Abstract:
In an in-flight refueling system of an aircraft having a recess therein containing a slipway leading to a fuel inlet port, an improvement is provided in the form of a guideway having a) a pair of lead-in lines on the surface of the aircraft which taper and converge towards the slipway and port and b) a plurality of dashes or bars on the surface, spaced longitudinally between the lead-in lines, a desired distance apart, to provide visual cues in aiding an operator in guiding a fuel boom and nozzle from a refueling aircraft to the slipway and port of a fuel receiving aircraft, to provide a visually more salient means to achieve a quick and effective refueling hook-up while avoiding or minimizing nozzle strikes that can damage the aircraft, the boom or its nozzle.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon. 
    
    
     RELATED APPLICATIONS 
     None. 
     FIELD OF THE INVENTION 
     This invention relates to an in-flight refueling guide for accurate delivery of fuel from one in-flight craft to another. 
     BACKGROUND OF THE INVENTION 
     The task of aerial refueling involves a fuel tanker aircraft and a receiver aircraft flying in close formation under very controlled flight conditions. The task of the refueling boom operator in the tanker is to take a long tubular refueling boom and manipulate it between the aerodynamic slipstreams of both aircraft so that it contacts the refueling receptacle on the receiving aircraft. This boom can move in three dimensions to affect a contact; movement is controlled by the tanker boom-operator. Once in position, the boom nozzle is mechanically linked to the receiver aircraft and the fuel can be transferred. This task is performed by the tanker aircraft boom-operator using controls in the tanker aircraft that allow the operator to fly the fueling boom into position. Manipulating the movement of the boom requires manual skill. It also requires considerable guidance as to the location of the refueling receptacle to create a visual refueling link between the two aircraft. To enhance this visual image for the boom operator, various lead-in line patterns have been used. Earlier lead-in line patterns did not provide very accurate guidance to the boom operator; the consequence was inadvertent boom contacts with aircraft structures other than the refueling port area. By not visually drawing the boom operators eyes toward the target, previous designs allowed connection and acquisition errors to occur. These errors in boom movement would often lead to structural damage to the receiver aircraft. 
     Examples of prior art lead-in line patterns are shown in FIGS. 4 and 5 hereof, which do not provide adequate directional, distance or rate of closure guidance of the fuel boom and nozzle to the fuel receptacle or port on the fuel-receiving aircraft. 
     Accordingly, there is need and market for a refueling guide that gives such adequate guidance and otherwise overcomes the above prior art shortcomings. 
     There has now discovered in-flight refueling system which provides enhanced guidance of a refueling boom in direction and relative motion, as it closes on the fuel port of the fuel receiving aircraft for greatly enhanced in-flight refueling. 
     SUMMARY OF THE INVENTION 
     Broadly the invention provides an enhanced in-flight refueling system for an aircraft having a slipway leading to a fuel inlet port in a recess in the aircraft, the improvement comprising, a guideway having, 
     a) a pair of lead-in lines on the surface of the aircraft which converge toward the slipway and port and 
     b) b) a plurality of marks on the surface spaced longitudinally between the lines a desired distance apart, 
     so that the lines and marks aid in guiding a fuel boom and nozzle from a refueling aircraft to the slipway and port. 
     The refueling guide of the invention can have recess doors which open &amp; close over the recess on hinges and when open, reveal padding over the hinges to protect them from contact with said nozzle. 
