Transportation system employing aircraft guided by rail

An aircraft which rolls along a guide rail at low speeds and attains aerodynamically airborne flight guided along the rail at high speeds. The guide rail structure includes I beams suspended end to end from spaced apart arches. The guide rails are mounted on the lower ends of the I beam and include flat bottom surfaces and curved upper surfaces that receive the wheels of the aircraft in the low speed operating mode. The upper surfaces are portions of elliptical surfaces to assure proper positioning of the aircraft wheels. In the high speed airborne mode of operation, proximity sensors on the aircraft sense the distance to the guide rail. Controls receive inputs from the sensors and adjust the flight path accordingly.

FIELD OF THE INVENTION 
This invention relates generally to the field of transportation and more 
particularly to a self-propelled aircraft which is capable of airborne 
flight along a guide rail and which rolls along the guide rail in terminal 
areas and at other times when not in flight. 
BACKGROUND OF THE INVENTION 
U.S. Pat. No. 4,402,272 to Lehl et al. discloses a transportation system 
which includes an aircraft guided along an elevated rail. The aircraft has 
wheels which roll on the rail structure when the vehicle is operating at 
low speeds such as when it is approaching or departing from terminal 
areas. The aircraft normally travels along the rail in airborne flight at 
high speed and is guided along the rail by a system that includes sensors 
and controls for adjusting the flight path according to inputs received 
from the sensors. In this manner, the aircraft and rail system accommodate 
slow speeds in terminal areas and high speeds between terminals. 
Although this type of system has considerable potential to achieve 
efficiencies in the transportation of passengers and cargo, further 
development work has indicated that there is room for improvement. In 
particular, the need for an air bearing between the guide rails and the 
aircraft involves considerable complexity both in the structures of the 
aircraft and rails and also in the pneumatic system required to supply air 
for the air bearing. The guide rail disclosed in the '272 patent is 
complicated and thus expensive to construct, primarily because the air 
bearing requires two round rails spaced apart from one another. The guide 
rail structure has two vertical plates, a top plate, the two round rails, 
and ribs that connect the rails with the rest of the structure. This 
complicated construction involves considerable expense. 
The guidance system of the aircraft is likewise rather complicated. Two 
concentric tubes are required to surround the round guide rails and 
provide the air bearing. In addition, a manifold and hose system is 
required to direct the air to the air bearing. The overall result is that 
the system is characterized by considerable complexity which increases the 
cost, the maintenance requirements, and the potential for operational and 
safety problems. 
SUMMARY OF THE INVENTION 
The present invention is directed to a transportation system which is 
reduced in cost and complexity compared to the system disclosed in U.S. 
Pat. No. 4,102,272. 
In accordance with the invention, an aircraft which carries passengers 
and/or cargo travels along an elevated overhead guide rail in alternative 
modes of travel. In a low speed mode which is generally used near 
terminals or when the craft is stopping or starting for other reasons, the 
aircraft rolls along the guide rail. In a high speed airborne mode of 
operation, the aircraft achieves aerodynamically airborne flight at a high 
speed and is guided along the rail by a precision guidance system. The 
guidance system includes sensors which are sensitive to the location of 
the rail and provide inputs to flight control components which adjust the 
path of flight according to the information received from the sensor. The 
sensors are preferably provided in modules which contain redundant pairs 
of sensors for added safety and reliability. 
The simplified construction of the guide rail and its support structure is 
an important feature of the invention. Ground mounted arches include 
upright posts or legs and a cross bar extending between the top ends of 
the posts. Carried on the arches are I beams which are arranged end to 
end. Each arch supports the adjacent ends of the I beams through a looped 
strap secured to the I beams and pinned to support bars which are mounted 
on the arch. 
