Abstract:
A vertical lift aircraft, such as a helicopter, can land in an area with impaired visibility such as fog. Around the landing area is a plurality of laser beam emitters. The emitters project a pattern of laser beams skyward. The helicopter finds the general area by spot-lights pointing up through the fog, or by navigation. As the helicopter approaches, it sends a radio signal, which is detected on the ground. The spot-lights are switched off and the laser emitters are switched on. The helicopter is positioned within the pattern so that the laser beams reflect off of a portion of the aircraft, such as the rotor blades. This forms a visual cue, which the pilot uses to maintain the position of the helicopter relative to the landing area and descends thereto.

Description:
BACKGROUND OF THE INVENTION 
     The weather condition known as fog causes a severe reduction in the visibility for pilots operating aircraft. Fog often restricts a pilot from flying a helicopter due to a reduced visibility and the potential inability for the pilot to identify a suitable location to land the helicopter. Fog does not restrict the mechanical operation of a helicopter, but rather the operational considerations of determining where the pilot can land the helicopter without crashing into adjacent trees or structures. The present invention incorporates laser beams to aid in the identification of an unobstructed landing site for a helicopter. The laser beam is normally invisible to the human eye unless suspended particles are present in the air, for the laser beam to reflect from. Fog, which can form above ground, is composed of suspended particles of moisture in the air. Fog makes visible the previously invisible laser beams, which are used to identify an unobstructed landing site. This lighting feature aids pilots in determining the location of an unobstructed landing, which had become obscured in the fog. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a suitable, unobstructed landing site identification lighting system that is more effective than existing landing pad lighting systems. 
     The present invention provides a method of guiding a vertical lift aircraft to a landing zone. A pattern of focused light beams is projected from the landing zone skyward. Skyward of the landing zone, the aircraft is positioned within the pattern. Part of the aircraft is illuminated with the pattern so as to form a visual cue as to the position of the aircraft relative to the landing zone. 
     In one aspect of the present invention, the focused light beams can be either beams of coherent or incoherent light. The focused light beams can comprise beams of visible light or invisible light, wherein the invisible light becomes visible when it strikes an object. 
     In another aspect of the invention, the landing zone has a predetermined shape and the pattern of the focused light beams has a shape that corresponds to the landing zone shape. In particular, the pattern of focused light beams can form a cylinder as it is projected skyward. 
     In another aspect of the present invention, the pattern of focused light beams can project vertically from the landing zone or at an angle to the vertical. 
     In still another aspect of the present invention, the aircraft is descended to the landing zone using the visual cue. 
     In still another aspect of the present invention, the aircraft comprises a helicopter having rotor blades. Parts of the rotor blades are illuminated with the pattern, wherein the visual cue appears on the rotor blades, readily visible to a pilot of the helicopter. 
     In still another aspect of the present invention, the approach of the aircraft to a position above the landing zone is detected. When detected, the pattern of focused light beams is then projected from the landing zone skyward. Detecting the approach of the aircraft can be accomplished by receiving a radio transmission from the aircraft. 
     In accordance with still another aspect of the present invention, spotlights are provided at the landing zone before the step of projecting the pattern of focused light beams so as to direct the helicopter to the general area of the landing zone. Alternatively, diverging laser beams are used to direct the helicopter to the general area of the landing zone. 
     In accordance with another aspect of the present invention, the light beams comprise a first color. A second color of light, being a different color than the light forming the cylinder is projected into a crossing pattern of focused light beams at a first altitude. A third color of light being a different color than the light forming the cylinder is projected into a crossing pattern of focused light beams at a second altitude. Thus, as the helicopter descends to the landing zone in the cylinder pattern of light, visual cues as to the altitude of the aircraft relative to the landing zone are provided by the different colors of crossing light. 
     The present invention also provides a system of guiding a vertical lift aircraft to a landing zone. The system includes an unobstructed area. A plurality of laser beam emitters are deployed in the area, with the emitters being arranged so as to project a pattern of light beams skyward. 
     In accordance with one aspect of the present invention, the system also includes a controller connected to the emitters. The controller includes a detector that detects the approach of the aircraft to the landing zone. The controller also includes a switch for operating the emitters upon the detection of the approach of the aircraft. 
     In accordance with another aspect of the invention, the emitters are first emitters and the light beams comprise a first color. The system also includes second and third emitters. The second emitters project a second color of light into a crossing pattern of light beams at a first altitude above the landing zone, while the third emitter project a third color of light into a crossing pattern of light beams at a second altitude. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Although the features of this invention, which are considered to be novel, are expressed in the appended claims, further details as to preferred practices and as to the further objects and features thereof may be most readily comprehended through reference to the following description when taken in connection with the accompanying drawings, wherein: 
     FIG. 1 is an overhead view of a helicopter landing pad of the present invention, in accordance with a preferred embodiment. 
