Abstract:
A method for controlling one or more of engine thrust cutback and engine thrust restoration is described which is related to aircraft environmental emissions abatement. The method comprises receiving aircraft location data from at least one navigational sensing system, comparing the aircraft location data against location data identifying an environmental emissions abatement area, and controlling at least one of thrust cutback and thrust restoration of the aircraft engines based on the comparing of aircraft location to the location of the environmental emissions abatement area.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to aircraft departure and landing noise abatement procedures, and more specifically, to methods and systems for implementing location based noise abatement procedures. 
   One means to reduce aircraft noise is to reduce thrust in the proximity of the noise-sensitive receiver. The relative position of the aircraft to a fixed receiver on the ground is an important factor in the resulting noise measured at the receiver location. 
   Current departure noise abatement procedures utilize aircraft altitude, or height, as a trigger for thrust reduction, thrust restoration, and subsequent aircraft acceleration. However, the location where an aircraft attains a specific altitude can vary due to operational and environmental factors. These operational and environmental factors can reduce the effectiveness of the altitude based noise abatement procedures, and may include, for example, aircraft type, a loading of the aircraft (passengers, cargo, and amount of fuel), and weather related conditions, just to name a few. 
   Due to the varying of the above mentioned operational and environmental factors, calculation and implementation of altitude-based thrust reduction cues are typically based upon conservative environmental and operational conditions. These conservative conditions ensure a thrust (and therefore noise emissions) associated with the aircraft engines is reduced to meet targeted noise constraints at one or more fixed ground receiver locations, without requiring calculating thrust reduction heights for actual environmental and operational conditions. To meet targeted noise constraints, specific departure noise abatement procedures may be based upon, and/or require the calculation of specific thrust reduction altitudes for a given set of operational and environmental conditions. Also, the procedures utilized to meet the targeted noise constraints, both for thrust reduction and restoration may be performed manually, and may not always be accurate and consistent. However, it is believed software tools are being developed that will calculate thrust reduction/restoration height cues that account for flight-specific operational and environmental conditions. 
   Current cues for thrust reduction, whether automatic or manual, are based upon the aircraft height above the ground, not relative lateral position to the receiver. A single, conservative, height-based reduction/restoration cue does not account for winds, piloting technique, non-design weights or other environmental and operational conditions. 
   Whether manually calculated or computer based, since conservative calculations are used, the aircraft that utilize these procedures tend to reduce thrust earlier than is necessary, and restore thrust later than is necessary, to meet the targeted noise constraints. Reduction of thrust earlier than necessary, and restoration of thrust later than necessary, reduces the efficiency of aircraft operation, for example, during take-off and landing maneuvers. 
   Additionally, flight-specific thrust reduction and restoration procedures should be calculated using current operational and environmental data, and with regard to pre-calculated thrust reduction and restoration procedures, such data may not be accurate at time of departure. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one aspect, a method for controlling one or more of engine thrust cutback and engine thrust restoration, as related to aircraft environmental emissions abatement is provided. The method includes receiving aircraft location data from at least one navigational sensing system, comparing the aircraft location data against location data identifying an environmental emissions abatement area, and controlling at least one of thrust cutback and thrust restoration of the aircraft engines based on the comparing of aircraft location to the location of the environmental emissions abatement area. 
   In another aspect, a flight management system for an aircraft is provided. The flight management system includes a flight management computer, at least one sensor system configured to provide a location of the aircraft to the flight management computer, at least one unit configured to provide the flight management computer with data relating to a position of one or more environmental emissions monitors, and a thrust management system. The thrust management system is communicatively coupled to the flight management computer which is operable to control operation of the thrust management system for meeting environmental emissions abatement standards, at least one of at least one of thrust cutback and thrust restoration based upon a comparison of aircraft location and environmental emissions monitor position by the flight management computer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagram illustrating an altitude based noise abatement procedure. 
       FIG. 2  is a diagram illustrating a location based noise abatement procedure. 