The guide member along which the aircraft travels is formed by guide rails 
which are mounted on the I beams and arranged end to end. The upper 
surface of each guide rail is curved in the shape of a portion of an 
elliptical surface. A bottom surface of the guide rail is formed by two 
flat plates which extend on opposite sides of the lower I beam flange and 
are co-planar with one another and with the flange. The elliptical surface 
is formed by curved plates which connect at their outer edges with the 
outer edges of the bottom plates and at their inner edges with the web of 
the I beam. Internal spacer plates are secured to extend between the top 
plates and bottom plates to strengthen and increase the rigidity of the 
guide rail structure. Longitudinal bars strengthen and reinforce the 
connections between the curved plates and the I beam web. 
This guide rail structure exhibits the necessary strength and yet is simple 
and economical to construct. It also allows the proximal aircraft surfaces 
to be constructed in a simplified manner. The sensors are located on 
aircraft surfaces that are closest to the guide rail and are able to 
accurately sense the aircraft position relative to the rail both 
vertically and side to side or laterally. The elliptical shape of the top 
guide rail surface assures that the aircraft remains properly positioned 
on the rail when it is operated in the low speed mode. This 
"self-centering" feature of the guide rail shape, combined with its 
simplified and economical construction, enhances the practicality of the 
transportation system and represents a considerable improvement. 
Advantages for this transportation system, compared to other high-speed 
ground transport systems are: (1) minimal maintenance of the rail since no 
high speed physical contact occurs; (2) intersecting another existing 
roadway is relatively easy and inexpensive since overflying is simply a 
matter of elevation by extending the arches; (3) the land under the track 
remains available for farming, animal grazing, etc.; (4) the initial cost 
for the track system is inexpensive compared to magnetic levitation; (5) 
all-weather operation is possible.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings in more detail and initially to FIGS. 1 and 2 
in particular, a transportation system constructed in accordance with a 
preferred embodiment of the present invention includes an aircraft which 
is generally identified by numeral 10. The aircraft 10 travels in two 
different operating modes along an elongated guide structure which is 
generally identified by numeral 12. The guide structure 12 is supported on 
a plurality of spaced apart arches which are generally identified by 
numeral 14. Each arch 14 has a pair of vertical posts or legs 16 which are 
spaced apart far enough to allow the aircraft 10 to travel between them. 
The lower ends of the legs 16 are suitably secured to the ground which 
underlies the aircraft. A horizontal cross member 18 extends between the 
upper ends of the legs 16 of each arch and is preferably integral with the 
legs. Each of the cross members 18 is located at an elevated position well 
above the ground. Curved vanes 20 extend between the adjacent legs 16 on 
each side of the support structure. The vanes 20 act as gust spoilers 
which deflect and disrupt winds directed sidewardly toward the aircraft 
10. The vanes 20 may be surfaced with sound absorbing material in order to 
perform a noise abatement function. 
Each elevated cross member 18 is provided with a pair of structural bars 
22. The bars 22 in each pair are shaped identically and are spaced apart 
and parallel to one another. Each bar 22 has a bent configuration and 
presents an apex 24 located a short distance below the center of the 
overlying cross member 18. 
As best shown in FIGS. 3 and 5, the apex 24 of each support bar 22 is 
provided with an ear 26. A metal strap 28 is looped around a horizontal 
pin 30 which extends between the ears 26, thus pinning the strap 28 to the 
support structure. Side to side adjustment of the strap 28 is effected by 
a suitable adjustment mechanism 32 (see FIG. 3 in particular). 
The guide structure 12 is formed by a plurality of guide rails 34 which are 
arranged end to end and carried on the lower ends of corresponding I beams 
36 which are secured to the straps 28. With particular reference to FIG. 
5, the I beams 36 are arranged generally end to end, with one of the 
straps 28 connecting with the adjacent ends of each pair of I beams 36. 
Suitable fasteners 38 are used to connect the straps 28 with the I beams 
36. The ends of the I beams 36 are spaced slightly apart to permit thermal 
expansion. 
