PROXIMITY WARNING SYSTEM FOR AIRCRAFT

• US 3,620,626 A
• Filed: 05/29/1969
• Issued: 11/16/1971
• Est. Priority Date: 05/29/1969
• Status: Expired due to Term

• Current Assignee: Edmundas Vambutas, Richard T. Daly
• Original Assignee: Edmundas Vambutas, Richard T. Daly
• Inventors: Richard, T. Daly, Vambutas, Edmundas
• Primary Examiner(s): Rodney D. Bennett, Jr.
• Assistant Examiner(s): S. C. Buczinski
• Application Number:
  US04/828,945
• Time in Patent Office: 901 Days
• Field of Search: 356/4,5 343/112.4,5DP 250/199
• US Class Current: 356/5.08
• CPC Class Codes: G01S 17/14 wherein a voltage or current pulse is initiated and terminated in accordance with the pulse transmission and echo reception respectively, e.g. using counters
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/933 of aircraft or spacecraft

Abstract

A simple, lightweight, inexpensive laser proximity warning system for aircraft operating under visual flight rules (VFR) conditions. Mounted on each fully equipped aircraft is a laser transmitter, a detector sensitive to laser radiation and a retroreflector. The laser transmitter and detector periodically scan a predetermined region of the space surrounding the aircraft. If another aircraft equipped with a retroreflector is within the predetermined region, the transmitted laser radiation will be returned to the detector which will activate an indicator in the cockpit to warn the pilot of the presence and approximate bearing of the other aircraft.

Claims

1. A proximity warning system for warning the pilot of a first aircraft of the proximity of a second aircraft, said proximity warning system comprising:

laser means mounted on said first aircraft for transmitting pulses of light;

retroreflector means mounted on said second aircraft for reflecting incident light back along the path of incidence;

detector means mounted on said first aircraft and having a field of view substantially coextensive with the beam of light transmitted by said laser light transmitter means so as to receive light transmitted by said laser light transmitter means and reflected by said retroreflector means;

timing means for measuring an interval of time equal to the time required for the transmission of an output pulse of laser light from said laser light transmitting means to a retroreflector mounted on a second aircraft at a predetermined maximum range from said first aircraft and back to said detector means mounted on said first aircraft;

means for starting said timing means upon the transmission of an output light pulse from said laser light transmitting means;

down counter means, the initial contents of said down counter means being representative of the predetermined maximum range of said second aircraft;

means responsive to said output signal from said detector means for starting said down counter; and

means responsive to said output signal from said timing means to stop said down counter means, the final contents of said down counter means being representative of the range of said second aircraft if said second aircraft is within said predetermined maximum range; and

indicator means responsive to said down counter means for indicating the proximity of said second aircraft when said second aircraft is within said predetermined maximum range.

2. The proximity warning system of claim 1 further comprising:

scanning means for causing said light transmitter means and said detector means to scan a predetermined region of the space surrounding said first aircraft;

sensing means responsive to said scanning means for producing an output signal representative of the instantaneouS direction of said beam of light from said light transmitter means;

said indicator means being responsive to said output signal from said sensing means to indicate the direction of said second aircraft.

3. The proximity warning system of claim 2 wherein said scanning means causes said light transmitter means and said detector means to scan in a horizontal plane so as to detect a second aircraft flying at approximately the same altitude as said first aircraft.

4. The proximity warning system of claim 1 wherein the time interval between output pulses from said laser light transmitter means is greater than the time required for transmission of light from said laser light transmitter means mounted on said first aircraft to said retroreflector mounted on said second aircraft at a predetermined maximum range and back to said detector means mounted on said first aircraft.

5. The proximity warning system of claim 1 further comprising a safety switch responsive to the airspeed of said first aircraft for shutting off said laser light transmitting means when said airspeed falls below a predetermined minimum speed.

6. The proximity warning system of claim 1 further comprising a safety switch actuated by the landing gear of said first aircraft for shutting off said laser light transmitting means when said aircraft is on the ground.

7. A proximity warning system for warning the pilot of a first aircraft when there is a second aircraft within a predetermined maximum range from said first aircraft and there is a possibility that the second aircraft may collide with said first aircraft within a predetermined minimum time, said proximity warning system comprising:

laser means mounted on said first aircraft for transmitting first and second beams of laser light of a predetermined wavelength, said first and second beams of laser light being separated by a predetermined angle;

retroreflector means mounted on said second aircraft for reflecting incident light back along the path of incidence;

detector means mounted on said first aircraft and having a field of view substantially coextensive with said first and second beams of laser light so as to receive laser light reflected by said retroreflector means mounted on said second aircraft, said detector means producing an output signal upon detection of light of the wavelength produced by said laser means;

scanning means for causing said first and second beams of laser light from said laser means and said field of view of said detector means to scan a predetermined region of the space surrounding said first aircraft;

first calculating means responsible to an output signal from said detector means corresponding to a reflection of said first beam of laser light for calculating the range of said second aircraft relative to said first aircraft;

second calculating means responsive to an output signal from said detector means corresponding to a reflection of said second beam of laser light for calculating the range of said second aircraft relative to said first aircraft;

third calculating means for subtracting the range calculated by said second calculating means from the range calculated by said first calculating means in order to calculate the range rate of said second aircraft relative to said first aircraft;

fourth calculating means for calculating the threshold range rate which would prevent a danger of possible collision within said predetermined minimum time interval;

comparison means for comparing said range rate calculated by said third calculating means with said threshold range rate calculated by said fourth calculating means; and

indicating means responsive to said comparison means for indicating a possible collision if said range rate calculated by said third calculating means is greater than said threshold range rate calculated by said fourth calculating means.

8. The proximity warning system of claim 7 further comprising sensing means responsive to said scanninG means for producing an output signal representative of the instantaneous direction of said first and second beams of laser light, said indicating means being responsive to said output signal from said sensing means to indicate the bearing of said second aircraft relative to said first aircraft.