       FIG. 3  is a flowchart describing the location based noise procedure of  FIG. 2 . 
       FIG. 4  is a block diagram of a flight management system. 
       FIG. 5  is a diagram illustrating the benefit of the location based noise procedure of  FIG. 2  compared to the altitude based noise abatement procedure of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a diagram functionally illustrating a currently used, altitude-based noise abatement procedure. A monitor  10  is located a distance form runway  12  to measure the noise, and other environmental emissions from aircraft that have taken off from runway  12 . A similar configuration may be utilized to measure environmental emissions from landing aircraft.  FIG. 1  further includes a depiction of three aircraft ascending from runway  12 . For clarity it should be noted that all of the aircraft are of the same type. Aircraft  20  is the lightest of the three based on the amount of one or more of fuel, passengers, and cargo loaded thereon. Aircraft  22  is the heaviest of the three and aircraft  24  is loaded to have a weight in between aircraft  20  and  22 . As used herein, environmental emissions includes, but is not limited to, noise emissions. 
   As is illustrated in  FIG. 1 , heavy aircraft  22  attains the thrust cutback height  30  (altitude) at a point farther from runway  12  than do aircraft  20  and  24 . As further noted in  FIG. 1 , the point  32  where aircraft  22  attains the thrust cutback height  30  is denoted as a critical point in the noise abatement procedure design. More directly, point  32  is the point closet to monitor  10  where any of the differently loaded aircraft  20 ,  22 , and  24  will attain the pre-defined thrust cutback height. Therefore, based on the desired environmental emissions level, an altitude associated with point  32  (based on the noise level detected by monitor  10 ) is utilized as the altitude for thrust cutback, regardless of aircraft loading, and regardless of aircraft position with respect to monitor  10 . Since the environmental emissions procedure is altitude based, and although aircraft  20  and  24  attain such an altitude ( 34  and  36  respectively) sooner than aircraft  22 , and farther from monitor  10 , they cut back thrust earlier than would be necessary to meet the environmental emissions requirements. Cutting back thrust sooner than is necessary to meet environmental emissions requirements is detrimental to the efficient operation of aircrafts  20  and  24 . 
   A similar problem is encountered when an altitude for thrust restoration is attained. As illustrated in  FIG. 1 , aircraft  20 , since it is lighter, is the first of the aircraft to reach an altitude where the thrust can be restored. More specifically, point  42  is the point closet to monitor  10  where any of the differently loaded aircraft  20 ,  22 , and  24  will attain the pre-defined thrust restoration height. Therefore, based on the desired environmental emissions level, an altitude associated with point  42  (based on the noise level detected by monitor  10 ) is utilized as the altitude for thrust restoration, regardless of aircraft loading, and regardless of aircraft position with respect to monitor  10 . Since the environmental emissions procedure is altitude based, and although aircraft  22  and  24  attain such an altitude ( 44  and  46  respectively) later than aircraft  20 , and farther from monitor  10 , they restore thrust later than is necessary to meet the environmental emissions requirements. Similar to early cut back of thrust, restoration of thrust later than is required to meet environmental emissions requirements is detrimental to the efficient operation of aircrafts  22  and  24 . 
   To summarize, and with respect to  FIG. 1 , it would be beneficial to implement a environmental emissions abatement procedure that would allow aircraft  20  and  24  to be closer in position to monitor  10  before thrust is cutback. Similarly, it would be beneficial to implement an environmental emissions abatement procedure that would allow aircraft  22  and  24  to be closer in position to monitor  10  when thrust is restored. 
     FIG. 2  is a diagram illustrating a location based noise abatement procedure according to the present invention. A monitor  60  is located a distance form runway  62  to measure the noise, and other environmental emissions from aircraft that have taken off from runway  12 . A similar configuration may be utilized to measure environmental emissions from landing aircraft.  FIG. 2  also includes a depiction of three aircraft, all of the same type, ascending from runway  62 . Aircraft  70  is the lightest of the three based on the amount of one or more of fuel, passengers, and cargo loaded thereon. Aircraft  72  is the heaviest of the three and aircraft  74  is loaded to have a weight in between aircraft  70  and  72 . 
