Patent Publication Number: US-2007115140-A1

Title: Egpws flap position enhancement

Description:
BACKGROUND  
      Proper procedure for a commercial aircraft to take-off from a given runway includes as a first step the selection or an initiation of take-off flaps. Referring to  FIG. 1 , a prior art wing assembly  10  includes a wing body  11 . Attached to the wing body  11  is a slat  13  and a flap assembly  15 . The flap assembly  15  includes a first flap  15 A, a second flap  15 B, and a third flap  15 C are designatively extended from the wing body  11  upon take-off. By extending the slat  13  and the flap assembly  15 , the pilot increases the surface area of the wing assembly  10  while enhancing the curvature or chord of the upper wing surface to greatly enhance the lift generated as the wing assembly  10  passes through the air. The enhanced lift generated by the extension of the slat  13  and the flap assembly  15  enables the heavily ladened aircraft to take-off from the runway.  
      Failure to extend the flap assembly  15  and, where available, the slat  13  may have catastrophic consequences as in the 5 Sep. 2005 take-off accident at Medan, Indonesia when a B-737 aircraft failed to generate suitable lift on take-off due to the failure to extend the slat  13  and the flap assembly  15 . The pilot, after entering the runway, had not set the flaps for take-off. Once the pilot had noticed the flaps, the aircraft was already “at speed.” Lacking sufficient lift, the aircraft crashed shortly after takeoff. No aircraft malfunction was noted.  
      What is needed, then, in the art are systems and methods for generating an enunciated warning when the flap assembly  15  is not extended before take-off from a runway.  
     BRIEF SUMMARY OF THE INVENTION  
      A processor, software code, and a method are presented for generating warning indicating that flaps are not suitably in a take-off position. A first component is configured to receive a first signal indicative of one of a group of flaps positions, the group including a take-off position. A second component is configured to receive a second signal indicative of an aircraft position. A third component is configured to compare the aircraft position to the contents of a database and to, by the comparison, determine whether the aircraft position is within a runway perimeter. A fourth component is configured to generate an alarm when the aircraft is within the runway perimeter and the flaps position is not the take-off position. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
      The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.  
       FIG. 1  is a cross-section of a wing assembly according to the prior art;  
       FIG. 2  is a block diagram of an EGPWS processor assembly; and  
       FIG. 3  is a flowchart indicating the method by which non-deployed flaps are indicated prior to take-off. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 2  indicates an enhanced grown proximity warning system (“EGPWS”) processor assembly  20  including an EGPWS processor  36  in operative communication with a database  39 , the database  39  configured to contain surface terrain, obstacle, and airport information including information as to the location of airport runways. Additionally, the EGPWS processor  36  receives information from a sensor assembly  22 . By way of non-limiting example, the sensor assembly  22  includes a ground speed sensor  24 , a ground track sensor  26 , an aircraft heading sensor  28 , and an aircraft position sensor  30 . Operative communication between the EGPWS processor  36  and the sensor assembly  22  is facilitated by a flight instrumentation data bus  33 . The flight information data bus  33  may be any communicative linkage between either the sensor assembly  22  as a whole or a network of communicative links between each of the distinct sensors such as the aircraft position sensor  30 . The EGPWS processor  36  is configured to output information through one or more of an audio output  42 , a warning light  45 , and a display  48  such as a heads up display or an instrument panel configured to include a cathode ray tube or other form of video graphic display.  
      Beginning at the aircraft position sensor  30 , a position of the aircraft is derived. Non-limiting examples of an aircraft position sensor  30  would be a global positioning satellite (“GPS”) receiver configured to derive an aircraft position based upon received timing signals. Other such aircraft position sensors include LORAN and other radio triangulation systems. The invention is not limited to devices that are autonomous within the aircraft. The aircraft position sensor  30  may also include receiving means configured to receive an aircraft position from an outside source such as a ground traffic control facility or via LAAS (Local Area Augmentation System) or WAAS (Wide Area Augmentation System).  
      Communicated to the EGPWS processor  36  through the flight instrumentation data bus  33 , the aircraft&#39;s position is compared to the contents of the database  39  to determine if the aircraft is within a defined perimeter surrounding runways stored within the database  39 .  
      For the purposes of an embodiment, the flap assembly  15  ( FIG. 1 ) need be extended only within the perimeter defining the runway resident in the database  39 . Embodiments presume the aircraft will only take-off on runways existing within the database  39 . A special case occurs where two runway&#39;s resident within the database  39  are defined to cross. Crossing runways are frequently used to maximize the utility of airport installations by allowing more frequent landings from distinct directions. For the purposes of this application, one runway resident in the database  39  will include both of the distinct nomenclature when a runway is used for approaches in diametrically opposed directions. For instance, a runway running from north to south is alternately described as runway  36  or runway  18  depending upon whether the use is from the north or the south.  
