Note: Descriptions are shown in the official language in which they were submitted.
CA 02840823 2014-01-28
=
1
VERTICAL TAKE-OFF AND LANDING
ROADABLE AIRCRAFT
FIELD OF THE INVENTION
The invention relates to a type of roadable aircraft which in one
configuration
operates like a convention road vehicle, and in another configuration operates
like a
highly manoeuvrable multicopter with vertical take-off and landing ability.
BACKGROUND
Concepts of vehicles which can be driven on land and flown in the air have
been
proposed ever since the first automobiles and aircrafts were invented. A
century later
in spite of many developments in automobile and aircraft technology, a
roadable
aircraft which may have useful application still remain to be invented.
Roadable aircrafts are commonly known by several other names such as flying
cars, flying jeeps, and others. The design of roadable aircrafts is an
exercise of
intense compromise in the choice of concept, performance and appearance. The
design of roadable aircrafts is made difficult basically because of the
conflicting
design requirements of aircrafts and road vehicles. Aircrafts need fixed-wings
or
rotary-wings of significant size in order to achieve flight with reasonable
efficiency.
Road vehicles on the other hand, have considerable size and shape restrictions
so
that they can fit in the general traffic, and use public infrastructures such
as roads,
tunnels and bridges. Roadable aircrafts usually need to undergo complex
transformation whenever they switch between road and flight configurations.
Practical concepts of roadable aircraft require design solutions which enable
the
flight components, such as the wings or rotors, to be easily deployed or
stowed away
in a compact arrangement whenever required, and preferably within the vehicle.
The
transformation should further necessitate minimal effort of the user, and is
preferably
automated.
CA 02840823 2014-01-28
= = 2
Over the years, many concepts of roadable aircraft with a wide variety of
shapes
and performances have been proposed. However, most of these concepts failed to
meet general acceptance. Roadable aircrafts which are based on fixed-wing or
unpowered rotary-wing concepts, can only be operated from an airport facility
or
require at least a runway in order to take-off and land. Those based on
powered
rotary-wings which are not shrouded still need to be operated from helipads or
dedicated areas away from obstacle for safety reasons. The need of a roadable
aircraft is quite questionable. As a matter of fact, roadable aircrafts would
always
have poor flying performance compared to aircrafts in general. The extra
features
and components that are included in these vehicles constitute an extra weigh
penalty
and also degrade the aerodynamic significantly. However in spite of the
obvious
disadvantage, roadable aircrafts can have useful applications.
The need of a roadable aircraft, with vertical take-off and landing (VTOL)
capabilities is strongly felt in the way warfare is conducted in the modern
days. Given
that no existing design concepts met the requirement for such a vehicle, DARPA
which is an agency of the US department of defence launched a public
solicitation
recently in the hope that a practical solution may be found. Aircrafts and
helicopters,
as has been found by experience, are not very effective in guerrilla warfare
or any
other military missions conducted in urban setting. In these setting, the
military still
have to rely on land vehicles. Land and road vehicles have increasingly become
more and more vulnerable to ambushes as they are confined to predictable
routes,
and the weaponry of the insurgent has gradually increased in sophistication.
VTOL
roadable aircrafts would have the ability to avoid these treats, and fly above
obstacles and damaged infrastructures. VTOL roadable aircrafts would also be
able
to operate in very rugged terrain where conventional off-road vehicles would
be
ineffective. The ability of these types of vehicles to effectively carrying
out missions
with fewer casualties would allow significant cost reduction compared to land
vehicles. VTOL roadable aircrafts can also fulfill several of the missions
that are
traditionally reserved for helicopters more cost effectively. Roadable
aircrafts would
operate as land vehicle most of the time, and flying only in case of
necessity. The
reduction in flying time results in appreciable saving in fuel and maintenance
cost
compared to helicopters, while maintaining many of the operational advantages.
Similarly, these types of vehicles can have useful non-military application.
These
CA 02840823 2014-01-28
=
= 3
vehicles can be used in areas where road infrastructures are few and poor.
They can
be used on humanitarian missions in disaster areas, when infrastructures have
been
partly destroyed following an earthquake or rended inaccessible due to
flooding or
other fatalities. These vehicles could also be routinely used in cities, as
air
ambulances or security patrols, which would avoid traffic jams and access
areas
faster and more effectively than helicopters.
VTOL roadable aircrafts which can meet these challenging requirements need to
be of convenient shape and size, have good road qualities, and at the same
time
have a reasonable flight range and efficiency. Given that such a vehicle would
3.0
operate mostly at low altitude with numerous landings in unprepared locations,
it
should have good hovering capability and excellent manoeuvrability at low
speed,
similar to helicopters. The conversion time between road and flight
configurations
need to be very short, and transformation preferably achieved without the need
of
having to stop, since such vehicle may have to operate in hostile environment.
