This invention relates to a hybrid air vehicle (HAV) and in particular
to an air vehicle which combines characteristics of an airplane, a lighter-than-air
airship and a hovercraft.
In the past, attempts have been made to provide aircraft with both
aerodynamic and aerostatic lift. Thus rigid and non-rigid gas-filled airships, which
are normally lighter-than-air, are capable of taking off even though overloaded
to the point that they are heavier-than-air. Such air vehicles, however, have been
generally in the form of prolate ellipsoids of approximately circular cross-section,
and the aerodynamic lift imparted to such air vehicles is minimal when compared
with a conventional airfoil with the same planform area.
Since the lift in conventional airships is primarily aerostatic brought
about by the hull being filled with lighter than air gas, such as helium, their
cargo-carrying capability is limited by the volume of the gas envelope, and the
total lift at best corresponds to little more than the weight of the air displaced
by the gas envelope. Furthermore, in conventional cargo-carrying airships problems
are encountered in loading and unloading the cargo and of dispersing concentrated
Lighter-than-air airships are incapable of taxiing on their landing
fields, and take-off and landing procedures are consequently very complex, requiring
costly equipment and large number of persons in ground crews. On the other hand,
conventional cargo airplanes, while they are capable of taxiing, have high take-off
and landing speeds.
In GB-A-1,245,432 there is disclosed an aircraft which takes advantage
of both the lift provided by a lighter-than-air gas and aerodynamic lift. The aircraft
has an enclosed aluminium hull containing a lighter-than-air gas and which is delta-shaped
in plan form and has an ellipse-like cross-section throughout substantially all
of its length. The delta wing shape and low aspect ratio of the design provides
a high cargo capacity as well as good aerodynamic performance. The aluminium hull
is inflated with helium and cargo and fuel compartments are provided inside the
hull suspended by numerous high-strength steel cables which distribute the concentrated
load of the cargo and fuel compartments over the large area of the upper shell of
the body. The propulsion system is arranged at the rear of the aircraft so that
the propulsion system is effectively behind the drag producing system. As a result,
the momentum loss of the flow due to the deceleration of the drag system is compensated
by the accelerating action of the propulsion system, thus restoring the original
velocity of the air with respect to the aircraft. Because of its excess gross weight,
and because it is provided with landing gear, the aircraft is capable of taxiing
on the ground in the same manner as a conventional multi-engine aircraft.
The aircraft described in GB-A-1,245,432 is more akin in design to
an airplane than to an airship, the majority of the lift being provided by the aerodynamic
delta shape of the hull. The hull is formed as a rigid framework of aluminium panels
and the load compartment is housed within the hull. The width of the aircraft at
its stern is about 75% of the length of the aircraft. Thus for an aircraft having
a length of about 305 m, the width at the stern of the aircraft will be about 230
m. This places severe limitations where the aircraft can take off and land because
of the need to have a flat runway capable of catering for such a wide aircraft.
Disclosure of Invention
An object of the present invention is to provide a hybrid air vehicle
having characteristics of an airplane and a lighter-than-air airship. It is also
an object of the invention for the air vehicle to have hovercraft-type air cushion
landing gear units.
Another object of the invention is to provide a hybrid air vehicle
having a relatively low height, contoured gas-filled hull.
A further object of the invention is to provide a hybrid air vehicle
having a non-rigid contoured hull which preferably has a contour along its length.
According to the present invention there is provided a hybrid air
vehicle having a gas-filled contoured flattened hull and including a pair of longitudinally
extending side lobes defining, on the underside of the hull, a longitudinally extending
central recess, a payload module received in said central recess and air cushion
landing gear units on the underside of said side lobes of the hull, the landing
gear units being spaced apart on either side of the payload module.
Suitably the air vehicle combines features or characteristics of an
airplane, a lighter-than-air airship and a hovercraft. Ideally the air vehicle will
generate approximately one-quarter to one half of its lift aerodynamically through
its lifting-body shape and approximately one half to three-quarters through the
buoyancy of the gas, e.g. helium, of its gas-filled hull.
By providing the landing gear units on the underside of the hull side
lobes, they can be relatively widely spaced apart to improve the stability of the
air vehicle when on the ground and when landing and taking off. There are a number
of advantages in the landing gear units being air cushion landing gear units. For
instance, after the air vehicle lands and the air supply is turned off, or reversed,
the air vehicle will be gently lowered down. By appropriate design, the payload
module can be arranged to be lowered with the air vehicle so as to be in a position
where cargo can be easily off-loaded from a ramp of the payload module. With air
cushion landing units, there is not the need to have perfectly flat runways for
the air vehicle to land and take-off. Thus the air vehicle can land on any reasonably
flat surface, even on water.