     FIG. 2 is a schematic front view of the helicopter landing pad with illuminated light beams and hovering helicopter. 
     FIG. 3 is a schematic side view of the helicopter landing pad with illuminated light beams and hovering helicopter. 
     FIG. 4 is a schematic view on the invention in its preferred embodiment illustrating the light beams as extending straight up. 
     FIG. 5 is a schematic view on the invention illustrating the light beams as extending at an angle. 
     FIG. 6 is a schematic alternate view on the invention illustrating crossing light beams of plural colors. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the drawings, like reference numerals designate corresponding parts throughout the several views. The present invention provides a method of indicating the location of a suitable landing site or zone, in conditions of fog. The landing site comprises an area that is unobstructed and arranged to allow for the landing of a helicopter. Upon arrival to an area obscured by fog, above which the helicopter  11  wishes to land, multiple laser beams  9  are produced around the perimeter of the circular shaped landing pad  1 . These multiple laser beams generate a circular column of light  10  projecting vertically into the fog-filled sky. The helicopter pilot then transitions the helicopter inside the circular column of laser beams and descends the helicopter safely down within the column of laser beams, to the unobstructed landing pad  1 . 
     In FIG. 1, there is shown a helicopter landing pad  1  consisting of a circle  3  around the landing pad  1 , with an H  5  located in the center of landing pad  1 . Multiple laser emitters  7 , which generate vertical light beams  9  (FIG.  2 ), are spaced an equal distance around landing pad circle  3 . 
     Each laser emitter  7  generates a beam  9  of laser light. The diameter of the individual laser beams  9  should be several inches so as to be readily visible. The laser emitters  7  are conventional, commercially available devices. The laser emitters  7  produce a tightly focused beam of coherent light that has excellent fog penetrating capabilities. Typically, fog is close to the ground and is not very deep. The laser beams produced by the emitters have sufficient power to produce a beam of such intensity that will penetrate to the top of the fog layer. 
     The laser emitters can produce a visible beam or an invisible beam. If an invisible beam is used, it is of a wavelength that produces a visible spot on an illuminated object. For example, there are lasers that produce beams of light that are ordinarily invisible in clear air; however, in fog, the beams of light become visible as they reflect off the fog particles. 
     The laser emitters  7  are positioned in a circular pattern around the landing pad circle  3 , so that the beams of light project skyward. The diameter of the circle  3  is less than the diameter of the helicopter rotor blades  13 . 
     Auxiliary lights  8 , which generate crossing laser light beams, are placed outside of landing pad circle  3  and will be more fully described in FIG. 6 which follows. In addition, lights  8  can provide spot light. 
     Referring now to FIGS. 2 and 3, there is shown a front and side view of a typical helicopter landing pad  1  with illuminated vertical light beams  9  and hovering helicopter  11 . Helicopter  11  has rotor blades  13 . As helicopter  11  hovers over the circle shaped landing pad  1 , rotor blades  13  pass through the circle of vertical light beams  9 . The pilot within helicopter  11  can look upwards seeing rotor blades  13  pass through vertical light beams  9 . The laser beams  9  illuminate portions of the spinning rotor blades. The illuminated portions are visible to the pilot, who positions the helicopter  11  within the circle of light beams  9  as the helicopter  11  descends toward landing pad  1 . 
     Tightly focused spot-lights  8  (see FIG. 4) are used to aid the helicopter pilot in determining the general area at which the unobstructed landing site is located. Once the general area is located the invention receives a radio signal from the approaching helicopter to turn off the focused spot-light beams and immediately turn on the laser beams. Though the focused spot-light beams work well in guiding the pilot to the general location of the unobstructed landing site, these focused spot-light beams tend to scatter ambient light throughout the general area illuminating a vast amount of the suspended moisture particles which make-up the fog and create a hindering obscurity to the pilot&#39;s visibility, while the pilot is trying to locate the exact landing site for the helicopter. The lasers however contain the projected light in a very narrow beam, eliminating the obscurity caused by the scattering light of the spot-light beams which tend to cloud the vision of a pilot in fog. 