It is
also important that the propulsion system can be safely operated in crowded
public
places, road or roof top. As such, the speed and temperature of the downwash
wind
from the propulsion system should not be harmful to humans and
infrastructures.
Similarly, the propulsion system should not become damage, or cause injuries
to
people in normal operating circumstances.
Concepts of VTOL roadable aircrafts that have been proposed in the past do not
have these desirable capabilities as mentioned above, in order to be effective
in
battlefields or as rescue vehicles. For example, both patents US 3261572 and
US
5915649 disclosed VTOL roadable aircrafts that make use of large open rotors
when
configured for flight. The large diameter of the open rotors achieve low disk
loading
with an acceptable efficiency and downwash comparable to helicopters. However,
the dangers inherent to open rotor impose many constrains and restrictions in
the
use of these vehicles. The use of VTOL concepts that that been tested in
aircrafts,
are not very encouraging either. VTOL concepts, such as tilt-wings, tilt-
rotors, rotor-
in-wings are complex technologies and for that reason are not widespread in
aircrafts even today, and most probably may not be suitable for application in
roadable aircrafts, where prolonged slow speed and manoeuvrability is of
upmost
importance.
CA 02840823 2014-01-28
" 4
SUMMARY OF THE INVENTION
The main object of the invention is to provide for a concept of a road or land
vehicle which can be configured into an efficient and highly manoeuvrable VTOL
aircraft.
Another object of the invention is to provide for a VTOL roadable aircraft
which
can be safely and quickly converted or transformed between ground and flight
configuration.
Also another object of the invention is to provide for a VTOL roadable
aircraft,
which can be operated safely in close proximity of humans and in urban
environment.
The embodiments of the invention achieve these objects by disclosing several
features. Accordingly, the concept of a roadable aircraft is disclosed
comprising of a
fuselage or the body of a road vehicle wherein the engine rotates the wheels
or a
plurality of propellers selectively, depending whether the vehicle is
configured for
road or flight. The invention comprises methods and means which enable several
shrouded propellers or rotors to be conveniently stowed one above another on
the
roof of the vehicle, so that each of the propellers can be designed almost as
large as
the legal permissible road footprint of the vehicle. The invention provides a
reliable
means which enable the propellers to be deployed and retrieved with minimum
effort
of the pilot. Means and method, describing how the rotor hubs of the
propellers
connect to the driveshaft of the powerplant onboard the vehicle, are also
provided.
When the vehicle is configured for flight the propellers are deployed and
positioned
laterally about the vehicle. The propellers are then powered in order to
produce the
required amount of thrust so as to enable flight. The combined large disk area
of all
the propellers ensures a low disk loading and better efficiency. The vehicle
is
operated similarly to air vehicles commonly referred as mutitirotor.
Embodiments of
the invention can be configured in quadcopters, or with lesser or higher
numbers of
propellers. The vehicle takes-off and lands vertically and is highly
manoeuvrable.
The claimed invention is a great improvement on earlier concepts of roadable
aircraft comprising of a plurality of rotors or propellers. In disclosed
patents as shown
in US 5505407 and US 2010/0294877 the shrouded or ducted rotors encased in the
CA 02840823 2014-01-28
body of the vehicle are of relatively smaller diameter with a significant high
disk
loading, making these vehicle unsuitable for prolonged hovering. Other earlier
disclosed proposals are either unpractical for road with the propellers
permanently
fixed to the side of the vehicle, or unsafe with the propellers purposely
designed
5 without shrouds so as to facilitate their retrieval and stowing. Designing
an
acceptable and reliable system that would deploy and retrieved shrouded
propellers
is challenging. In patent US 2013/0068876 the proposal comprises of a method
of
retrieving and stowing shrouded propellers on the side of the vehicle. The
proposed
system occupies much of the useful space inside the vehicle and at the same
time
limit access inside the vehicle from the side.
Air vehicle with a plurality of propellers or rotors is a widely tested
concept and is
indeed quite popular in unmanned drones. Manned air vehicles comprising of a
plurality of propellers such as the Curtiss- Wright VZ-7 have been
successfully tested
in the past. The use of a plurality of propellers in roadable aircraft is a
promising
concept. The ways and method how this can be successfully achieved, and the
invention itself will be best understood, by reference to the following
description in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The embodiments of the invention are described with reference to the following
drawings:
FIG. 1 is a perspective view of the vehicle configured for use on the road in
accordance with an embodiment of the present invention, with the propellers
stowed
in the storage compartment.
FIG. 2 is a perspective view of the vehicle shown in FIG. 1, configured for
flight
with the propellers deployed from the storage compartment.
FIG.3 is a top view of the vehicle in FIG. 1, with the storage compartments
removed in order to show the plurality of propellers stowed above the roof of
the
vehicle.