      In at least one embodiment, the EGPWS processor  36  is in operative communication with a flight management system (“FMS”). The FMS  35  provides to the EGPWS processor  36  information relating to the anticipated flight plan that is used for azimuth and vertical profiles of operation of a commercial aircraft.  
      Advantageously, the FMS  35  can communicate with the EGPWS processor assembly  20  by means of the EGPWS processor  36  connected through the flight instrumentation data bus  33 . In  FIG. 2 , information from the FMS  35  indicates when the aircraft is in a portion of the flight plan that is dedicated to preparation for take-off as that flight plan is programmed into the FMS  35 . After confirming the aircraft is at a position from which a take off has been programmed, the EGPWS processor  36  then by confirming that the aircraft is currently preparing for the take-off maneuver, the EGPWS processor  36  then checks the state of the flaps by means of the flap position sensor  32 . Connection with the FMS  35  obviates the need for the optional reference to aircraft ground speed  24  is necessary then only to confirm that the aircraft is in take-off configuration though such confirmation is not necessary to accurately predict take-off.  
      By such means as provided to the EGPWS processor  36 , the processor  36  determines that the aircraft is in pre-take-off mode, the processor  36  is configured to generate a warning to the pilot with suitable lead time to allow pilot correction of the error before committing to the take-off.  
      Embodiments include a software code stored upon a machine-readable medium (not shown) to instruct the EGPWS processor  36  to generate a warning. The software code directs the processor  36  to receive a first signal generated by the flap position sensor  32 . The flap position sensor  32  is configured to sense when the flaps are in a take-off position, though, optionally, the flap position sensor  32  may be additionally configured to sense the flaps in a number of distinct positions.  
      The software code further directs the EGPWS processor  36  to compare a signal received from the aircraft position sensor  30  to the contents of the database  39 . By the comparison, the EGPWS processor  36  determines whether the aircraft position is within the runway perimeter, taking the results of the comparison and designating the containing runway perimeter for purposes of later comparison to signals received from either of the ground track sensor  26 , the aircraft heading sensor  28 , or from signals from the FMS  35 . The EGPWS processor  36  generates an alarm when the aircraft is within the runway perimeter and the flaps position is not the take-off position.  
      In another embodiment, the software code directs the EGPWS processor  36  to receive an aircraft ground speed from the aircraft ground speed sensor  24 ; and then is optionally configured to suppress the alarm when the ground speed exceeds a threshold ground speed. The threshold ground speed may be designatable in some embodiments. Such an optional feature is useful in the suitable suppression of alarms on board aircraft that enter the perimeter by means of a landing maneuver. Once the landing occurs, the flap assembly  15  becomes superfluous for further flight and is appropriately retracted into the wing body  10  ( FIG. 1 ). During the landing, the retraction may occur at speeds in excess of those normally used to enter the runway from taxiways and therefore are not preparatory to take-off.  
      A distinct optional means of suitably suppressing the generation of alarms is based upon the heading of the aircraft relative to the runway direction. The difference between the heading of the aircraft and runway direction is known as a track angle. The EGPWS processor  36  will suppress the alarm when the runway track angle exceeds a threshold runway track angle, because it is unlikely that the aircraft would take off at headings wherein the track angle would exceed a designatable threshold.  
      Where an aircraft heading is not directly sensed from a compass or a navigation system, the aircraft heading may be derived from a vector difference between a first aircraft position and a second aircraft position. A second runway position is arbitrarily an aircraft position later in time than a first runway position. In alternate embodiments, the aircraft heading is sensed by a compass. Such compasses might include gyro compasses, ring laser gyros, or magnetic compasses.  
      The alarm is enunciated through any of the audio output  42 , the warning light  45 , or a warning generated on the screen display  48 . The audio output  42  may be as simple as a buzzer activated according to the EGPWS processor  36  or a synthesized or recorded voice indicating that the flaps are not in a take-off position. Any suitable alarm configured to attract the attention of the pilot without monopolizing it will be consistent with the ends of this invention.  
      Referring to  FIG. 3 , a method  100  for generating a “no flaps” warning, the begins at a start block  99 . Start may occur at power up or it may occur later after the recognition of the database  39 . Given the purpose of the method  100 , it is appropriate that the method  100  begin before the aircraft leaves a taxiway to break the perimeter of the runway as defined in the database  39 . If the flaps are in a take off deployment at a block  101 , no reason for a warning exists. The block  101  governs a conditional loop that will not allow the method  100  to move on until the flaps are in a position inconsistent with take-off.  
