Communications: electrical – Aircraft alarm or indicating systems – Flight alarm
Reexamination Certificate
1999-09-08
2001-01-23
Hofsass, Jeffrey A. (Department: 2736)
Communications: electrical
Aircraft alarm or indicating systems
Flight alarm
C701S009000
Reexamination Certificate
active
06177888
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to aircraft traffic control systems and methods, and, more particularly, to systems and methods for warning of and/or avoiding flying an aircraft into a wake of another nearby aircraft.
BACKGROUND OF THE INVENTION
The vortical wake shed from a flying aircraft can pose hazards for any aircraft that happens to fly into the wake. The turbulence and vortical air velocities of a wake can cause sudden alterations in the aerodynamic forces exerted on an aircraft flying into the wake, resulting in effects that can include buffeting or bumping of the aircraft, sudden changes in attitude of the aircraft, and sudden changes in altitude of the aircraft. The consequences of flying into a wake tend to be of greater concern at low altitudes, such as during takeoff and landing operations at an airport, because there may not be sufficient time and altitude to recover from a sudden wake-induced aircraft motion before the aircraft impacts the ground. Furthermore, the strengths of wakes produced by aircraft tend to be greater during relatively low-speed takeoff and landing operations than during higher-speed flight because the strength of a vortex shed from the tip of a lifting surface is inversely proportional to the air velocity over the surface. Thus, interference from aircraft wake turbulence is a significant problem that can compromise safe operation of an aircraft.
A number of systems have been proposed for detecting, warning of, and/or avoiding contact between an aircraft and the wake of another aircraft. For example, U.S. Pat. No. 5,845,874 describes a system and method for creating visual images of aircraft wake vortices by mathematical modeling of the vortices based on characteristics of the aircraft that is creating them. The vortex modeling also takes into account the effects of atmospheric conditions such as wind on the vortices. One embodiment described in the patent provides a visual “heads-up” display in an aircraft on which the simulated wake vortices are displayed for each aircraft in the vicinity of the subject aircraft. It is said that the display of the wake vortices enables the pilot to “see” the vortices so that he or she can identify and avoid them. A disadvantage of this system is that when many aircraft are sharing the same airspace with the subject aircraft, such as around a busy airport, the heads-up display could become so cluttered with the simulated wakes of the other aircraft that the pilot may have difficulty distinguishing the wakes that could pose a hazard from those that can be safely ignored.
SUMMARY OF THE INVENTION
The present invention seeks to overcome the above-noted drawback by providing, in preferred embodiments, a wake turbulence warning and caution system and method for an aircraft that alerts a crew member to a potential conflict with the wake of another aircraft only when the system determines that intersection of the aircraft with the wake is about to occur within a predetermined amount of time. Thus, the crew is able to concentrate on the wake or wakes that present real potential hazards without being distracted by an excess of information about other wakes that do not present hazard situations. Additionally, in certain preferred embodiments of the invention, the wake turbulence warning and caution system can utilize avionics components that are already mandatory equipment on larger commercial aircraft, and thus the wake turbulence warning and caution system can be implemented relatively easily and inexpensively without requiring new hardware in the aircraft or on the ground. More specifically, the system can be implemented by making changes in software in one or more programmable components of existing avionics components.
In accordance with a preferred embodiment of the invention, a wake turbulence warning and caution system for an aircraft includes a positioning unit aboard the aircraft and operable to determine a position of the aircraft relative to a fixed reference. The system also includes a traffic collision avoidance unit aboard the aircraft, the traffic collision avoidance unit being operable to transmit and receive signals indicative of at least an altitude of the aircraft transmitting said signals. The traffic collision avoidance unit is further operable to determine an altitude of a nearby aircraft having another traffic collision avoidance unit transmitting said signals, and to determine a range and bearing to the nearby aircraft. The system further includes a wake-tracking unit aboard the aircraft and arranged to receive the position of the aircraft from the positioning unit. The wake-tracking unit is operable to determine a position of the nearby aircraft relative to the fixed reference based on the position from the positioning unit and the altitude, range, and bearing of the nearby aircraft, to track a trajectory of a wake volume from the nearby aircraft, and to determine at least one of a distance and a time to closure between the aircraft and the wake volume of the nearby aircraft. The system also includes a warning and caution unit aboard the aircraft and in communication with the wake-tracking unit, the warning and caution unit being operable to provide an alert when at least one of the distance and time to closure is less than a predetermined threshold.
Preferably, the traffic collision avoidance unit includes a software-programmable component and the wake-tracking unit is implemented in software within said component. Standard traffic collision avoidance system (TCAS) units, which have become mandatory equipment on most commercial passenger aircraft, are suitable for use with the present invention. The wake-tracking unit's functions can be programmed into a standard TCAS unit.
Alternatively, on aircraft equipped with a flight management system having a software-programmable component, the wake-tracking unit's functions can be implemented in software within the programmable component of the flight management system. Still further, some of the wake-tracking unit's functions can be programmed into a TCAS unit while other functions are programmed into a flight management system. Additionally, some or all of the functions of the warning and caution unit can be implemented in software in a TCAS unit and/or a flight management system.
The wake turbulence warning and caution system preferably accounts for the effect of local wind on the trajectory of the wake volume from a nearby aircraft. To this end, the system preferably includes a system aboard the aircraft for determining magnitude and direction of local wind velocity, and the wake-tracking unit preferably is operable to adjust the trajectory of the wake volume to take into account shifting of the wake volume by the local wind. In a preferred embodiment of the invention, the positioning unit is operable to determine magnitude and direction of an inertial velocity of the aircraft relative to the fixed reference. The system for determining local wind velocity includes the positioning unit, an air speed detector operable to determine a true air speed of the aircraft, an aircraft orientation detector operable to determine orientation information of the aircraft including at least angle of attack and sideslip thereof, and a computational unit operable to compute local wind velocity magnitude and direction based on the inertial velocity, true air speed, and orientation information.
To calculate the shifting of the wake trajectory by the local wind, the wake-tracking unit advantageously is operable to store the trajectory of the wake volume in the form of a series of data points, each data point having associated therewith at least a position of the nearby aircraft and a time at which the nearby aircraft occupied said position. The wake-tracking unit is further operable to adjust the position portion of each data point of the trajectory based on the local wind velocity multiplied by the difference between current time and the time associated with said data point.
The wake turbulence warning and caution system preferably als
Cabot Michael A.
Chiang Nam Q.
Alston & Bird LLP
Hofsass Jeffrey A.
The Boeing Company
Tweel , Jr. John
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