Abstract:
An aircraft FMS/guidance system which provides for automated and immediate calculation of a preferred flight path and full heading, pitch-and-roll guidance along that path for paths of random origins, such as during late-occurring missed approaches and circling-to-land maneuvers.

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to aircraft guidance and flight management systems (FMSs), and more particularly relates to a system for calculating and guiding an aircraft along a preferred flight path from a random current location of an aircraft, and even more particularly relates to methods and systems for automatically and immediately providing heading, pitch-and-roll instructions when an aircraft is unable to follow published procedures or paths. 
   BACKGROUND OF THE INVENTION 
   In the past, pilots have often been given the sole responsibility for guiding their aircraft during events, such as missed approaches and circling maneuvers. Often the responsibility upon the pilot is considerable. 
   One example of a situation where a pilot is called upon to bear a considerable burden is during circling maneuvers. The Aeronautical Information Manual (AIM) from the Federal Aviation Regulations states the following:
         “Circling may require maneuvers at low altitude, at low airspeed, and in marginal weather conditions. Pilots must use sound judgment, have an in-depth knowledge of their capabilities, and fully understand the aircraft performance to determine the exact circling maneuver, since weather, unique airport design, and the aircraft position, altitude and airspeed must all be considered.”       

   The problem is compounded because the time for making all of these decisions is inherently limited owing to the fact that the aircraft is constantly moving, and the area for obstacle-free flight is limited. For example, the final approach obstacle clearance area is often 2.3 miles or less for most approach categories. This means that the pilot must react immediately and correctly on the first attempt. There often will not be a sufficient margin for making a circling error and later correcting such an error. 
   Attempts have been made to provide pilots with detailed guidance information and precise guidance for controlling the attitude of the aircraft. Synthetic vision systems have been proposed where a “tunnel through the sky” is displayed to a pilot. These synthetic vision systems have the capability of providing much needed assistance to the pilots. 
   While these synthetic vision systems may have many advantages in particular uses, they are often limited to calculating and displaying guidance along a published path from a predetermined starting point. These synthetic vision systems have heretofore been unable to provide a precise path and full heading, pitch-and-roll guidance from random locations of an aircraft, such as during missed approaches, especially late occurrences of missed approaches. 
   Consequently, there exists a need for improved methods and systems for aiding a pilot with full guidance information along a non-published preferred flight path with random origin. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a guidance system which reduces pilot workload and occasions for pilot error. 
   It is another object of the present invention to provide an enhanced situational awareness for a pilot at critical stages of flight. 
   It is yet another object of the present invention to provide a possibility for determining a better flight path than might otherwise be determined or even recommended under existing published procedures. 
   It is a feature of the present invention to utilize an adaptive FMS or other guidance system which automatically calculates a preferred flight path from any location of an aircraft. 
   It is a feature to provide full heading, pitch-and-roll guidance along a preferred flight of random origin. 
   It is another feature of the present invention to provide the pilot with the ability to select various situations, such as missed approaches and circle-to-land, etc., and in response thereto, provide automated path and full guidance information from random locations. 
   It is an advantage of the present invention to greatly reduce the occasion for pilot error during certain maneuvers, such as missed approaches and circling to land. 
   The present invention is a system and method for guiding an aircraft which is designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features and achieve the already articulated advantages. The present invention is carried out in a “pilot error-less” manner in a sense that the workload and judgment necessary to safely operate an aircraft in certain circumstances along a flight path of random origin has been greatly reduced, which reduces the occasions for pilot error. 
   Accordingly, the present invention is an aircraft guidance system including an FMS or other guidance system which automatically calculates a preferred flight path and provides full heading, pitch-and-roll guidance even where the origin of the preferred flight path is from a random location of the aircraft, away from published paths. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be more fully understood by reading the following description of the preferred embodiments of the invention, in conjunction with the appended drawings wherein: 
       FIG. 1  is a block diagram of an FMS/Guidance system of the present invention, which includes inputs for requesting path calculation and guidance for a plurality of circumstances. 
       FIG. 2  is a more detailed diagram of a system of  FIG. 1 , with constraints being shown for circling and missed approaches. 
   