Each air cushion landing gear unit suitably comprises flexible curtain
means surrounding an air cushion cavity and air means for supplying compressed air
to the air cushion cavity to provide a cushion of air for supporting the air vehicle
during landing and take-off. Preferably each air cushion landing gear unit includes
means for rapidly exhausting air from the air cushion cavity to provide a hold-down
force for holding the air vehicle in position on the ground both for general mooring
purposes and for compensating when the payload is being off-loaded.
In summary, therefore, the provision of widely spaced apart, inflatable
air cushion landing gear units allows takeoff and landing on all reasonably flat
surfaces, including raw land, swamps and water. On landing, the air cushion landing
gear units, combined with the low profile of the hull, provide enhanced stability
by means of sucking down (on ground) or flooding on-board tanks (on water) to aid
loading and unloading of cargo without elaborate tie-down systems. In flight, the
landing gear units are preferably retracted to improve aerodynamic lift of the hull.
The air vehicle is preferably of the non-rigid type comprising a flexible,
pressure stabilised multi-hull construction. The multi-hull design provides both
stability and manoeuvrability in flight. The low hull height relative to length,
coupled with the air cushion landing gear units provides a high degree of stability
on ground and ease of ground handling.
Conveniently the hull is prestressed and is made from flexible sheet
material, e.g. a composite material or laminated fabric material, which provides
a shell design tensioned by pressure. Thus the hull is suitably pressure-stabilised
without the need for the use of internal structure bracing. This approach reduces
the cost and weight of construction and provides resilience to the structural shell.
Suitably the hull includes a longitudinally extending top lobe arranged
between the side lobes at the top of the hull. In this case the hull suitably has
an outer envelope and a pair of internal longitudinally extending partition means
which converge downwardly towards each other, the space between the partition means
and the outer envelope defining the top lobe and the spaces outwardly of the partition
means defining the side lobes. The underside of the hull in the longitudinal direction
of the hull, at least in a central region where the payload module and landing gear
units are mounted, is generally flatter than the top side of the hull in the longitudinal
The hull lobes are gas-filled, typically with helium, and are isolated
from the other hull lobe(s). Each hull lobe may be compartmented along its length
- i.e. each hull lobe may comprise separate compartments separated from. each other
by partitions which allow flow of gas therebetween. The formation of multiple lobes
of helium bags is for safety/redundancy purposes. Catenary webs are suitably provided
for carrying loads between the cargo module floor and the outer shell.
Conveniently the two side hull lobes extend rearwardly further than
the top hull lobe and are provided with stern mounted drive motors. These propulsion
units operate in the wake of the hull which confers improved propulsion efficiency
and enables a more truncated (and hence a more helium lift efficient and more structurally
efficient) shape to be used for the rear section of the hull.
Separate motor means are also conveniently provided on each side of
the hull. The use of vectored thrust on at least some, preferably all, of the engines
allows vertical thrust vectors to act through the centre of gravity and centre of
pressure. Thus there is the facility for vertical take-off and landing (VTOL) and
zero roll take-off and landing (ZTOL) together with generally improved control.
The hull is suitably provided with tail fins which are typically disposed
at an angle to a vertical plane.
The hull is preferably made from flexible sheet material which is
preferably a laminated fabric material. Preferably the material is cut into flat
shapes which are joined together, e.g. by bonding, to form the correctly shaped
The hull preferably has a camber along its length, this providing
more efficient aerodynamic lift and also a flatter underside that gives a better
interface to the ground for loading, off-loading, mounting of hover cushion units,
Brief Description of Drawings
Embodiments of the invention will now be described, by way of example
only, with particular reference to the accompanying schematic drawings, in which:
Best Mode for Carrying Out the Invention
- Figure 1 is a view from below, from one side and from the front of an air vehicle
according to the invention;
- Figure 2 is a view of the air vehicle shown in Figure 1 as viewed from below,
from one side and from the rear;
- Figure 3 is a view of the air vehicle shown in Figure 1 as viewed from above,
from one side and from the front; and
- Figure 4 is a view from the front of the air vehicle shown in Figure 1.
Figures 1 to 4 show a pressure-stabilised, preferably non-rigid, air
vehicle, generally designated by the reference numeral 1, having a hull 2 with a
flattened, generally elliptical cross-section throughout most of its length. The
hull 2 is formed of two longitudinally extending side lobes 3 and 4 and a longitudinally
extending top lobe 5 which does not extend rearwardly as far as the side lobes.