CA 02840823 2014-01-28
6
=
FIG.4 is a top view of the vehicle in FIG. 2, with the storage compartments
removed and shows the propellers in a deployed position for flight, in
accordance to
the present invention.
FIG.5 is a front view of the vehicle in FIG. 2, configured for flight with the
propellers deployed.
FIG.6 is a top view of another embodiment of the invention comprising of a
plurality of propellers, with the top cover of the storage compartment
removed.
FIG. 7 is a perspective view of the transmission pod which secures the
propeller
to the structure of the vehicle, in accordance with the present invention.
FIG.8 is a side elevation of the vehicle shown in FIG. 1, illustrating the
internal
schematic layout of the powerplant, the transmission, and the driveshafts with
connect the propellers and the wheels.
FIG.9 is a perspective view of another embodiment of the present invention
with
individual drive systems showing the layout of the plurality of powerplants
and the
transmission system.
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the invention are described with reference to the accompanying
drawings. Corresponding components in different drawings and components having
similar functions in all the drawings are designated by the same numerals.
While one
particular embodiment of the invention is described in detail, one skill in
the art will
understand that other embodiments may have different structures and could be
based on a variety of methods of constructions, designs, and choice of
technologies.
General concept:
FIG.1 shows the vehicle 100 when it is configured for use on the road. The
vehicle 100 has the appearance and features of a typical road vehicle. The
vehicle
100 is designed to have off-road abilities, but other embodiments of the
invention
may be designed for better or worse road conditions, and may also include
CA 02840823 2014-01-28
.. . = 7
'
amphibious abilities. The coachwork 101 of the vehicle 100 has preferably
the box-
shape appearance of a van, which may be of monocoque construction or mounted
on a chassis or frame which support all components of the vehicle 100. A
plurality of
wheels 102 support the vehicle 100 on the ground, and enable motion of the
vehicle
100 when any of the wheels 102 are powered by the powerplant on board. The
wheels 102 are fitted with suspension mechanisms for good road handling
capacity
and comfort. Side doors 103 enable easy access inside the vehicle 100. The
interior
is designed according to requirement to suit the number of passengers and the
type
of goods expected to be carried inside. In FIG. 8 the embodiment comprises of
a
number of front and back seats 111, in accordance to a layout common in
typical
road vehicles with a cargo space at the rear. Since the vehicle 100 is also an
aircraft,
great effort is taken in optimising overall design so as to reduce weight,
where
intensive use is made of light construction material, so as to maximise the
payload
during flight.
When the vehicle 100 is configured for flight as shown in FIG. 2, a plurality
of
propellers 104 are deployed from the storage compartment 105 on either side
around the vehicle 100 and firmly locked into flight position. The process of
conversion transforms the vehicle 100 into an aircraft which resembles a
quadcopter,
with similar flight capabilities and characteristics. Other embodiments of the
invention
may comprise of any suitable numbers of propellers 104. The operation of the
propellers 104 produces aerodynamic lift, which enable the vehicle 100 to
achieve
flight with a high degree of manoeuvrability and appreciable efficiency. The
propellers 104 in the illustrated embodiment are shrouded, with the upper and
lower
openings preferably covered by wire mesh or wire guards, so as to enable very
safe
operation in close proximity to people and structures. As used herein, the
term
"propeller" refer to a system comprising of a plurality of blades or wings
secured to a
rotating hub so as to produce aerodynamic thrust, including those rotor and
rotary-
wing systems that are used in air vehicles such as helicopters and multi-
rotors
aircrafts. The propeller could in some other embodiments of the invention
comprise
of a plurality of small pulsejet or jet engines assembled together in order to
have the
general shape of the propeller shown in the accompanying drawings. The term
"propeller" would also generally refer to any kind of thrust or lift producing
devices
CA 02840823 2014-01-28
' .
, 8
=
=
= designed and adapted so as to have the functional ability to be
retrieved, deployed
and stowed as described in this application.
Stowing the propellers 104 one above another, on the roof of the vehicle is a
fundamental aspect of the invention. This enables several propellers 104 of
appreciable large diameter to be fitted to the vehicle 100, so that the
vehicle has a
small footprint when it is configured for road. The diameter of each of the
propellers
104 may be designed as large as it is practically possible in order to
maximise
efficiency, but not exceeding the maximum dimension allowable for road
vehicle, if
the vehicle 100 is to be used on public road. In general, the diameter of each
of the
propellers 104 will be as large as the width of the vehicle 100.