With particular reference to FIGS. 3 and 4, each I beam 36 has a horizontal 
top flange 36a, a horizontal bottom flange 36b, and a vertical web 36c 
which extends between the centers of the flanges 36a and 36b. Each of the 
guide rails 34 includes a pair of flat bottom plates 40 which extend 
horizontally from the opposite side edges of the bottom flange 36b. The 
plates 40 and flange 36b are co-planar and cooperate to provide a 
horizontal flat bottom surface of each guide rail 34. The upper surface of 
each guide rail is provided by a pair of curved plates 42. The outer edge 
of each plate 42 connects with the outer edge of the corresponding bottom 
plate 40. The plates 32 intersect with the web 36c and are connected with 
the web at their inside edges. Longitudinal reinforcing bars 44 are 
applied at the intersections between the top plates 42 and the web 36c to 
strengthen and reinforce these connections. The top surfaces of the upper 
plates 42 cooperate to provide a curved top surface of each guide bar 34 
which has the shape of a portion of an elliptical surface. Each guide rail 
34 is strengthened and made more rigid by a pair of spacer plates 46 which 
extend from the outer edges of the lower flange 36b to connection with the 
respective top plates 42. 
The adjacent ends of the guide rails 34 are connected in a manner 
accommodating thermal expansion and contraction. A pair of sleeves 48 are 
welded or otherwise secured to the end portions of each guide rail 34. The 
sleeves 48 are located within the guide rail near their opposite side 
edges. As best shown in FIG. 5, the sleeves 48 in the adjacent ends of the 
guide rails are aligned with one another, and each pair of aligned sleeves 
48 receives a pin 50. The pins 50 and sleeves 48 maintain the adjacent 
ends of the guide rails in alignment while accommodating expansion and 
contraction caused by thermal effects. In this manner, the guide rails 34 
are mounted end to end and provide a substantially continuous guide rail 
which is arranged to provide the desired path of travel of the aircraft 
10. Turns of the guide rail structure may be banked, and the curvature of 
the turns should be no more abrupt than can be accommodated by the 
aircraft. 
Referring to FIG. 1 in particular, the aircraft 10 has a tubular main body 
52 which provides a cabin compartment for passengers and/or cargo. The 
body 52 may be provided with windows 54 and doors 56 near the front and 
back of the craft. A cockpit 58 at the front end of the aircraft is 
suitable for accommodating one or more crew members and has a window 60 
which provides an unobstructed view from the cockpit. A pair of forward 
wings 62 extend laterally in opposite directions from the forward end of 
the aircraft body 52. Each of the forward wings 62 may have suitably 
controllable forward flaps (not shown) as well as controllable rearward 
flaps 64. The forward wings 62 are located low on the aircraft body. 
The aircraft also has a pair of rear wings 66 which are mounted near the 
back end of the aircraft on the opposite sides of an elongated box 
structure 68 mounted on top of the aircraft body 52. The rear wings 66 
extend laterally in opposite directions from the aircraft and may be 
provided with controllable forward flaps (not shown) and controlled 
rearward flaps 70. 
Additional control of the aircraft flight path is provided by forward and 
rearward fins 72 and 74, respectively. The fins 72 and 74 are oriented 
vertically and extend downwardly from the bottom of the aircraft body 52 
near its respective front and back ends. The back edge of the forward fin 
72 has a controllable rudder 76. A similar controllable rudder 78 is 
provided on the back edge of the rear fin 74. 
The aircraft is provided with a suitable propulsion system which may 
include a pair of high bypass turbo fan engines 80 or electric 
motor-driven ducted propellers 81 (see FIG. 6). The engines 80 or 81 are 
mounted on opposite sides of the box 68 near the center of the aircraft 
body 52. 
