Lighting systems for landing in a degraded visual environment

Abstract

Lighting systems and methods for landing in a degraded visual environment are disclosed. The lighting systems comprise one or more lighting units mounted to an aircraft operable to hover near a landing zone. Each lighting unit is operable to provide adjustable illumination to the landing zone, and has a radiant power output between a minimum and a maximum. The minimum radiant power output is just sufficient to allow a pilot to distinguish features in the landing zone when below a first altitude wherein the downwash from the aircraft rotors, propellers, or engines begins to raise particulates from the landing zone and continues to be just sufficient to allow the pilot to distinguish features as the pilot descends from the first altitude to termination at the landing zone, and the maximum radiant power output is less than about five times the minimum radiant power output.

What is claimed is: 
     
         1 . An aircraft lighting system comprising
 one or more lighting units mounted to an aircraft, the aircraft operable to hover near a landing zone,   wherein each lighting unit is operable to provide adjustable illumination to an illuminated area in the landing zone, and   wherein each lighting unit has a radiant power output between a minimum and a maximum,   wherein the minimum radiant power output is just sufficient to allow a pilot to distinguish features in the landing zone when below a first altitude wherein the downwash from the aircraft rotors, propellers, or engines begins to raise particulates from the landing zone and continues to be just sufficient to allow the pilot to distinguish features as the pilot descends from the first altitude to termination at the landing zone, and   wherein the maximum radiant power output is less than about five times the minimum radiant power output.   
     
     
         2 . The aircraft lighting system of  claim 1 , wherein each lighting unit comprises a plurality of lighting elements emitting light at a plurality of wavelengths. 
     
     
         3 . The aircraft lighting system of  claim 2 , wherein the plurality of wavelengths can produce white, green, and infrared illumination. 
     
     
         4 . The aircraft lighting system of  claim 2 , wherein the plurality of lighting elements comprise light emitting diodes (LEDs). 
     
     
         5 . The aircraft lighting system of  claim 1 , wherein the illuminated area of the landing zone is approximately equal in size and shape to the field of view of a pilot or crew member looking through a chin bubble or a side door or window of the aircraft. 
     
     
         6 . The aircraft lighting system of  claim 5 , further comprising a shroud, wherein the shroud is operable to limit the emission of light to a direction toward the illuminated area of the landing zone. 
     
     
         7 . The aircraft lighting system of  claim 1 , wherein each lighting unit further comprises one or more lasers aimed generally in the direction of the illuminated area of the landing zone. 
     
     
         8 . The aircraft lighting system of  claim 7 , wherein each lighting unit comprises a plurality of lasers emitting light at a plurality of wavelengths. 
     
     
         9 . The aircraft lighting system of  claim 8 , wherein the plurality of wavelengths comprise red, green, and infrared. 
     
     
         10 . The aircraft lighting system of  claim 8 , wherein the plurality of lasers comprise semiconductor lasers each having a power output of between 0.1 mW and 1.0 mW. 
     
     
         11 . The aircraft lighting system of  claim 7 , wherein the one or more lasers create a pattern onto the landing zone which changes as a function of altitude. 
     
     
         12 . The aircraft lighting system of  claim 11 , wherein a spot projected from the one or more lasers on the landing zone changes size as a function of altitude. 
     
     
         13 . The aircraft lighting system of  claim 11 , wherein a spot projected from the one or more lasers onto the landing zone changes shape as a function of altitude. 
     
     
         14 . The aircraft lighting system of  claim 11 , wherein two spots projected from the one or more lasers onto the landing zone have a separation which changes as a function of altitude. 
     
     
         15 . The aircraft lighting system of  claim 1 , wherein the particulates comprise dust or sand. 
     
     
         16 . The aircraft lighting system of  claim 1 , wherein the particulates comprise water, snow, or ice. 
     
     
         17 . A method for illuminating a landing zone comprising
 providing one or more lighting units to an aircraft, the aircraft operable to hover near the landing zone,
 wherein each lighting unit is operable to provide adjustable illumination to the landing zone, and 
 wherein each lighting unit has a power between a minimum and a maximum, 
 wherein the minimum power is just sufficient to allow a pilot to distinguish features in the landing zone from below a first altitude wherein the downwash from the aircraft rotors, propellers, or engines begins to raise particulates from the landing zone and continues to be just sufficient to allow the pilot to distinguish features as the pilot descends from the first altitude to termination at the landing zone, and 
 wherein the maximum power is less than about five times the minimum power; 
   during an approach or landing of the aircraft, leaving the lighting units off until the aircraft descends below the first altitude, and   turning the lighting units on below a second altitude wherein the second altitude is below the first altitude.   
     
     
         18 . The method of  claim 17 , wherein the second altitude is about 20 ft.