   As is illustrated in  FIG. 2 , all of the aircraft  70 ,  72 , and  74  attain the thrust cutback location  80  at a point that is the same lateral distance from monitor  60 . As further illustrated by  FIG. 2 , the point  82  where aircraft  72  arrives at the thrust cutback location  80  is a different altitude than is points  84  and  86 , which are associated with aircraft  70  and  74  respectively. Specifically, thrust cutback location  80  is the location, relative to monitor  60 , where any of the differently loaded aircraft  70 ,  72 , and  74  will cutback on thrust, regardless of altitude. 
   Therefore, based on the desired environmental emissions level, thrust cutback location  80  (based on the noise level detected by monitor  60 ) is utilized as the location for thrust cutback, regardless of aircraft loading, and regardless of aircraft altitude with respect to monitor  60 . Since the environmental emissions procedure is location based, that is, aircraft  70 ,  72 , and  74  arrive at thrust cutback location  80  at various altitudes, they cut back thrust at a time that allows for more efficient operation of the aircraft than is accomplished using the above described altitude based methods. 
   Similar benefits are found when a location for thrust restoration is attained. As illustrated in  FIG. 2 , all of the aircraft  70 ,  72 , and  74  attain the thrust restoration location  90  at a point that is the same lateral distance from monitor  60 . As further illustrated by  FIG. 2 , the point  92  where aircraft  72  arrives at the thrust restoration location  90  is at a different altitude than is points  94  and  96 , which are associated with aircraft  70  and  74  respectively. Specifically, thrust restoration location  90  is the location, relative to monitor  60 , where any of the differently loaded aircraft  70 ,  72 , and  74  will restore an amount of thrust, regardless of altitude. 
   Therefore, based on the desired environmental emissions level (e.g., a noise level detected by monitor  60 ), thrust restoration location  90  is utilized as the location for thrust restoration, regardless of aircraft loading, and regardless of aircraft altitude with respect to monitor  60 . Since the environmental emissions procedure is location based, that is, aircraft  70 ,  72 , and  74  arrive at thrust restoration location  90  at various altitudes, and they restore thrust at a time that allows for more efficient operation of the aircraft than is accomplished using the above described altitude based methods. 
     FIG. 3  is a flowchart  100  further illustrating the location based environmental noise abatement procedure depicted in  FIG. 2 . Specifically, an aircraft receives  102  location data for one or more environmental emissions monitors. In one embodiment, receiving  102  location data would include loading one or more of the flight management system computers with a database of monitor locations, for example, at a ground based aircraft maintenance station. Of course, wireless software loading methods for aircraft in flight are also known and may be modified to include a capability of uploading database of monitor locations. Monitor location includes, but is not limited to, latitude and longitude locations for the environmental emissions monitors and one or more surrounding latitude and longitude locations identifying where aircraft engine thrust is to be cutback or restored. 
   Referring again to flowchart  100 , once the aircraft is loaded with environmental emissions monitor data and is in flight, aircraft position is monitored  104 , for example, using a flight management system, with respect to the environmental emissions monitor location data. Aircraft engine thrust cutback and restoration, for abatement purposes, are controlled  106 , based on a comparison of aircraft position and environmental emissions monitor position. 
     FIG. 4  is a block diagram of a flight management system  150  that is utilized to perform the location based environmental emissions abatement procedures described with respect to  FIGS. 2 and 3 . Flight management system  150  includes a flight management computer  152  receiving data from one or more of, for example, a global positioning system (GPS)  160 , an air data/inertial reference system  162 , communications and navigation radios  164 , flight control surface position monitors  166 , navigation and aircraft performance databases  168 , and operational data databases  170 , which are commonly referred to herein as sensors  172 . In one embodiment, flight management computer  152  is configured to provide at least lateral control, vertical control, and thrust management control for an aircraft. In performing these functions flight management computer  152  provides data related to these function to one or more of a primary flight display  180 , a navigation display  182 , an engine indication and annunciation display  184 , and a heads up display  186 . 
