BACKGROUND OF THE INVENTION

The present invention relates to an anti-collision system and, more particularly, to an automatic system for enhancing the conspicuousness of an aircraft to the crew of second aircraft posing a collision threat.

The primary mechanism of midair aircraft collision avoidance is a flight crew's application of the “see and avoid” principle. This principle is sufficiently significant to be codified in regulations related to flight operations. For example, U.S. Federal Aviation Administration (FAA) regulation, 14 C.F.R. §91.113, requires “when weather conditions permit, regardless of whether operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft.”

The conspicuousness of an aircraft intruding on the airspace of another aircraft is significant to the timeliness of visual acquisition of the intruder by the crew of the other aircraft. Aircraft are equipped with external recognition lights to enhance their conspicuousness to other air traffic. Recognition lights include a position light system, including red and green forward lights indicating the right and left sides of the plane and a rear mounted white light. FAA regulations also require an anti-collision light system comprising sufficient numbers of flashing lights arranged to illuminate the vital areas around the airplane, considering its physical configuration and flight characteristics. The anti-collision light system must cover a field extending 75 degrees above and below the horizontal plane of the aircraft.

Despite the required external recognition lights and the attention given to the “see and avoid” principle, studies have shown that the primary cause of midair collisions is the failure of a pilot to see another aircraft that poses a threat of collision. Therefore, since the early 1990's, U.S. federal regulations have required that aircraft be equipped with a Traffic Alert and Collision Avoidance System (TCAS) (also known as Airborne Collision Avoidance System (ACAS)) to supplement the “see and avoid” principle. TCAS is an airborne radio system that locates and tracks the progress of aircraft equipped with beacon transponders. A TCAS transmitter in a first, tracking aircraft interrogates transponders of potentially intruding aircraft within range of the system (usually up to about 40 miles). Responding signals or replies from the transponders of aircraft in range are received through a directional antenna by a receiver in the tracking aircraft. The identification and altitude of the intruder are obtained from the replies and the distance and heading of the intruder is calculated and tracked by a TCAS computer in the tracking aircraft. The relative positions of intruders tracked by the TCAS computer are displayed in the tracking aircraft's cockpit.

If the TCAS computer calculates that an intruder is within approximately 35-40 seconds of a potential collision, the system will issue a traffic advisory (TA) indicating to the crew of the tracking aircraft that the intruder is a potential threat. The crew must visually locate the threat and may maneuver vertically with the assistance of air traffic control to resolve the threat. If the aircraft is equipped with a TCAS I system, advisories are limited to traffic advisories. If the tracking aircraft is equipped with a more comprehensive TCAS II system, the traffic advisory will be followed by an resolution advisory (RA) if the intruder approaches within approximately 20-30 seconds of a collision. The TCAS II system can determine whether the intruder is climbing, diving, or in level flight and will advise the pilots of the two aircraft of evasive vertical maneuvers to resolve the course conflict. Even with the TCAS system, the ability to quickly visually locate an intruder is important to avoiding midair collision hazards.

In addition to the position and anti-collision light systems, aircraft are equipped with taxi and landing lights used to illuminate the runway during take-off and landing. The bright landing lights may be used to increase the conspicuousness of an aircraft. For example, a voluntary FAA safety program, “Operation Lights On,” recommends turning landing lights on during takeoff and when operating below 10,000 feet, day or night, especially within 10 miles of an airport or under conditions of reduced visibility. Aircraft may also include other external lights such as de-icing lights, strobe lamps, and rudder illumination that can be manually activated to increase conspicuousness and enhance visual acquisition of the aircraft. Switching combinations of these additional lights “on” and “off” can further improve the conspicuousness of the aircraft. Lighting controllers are available that automatically switch individual lights or lighting systems “on” and “off” when activated by the pilot. However, manual light activation can be unreliable, particularly when the aircrew busy searching for approaching traffic.