The combined larger disk area provided by all the propellers 104 together
enables considerable reduction in the disk loading, leading to lower power
requirement and higher flight efficiency. This further enable a reduction in
the size
and power rating of the powerplant fitted in the vehicle 100. By optimising
the design
of the vehicle 100, it is practically possible to achieve disk loading to
within 10 lb/sq.
ft or even less. Such roadable aircraft would have flight efficiency and range
practically equivalent to some typical helicopters. Other embodiments of the
invention may also be designed to operate at a disk loading relatively higher
than in
helicopters when the flight efficiency is of lesser concern, especially when
flight is
occasional and of short duration.
A mechanical means is also disclosed which secure the propellers 104 to the
vehicle 100, while at the same time enable the propellers 104 to be stowed
above
one another on the roof of the vehicle 100, and to be readily deployed on the
side of
the vehicle whenever required. The disclosed method also enables the
propellers
104 to be deployed or retrieved as required with relative simplicity, as will
be
described further.
Transmission pod and propeller deployment and retrieval system:
The storage compartment 105 as shown in Fig. 1 and Fig. 2 is an enclosed
volume or space with several openings 110 on the sides. The propellers 104 are
stowed inside the storage compartment 105 when the vehicle 100 is configured
for
road. When the vehicle 100 is configured for flight, the propellers 104 pivot
about
CA 02840823 2014-01-28
9
their respecting supporting elements out of the storage compartment 105
through the
openings 110.The openings 110 will usually be equipped with suitable shutters
or
covering mechanism which would prevent the ingress and accumulation of dust
and
particles in the propellers 104, while they are stowed away for long duration.
The
storage compartment 105 also accommodates the mechanisms that secure and
operate the propellers 104. The storage compartment 105 contributes to provide
an
ecstatic appearance to the vehicle 100 when it is configured for road, with
the
propellers 104 retrieved inside the storage compartment 105. The storage
compartment 105 also provides protection to the propellers 104 and associated
components from damage and degradation when the vehicle 100 is used as a road
vehicle in a hostile environment. In other embodiments of the invention where
the
aim to reduce weight penalty is high, the storage compartment 105 may simply
denote or describe the space above the roof 108 of the vehicle 100 where the
propellers 104 can be retrieved and stationed while not in use.
In FIG. 3 and FIG. 4, the storage compartment 105 has been removed in order to
shows with clarity the propellers 104 in the retrieved and deployed positions
on the
roof 108 of the vehicle 100. Each propeller 104 is secured to the vehicle 100
at
appropriate location around the edge of the roof 108, as shown on a mechanical
system that is labeled as the transmission pod 50. The transmission pod 50 is
an
important aspect of the invention which combines together several functions in
order
to enable reliable operation of the vehicle 100. The transmission pod 50
comprises:
a means to secure the propellers 104 to the vehicle 100; a means to connect
the
driveshaft from the engine side to the rotating part of the propellers 104; a
means to
enable the propellers 104 to pivot about the point of support so that the
propellers
104 can be deployed for flight or retrieved in the storage compartment 105;
and a
means to lock the propellers 104 in the deployed or retrieved position.
Each propeller 104 is secured to the side of the vehicle 100 at a different
height,
so that each propeller 104 can occupy separate levels inside the storage
compartment 105, as shown in FIG. 5. Hence the propellers 104 do not cross the
path of each other, as they pivot between the deployed and retrieved position.
It is
understood that the diameter of the propellers 104 need to be correctly
chosen, so
that they can pivot and freely move into the space between the plurality of
adjacent
CA 02840823 2014-01-28
transmission pod 50 which secure the others propellers 104, while being
retrieved for
storage or deployed for flight.
When the propellers 104 are deployed for operation, they are preferably
positioned as shown in FIG. 4. Viewed from the top, the propellers 104 are
5
positioned so that they are lateral and symmetrical about the vehicle 100, as
this
arrangement simplifies the flight control process and systems. View from the
front
however, the propellers 104 are off-set relative to each other, as shown in
Fig. 5.
However as the thrust of the propellers 104 are generally directed
perpendicular to
the horizontal plane of the vehicle 100, this dissymmetry has little
significant
10
incidence on the flight characteristics of the vehicle 100, which in any case
can be
easily compensated by adjusting the amount of thrust from the propellers 104
individually, if required. The low center of gravity of the vehicle 100
relative to the
resultant lift produced by the propellers 104 on the other hand, greatly
contributes to
the stability of the vehicle during flight.
The illustrated embodiment of the invention comprises of four set of
transmission
hub 50, where each of the transmission pod 50, support a single propeller 104.
The
vehicle 100 is also designed to have a rather square footprint so as to
maximise the
area of the propellers 104 that can be stowed within the available footprint
of the
vehicle 100. Other embodiments of the invention can comprise of different
numbers
of transmission pod 50. In some yet another embodiment more than one set of
propeller 104 may be secured and powered by the same transmission pod 50.