   Flight management computer  152  further communicates with one or more control display units (CDUs)  190  and  192 , which provide a capability to input commands and computations to flight management computer  152 . As indicated in the block diagram of flight management system  150 , flight management computer  152  provides control of both vertical navigation functions  200  and lateral navigation functions  202 , thereby providing control commands to one or both of an autopilot/flight director system  210  and an automatic throttle control system  220  (which is sometimes referred to herein as a thrust management system). 
   With regard to an environmental emissions function, flight management computer  152  is provided with position (location) data for one or more environmental emissions monitors, for example, from operational data databases  170  or from one of CDUs  190  and  192 . Then based on aircraft position data received from one or more of GPS  160 , air data/inertial reference system  162 , or other sources, flight management computer  152  controls thrust cutback and restoration, for example, via commands sent to automatic throttle control system  220  as described above with respect to  FIGS. 2 and 3 . Aircraft position with respect to environmental emissions monitors is also controlled by flight management computer  152  through the vertical and lateral navigation functions  200  and  202 . 
     FIG. 5  is a diagram illustrating the benefit of the location based noise abatement procedure of  FIG. 2  compared to the altitude based noise abatement procedure of  FIG. 1  when such procedures are implemented within an aircraft flight management system. Referring specifically to  FIG. 5 , an environmental emissions monitor  250  and runway  252  are shown. Two aircraft of the same type and/or weight, (e.g., aircraft  260  and  262 ) are also shown. Aircraft  260  is illustrated as using the altitude based thrust cutback process and aircraft  262  is illustrated as using the herein described location based thrust cutback process. 
   When thrust cutback is based on altitude (height), while recognizing that attainment of altitude is a function of aircraft type and loading, the currently utilized environmental emissions abatement procedures may result in thrust cutback at a location that is farther away from monitor  250  than is needed to meet, for example, a noise abatement standard. As is illustrated in  FIG. 5 , by using a location based thrust cutback procedure to meet the noise abatement standards, a height benefit is attained over a similar aircraft using the height based procedure. This height benefit represents an efficiency in aircraft operation. It should be noted that utilization of location based environmental emissions abatement procedures results in thrust cutback altitudes that exceed the currently used minimum thrust cutback altitudes. While noise abatement is important, safety of flight is paramount, and the altitude based noise abatement procedures are based on a minimum altitude, which the above describe location based procedures meet or exceed. 
   A thrust reduction (cutback)/restoration cue that is based on a relative location or flight path distance selected to meet noise targets ensures thrust reduction occurs at the correct location despite adverse environmental and operational conditions, and allows favorable environmental and operational conditions to further reduce noise at the receiver (monitor) location. Additionally, a location-based thrust reduction cue reduces thrust at the correct location relative to the noise sensitive location regardless of environmental and operational factors. 
   The above described systems and methods relating to location-based thrust reduction and restoration therefore provide reliable noise reduction regardless of operational and environmental conditions, and therefore result in a further reduction in the noise at a receiver location when favorable environmental and operational conditions exist. 
   Still further, a location-based thrust reduction and restoration scheme can simplify training and dispatch requirements for operators who calculate flight-specific thrust reduction/restoration heights. The simplification results as location based methods are amenable to encoding in flight navigation databases allowing automated loading and execution of departure noise abatement procedures by the flight crew. Automated thrust reduction and restoration method also reduce flight crew workload and provide an increase accuracy over known thrust reduction and restoration methods. 
   Other embodiments are contemplated which utilize a combination of the currently known altitude based methods and the herein described location based thrust cutback and restoration methods. For example, in one embodiment, thrust cutback may be based on location and thrust restoration based on altitude. In another embodiment, thrust cutback may be based on altitude and thrust restoration based on location. 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.