The hull is made from reinforced sheet material, e.g. a high strength laminated
fabric, and comprises an outer envelope 6 and inner, longitudinally extending partition
walls 7 and 8 (see Figure 4) extending between the top and bottom of the hull. The
partition walls 7 and 8 converge downwardly towards each other and serve to define
the side lobes 3 and 4 and the top lobe 5. Each hull lobe may include transverse
partition walls at spaced apart positions along its length which may extend partly
between the top and bottom walls or, alternatively, may have openings therein to
permit the contained helium gas to pass, albeit in a restricted manner, between
The sheet material from which the hull is formed is cut into precise,
flat shapes which are bonded together to provide the precise curved shape of the
hull. When the lobes are filled with helium the pressure stabilised hull is formed
having a camber along its length. The two side lobes 3 and 4 are in effect joined,
or positioned close together, at the underside of the hull and define a central
longitudinal concave surface or recess 9 along the length of the hull. The wedge
shaped top lobe 5, which is positioned between the side lobes 3 and 4, provides
the top of the hull with a smooth curved convex surface. The inflated air vehicle
hull is of a flattened form and has a generally aerodynamic shape which is able
to provide aerodynamic lift to the air vehicle. Typically, with the design illustrated,
approximately one-quarter to one half of the vehicle lift is provided aerodynamically
through its lifting body shape and approximately one half to three-quarters of the
vehicle lift is provided by the buoyancy of the hull gas, e.g. helium. In longitudinal
section, the hull has a generally greater convexity on the top side than on the
The underside of the air vehicle 1 includes a longitudinally extending
payload module 10 carried by the hull and positioned in the recess 9 and air cushion
landing gear units 11 and 12 on the hull lobes 3 and 4, respectively. The positioning
of these units is facilitated by the generally flatter underside of the hull along
the length of the hull, at least in a central portion of the hull where these units
are located. Each landing gear unit typically comprises a flexible skirt defining
an air cavity into which pressurised air can be blown to provide an air cushion
for supporting the air vehicle during landing, taking-off and taxiing procedures.
Although not shown, means may also be provided to rapidly exhaust air from the air
cavity so that a suction or hold-down force is applied to hold the air vehicle down
in position on the ground. The relatively widely spaced apart air cushion landing
gear units, combined with the low height of the hull compared with its length, give
the vehicle a high degree of stability when landed enabling elaborate tie-down systems
to be dispensed with (although less elaborate tie-down systems may be required in
addition to the suck-down air cushion landing gear units.
A particular advantage of the use of air cushion landing gear units
is that the air vehicle can land and take-off from any reasonably flat surface,
including unimproved raw land, swamps, marshland and water, e.g. sea. A special
runway is not required as with aircraft having wheeled undercarriages. Furthermore
cross-wind landing gear drag is reduced or eliminated. The landing gear units 11
and 12 are positioned widely apart to provide the air vehicle with stability during
landing and take-off.
The top lobe 5 does not extend fully to the rear of the air vehicle.
Thus the rear end of the air vehicle is formed by the spaced apart ends of the two
side lobes 3 and 4. Motors 13 and 14 are mounted at the stern of the lobes 3 and
4, respectively, and these motors may be mounted to swivel to provide both vertical
and horizontal vectoring. Additional motors 15 and 16 are mounted on each side of
the hull and are also preferably mounted to swivel to provide vertical and horizontal
vectoring. The use of vectored thrust engines positioned to allow vertical thrust
vectors to act through the centres of gravity and pressure of the hull enables vertical
landing and takeoff of the air vehicle.
Towards the rear end of the hull, four angled stabilising fins 17
- 20 are arranged.
Although not shown, catenary webs are provided for carrying loads
between the floor of the payload module 10 and the outer shell of the hull.
In use when the air vehicle lands and the air within the air cavities
is released and suction applied to hold the air vehicle down, the air vehicle will
settle down gently bringing the payload module 10 close to the ground. The module
suitably has a let down ramp (not shown) to allow wheeled vehicles to drive into
and off from the payload module in the manner of a roll on/roll off container ship
or the like. The low hull height relative to length, coupled with suction provided
by the air cushion landing gear units, give the air vehicle a high degree of stability
on ground and ease of ground handling.
The air vehicle is designed to be able to transport large loads safely
over long distances. By way of example, the air vehicle described and illustrated
typically has a length of 307 m, a height of 77 m and a width of 136 m. Such an
air vehicle has a hull envelope volume of 2,000,000 m3, a range of 4,000
nautical miles and a flying altitude of up to 9,000 feet. The air vehicle typically
has a cruise speed of 100 KTAS and a maximum speed of 110 KTAS. The payload is 1,000,000
kg with a deck space which is 80 m long, 12 m wide and 8 m high. Smaller versions
can be constructed, for example down to payloads of less than one tonne.
While the invention has been illustrated and described as embodied
in a specific design of hybrid air vehicle, it is not intended to be limited to
the details shown since various modifications and structural changes may be made
without departing from the invention defined in the following claims.