     Definitions: 
     By “slipway” as used herein, is meant a sloping surface descending from the surface into a recess in an aircraft and leading to a fuel inlet port therefor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become more apparent from the following detailed specification and drawings in which: 
     FIG. 1 is a fragmentary perspective schematic view of aircraft refueling components; 
     FIG. 2 is a fragmentary elevation schematic view, partly in section, of the fueling guide embodying the invention, in operation; 
     FIG. 3 is a fragmentary perspective schematic view of the refueling operation shown in FIG. 2; 
     FIG. 4 is a schematic plan view of refueling guidelines according to the prior art; 
     FIG. 5 is a schematic plan view of another set of refueling guidelines according to the prior art; 
     FIG. 6 is a fragmentary perspective schematic view of a refueling guide embodying the present invention; 
     FIG. 7 is a fragmentary sectional elevation schematic view of part of the refueling guide of FIG. 6 taken on lines  7 — 7 , looking in the direction of the arrows and 
     FIG. 8 is a fragmentary elevation schematic view of a part of the inventive refueling guide of FIG. 6 taken on lines  8 — 8 , looking in the direction of the arrows. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings, the invention is a collection of design elements applied to the surface of an aircraft, that provides  3 -dimensional information to the boom operator of, e.g., a tanker aircraft, by the novel use of several two dimensional principles of perspective. A fueling guide of the invention also incorporates numerous rules of human visual perception as elements. 
     As shown or indicated in FIGS. 2,  3  &amp;  6 , external lead-in lines are configured to form a visual pathway to the refueling-receptacle on the receiver aircraft. They include a pair of tapered lines  10  &amp;  12 , applied to the receiving aircraft surface  14 , that converge at a location suitable for positioning a refueling boom nozzle  19  of known dimensions (on boom  18 ) into a receptacle or port  22  of known dimensions. These lines are tapered so that the right eye follows the right line and the left eye follows the left line with both lines being within the instantaneous field of view of the boom operator when the aircraft is within a reasonable refueling distance (less than  100  feet distant). The taper of these two lines  10  &amp;  12  is designed to create a band or target of eye focus. The external (outboard) portion of both the right and left lines  12  &amp;  10  describes an intersection point at the maximum distance allowable to effect a correct contact of the boom nozzle  19  with the receiver fuel receptacle or port  22 . The inside taper of both lines is designed to provide a minimum range of depth for the boom nozzle to effect a contact, e.g., with the beginning of the slipway  20  at “A” shown in FIG.  6 . 
     The taper of both lines  10  &amp;  12  is designed to create the best visual image convergence when the boom is at the proper distance position for refueling. 
     This convergence of the right side lines and the left side lines (as a result of their size and taper) thus serves to create a target range (not just a singular focal point) in which the boom operator can effectively connect to the receiver aircraft without over extending or under extending the boom  18 . 
     Also provided are marker bars  24 ,  26  &amp;  28  which are applied to the aircraft surface laterally relative to the centerline of the aircraft, and are designed to provide depth as well as motion cues to the boom operator. They are set at a known distance from the target and are of a known size (thickness). 
     The marker bars  24 ,  26  &amp;  28  are evenly spaced at, e.g., one-foot intervals. As each bar is passed over by the boom nozzle  19 , the boom operator is provided with the knowledge that such nozzle has a set distance to go to effect contact. The marker bars also indicate the relative closure rate of the descending boom nozzle  19  to the slipway  20  and port  22 , information that can be used to accelerate or retard the boom&#39;s movement, so as to affect a gentle contact with the slipway  20  and/or port  22 . 
     As noted previously, lead-in lines systems have used parallel lines with distance indicating lines terminating in hooks outside of the lead-in lines, as indicated in FIGS. 4 &amp; 5 hereof. Thus in FIG. 4, lead-in lines  30  &amp;  32  are parallel with outside distant lines  34  &amp;  36  terminating in hooks  38  &amp;  40 , which lead-in lines  30  &amp;  32  give the direction to fuel a recess  42 , covered by closed recess doors  44  &amp;  46 , as shown. 
     Similarly, the guide way  50  of FIG. 5 has parallel lead-in lines  52  &amp;  54 , distance indicator lateral lines  56 ,  58  &amp;  60  outside of the parallel lead-in lines  52  &amp;  54 , which lateral lines terminate in hooks respectively,  62 ,  64  &amp;  66  and which lead-in lines  52  &amp;  54  point generally in the direction of fuel recess  68  and fuel port  70 , as shown in FIG.  5 . 