Other
embodiments of the invention may be design to have a rectangular footprint,
and in
these cases the plurality of propellers 104 are stowed, one above another and
side
by side. One such embodiment of the invention is shown in Fig. 6, where the
vehicle
300 has the length about twice the width, with as many as eight propellers 104
deployed around the vehicle. When the vehicle 300 is configured for road, the
eight
propellers 104 are stowed on four separate levels, whereby on each level two
propellers 104 are stowed side by side. A single transmission pod 50 is used
to
secure and power two set of propellers 104.
As shown in FIG. 7, the propeller 104 comprises of a hub 57 with a plurality
of
blades 71, rotatably mounted within a set of support frames 72. The support
frames
CA 02840823 2014-01-28
11
72 also secure the shroud 73 so as to make the operation of the blades 71
safe. The
top and bottom openings of the propeller 104 may be further covered with wire
guards so as to enhance safety. The support frames 72 of the propeller are
solidly
secured to the support component 52. As the support component 52 is rotatably
mounted to the shaft 51, this enable the propeller 104 to be pivoted about the
longitudinal axis of the shaft 51. This mechanism allows the propeller 104 to
be
pivoted about, so as to be deployed for flight or retrieved and stowed above
the roof
of the vehicle 100. As the shaft 51 is also used as a means to transfer
rotational
mechanical energy from the engine to the rotor hub 57, the shaft 51 is also
rotatably
io mounted to the structures of the vehicle 100 by at least one support
component 53.
In the illustrated embodiment, the gearbox 58 which connect the lower end of
the
shaft 51, also provide addition support to the shaft 51, and also rotatably
secure the
shaft 51 to the structure of the vehicle 100. In other embodiment additional
support
component 53 may be required to reliably secure the shaft 51 to the structure
of the
is vehicle 100. The rotatable support components 52 and 53 comprise of
roller or thrust
bearings enclosed within appropriate housing arrangements, which minimise
friction
between the connecting parts.
The upper support component 52 is made to rotate clockwise and anticlockwise
by some define amount about the axis of the shaft 51 by the operation of a
worm
20 drive mechanism. This enable the propeller 104 to pivot in and out of
the storage
compartment 105 as required during configuration for road or flight. As shown
in FIG.
7, the worm drive mechanism comprises of a worm gear 54 which is secured to
the
upper support component 52, and a worm 55 which is connected to the drive
shaft of
the motor 56. The motor 56 is secured to the fixed structure of the
transmission pod
25 50 on the roof 108, within the spare space of the storage compartment 105.
The
motor 56 is preferably an electrical stepper motor which has the advantage of
having
relatively simple positioning control system, however any other type of
electric motor
or any suitable electrical, mechanical, or pneumatic device with a reliable
positioning
system can be used. A means to lock the upper support component 52 in the
desired
30 position as required by the operating configuration of the vehicle 100
is provided. A
non-reversible worm drive has the advantage not to require such locking
mechanism. However, addition securing devices may be included, if the gears of
the
CA 02840823 2014-01-28
= 12
worm drive may not withstand prolonged mechanical stresses, or if some other
types
of reversible gear mechanisms are used.
The shaft 51 also transfers the rotational energy from the powerplant to the
rotor
hub 57. The shaft 51 can be relatively short in some embodiments, wherein the
lower end connects to the transmission shaft of the powerplant by a
combination of
suitable coupling devices, such as gearbox and additional transmission shafts
which
are routed in any convenient way in the vehicle. In the illustrated
embodiment, the
shaft 51 is a continuous vertical shaft which connects to a gearbox 58 in the
lower
section of the vehicle 100. The gearbox 58 couples the shaft 51 to the
horizontal
transmission shaft 59, which connect to the transmission 205 below the cabin
of the
vehicle 100 as shown in Fig. 8. The upper end of the shaft 51 is coupled to a
sprocket gear 60 which transfer the rotational energy to another sprocket gear
61
secured to the rotor hub 57 by mean of a roller chain 62. Other means of
suitable
mechanical power transmission systems such as belt drive or gearbox and drive
shaft mechanism may also be used. The overall gear ratio of the drive system
from
the rotor hub 57 to the output shaft of the engine 200 has to be as per design
requirement so that the rotational speed of the rotor hub 57 is within the
required
operating range. In other embodiments, as shown in Fig. 6, the transmission
pod 50
may comprise of additional support component 52 with separate worm drive to
secure and operate addition propeller 104.
Persons of skill in the art will understand the mechanical system which secure
the
propellers 104 to the vehicle 100 and which enable retrieval and deployment of
the
propellers, as described herein is not limited to the specific embodiment just
described. Thus any other securing means may be provided which can reliably
deployed the propellers 104 from the roof of the vehicle 100, and then
positioned the
propellers 104 on the side of the vehicle so as to enable flight, and which
later may
be retrieved back on the roof of the vehicle so as to enable operation as a
road
vehicle, as and when required. Similarly, while in the description herein a
mechanical
means is used to transfer power from the powerplant to the rotor hub 57, in
other
embodiments of the invention other means based on electrical or compressed
fluid
may be used. In yet other embodiment, the powerplants may be contained within
the
individual propellers 104.