      When the flaps are in a position other than that of take off, the method  100  optionally moves to determine the speed of the aircraft at a block  104 . Where the aircraft speed is in excess of a configured threshold, the action of the aircraft is inconsistent with take-off or with corrective action. The addition of this optional step presumes that the action of the aircraft has been monitored throughout and that the opportunity to warn of an inconsistent flap position has already occurred if the aircraft had come up to speed rather than to slow down to speed. Thus, where the speed is in excess of a configurable speed inconsistent with take-off, there is no need to warn and the method  100  returns to monitor flap position.  
      At a block  107 , the position of the aircraft is determined. In this usage position refers to a locus rather than an attitude or state. The purpose of determining a position is to place the aircraft within the mapped area contained within the database  39  at the block  107 . Generally, the determining of the aircraft&#39;s position is based upon the receiving a second signal indicative of an aircraft position. The second signal might be from a GPS, from a LORAN device, or from an Inertial Navigation System. Additionally, it may be a signal relayed from the tower. In any event, at the block  104 , the method determines an aircraft position.  
      At a block  110 , the method  100  determines whether runways exist within a radius closest to the determined position of the aircraft. Such a determination is based upon a comparing of the aircraft position to the contents of the database  39  and to, by the comparison, determining whether the aircraft position is within a runway perimeter or within a configurable distance therefrom. Positions of runways are not relevant outside of a configurable distance from the aircraft position, the configurable distance being chosen to anticipate entry onto the runway. When the distance is too great, there is no immediate likelihood that the aircraft will immediately begin a take-off maneuver thereby granting greater time for generating an alarm when the aircraft is within the runway perimeter and the flaps position is not the take-off position.  
      Where, rather than being too far away from a runway, an aircraft is within a designatable radius of two distinct physical runways (in fact, each physical runway is designated as two distinct runways allowing diametrically opposed approaches and landings or take-offs, thereby doubling the number of physical runways), the aircraft will select between the two physical runways based upon a track angle. One such instance is where crossed runways serve a single airport; a second exists where runways are parallel. In either instance, it is important to know which of the runways is the appropriate to determine the intent of the pilot of the aircraft. To that end, the track angle is used.  
      A track is the resultant direction of actual travel projected in the horizontal plane and expressed as a bearing. A track is the component of motion that is in the horizontal plane and represents the history of accomplished travel. An aircraft develops a track as it moves in the horizontal plane. A track angle is an offset between the aircraft heading angle and the track of a hypothetical aircraft traveling the length of the runway parallel to its lateral edges.  
      To determine a heading of the aircraft at a block  113  there might be any of several known methods. The easiest of these methods is to determine a heading of the aircraft by compass means. On the ground when taxiing, a heading of the aircraft exactly corresponds with the course over ground because the effect of crosswinds is negligible due to the traction of the tires. Where the aircraft points is where the aircraft goes.  
      Another method is to determine a first position of the aircraft and a second position of the aircraft, the second position succeeding in time the first by an interval configured to give a good approximation of the general movement of the aircraft. A vector difference in position will determine a direction of movement. The direction of movement is suitable for the purposes of the invention.  
      Still another non-limiting method of determining a heading is from the FMS  35 . The heading for any given movement of the aircraft is readily determined by the FMS  35  for navigational purposes. Other methods that exist will also serve to establish an aircraft heading for the further purpose of establishing a track angle.  
      The method  110  set forth in  FIG. 3  includes a nonlimiting example of the comparison of track angles to determine a runway. In the nonlimiting example, a runway has only its principal direction such that there are two entries for a north-south runway equating to runways  18  and  38  or runways oriented at 180 and 360 degrees respectively. In the nonlimiting example, the aircraft is within the configurable radius of both physical runways and at a speed not in excess of normal runway taxiing. The heading is determined at the block  113  and it is compared with the first runway within the configurable radius at a block  116 . If the difference between the runway track angle and the heading exceed the configurable threshold, the method  100  goes on to a block  118 , if not, at a block  124 , the deploy flaps alert is sounded.  
      Similarly for each of the decision blocks  118 ,  120 , and  122 , the runway track angle is compared to the heading of the aircraft, the method  100  compares them in sequence to the aircraft heading to find the runway to a configurable threshold. When any of the track angles of the runways are within a configurable threshold angular difference between them and the heading, the method proceeds to the block  124  to sound the alert, otherwise, the method returns to the decision block  101  to check if the flaps are deployed.  
      While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.