As best shown in FIGS. 3 and 4, the top of the box 68 is provided with a 
central longitudinal slot 82 which connects with a larger passage 84. The 
slot 82 and passage 84 extend the entire length of the box 68. The I beam 
webs 36c extend through the slot 82, and the guide rails 34 are located 
within the passage 84. 0n its opposite side portions, the passage 84 has 
flat bottom surfaces 84a which are horizontal surfaces parallel to and 
lying below the bottom plates 40 of the guide rails 34. The upper portion 
of the passage 84 is bounded on its opposite sides by curved surfaces 84b 
which may be portions of elliptical surfaces generally conforming with the 
shape and curvature of the top plates 42 of the guide rails. Flat vertical 
surfaces 84c are located on opposite sides of a neck portion formed at the 
area of intersection of slot 82 with passage 84. Surfaces 84c are spaced 
on opposite sides of the webs I beam 36c. 
Each side of the box 68 is provided with a pair of sensor modules 86 which 
are located near the front and back ends of the aircraft body 52, as best 
shown in FIG. 1. The sensor modules 86 may be slid laterally in and out of 
suitable compartments which receive them, and they may be locked 
releasably in place by suitable fastening mechanisms (not shown). Each 
sensor module 86 includes a pair of lower proximity sensors 86a, a pair of 
intermediate proximity sensors 86b, and a pair of upper proximity sensors 
86c. The pairs of sensors in each module are redundant such that only one 
of the sensors 86a, one of the sensors 86b and one of the sensors 86c in 
each module is active at a given time. If one of the sensors in any of the 
modules malfunctions, the paired sensor automatically takes over the 
sensing function, and a suitable indication of the malfunctioning sensor 
is given in the cockpit or elsewhere so that corrective action can be 
taken to repair or replace the malfunctioning sensor. 
As best shown in FIG. 3, the modules 86 on opposite sides of the box 68 
oppose one another. The lower sensors 86a are located on the bottom 
surfaces 84a, the intermediate sensors 86b are located along the curved 
surfaces 84b, and the upper sensors 86c are located on the vertical 
surfaces 84c. The sensors 86a, 86b and 86c may be conventional proximity 
sensors which sense the distance from the sensor to the corresponding 
conductive surface toward which the sensor is directed. For example, the 
lower sensors 86a are directed toward the bottom plates 40 and are able to 
precisely sense the distance between the sensors 86a and the plates 40. 
Sensors 86b function similarly to sense the distance between them and the 
curved top plates 42. Each sensor 86c senses the distance between it and 
the I beam web 36c. 
As shown diagrammatically in FIG. 6, the transportation system has a flight 
control computer 88 which receives inputs from the sensors 86a, 86b and 
86c. The flight control computer 88 provides an output to a forward wing 
flap drive 90 which responds to the computer output signal by suitably 
adjusting the corresponding front wing flap 64 (and/or the flap on the 
forward edge of the front wing). Another output from the computer 88 is 
applied to a rear wing flap drive 92 which suitably adjusts the flap 70 
(and/or the controllable flap on the front edge of the corresponding rear 
wing 66). A forward rudder drive 94 also receives an output signal from 
the computer and responds by suitably adjusting the front rudder 86. 
Similarly, a rear rudder drive 96 is controlled by the computer 88 to 
adjust the rear rudder 78 in a manner to achieve the desired flight path. 
The computer 88 is programmed to maintain preselected distances between 
the sensors 86a, 86b and 86c and the corresponding surfaces of the guide 
structure in order to maintain the flight path of the aircraft in the 
proper relationship to the guide structure. 
As further shown in FIG. 6, the flight control computer 88 may provide an 
output signal to a wing rotation drive 98. Because the aircraft 10 must 
fly parallel to the guide structure and is unable to "crab into the wind" 
in the manner of a conventional aircraft, somewhat unusual aerodynamic 
devices may be provided on the aircraft. For example, the wings may be 
fully pivoting or variable camber structures, the aircraft fins may be 
fully pivoting vertical stabilizers, jet deflectors may be provided, 
and/or the aircraft may have hinged wing tips. One or more of these 
devices may be suitably controlled by the wing rotation drive 98 in a 
manner to achieve the desired flight path. To add more roll stability to 
counter the effect of side winds, a hinged wingtip (not shown) may be 
provided on the forward wing. This is a novel device for aircraft 
aerodynamic control and is necessitated by the requirement that the 
vehicle remain aligned with the guideway rather than "crabbing" into the 
wind as airplanes do. This must be a rapid response wing tip deflector 
which is actuated by a suitable power driven actuator. A hinged wing tip 
control 99 controls the actuator for the hinged wing tips. 