Campanella, U.S. Pat. No. 3,652,981, discloses a proximity warning system based on detection of an exterior flash lamp or strobe by an electro-optical sensor of a tracking aircraft. The output of the electro-optical sensor is displayed in the cockpit to warn of threatening traffic. In addition, an aural tone may sound to draw the pilot's attention to the situation. In one embodiment, the flash lamp is of an intruding aircraft can triggered by a signal from an airborne weather radar of the tracking aircraft. Once triggered, the flash of the lamp of the intruding aircraft is detected by the electro-optical sensor of the tracking aircraft to produce a warning. While the electro-optical sensor may be able to distinguish between the flash lamp of the proximity warning system and the flashing lamps of the anti-collision warning system on the basis of flash rate, an additional flashing lamp may not significantly enhance the conspicuousness of the aircraft to human observers and the conspicuousness of the tracking aircraft is unchanged by the system. The activation of the flashing light requires that the tracking aircraft be equipped with weather radar and that the potential intruder be equipped an additional radio receiver to detect scanning by the radar of the tracking aircraft. Further, the use of weather radar as part of a reliable proximity warning system is precluded by the limited geometry of the radar beam.

What is desired, therefore, is system that in response to detection of a potential collision threat automatically activates external lighting of an aircraft to enhance its conspicuousness.

SUMMARY OF THE INVENTION

The present invention overcomes the aforementioned drawbacks of the prior art by providing an anti-collision apparatus for an aircraft comprising a transmitter transmitting a transponder interrogation; at least one transponder receiving the interrogation and transmitting a reply thereto; a receiver receiving the reply; a computer interpreting the reply to designate at least one transponder as a threat; and a controller illuminating at least one external light of the aircraft in response to the designation of the threat by the computer. The anti-collision apparatus automatically responds to the designation of intruder as a collision threat by the Traffic Control Avoidance System (TCAS) by illuminating external lights of the a tracking aircraft. The external lights include the aircraft's taxi lights, landing lights, rudder illumination lights, deicing lights or additional strobe lights. The controller can steadily illuminate or alternately illuminate and obscure individual lights or systems of lights to give the appearance of motion and increase the visual conspicuousness under various weather and lighting conditions. Different lights can be illuminated or lights can be turned “off” and “on” at a differing rate when the intruder approaches the tracking aircraft and becomes a more immediate threat of collision.

The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view of two aircraft approaching each other on potentially intersecting flight paths.

FIG. 2

is a block diagram of the anti-collision system of the present invention.

FIG. 3

illustrates an exemplary cockpit display for a Traffic Control Advisory System (TCAS).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A tracking aircraft

10

and an intruder

12

approaching each other on potentially intersecting flight paths are illustrated in FIG.

1

. The tracking aircraft

10

is equipped with position lights

14

and, one or more, flashing anti-collision lights

16

. In addition to the position

14

and anti-collision

16

lights, the tracking aircraft

10

is equipped with a combination of landing lights

18

, taxi lights

20

, de-icing lights

22

, strobe lights

24

and lights to illuminate a logo on the aircraft's rudder

26

. If the tracking aircraft is a rotor craft it would also be equipped with rotor lights. Likewise, the intruder

12

is equipped with position lights

28

and anti-collision lights

30

and may be equipped with additional lighting systems (not illustrated) similar to those of the tracking aircraft

10

.

If operated in controlled airspace, both aircraft will also be equipped with a Traffic Collision Avoidance System (TCAS), Airborne Collision Avoidance System (ACAS), Traffic Collision Avoidance Detection (TCAD), Traffic Advisory System (TAS) or similar proximity warning system (hereinafter referred to collectively as TCAS). Referring to

FIG. 2

, the TCAS system

50

of the tracking aircraft

10

comprises one or more antennae, including a directional antenna

52

, a transmitter

54

, a receiver

56

, a computer

58

, and a cockpit display unit

60

. The transmitter

54

of the tracking aircraft

10

interrogates or transmits a radio signal to the air traffic control transponders of aircraft in the vicinity. If an aircraft in range of the TCAS system is equipped with a transponder

64

, an interrogation signal

62

from the TCAS transmitter

54

of the tracking aircraft

10

will cause a reply or responding signal

66

by the intruder's transponder

64

. The reply identifies the intruder and its altitude. The TCAS computer

58

uses the time differential between the interrogation and the reply to determine the distance to the intruder

12

. The TCAS computer

58

determines the direction of the intruder

12

relative to the tracking aircraft

10

from signal variations in the segments of the directional antenna

52

. The computer

58

causes the relative positions of the tracking aircraft

10

and other aircraft in the vicinity, including the intruder

12

, to be displayed on a TCAS display

60

in the cockpit of the tracking aircraft

10

.