   DETAILED DESCRIPTION 
   Now referring to the drawings wherein like numerals refer to like matter throughout, there is shown an aircraft guidance system of the present invention, generally designated  100 , which includes an FMS  102 . FMS  102  is preferably a modified FMS from the prior art. FMS  102  is preferably an FMS as is used in the Synthetic Vision Information System (SVIS), which has been under development for and testing by Rockwell Collins Inc. of Cedar Rapids, Iowa and the National Aeronautics and Space Administration (NASA) Aviation Safety Program for several years. This FMS  102  could be nearly identical to the FMS used in the prior art SVIS systems, with a few modifications. As was done with the prior art SVIS, an airport database  104  would be coupled to the FMS  102  to provide runway, obstacle and published procedure data. As is done in the prior art SVIS, aircraft flight and navigation states  101  are provided as inputs to the FMS  102 . As is done in the prior art SVIS, another input into the FMS  102  would be a pilot-selected published instrument procedure  112 , which is of the type which has a known point of origin. The FMS  102  would generate, as is done in prior art SVIS, a calculated pathway  114 . This is the “highway in the sky” and one of the reasons for the moniker “synthetic vision.” It should be understood that the present invention does not always require a calculated pathway  114 . Many of the advantages of the present invention could be achieved by giving the pilot heading, pitch-and-roll guidance through a flight director. This, too, is known in the art to provide this type of guidance for pilot-selected instrument published procedure  112 . 
   The system  100  of the present invention could be constructed nearly identically to prior art SVIS, but with the addition of key inputs, such as takeoff/missed approach mode selection/reselection  106 , selected runway  108 , and circle-to-land mode selection  110 . 
   Now referring to  FIG. 2 , there is shown a logic diagram of a process which would preferably be implemented in a modification to prior art software to FMSs used in prior art SVISs.  FIG. 2  is focused on the constraints applied for a circling approach maneuver. It is believed that similar constraints would be made for a missed approach maneuver. The details of such constraints would vary, depending upon the particular implementation. However, after reviewing this description, one skilled in the art could readily adapt the logic shown in  FIG. 2  to address a missed approach scenario.  FIG. 2  shows details about how both horizontal and vertical paths to touchdown are determined. A system generally designated  200  is shown having a first accumulator  202  of constraints, which has as inputs the following representative inputs: obstacle clearance assurance (radius from end of runway); published circling constraints; aircraft airspeed and maximum bank angle. The magnitude and direction of the wind is an input into both first accumulator  202  and second accumulator  204 . Similarly, the position of the aircraft at the point of selection of the circling procedure, as well as current position of the aircraft, is provided to both accumulators  202  and  204 . Accumulator  202  considers all of the inputs and generates, among other things, a maximum turn radius. Accumulator  204  accepts as inputs wind, position, aircraft altitude above touchdown point, maximum descent rate (MDR), nominal maximum descent path to runway. Accumulator  204  generates a vertical path constraint which is combined with the horizontal path constraint (max turn radius) by both combiners  206  and  208  to generate horizontal and vertical paths respectively. 
   In operation, the system and method of the present invention could function as follows: 
   A pilot is approaching an airport on a published instrument approach procedure, with the intent of executing a circle-to-land maneuver to a specified runway, selected using selection means  108  on FIG.  1 . Upon acquiring visual contact with the airport and runway environment, the pilot selects the circle-to-land guidance mode, using selection means  110 . The FMS  102  accesses information about the airport and published circle-to-land constraints from database  104 , along with aircraft flight and navigation states  101 . It uses this information to generate detailed pitch-and-roll guidance for the pilot to follow, in order to arrive safely and comfortably at the landing runway threshold. 
   While maneuvering to land, for some reason, the pilot loses visual contact with the runway at a late stage in the approach; e.g., an unexpected patch of ground fog obstructs the pilot&#39;s visibility. 
   The pilot then selects the missed approach selection  106  from a previously selected runway  108 . The FMS  102  accesses information from the database  104  about the particular airport and gathers aircraft flight and navigation states (position, speed, attitude, etc.) and considers the constraints as described with respect to  FIG. 2  above, and generates detailed guidance for the pilot to follow. The guidance can include a calculated pathway  114  and/or a pitch-and-roll guidance  116  via a flight director, etc. In a preferred embodiment of the present invention, the guidance information would be presented to the pilot in a style and manner similar or identical to ways such information is presented to a pilot using prior art SVISs for pilot-selected published instrument procedures. 
   In view of the high level of skill in the art known by designers of prior art SVISs, it is thought that the method and apparatus of the present invention will be understood from the foregoing description and that it will be apparent that various changes may be made in the form, construct steps and arrangement of the parts and steps thereof, without departing from the spirit and scope of the invention or sacrificing all of their material advantages. The form herein described is merely a preferred exemplary embodiment thereof.