Additional stabilization and/or control may be provided by a pair of 
anti-roll/yaw gyroscopes 100 which are located near the front and back 
portions of the aircraft body 52 (see FIG. 1). A pair of anti-pitch/roll 
gyroscopes 102 (FIG. 1) may likewise be provided near the front and back 
portions of the aircraft. The gyroscopes 100 and 102 may be constructed 
conventionally and arranged to provide flight stability and counteract the 
effects of lateral wind gusts and head wind gusts applied to the aircraft. 
The aircraft 10 is provided with pairs of front and rear wheels 104 which 
are mounted to the box 68 near its front end and toward its rear end, as 
best shown in FIG. 1. Referring additionally to FIG. 4, each wheel 104 is 
mounted within the box structure 68 and projects downwardly through 
surface 84b into the opening 84. In the low speed mode of operation, the 
wheels 104 contact and roll on the elliptical surfaces provided by the 
curved plates 42 of the guide structure. The rotational axis of each wheel 
104 is parallel to a line tangent to the surface of plate 42 at the place 
of contact between the wheel and the plate 42. Thus, the wheels 104 
provide a "self-centering" feature which assures that the aircraft will be 
suitably centered on the guide rail 34 in the low speed mode of operation. 
Each wheel 104 is driven by a conventional electric drive unit 106. 
Electrical power for the ducted propellers 81, drive units 106 and other 
electrically operated devices may be provided by conductor wires 108 which 
are mounted to extend along the center of the lower I beam flange 86b. The 
wires 108 are insulated from the I beam by an insulator 110. Conductors 
(not shown) leading from a suitable power source connect with the 
conductor 108 which functions in the manner of a conventional trolley 
wire. The conductor 108 is engaged by a spring loaded electrical contact 
112 carried on the aircraft 10 and insulated by a suitable insulator 114. 
Suitable wiring (not shown) extends from the contact 112 to the drive 
units 106 and other electrically operated devices within the aircraft. As 
can be seen by comparing FIGS. 3 and 4, the contact 112 can extend and 
retract to accommodate both airborne and rolling travel of the aircraft 
while maintaining electrical contact with wire 108. 
The contact 112 may take the form of an arm having universal joints (such 
as ball and socket joints) on both ends. The top end of the arm is guided 
along a channel. The electric power may be three-phase power, with the 
three conductor wires of the electrical system contacted by sliding 
brushes (not shown) carried on the top end of the contact 112. This type 
of system allows continuous supply of power from the rail system to the 
vehicle. 
As an alternative to the turbofan engines 80 and the electrical drive units 
106, the propulsion system for the aircraft may be provided by ducted 
propellers housed in external nacelles 81 (FIG. 6) and powered by electric 
motors (not shown). In this case, the propellers provide propulsion for 
the airborne flight of the aircraft and also for the low speed rolling 
operation of the aircraft, the wheels 104 being idle or free wheeling 
units. Braking is accomplished by reverse pitch of the propellers. 
Electrical power for the drive motors of the propellers is provided 
through the conductor 108 and contact 112. 
To counter the effect of a steady side wind, thruster vanes 81a at the aft 
end of the propulsion cowling 81 direct the exiting air to create a 
transverse force preventing transverse movement of the vehicle. 
While propulsion can be provided by either turbofan engines or electric 
ducted propellers, the propellers have a number of benefits and are 
preferred in most applications. The ducted propeller drive system is 
advantageous in that it is quiet, non-polluting and reduced in weight 
because there is no need to carry fuel (which can make up 30% of the 
weight of a transport aircraft). Also, there is no need for fueling stops. 
Because terminals would likely be in downtown areas or other areas of 
dense population, fueling with jet fuel at terminals is impermissible. 
