
     In the preferred embodiment, the display units further comprise touch screen capability, so that displays can be generated which allow the pilot or flight crew to adjust the setting of the flight instrument. Thus, via direct electronic control, the pilot or flight crew can select functions displayed on the display unit to, for example, change frequencies on a communications or navigation radio, adjust the directional gyro display for drift, or adjust the altimeter setting. This information, transmitted via the standardized cable from the display unit to the computation device, can be used to update the state of the computation device and thus the display unit. Further, this information can be provided to the bus through the use of additional data lines, allowing every computation device on the bus effectively simultaneous access to the information provided by the pilot or flight crew. 
     As those of skill in the art will recognize, instead of touch screens, the display units can be supplemented as necessary with hardware such as selector knobs, buttons, and the like without departing from this invention. However, doing so imposes additional penalties of cost, incompatibility, and loss of redundancy which are to be avoided, if possible. 
     It will further be understood that a computation device may have links to multiple display units. Such situations will necessarily be the case if a computation device is designed to perform a function such as that provided by a traditional navigation radio, which would require one display unit to serve as the traditional radio faceplate and a second display unit to serve as the indicator. Further, a multi-function computation device might provide secondary information to multiple display units, rather than combining all of the displays into a single unit. 
     This invention overcomes many of the problems inherent with current avionics systems. The modularity involved allows various avionics to be quickly added or removed from an airplane without affecting the functioning of any other avionics function. Further, upgraded radios, global positioning systems, or other avionics can be installed without paying for, or installing, new displays. Displays can be moved, removed, replaced, or repaired without the cost of an attached avionics system. Further, the ready availability of flight sensor data on the bus allows for advances in flight safety, such as the ability to automatically transmit encoded forms of all available sensor data in an emergency. Thus, this invention, in conjunction with the appropriate software and hardware, could provide a “poor man&#39;s black box” for aviation, and allow accident investigators unprecedented access to enhanced information. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of one embodiment of the invention 
     FIG. 2 is a schematic view of one embodiment of the connections between the bus, computation devices, and display units. 
     FIG. 3 is a schematic view of one embodiment of a display unit. 
     FIG. 4 is a schematic view of an alternative embodiment of a bus of the invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, one embodiment of the invention is shown. Sensors  10  are coupled via information lines  12  to a initial bus  14 . The sensors  10  of the preferred embodiment include at least one axis of solid-state gyroscopic information, and preferably would include three axes of such information. In the preferred embodiment, raw data from the sensors  10  is connected to a device  19  comprising a digitizer, which provides digitized values of the raw data to the bus  18 . Alternatively, some or all of the sensors  10  may incorporate such digitizers, or such digitization may occur for the data from one or more of the sensors  10  by using discrete digitizers, or some or all of the raw data, especially that from such devices as ram or static air intakes or radio antennas, may be carried on the bus  18  in raw form. The device  19  may also comprise a multiplexer, to allow at least some of the data lines in the bus  18  to carry information from a plurality of sensors  10 . Regardless of such variations, bus  18  provides information from a plurality of sensors to a plurality of connectors, such as sockets  16 . 
     As will be recognized from this schematic view, the number of sensors  10 , the number of information lines in the initial bus  14 , the number of information lines in the bus  18 , and the number of connectors, such as sockets  16  which will actually be used is not reflected in the drawing. Further, in the preferred embodiment, the design of the bus  18  will include information lines for devices which may not exist in a particular airplane. For example, the specification for the bus  18  may include information lines for use with cylinder head temperature (CHT) sensors, even though such sensors may not be installed on every airplane. However, such a configuration allows such sensors to be easily installed later by connecting them to the appropriate inputs to the bus  18 , and allows a CHT “gauge” to be quickly installed by plugging an appropriate computation device  20  into an available socket  16 . Similarly, the number of sockets  16  which will be installed will vary with both the initial requirements of the aircraft and the need for future expansion. It is likely that sockets  16  will be available in pre-manufactured groups of five, ten, or some other convenient number, and connected to the existing bus  18  via bus expanders, e.g., cables. 
     Referring to FIG. 4, one example of such an expansion arrangement is shown schematically. First and second bus sections  414 ,  418  comprising sockets  416  are interconnected to each other via couplers  410  and cable  412 . Also shown by example in FIG. 4 is that second bus section  418  comprises more information lines than does first bus section  414 . Thus, computation devices attached to second bus section  418  may have available the information from first bus section  414 , as well as additional information. Such a configuration may be used when it is desirable to isolate some sensor information, such as antenna connections which may create radio-frequency interference with some computation devices. 