Referring to

FIG. 3

, the TCAS cockpit display

60

indicates the positions

80

,

82

, and

84

and altitudes

86

,

88

, and

90

of aircraft in range of the TCAS system relative to the tracking aircraft

92

. For example, “+18”

86

indicates that an aircraft is 1800 feet above the tracking aircraft and “−0.7”

90

indicates that a second aircraft is 700 feet below the tracking aircraft

92

as displayed on the exemplary display

60

. If the tracking aircraft

10

and the intruder

12

are both equipped with a more comprehensive TCAS II system the display

60

will also indicate whether the intruder is climbing or descending at more than 500 feet per minute as indicated by an upward

94

or downward

96

pointing arrow.

When the intruder

12

is within approximately 45 seconds of its closest approach to the tracking aircraft

10

, based on the calculated flight paths of the two aircraft, the computer

58

designates the intruding aircraft

12

as a collision threat based on the computer's interpretation of the intruder's transponder reply

66

. When the intruder

12

is designated as a collision threat a traffic advisory (TA) is issued. Typically, a TA is indicated by a change in the shape of the aircraft symbol on the display

60

. For example, the shape of the symbol might change from a diamond

80

to a circular dot

82

. The TCAS may also include an annunciator that produces an audible warning, such as “traffic, traffic.” When a TA is issued, the crew of the aircraft must attempt to locate the intruder

12

visually so that the conflict between the aircraft can be resolved. Aircraft with TCAS I systems are authorized to ascend or descend 300 feet, with approval of air traffic control, to resolve a traffic conflict.

Larger commercial passenger aircraft are required to be equipped with a more capable TCAS II system. In addition to the traffic advisory, the TCAS II system will issue a resolution advisory (RA) indicating a more immediate threat when the aircraft are approximately 35 seconds from their point of closet approach. When the resolution advisory is issued the aircraft symbol on the exemplary display

60

changes shape and the annunciator issues an audible maneuvering warning such as “climb, climb” to resolve the conflict. The TCAS II system includes provisions to coordinate with the TCAS II system of other aircraft to avoid mirror image maneuvers that would continue the flight path conflict between the aircraft.

When a traffic advisory is issued, the crew of the aircraft will attempt to visually locate the aircraft posing a collision threat. If both aircraft are equipped with the TCAS system, both crews will be seeking to visually locate the other craft when a traffic advisory is issued by the respective TCAS systems. While aircraft are equipped with position

14

and

28

and anti-collision lights

16

and

30

to aid in visual detection of the airplane, other lighting systems of the aircraft can be used to enhance the conspicuousness of the airplane. These additional lighting systems can include landing lights

18

, taxi lights

20

, de-icing lights

22

, strobe lights

24

and rudder illumination lights

26

. These additional lighting systems can be manually activated by the flight crew or the aircraft can be equipped with a lighting controller to automatically activate and deactivate predetermined individual lights or systems of lights when the controller is manually activated by the flight crew. However, manual activation of the various lighting systems requires diversion of the crew's attention from seeking to visually locate the intruder. The present inventor concluded that a signal from the TCAS system could be used to automatically illuminate external lights to enhance the conspicuousness of the aircraft when a threat is detected and timely visual acquisition of the aircraft is paramount.

Referring again to

FIG. 2

, when a traffic advisory is issued by the TCAS system of an aircraft equipped with the anti-collision system of the present invention, a signal is sent from the TCAS computer

58

to a light controller

68

. The light controller

68

activates selected external lighting systems

70

and

72

of the tracking aircraft

10

to enhance the airplane's conspicuousness and increase the likelihood and timeliness of visual acquisition by the crew of the intruder

12

. The light controller

68

can alternately activate and deactivate predetermined lighting systems

70

and

72

which can include the landing lights

18

, taxi lights

20

, deicing lights

22

, strobe lights

24

and rudder illumination

26

as illustrated in FIG.

1

. Alternately illuminating and obscuring individual lights or groups of lights spaced apart on the aircraft creates an illusion of side-to-side motion further enhancing the conspicuousness the aircraft. If lights are in close proximity, simultaneously activating and deactivating the lights can increase their conspicuousness. The lighting systems may be repeatedly activated and deactivated to create a flashing light or steady illumination may be maintained. Steady illumination may be preferred if clouds, rain or snow is present. Further, the frequency of activation and deactivation of selected lighting systems or the particular lighting systems activated can be changed in response to the issuance of a resolution advisory by the TCAS system when the intruder approaches within an area of more immediate collision threat. Altering the rate of flashing or the systems illuminated increases the conspicuousness of the aircraft.

All the references cited herein are incorporated by reference.

The terms and expressions that have been employed in the foregoing specification are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.