Thus, a fuel carrying craft would require an added stop at a fueling depot 
away from heavily populated areas. Ducted propeller drives are also better 
able to make use of side-vectored thrust which can be obtained through the 
use of simple vanes. With propeller systems, the wheels need not be 
driven, as previously indicated. Finally, fore and aft forces on the rail 
system are eliminated, and thrust and braking can both be accomplished by 
variable and reversible blade pitch. Forces on the arches in their weakest 
direction are thus avoided. 
As shown in FIG. 6, the front and rear parts of the vehicle are equipped 
with sets of buffer wheels 116 which are preferably surfaced with hard 
rubber. Their purpose is to prevent metal to metal contact if the craft 
should undergo a large deflection. The main wheels 104 assist in the 
buffering function. The buffer wheels 116 are in a transverse plane which 
is offset from but near the proximity sensors. 
It is contemplated that the transportation system may have tracks allowing 
two vehicles to travel in opposite direction. In the two track system, the 
rails can be located side by side or one above the other and supported in 
a manner similar to but somewhat more complicated than what has been shown 
and described. 
In operation, the transportation system may be used to transport passengers 
and/or cargo between terminals located along the guide structure 12. After 
the passengers and/or cargo have been loaded into the aircraft, the drive 
units 106 are activated to propel the aircraft 10 along the guide 
structure 12 in the low speed mode of operation wherein the wheels 104 
roll forwardly along the upper plates 42 of the guide rails 34. Normally, 
the terminal area will be in an area where noise is objectionable, so the 
engines 80 will usually not be operated until the aircraft is well away 
from the terminal area. The engines 80 can be activated to propel the 
aircraft as it approaches flying speed (such as 70-80 knots). The 
aerodynamic capabilities of the aircraft will then provide sufficient lift 
to lift the aircraft slightly from the position shown in FIG. 4 to the 
flight position shown in FIG. 3. Then, the wheels 104 will be displaced 
from the guide rail 34 so that undue friction is avoided. In the high 
speed airborne operating mode of the aircraft which is depicted in FIG. 3, 
the guidance system operates to automatically maintain the aircraft in the 
programmed position relative to the guide rail 34 (the position shown in 
FIG. 3). 
Prior to the approach of the aircraft to another terminal, the speed is 
reduced to less than that necessary to maintain airborne flight, and the 
aircraft is lowered from the position of FIG. 3 to the position of FIG. 4 
wherein the wheels 104 are in contact with the guide rails 34. The 
aircraft is thereafter propelled in the low speed mode to the terminal 
area, at which point the aircraft is stopped for unloading and/or loading 
of passengers and/or cargo. It is noted that the wheels 104 remain in a 
position to come into contact with the guide rails whenever the aircraft 
loses flying speed. Two or more aircraft can be coupled together (see FIG. 
1) by conventional coupling devices to provide a multiple unit "train" of 
aircraft. 
The construction of the guide rail 12 and its supporting structure is 
simple and economical. In addition, the upper sensors 86c are located such 
that they can precisely control the side to side position of the aircraft 
by sensing the position of the I beam web 36c. The lower sensors 86a are 
located on the flat surfaces 84a and sense the distance to similar flat 
surfaces on plates 40 to provide precise guidance of the aircraft. Thus, 
the configuration of the guide rail 34 and its support structure 
(especially the I beam 36) enhances the precision of the guidance system. 
From the foregoing, it will be seen that this invention is one well adapted 
to attain all the ends and objectives hereinabove set forth together with 
other advantages which are obvious and which are inherent to the 
structure. 
It will be understood that certain features and subcombinations are of 
utility and may be employed without reference to other features and 
subcombinations. This is contemplated by and is within the scope of the 
claims. 
Since many possible embodiments may be made of the invention without 
departing from the scope thereof, it is to be understood that all matter 
herein set forth or shown in the accompanying drawings is to be 
interpreted as illustrative and not in a limiting sense.