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 fig2 & 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 fig6 . 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 fig4 & amp ; 5 hereof . thus in fig4 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 fig5 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 fig5 . the problem with the lead - in lines of fig4 & 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 fig3 with the fuel boom 18 and its fuel nozzle 19 blocking the operator &# 39 ; s view of slipway and port , parallel guidelines , per fig4 & 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 fig5 ; 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 fig6 - 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 fig3 & 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 .