CA 02840823 2014-01-28
. . .
13 -
The propeller 104 is designed for maximum efficiency as the diameter of the
rotor
is limited by the maximum allowable footprint of the vehicle 100. The
thickness of the
propeller 104 is also preferably made as small as it is practically possible,
so that the
storage compartment 105 is not excessive bulky and the vehicle is of an
acceptable
overall height. Such consideration would influence many of the design of the
propeller such as the number of blades 71, the speed of rotation of the hub
57, the
shape of the shroud 73. The blades 71 can be designed to have a fixed pitch so
as
to simplify the construction of the rotor hub 57. However blades 71 with
variable pitch
rotating at fix speed has the advantages of reducing the design complexity of
the
transmission 205, especially when a single engine 200 is used to power all the
propellers 104 at the same rotational speed. Efficiency of the propeller 104
and the
amount of aerodynamic thrust can be further increased by using a pair of
contra-
rotating propeller blades preferably within the same shroud 73. In this
arrangement
the sprocket gear 61 drives two separate set of blades on two separate rotor
hubs
57, about the same axis in counter-rotation by mean of appropriate gear
mechanism
within the two rotor hubs 57.
Powerplant and transmission:
The poweplant as understood in the description herein refer to the equipments
and the power source on board the vehicle 100 which drive the propellers 104
by
any suitable transmission system. As shown in FIG. 8, the vehicle 100 is
powered by
an engine 200 in both it roadable and in flight mode. The engine 200 can be of
any
type such as, combustion, electrical, gas turbine, or of any hybrid design, as
long as
it can reliably and efficiently power the vehicle 100 in both modes. The
engine 200
may also comprise of a plurality of independent engines couple together so as
to
increase reliability. Given that the power requirement during and flight mode
are very
different, embodiments of the invention may comprise of one type of engine to
power
the vehicle during road configuration, and another type of engine to power the
vehicle during flight configuration. One possible choice of powerplant is the
turboshaft engine. Turboshaft engines are widely used to power helicopters
because
of their high reliability, high energy output, compactness and low weight.
During road
configuration the wheels 102 may be driven by less powerful alternative engine
or
CA 02840823 2014-01-28
14
electrical motors which run on energy produced by the same turboshaft engine
and
stored in electrical accumulators.
The wheels 102 are powered in a four-wheel drive arrangement by the engine
200 through the transmission or gearbox 201, the shaft 202 and the
differentials 203.
Other embodiments of the invention may be designed as front-wheel or rear-
wheel
drive. The propellers 104 are powered through a set of horizontal drive shafts
59
connected to the gearbox 205. The gearbox 205 is powered by the engine 200
thorough the transmission 201. The design of the gearbox 205, as will be
described
further depend on the choice of propeller 104 which maybe of the fixed or
variable
pitch type. The transmission 201 drives the wheels 102 or the propellers 104
selectively with the appropriate gear ratio. The transmission 201 may allow a
rolling
take-off, that enables the vehicle to transit from road to flight mode without
the need
to stop. During rolling take-off, the transmission 201 continues to power the
wheels
102 until the vehicle 100 has taken-off from the ground.
It should be understood that the transmission systems and the shafts system
which couple the wheels 102 and the propellers 104 to the engine 200 can be
designed in a variety of ways. In the illustrated embodiment separate gearbox
devices 201 and 205 has been preferred. In another embodiment a single gearbox
may be used instead, with as many outgoing shafts to rotate the propellers 104
or
the wheels 102. In yet other embodiment a single outgoing driveshaft from the
main
transmission gearbox may be made to drive the wheels 102 or the propellers 104
with the help of appropriated coupling and clutch mechanism.
Given that the vehicle 100 is designed for flight, the mass center of the
vehicle
100 is generally located in the middle in alignment with the resultant lift
produce by
the propellers 104, so as to achieve a stable and controllable flight. As
such, a rear
mid-engine arrangement is preferred as it enables the engine 200, which is
heavier
and more bulky than engine commonly used in conventional road vehicle, to be
installed without major difficulty, while the passengers and payload are
located rather
at the front. This arrangement enables a good weight distribution, while at
the same
time provides good forward vision for the driver/pilot necessary during slow
flight and
CA 02840823 2014-01-28
=
precise manoeuvring. The rear location of the engine 200 also ensures a
reduction
of noise level inside the cabin.
Flight control:
In order to achieve flight, the four set of propellers 104 are operated in a
similar
5 way as a conventional quadcopter or other multirotor vehicles. The plurality
of
propellers 104 produces thrust generally directed downward which enable the
vehicle 100 to achieve vertical take-off, vertical landing, hover, and
horizontal flight.