     Referring now to FIG. 4, is a view of the invention in its preferred embodiment where helicopter  11 , approaching landing pad  1  which is obscured by fog, can hover at a high altitude, above obstructions such as trees  17  or tall electrical line towers  19 . Helicopter  11  is normally equipped with a radio with the ability to transmit radio signals on various frequencies. The helicopter radio can transmit a signal on a prescribed radio frequency to be received by radio receiver  21 , which is located adjacent to, and connected to switch on and off laser emitters  7 . Upon detection of the prescribed radio signal from helicopter  11 , radio receiver  21  will switch on the laser emitters  7 , which produce vertical light beams  9 . Upon visual detection of vertical light beams  9  reaching far into the fog filled skies above landing pad  1 , the pilot of helicopter  11  can then follow a transition path  15 , to position helicopter  11  inside the circle of vertical light beams  9 . Once helicopter  11  is positioned inside the circle of vertical light beams  9  the pilot can land the helicopter  11 , within vertical light beams  9 , onto landing pad  1 . While the pilot descends helicopter  11 , within vertical light beams  9 , the pilot can monitor the position of the helicopter  11 , within vertical light beams  9 , by looking upward at rotors blades  13 , and seeing the reflections of vertical light beams  9  created on rotor blades  13  as they pass through vertical light beams  9 . Having the helicopter pilot monitor the reflections of vertical light beams  9  avoids the danger of the pilot trying to look downward at vertical light beams  9  and having the pilot&#39;s vision impaired by the intense light shining directly into the pilot&#39;s eyes. The pilot can look out of the front and side windows to view the illuminated rotor blades. When properly positioned above the landing pad  1 , a circle of light appears on the rotor blades forming a visual cue for the pilot. By positioning the helicopter so that the helicopter stays centered within the circle, the pilot properly positions the aircraft over the landing pad  1 . In the event rotor blades  13  no longer reflect the light from vertical light beams  9 , the pilot can assume the helicopter  11  has drifted out of the preferred descent path for landing and can then take appropriate steps to reposition helicopter  11  to a proper descent path  15 , within the circle of vertical light beams  9 . 
     Referring now to FIG. 5, there is shown a view of one embodiment of the invention illustrating the light beams  9  projecting at an angle to allow for a helicopter  11  landing glide-slope. This allows the pilot to come into the landing zone at an angle. The pilot of helicopter  11  is required to descend helicopter  11  in an angled approach slope to allow helicopter  11  to descend along that same slope in an auto-rotation mode, in the event the engine of helicopter  11  were to cease operation. 
     Referring now to FIG. 6, there is shown a view of an alternate embodiment of the invention where auxiliary lights  8  generate crossing blue laser beams  23  which intersect at an altitude of eighty feet, crossing green laser beams  25  which intersect at an altitude of twenty feet, and crossing yellow laser beams  27  which intersect at an altitude of ten feet, are illuminated as an aid to determine various altitudes. These crossing patterns can be located outside of the cylinder of light beams  9 , and within visual range of the pilot. The pilot of helicopter  11  can adjust the helicopter rate of descent as he recognizes the helicopter  11  descending through the changing altitudes identified by the appropriate laser beam color of blue, green or yellow. Once the helicopter  11  descends to the lowest yellow crossing laser beams  27  the pilot can minimize the helicopter  11  rate of descent to allow for a gentle landing. The altitude, at which the various crossing laser beams intersect, can be modified to the preference of any particular helicopter pilot. 
     In a practical application of the preferred embodiment of this new invention, the following tasks will be performed: 
     1. Return of a helicopter to the area of a landing pad obscured by fog 
     2. Helicopter pilot transmits radio signal to ground based landing pad receiver 
     3. Landing pad receiver activates landing pad light beams 
     4. Helicopter transitions into circular shaped column of light beams 
     5. Helicopter descends within circular shaped column of light beams 
     6. Helicopter pilot recognizes crossing laser altitude markers 
     7. Helicopter pilot reduces helicopter rate of descent 
     8. Helicopter pilot gently lands helicopter on unobstructed landing pad 
     The individual laser beams can be operated on and off, so as to produce a sequence of laser beams flashing around the unobstructed landing site. 
     The laser beams can be substituted with beams of light which are made up of light generated in the visible spectrum, and are visible to the human eye without the need for fog or smoke in the air, or light generated in the infrared spectrum, visible by night-vision goggles with the ability to detect infrared light. By using this infrared light aspect of the invention a helicopter, in a covert military operation, can land without the use of any, landing pad, lighting systems; allowing the helicopter to land in a more concealed manner. The beams can be either coherent or incoherent light. 
     The individual laser beams can be diverging beams. Diverging beams allow for wider area of light at higher altitudes, giving pilots a larger display or array to look for, as they attempt to locate the landing site for the helicopter. 
     Although the present invention has been described in conjunction with a helicopter, it can be used with other types of aircraft that are capable of vertical landings. For example, there are Vertical Takeoff and Landing (VTOL) aircraft, as well as Tilt Wing and Tilt Rotor Aircraft. 
     The pattern of light that is projected skyward need not be circular. It can be some other shape. 
     As an alternative to using spotlights to guide the helicopter to the general area of the landing area, the pilot can used navigational tools such as Global Positioning System (GPS). 
     Although the invention has been described as using laser beams that are visible in fog-filled air, the laser generators could be adapted to project light beams, which are visible in clear air. 
     Although an exemplary embodiment of the invention has been disclosed and discussed, it will be understood that other applications of the invention are possible and that the embodiment disclosed may be subject to various changes, modifications, and substitutions without necessarily departing from the spirit of the invention.