     The problem with the lead-in lines of FIGS. 4 &amp; 5 is, while the respective parallel lead-in lines indicate the direction to the respective fuel ports, the distance to slipway and fuel port is vague because per FIG. 3 with the fuel boom  18  and its fuel nozzle  19  blocking the operator&#39;s view of slipway and port, parallel guidelines, per FIGS. 4 &amp; 5, can not give the precise location of the beginning of the slipway and fuel port therebehind, which can cause the nozzle  19  to strike the aircraft surface  8 , before arriving at such slipway and port such as slipway  68  and port  70  shown in FIG. 5; hence the advantage of the converging lead-in lines  10  &amp;  12  with interior lateral bars  24 ,  26 , &amp;  28  therebetween, which closely indicate the distance the descending nozzle  19  has to travel to engage the reinforced slipway  20  and its associated port  22 , as shown or indicated in FIGS. 6-8 hereof. That is, the guideway  25  of the invention provides the accurate information as to direction and distance to slipway and fuel port, though they be behind the descending boom  18  and nozzle  19  thanks to the multi visual cues of converging and tapering guidelines  10  &amp;  12  and of lateral distance bars  24 ,  26 , &amp;  28  i.e. the guideway  25  of the invention shown, e.g., in FIGS. 3 &amp; 6. That is, the multi visual cues provided by the guideway of the invention include those of direction, distance to go and rate of closure of nozzle to slipway and port. 
     Thus while the overall movement of each aircraft is controlled by its respective pilot, the boom operator is responsible for connecting the two aircraft safely and effectively, without causing collisions or damage to either aircraft. The boom operator controls the movement of the boom by hydraulic or aerodynamic means, through hand-operated controls, thus the boom operator requires accurate visual information or cues from the receiving aircraft to provide depth, distance and closure rate information in order to effect the hook-up without damaging either aircraft, the boom or the boom nozzle. The converging and tapering line pattern of the guideway of the present invention provides a visually more salient means to assist the boom operator in attaining a quick and effective refueling hook-up. 
     The guideway patterns of the invention thus create a focal range that is calculated to focus the boom operator&#39;s eyes on a segment of the receiver aircraft&#39;s refueling zone (the slipway) that is designed to take the force of the boom nozzle impact prior to the boom nozzle contacting the receptacle or port. The slipway area of contact is suitably reinforced to withstand the nozzle impact; other areas of the aircraft are not. Visual contrast is substantially enhanced by providing tapered lead-in lines. Depth perception is provided by using horizontal markings within the tapered converging lines; the boom operator can judge distance, as well as rate of movement of the boom relative to those markings. This effect allows the boomer to judge the rate of closure by comparing the movement of the boom to marks on the aircraft. That is, the present invention provides direction, depth, motion and distance visual cues to the tanker boom operators, allowing the tanker to receiver connection to be completed quickly and accurately. 
     The invention is a significant improvement in air-refueling lead-in line inventions. It provides quicker, more accurate visual cues to the air-refueling tanker boom operator, so that their acquisition and contact with receiver aircraft is safer and more effective than previous lead-in line systems. This invention is important for in-flight refueling in general, because it will reduce damages due to inadvertent boom strikes on receiver aircraft. These inadvertent strikes to unreinforced areas of the receiver aircraft have been due in part to a lack of proper visual cues available to the boom operator. This lack of cues can result in misjudged distance, depth and closure rates of refueling boom to receiver aircraft, which in turn cause collisions of the boom nozzle with unprotected aircraft structures. This invention addresses these problems by providing accurate visual cues to the boom operator on the tanker aircraft. This allows faster, more accurate contacts to be made between the two aircraft, with less damage potential. 
     This invention can be adapted to any aircraft capable of being refueled in flight, which has space available for air refueling lead-in lines. Possible uses for the invention include for any craft intended for in-flight refueling, including aircraft, present and future and unmanned aircraft as well as for spacecraft.