The plurality of propellers 104 operates coaxially so that the reactions of
the
propellers 104 on the vehicle 100 cancel each other mutually during normal
10 operation, so the need of lateral anti-torque rotor as found in most
conventional
helicopter is avoided. The propellers 104 are positioned preferably
symmetrically and
laterally opposite each other. The resultant thrust generated by the
propellers 104
need be aligned with the center of gravity of the vehicle 100, in order to
achieve
stable flight. The propellers 104 are preferably of identical construction.
Lateral
15 displacement and forward flight is achieved by pitching the vehicle 100 in
the
direction of the flight. Pitching is generally done by varying the thrust of
single or
group of propellers 104 relative to other group of propellers 104. Yaw control
can be
achieved by modulating the speed of one or group of propellers 104 relative to
other
group of propellers 104 so that the reactions of the propellers 104 on the
vehicle 100
do not completely cancel each other. The resulting turning moment causes the
vehicle 100 to turn about its vertical axis and hence to be steered in the
desired
direction.
The pitch of the blades 71 may be permanently fixed or adjustable. When the
pitch of the blade 71 is adjustable, the rotor hub 57 will generally rotate at
constant
speed and the amount of aerodynamic thrust is modulated by adjusting the pitch
of
the blades 71. The gearbox 205 is of simple mechanically construction because
all
the outgoing shafts 59 rotate at the same speed. When the pitch of the blades
71 is
fixed, the modulation of aerodynamic thrust is achieved by modulating the
speed of
rotation of the rotor hub 57. In this case the gearbox 205 would include means
to
modulate the speed of rotation of the outgoing shafts 59 independently. Such
CA 02840823 2014-01-28
..
. . ,
'= 16
-
=
means may comprise of externally mounted devices on the outgoing shafts 59
such
as fluid coupling mechanisms or electromagnetic clutches.
The propeller 104 may comprise of two set of rotor hubs 57 with respective
blades 71 operating in counter-rotation similar to contra-rotating propellers
or rotors,
within a single shroud 73. In spite of the relative mechanical complexity of
the
design, such contra-rotating propellers 104 are of particular advantage for
use in the
vehicle 100 where the total disk area remains limited by the dimension of the
storage
compartment 105, and legal restriction. As contra-rotating propellers 104
produce
more thrust for a given disk area, they contribute significantly in reducing
the size of
the engine 200, and improve the efficiency of the vehicle 100. The contra-
rotating
blades of the propellers 104 may be of the fixed pitch or variable pitch type,
and
would require the appropriate control mechanism, as described earlier in order
to
vary the thrust for flight control purposes. Because contra-rotating
propellers are
generally torque neutral, varying one or group of propellers 104 would not
provide
yaw control on the vehicle 100. The torque necessary for control of the
vehicle 100
could be generated by winglets installed in the downwash of the propellers
104, or
by small lateral thrusters installed at appropriated location on the body of
the vehicle
100. These thrusters may be powered preferably by compressed air generated by
the engine 200.
Flight control may be achieved to some extent by displacing the resultant lift
of
the propellers 104 with reference to the center of gravity of the vehicle 100.
By
operating the worm 55, the relative position of the propellers 104 around the
vehicle
100 may be modified during flight. For example, in order to move the vehicle
100
forward, the propellers 104 are displaced backward. As the result, the
resultant lift
generated by the propellers 104 are relocated behind the center of gravity of
the
vehicle 100, pitching the vehicle 100 downward and initiating forward
movement.
Repositioning of the propellers 104 may be also necessary in order to align
the
center of lift with the mass center of the vehicle 100 for the purpose of
stationary
hover or precision landing, especially when the payload and passengers are not
evenly distributed.
CA 02840823 2014-01-28
17
Operation:
When configured for road, the vehicle 100 is operated like a conventional four
wheel-drive vehicle. The wheels 102 are powered by selecting the appropriate
gear
ratio in the transmission 201 and by modulating the engine power output with
the aid
of a classical foot petal. The transmission system may be manual or of the
automatic
type. Steering wheel 112 as shown in FIG. 8, or other equivalent system
controls the
direction of travel by operating on the wheels 102 same like in convention
road
vehicle.