     Referring again to FIG. 1, computation devices  20  perform their functions by obtaining information they need from sensors  10  via the bus  18  and utilizing hardware, software, or a combination thereof to generate secondary information and create an appropriate visual display. The visual display information is transmitted to display units  26  via standardized cables  22 , which can be connected to the display units  26  by couplers  24 . The display units  26 , which are preferably TFT liquid crystal displays, can be used to display the secondary information in graphical, digital, or a combination of graphical and digital form. Those of skill in the art will recognize that the displays depicted in FIG. 1 are for illustrative purposes only, and are not limitations on the possible avionics functions which can be performed by computation devices of this invention. As will also be recognized by those of skill in the art, the secondary information may include raw data from sensors  10  which has been put in displayable form. 
     The display units  26  may be affixed to an avionics panel by use of set screws  28 , or by other appropriate attachment means. 
     Those of skill in the art will recognize that the generation of the visual display based on the secondary information generated by computation devices  20  can occur in a separate location. That is, the visual display generators do not have to be integrated on the same printed circuit boards as the computation devices  20 . However, such an arrangement would require additional cabling and circuitry, and would introduce unnecessary inefficiencies to the system. 
     Referring to FIG. 2, an embodiment of a computation device  211  is schematically shown. A printed circuit board  210  comprises an edge-tab connector  212  which is insertable in socket  216 . Information from the bus (not shown) is obtained electronically by conductive fingers  214 . Those of skill in the art will recognize that fingers  214  may be printed on both sides of the printed circuit board  210  and will provide selective connections to those information lines in the bus which are needed for the function to be performed by the computation device  211 . Fingers  214  are connected to the computational section  215  of the computation device  211  via connectors  213  (some of which are omitted for clarity). The computation section  215  is shown in schematic form only, and may comprise one or more discrete devices utilizing hardware, software, or a combination thereof to perform an avionics function utilizing the information obtained from the bus via fingers  214 . Secondary information generated by the computation section  215  is transmitted via a first data pathway  219  to a video display generator  217 , which in turn sends control signals for a display unit (not shown) via a second data pathway  221  to first coupler  218 , and thence to standardized cable  220  and second coupler  222 . In the preferred embodiment, the display unit (not shown) will comprise touch-screen capability, so that information input by the pilot or flight crew can return via second coupler  222 , standardized cable  220 , first coupler  218 , and third data pathway  223  to the computation section  215 . Thus, the avionics function performed by the computation device  211  can utilize both data from the airplane and from the pilot or flight crew. 
     In the event of a sensor failure and corresponding loss of data from the bus, the computation section  215  can continue to perform as much of its normal function as possible, while simultaneously providing the pilot or flight crew with diagnostic information regarding what portion of its raw data is missing. Thus, the system has the ability to self-diagnose and aid in repairs when a component fails. 
     Referring to FIG. 3, an embodiment of a display unit is shown. Standardized cable  320  is attached to the display unit  310  via coupler  322 . Set screws  328  may be used to securely position the display unit  310  on an avionics panel (not shown). Graphical and digital information received from a computation device (not shown) is displayed on the face of the display  312 . Additionally, in the preferred embodiment, the display unit  310  comprises touch screen capability, allowing “buttons”  314  for input from the pilot or flight crew to be displayed. In the example shown in FIG. 3, a “directional gyro” compass is displayed in its traditional (that is, standard discrete instrument) format, with an additional digital display showing current indicated heading at the center. “Buttons”  314  allow the pilot or flight crew to adjust the current reading of the compass to agree with the airplane&#39;s magnetic compass. As those of skill in the art will recognize, the ability to generate such displays under software control allows the display to incorporate “buttons” appropriate to the avionics function being displayed, such as radio frequency control inputs for radio displays, or barometric pressure adjustment inputs for altimeter displays. 
     In accordance with the above, this invention provides flexibility, built-in redundancy capability, and the capacity to provide lower-cost avionics of equivalent or better quality than currently available products to the end user. Those of skill in the art will recognize that the above examples are illustrative and not limiting, and that variations can be constructed without departing from the spirit of the invention.