Conversion between ground and flight mode is preferably automated and is
enable by a command from the driver in the cabin. Activation of the flight
mode
operates the motors 56 on each of the transmission pod 50, which by turning
the
respective worms 55 deploy, position and lock all the respective propellers
104 in the
flight position. The gearbox 205 is engaged to the transmission 201 and the
propellers 104 are ready to operate. During flight, the engine 200 is control
by a
governor mechanism with limited control by the pilot. When the propellers 104
are of
the fixed pitch type, the pilot may only need to modulate the speed of the
engine 200
within permissible range for safe operation. In the case the propellers 104
are of the
variable pitch type with collective control, the engine 200 is then operated
most likely
at a constant optimum speed. More elaborate automatic control system would
reduce the workload of the pilot by automatically handling certain part of the
flight
operation such as: hovering; maintaining safe flight altitude during
horizontal flight;
take-off; and landing, while the pilot mostly handle flight direction and
speed. The
flight commands are given by any appropriate input devices such as joystick,
pedals
and keypads to the control systems which in turn control the thrust produced
by the
propellers 104 as necessary to produce the necessary pitch inclination, the
amount
of yaw control, or operate any other necessary actuators and control surfaces.
The
control systems would further include many safety features that eliminate
erroneous
input from the pilot. The vehicle 100 might likewise include flight navigation
equipments in accordance with the nature of the mission the vehicle is
designed for.
While the vehicle 100 internal and external design may be very similar to road
vehicle, it may comprise of many other features that have significant
importance in
CA 02840823 2014-01-28
18
such flying machine. An access trap 106, as shown in FIG. 1 is provided on the
roof,
and is accessible from inside the cabin only when the propellers 104 are
deployed.
This enables the vehicle 100 to be used as a hovering platform in specific
cases
when it is more convenient to carry out mission from the roof of the vehicle
100, for
example reaching side of tall buildings, cliffs, or under overhanging
structures such
as bridges.
Vehicle 100 which comprises of propellers 104 with fixed pitch blade 71 would
have no autorotation capability. The propellers 104 with variable pitch blade
71 may
provide some autorotation capability if they have sufficient inertia. In
either case, an
emergency ballistic parachute 107 is provided on the roof of the vehicle 100.
Deployment of the ballistic parachute 107 enable the vehicle 100 to drop
safely to
the ground in case of flight emergency situation, such as; complete engine
failure,
dissymmetry of lift due to failure of propellers 104, loss of flight control,
and other
major components failure.
Embodiment with multiple engines:
Redundancy of vital components is an important issue due to poor autorotation
ability. Engine failure can be easily overcome by the use of more than one
engine in
order to power the propellers 104. Hence the engine 200 may comprise of two or
more engines coupled together and power the transmission 201 through a common
zo driveshaft. In the case of failure of any of the engines, the faulty
engine is
automatically disconnected, while the others engines continue to operate,
enabling
the vehicle 100 to land safe or if necessary to complete the flight mission.
While several configurations of multiple-engine design are possible, one
advantageous concept is when each propeller 104 or group of propellers 104 are
powered by separate engine. As shown in FIG. 9, each vertical shaft 51
connects to
a separate engine 201. The engines 201 are mounted close to their respective
vertical shafts 51, in a convenient and compact arrangement mounted on the
side of
the vehicle 100. Since the engines 201 drive the respective wheels 102 and the
propellers 104 independently, the design enables significant reduction in the
weight
of the vehicle 100. The need of transmission and differential systems are
eliminated.
The length of the interconnecting drive shafts is also significantly reduced.
Since the
CA 02840823 2014-01-28
19
speed of each of the propeller 104, or group of propellers 104 can be
independently
controlled by modulating the speed of their respective engine 201, the flight
control is
simplified, together with the elimination of several related mechanical
systems. The
need of complex transmission system or collective control system for
propellers 104
with variable pitch, as described earlier are not required. The
synchronisation
between the multiple engines 201 are carried by an electronic control system
rather
than by mechanical means. In order to further improve redundancy a set of
driveshafts 203 may be provided, which through a system of clutches ensure
that in
case of single or multiple engines failure, power can be transferred from any
of the
healthy engines 201 to any of the propellers 104. These driveshafts 203 may be
of
lighter construction as they are design for use on rare occasion and for short
duration.
Embodiments of the present invention would comprises of a fuselage or body
that
have the appearance and ability of a wide range of road vehicles, such as
microcars,
city car, sport cars, off-road and all-terrains vehicles. Embodiments of the
invention
are not limited to four-wheel vehicles but could be adapted to three-wheelers
or
vehicles comprising of a plurality of wheels. While the invention offers many
advantages for use on the road, other embodiment may be optimised for flight.
Embodiments of the invention would comprise of rotors embedded in a shroud or
structure, which may be able to generate aerodynamic lift as fixed-wings, and
hence
improve the flight range and efficiency. Such vehicle may include additional
wings
and propellers to produce horizontal thrust. Embodiment of the invention could
be
manned or unmanned drones designed to operate in specific environments and
missions.
While the above description has detailed the features of the invention it is
understood that various omission, substitution and changed may be made by
those
skilled in the arts without departures from the spirit and scope of the
invention, and
that the specification and drawings are to be considered as merely
illustrative and
not limiting:
