GB2628223A

GB2628223A - Aircraft systems

Info

Publication number: GB2628223A
Application number: GB2401730.3A
Authority: GB
Inventors: Seyed Mohseni Mohammad; Waters Glenn
Original assignee: Arc Aerosystems Ltd
Current assignee: Arc Aerosystems Ltd
Priority date: 2023-02-10
Filing date: 2024-02-08
Publication date: 2024-09-18
Also published as: GB202301926D0; GB202401730D0

Abstract

External power for pre-rotation of gyrocopter, an autogyro or compound aircraft 1. The aircraft 1 having at least two main landing gears 22, 26 and a nose landing gear 24, each landing gear including a wheel 22, the connection system comprising a ground-based connector unit 30, 31, 32 associated with each landing gear and adapted to engage with a wheel when the aircraft is driven in a forward direction on its landing gear towards the connector unit, male and female connectors 56, 54 of a landing gear and an associated connection unit being adapted to engage mechanically and electrically as the wheel 22 rolls in the forward direction onto the connector unit, the male and female connectors 56, 54 associated with the nose landing gear 24 being adapted to engage mechanically and electrically after the male and female connectors 56, 54 associated with the main landing gear have engaged. Control data may also be transferred though the connectors.

Description

Aircraft systems

FIELD OF THE INVENTION

The present invention relates to the connection of ground-based power supply systems to an aircraft, particularly but not exclusively the electrical connection between a manned or unmanned gyrocopter, autogyro or compound aircraft and a ground-based electrical system. More specifically, the present invention relates to aircraft electrical pre-rotation system connection methods, and related hardware arrangements of manned or unmanned types of gyrocopters, auto gyros and/or compound aircraft.

BACKGROUND ART

A gyroplane is an aircraft that generates lift by free spinning of an unpowered rotor. A powered propeller, often (but not exclusively) located toward the rear of the aircraft, provides the aircraft with forward motion. Forward thrust initiated by the propeller drives the aircraft forward and causes the rotary wing to autorotate, generating lift and maintaining altitude in flight.

Gyroplanes typically require some take-off and landing runway length. The take-off field length may be reduced, however, by pre-rotating the rotor whilst the aircraft is on the ground. In a typical arrangement, a clutched and gearbox system connected to the gyroplane engine is provided for pre-rotation of the rotor. However, the lift produced in pre-rotation phase is not sufficient to eliminate the need for a runway.

There is a need for a gyrocopter pre-rotation system that provides sufficient lift to enable vertical take-off. US 2018/065734A1 discloses the use of external power to pre-rotate the rotor, in the form of a mechanical drive located under the take-off pad. The gyroplane is positioned above a drive shaft extending upwardly from the pad and the drive shaft is connected. During this process, the gyroplane is restrained by clamps attaching to the wheels or other undercarriage so as to resist reaction forces arising from the applied torque. This avoids the need to provide a collective pitch control for the rotor which is said to be undesirable.

Pre-rotation of the rotor requires significant amounts of power and, if the aircraft is the source of this power, then the aircraft's power supply (fuel or electrical battery) is reduced and its subsequent range is diminished. It is therefore advantageous to use a ground-based power source to provide power for pre-rotation. By driving the on-board motor electrically, from an off-board system, this enables aspects of the aircraft's systems to be put to multiple uses thus saving weight and allowing more flexible operation. US2019/077501 and U52020/156776 outline in general terms the provision for ground based electrical and other services to power elements of air-vehicle operations, including pre-flight rotation of an autogyro rotor, but neither give any details about how the electrical connection to the aircraft may be implemented. The act of connecting a ground-based power supply to an aircraft while it is preparing to take-off poses various problems, such as the time taken, the possibility of not making a good connection or of connecting incorrectly, the risk of electrical arcing during the connection process.

SUMMARY OF THE INVENTION

The present invention is predicated on the realisation that a connection arrangement which is associated with the aircraft landing gear and the usual tricycle undercarriage arrangement common to most aircraft, including compound aircraft, and which utilises the forward motion of the aircraft as it prepares to take-off can address many of the problems that arise when using an off-board power supply to supplement an aircraft's onboard power supply for take-off.

The present invention therefore provides an electrical connection system between a gyrocopter or compound aircraft and a ground-based electrical system, the aircraft having at least two main landing gears and a nose landing gear, each landing gear including a wheel, the connection system comprising a ground-based connector unit associated with each landing gear and adapted to engage with a wheel when the aircraft is driven in a forward direction on its landing gear towards the connector unit, at least one male connector being provided on one of the landing gear and the associated connector unit and at least one female connector being provided on the other of the connector unit and the associated landing gear, the male and female connectors of a landing gear and an associated connection unit being adapted to engage mechanically and electrically as the wheel rolls in the forward direction onto the connector unit, the male and female connectors associated with the nose landing gear being adapted to engage mechanically and electrically after the male and female connectors associated with the main landing gears have engaged. Such an arrangement allows for automatic connection of the aircraft to a ground-based electrical power supply, and the sequential engagement as the aircraft moves forwardly means that the engagement of the nose landing gear connectors after those on the man landing gears have already engaged means that the later engagement can serve as a signal to actuate the power supply to the main landing gear connectors safely, with no risk of electrical arcing. The engagement can be achieved quickly without requiring an operator to assist and, because the ground-based connectors are fixed, the onboard connectors can be fixed in complementary positions so as to remove the risk of incorrect connection.

The male and female connectors of a landing gear and an associated connection unit may be adapted to disengage mechanically and electrically as the wheel rolls in the forward direction off the connector unit, the male and female connectors associated with the nose landing gear being adapted to disengage mechanically and electrically before the male and female connectors associated with the main landing gear have disengaged. The advantage of this arrangement is that the disengagement of the nose landing gear connectors can act as a signal to turn off the power supply to the main landing gear connectors safely, with no risk of electrical arcing as the main landing gears subsequently disengage.

Later engagement of the nose landing gear connectors may be achieved if the connection unit associated with the nose landing gear is located a greater distance in the forward direction away from the connection units associated with the main landing gear than the distance between the nose landing gear and the main landing gear in the forward direction. This requires that the connectors be in some way flexible, so as to allow the aircraft to continue moving forwardly with the main landing gear connectors engaged while waiting for the nose landing gear connectors to engage. Additionally or alternatively, the ground connection units may be located exactly the same distance apart as the landing gears, but the connectors on the nose landing gear may be located behind the wheel axle and the connectors on the main landing gears may be located ahead of the wheel axles.

Additionally or alternatively the male and female connectors when engaged may form a linkage having a first rotatable joint at one end mounted to the connection unit and a second rotatable joint at the other end mounted to the landing gear, so that the linkage may pivot as the aircraft moves in the forward direction, the vertical distance of the second rotatable joint associated with the main landing gear above the ground being greater than the vertical distance of the second rotatable joint associated with the nose landing gear above the ground.

Such an arrangement means that to pivot through the same angle, the connectors mounted to the nose landing gear need to move a shorter horizontal distance than do the connectors mounted to the main landing gears; this can be used to both allow the nose connectors to engage last and also to disengage first. This angle of pivot can be utilised also to help locate the connectors for engagement, with the ground connector facing rearwardly and slightly up and the landing gear connector facing forwardly and slightly down, so that as the aircraft moves forwards the connectors are guided to engage together. This does require accurate location of the aircraft-mounted connectors relative to those on the ground, and this may be achieved if each ground-based connection unit comprises an open-ended channel, or trough, which is shaped to receive, guide and align a wheel as it rolls onto the connection unit and into the channel -a suitable shape could be a pair of upstanding ribs which increase in height and grow closer together in the forward direction, thus acting to "gather" a wheel and then guide it into the correct position for engagement.

Disengagement of the connectors may be accomplished by the connectors simply pulling apart; this can be done by making the pivot angle between the engagement and disengagement positions obtuse (i.e. greater than 90° and less than 180°).

At least some of the connectors may be for conducting electrical power from the ground-based electrical system to the aircraft, and these connectors can be provided on the main landing gears.

At least some of the connectors may be for conducting data and/or control signals between the ground-based electrical system and the aircraft. The connectors provided on the nose and/or landing gears can be retractable. There may be a control unit adapted to receive and transmit data signals from and to the aircraft, and to activate and deactivate a power supply to selectively provide electrical power to the aircraft.

The system in accordance with the invention will not need human interaction from either the on-board crew or ground-based staff external to the aircraft, which will increase safety and reduce costs. Connection of the aircraft with ground based electrical energy supply is enabled automatically and completely by the positioning of the air vehicle at a specific location relative to the ground connection units -which will provide the ground connections for power, data and control. This will be completed automatically without the need for any direct human intervention or actions.

The main power connectors, which are positioned in front of both of the main landing gear axles (LH & RH) will make initial contact and they will remain in contact while the aircraft moves further forward -until the point which the power/data enabling contact -positioned behind the axle on the nose (or tail) Landing Gear has made contact. It is the contact of the power/data enabling connection that provides assurance that the aircraft is in the correct position and that the main power supply can be safely enabled.

The off-board power supply system preferably also includes a retaining means for locating and retaining an aircraft landing gear component, such as suitably located recesses on a surface.

An on-board pre-rotation system for a gyrocopter or compound aircraft, may comprise an electrical connection system as described, a power supply, an electric motor, and a controller. It can further comprise a power supply, such as a battery pack and/or an off-board power supply.

The electric motor can be an AC motor. Where the connector is adapted to connect to a DC current, the on-board aircraft power supply system can further comprise an inverter.

Ideally, the on-board pre-rotation system further comprises a reverse current relay.

An aircraft may comprise the onboard elements of the electrical connection system as defined above. The aircraft may comprise the on-board pre-rotation system defined above, a variable pitch rotor, and a rotor head connecting the variable pitch rotor and the on-board aircraft power supply system. Such an aircraft can further comprise a landing gear strut with power connectors for connection to an off-board pre-rotation system as defined above.

Thus, embodiments of the aircraft of the present invention can comprise an electric pre-rotator to spin up the rotor while on the aircraft is on the ground. This allows the aircraft to achieve short take-off and vertical take-off via a manoeuvre known as a jump take-off, by spinning the rotor while feathered to greater than the required flight speed and swiftly increasing the blade angle via a collective pitch control. The electric motor is disengaged at some point, ideally once the aircraft lifts off the ground. The flight can then continue onward, the blade pitch angle being adjusted manually by the pilot or (preferably) automatically by an autopilot.

External power for pre-rotation of gyrocopter, an autogyro or compound aircraft is provided in the form of electrical contacts beneath the aircraft which connect to corresponding contacts on the aircraft undercarriage. Ideally, positive and negative contact is made via each main undercarriage leg of a tricycle undercarriage, and a control or data signal is established via the nose or tail wheel. A controller activates the positive and negative power connections in response to a data handshake via the third connection. The electrical contacts can be in the form of conductive rods or other formations extending upwardly from a recess in the pad beneath the aircraft, which make contact with corresponding electrical contacts on the respective undercarriage legs. Formations such as ridges or recesses can be provided in the pad to guide the aircraft wheels into the correct location.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way of example, with reference to the accompanying figures in which; Figure 1 is a first perspective view of a compound aircraft; Figure 2 is a second perspective view of a compound aircraft; Figure 3 is a perspective view of a part of an embodiment of an electrical connection system between a gyrocopter or compound aircraft and a ground-based electrical system in accordance with the present invention; and Figure 4a is an enlarged view of the starboard main landing gear shown in Figure 2 located on the aircraft pre-rotation connection system shown in Figures 2 to 3, and Figure 4b is an enlarged view of the nose landing gear shown in Figure 2 located on the aircraft pre-rotation connection system shown in Figures 2 to 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The description below is applicable to autogyro aircraft and to compound aircraft, i.e. aircraft having both an auto rotatable rotary wing and a fixed wing, such as that shown in figure 1. In both forms, forward thrust is provided by the main engines/motors, often driving a propeller. That powertrain can be either a combustion engine, electric motor, or hybrid configuration. In addition, an electric motor is provided for the rotary wing and used to pre-rotate the rotary wing prior to take-off. It is also available to provide additional assistance to the rotary wing at other times such as during take-off and landing. In alternative embodiments using electric main engines/motors, the on-board system can be coupled with the main motor.

The compound aircraft 1 of figure 1 comprises an unpowered rotor 10 arranged atop a fuselage 11. A pair of engines 12, 13 are mounted on fixed wings 14, 15. The engines 12, 13 provide power to propellers 16, 17.

The compound aircraft 1 has landing gear 20 arranged in a tricycle configuration. In the present embodiment, each gear of the landing gear 20 comprises a retractable gear 21 carrying a wheel 22.

In the second view of the compound aircraft 1 as shown in figure 2, all three landing gears of the tricycle gear configuration of the landing gear 20 can be seen. The nose landing gear 24 (shown in more detail in Figure 4b), comprising retractable gear 21 supporting wheel 22, is capable of being stowed within the fuselage 11 behind nose gear door 23. Starboard main landing gear 25 (shown in more detail in Figure 4a) and port main landing gear 26 have a similar configuration, with retractable gear supporting wheels 22.

Figures 1 and 2 also show components of an electrical connection system between a gyrocopter or compound aircraft and a ground-based electrical system in accordance with the present invention. Wheel locators 30, 31, 32 are shown in a configuration compatible with that of the landing gear 20. Wheel locator 30 is arranged for cooperation with the nose gear 24. Likewise, wheel locator 31 is arranged for cooperation with main landing gear 25 and wheel locator 32 is arranged for cooperation with main landing gear 26. Each wheel locator 30, 31, 32 can be a wheel locator assembly as shown in more detail in Figures 4a and 4b.

The aircraft 1 includes three landing gears comprising wheels 22, and the invention envisages providing electrical power for pre-rotation via the parts of that landing gear which extend to and contact the ground such as a take-off pad 33. A restraint system can be provided, if necessary, to fit various types and sizes of undercarriage and hold the aircraft 1 in place during pre-rotation.

The off-board, ground-based system can optionally include restraint systems to retain the gyrocopter in position during connection to the off-board system and/or during the pre-rotation phase. Each wheel locator 30, 31, 32 has a retaining means for retaining a corresponding landing gear 20 component. In the embodiment shown in Figure 3 and described in more detail with reference to Figures 4a and 4b, the wheel locators 30, 31, 32 comprise a recess for locating an aircraft wheel 22. One or more of the wheel locators 30, 31, 32 has a means of restraining a landing gear 20 component to ensure the aircraft 1 is correctly positioned with respect to the pre-rotation system, and/or retained in position. In a preferred embodiment, the restraint system is arranged to connect to the nose landing gear 24 assembly.

The ground-based system is located at a fixed point on or adjacent an apron or other suitable location on an airfield. The ground-based system forms a part of the airfield infrastructure. However, in alternative embodiments, the off-board system components can be on a portable device or directly attachable to the ground at a location in the airfield operational environment. In the embodiment of Figure 3, the ground-based system comprises a take-off pad 33 in a suitable location.

The off-board system comprises a power supply in the form of a ground supply unit having a ground power connector 37, shown schematically in Figure 3, and for clarity without the connections to the ground supplier unit connectors 34, 35, 36 (further described below). The ground supply unit can be provided as battery packs or a connection to a ground power supply that is an extension of the airfield power supply infrastructure. The ground-based system also comprises data connection apparatus. A data connector 38, 39, 40 is provided on each wheel locator 30, 31, 32 for association with the landing gear 20 apparatus in close proximity, so as to communicate data and control signals between the aircraft 1 and a ground-based control unit 41 (shown schematically in Figure 3, and for clarity without the connections to the data connectors 38, 39, 40).

Referring now to Figure 4a, which shows the starboard side main landing gear 25 located on ground-based connection unit 31, the connection unit 31 is formed into an open-ended channel shape, having two upstanding wings 50a, 50b separated by a channel piece 50c. When seen from above, the wings 50a, 50b narrow in the direction of arrow A, which is the direction of forward movement of the aircraft 1; this narrowing serves to guide the wheel 22 and the landing gear 25, as the aircraft moves forwardly, into a central position in the connection unit 31.the height of the upstanding wings 50a, 50b also increase in the forward direction towards the centre of the connection unit, so that the wings 50a, 50b also serve to align the wheels closely to the forward direction, thus accurately positioning and orienting the landing gear 25 relative to the connection unit 31 for the engagement of the connectors.

To the front and rear of the axle 52 of the main landing gear wheel 22 are mounted two elongate female connectors 54 which are adapted to engage with elongate male connectors 56 mounted to the ground connection unit 31. These connectors are preferably mounted on the inboard side (i.e. towards the centreline) of the aircraft. When the connectors are engaged and forming a mechanical and electrical connection, one connection is for supplying electrical power, and the other connection is for communicating data and/or control signals. The connectors 54 are mounted to the landing gear by a rotatable joint (not shown), and the connectors 56 are mounted in a pivoting socket 58 in the connection unit 31 so as to be able to pivot in the direction of arrow A, about an axis parallel to axle 52. The male and female connectors are of a snap fit type, adapted to engage when they are under compression in a direction along their elongate lengths and to disengage when they are under tension in that direction. One or both of connectors 54, 56 is resilient in the elongate direction, to allow for the vertical component of the pivoting motion of the linkage at its upper end, distal from the pivot point; additionally or alternatively the socket 58 allows the male connectors to move in the elongate direction relative to the connection unit 31, also to allow for the vertical component of the linkage pivoting motion. A similar arrangement is provided on the port side main landing gear, with the power connector on the starboard side being for DC positive and that on the port side being for DC negative/ground.

Turning to the nose landing gear 24 and associated connection unit 30 shown in Figure 4b, many of the features are similar to that in Figure 4a, but the landing gear-mounted female connector shown is mounted behind the axle 52; in this drawing the narrowing of the channel 50c in a direction parallel to the axle 52 towards the centre of the connection unit 30 (which guides and starts to align the wheel 22) is more clearly shown, as is the increase in height of the upstanding wings 50a, 50b towards the centre of the connection unit (which raises the height of the male connector 56, which in turn lifts the lower end of the downwardly-projecting female connector 54 attached to the landing gear reducing the risk that this might impact with anything on the ground). The upstanding wings are parallel at the centre of the connection unit, giving the channel 50c parallel sides which hold the wheel in a forward direction. The nose landing gear 24 has two connectors 54, one is shown on the port side of the landing gear, the other being invisible on the other side of the nose wheel; one of these connectors is a power enabling connector and the other is a data/control signal connector.

Engagement of any one of the landing gear-mounted female connectors with its associated ground-mounted male connector is as follows. The aircraft 1 moves in the forward direction A and the wheel 22 enters the channel 50c and the upstanding wings 50a, 50b straighten the wheel 22 and guide it toward the connection point. The female connector 54 is biased so as to adopt a rest position at which its elongate length is inclined downwardly at between about 30° and about 600; the male connector 56 is biased to adopt a complementary upward angle. As the ends of the connectors come into contact, the male connector 56 enters the female connector 54 and, as the forward movement of the aircraft 1 continues, the connectors snap into mechanical engagement and form an electrical contact. Continued forward movement of the aircraft 1 causes the two connectors to rotate slightly, overcoming the bias holding them at their rest angles, so that the linkage formed by the engaged connectors pivots about an axis parallel to that of the axle 52. At this point the aircraft is braked so as to stop moving forward and the external power supply can be connected to the aircraft to power pre-rotation of the rotor, and data and control signals passed between the aircraft and the ground-based controller. When there is no further need for the aircraft to draw power from the ground-based supply, the brakes are released so that the aircraft moves forwards again, and the linkages continue to pivot; eventually, the linkages have pivoted to a position where there is tension between the male and female connectors (and means may be provided in the connection unit to limit the extent to which the male connector is allowed to pivot to add to this effect), and they snap out of connection and disengage. Additionally or alternatively, a control signal may power a release mechanism within the connectors to allow them to disengage when the pivots have reached a predetermined angle. Thus engagement and disengagement of the connectors is automatic, requiring no interaction from either the on-board crew or ground-based staff.

As described above, the connection system is arranged so that on engagement main landing gear connectors engage first, followed by the nose landing gear connectors, and so that following further forward motion of the aircraft the connectors disengage, the nose landing gear-mounted connectors before the main landing-gear-mounted connectors. It is the contact of the power/data enabling connection on the nose landing gear that provides assurance that the aircraft is in the correct position and that the main power supply to the aircraft main landing gear connectors can be activated. This ensures that power is only connected to the aircraft after the main power connectors are securely engaged. No current will be passed until the Management/Data system has ensured that all power contacts are securely enabled with all the circuits resistances in the expected nominal values. When ground power is no longer required, the aircraft will position/move further forward and the nose power enabling connector will be the first to disengage. This disengagement will provide signalling to disconnect current from the main landing gear connectors before they are also disengaged. This will mean that there is no high current power provided to the main connectors while they are disengaging, thus removing the likelihood or electrical arcing and other undesired effects as the aircraft begins take-off. The aircraft data system is preferably electrically isolated from the off-board data system by the use of an opto-isolator device, ensuring that no external electrical input can affect the on-board control, data and management systems. The whole operation is monitored with a controller 41; this uses the data communicated between the onboard and off-board systems to monitor the power transmission. The controller can communicate with any of the systems through a communication signal line, ideally installed on the nose landing gear to allow a connection between the on-board and off-board systems. The controller uses embedded software to carry out the programmed actions. These actions can include starting current flow, stopping current flow, current change and cut-off. It can carry out other functions, such as the automatic disengagement.

The system in accordance with the invention will allow external power to be safely supplied to the aircraft without the need for external plugs, connectors or wires. It will also remove the need for air or ground crew to enable these connections or handle high power connections, thereby enhancing safety and reducing costs. The system uses standard aerospace practices and components. It will be compliant under current aerospace certification standards.

In embodiments in which the aircraft 1 comprises an on-board pre-rotation system, the on-board pre-rotation system has an AC or DC electric motor, a controller, and a power source. In a preferred embodiment, the power source is a battery pack. In a preferred embodiment, the electric motor is mounted within the rotor head and is directly connected to the unpowered rotor blade 10.

In a preferred embodiment, the control actuators are coupled to the rotor hub. A controller is installed close to the electric motor, with three cables connecting the controller to the AC motor. In embodiments in which a six-phase motor is utilised, there will be six associated sets of cables. The controller controls adjustments to the motor speed, and inverting DC to AC (if needed). The controller has input feeds from two positive and two negative DC cables, the DC cables terminating on struts with high-voltage connectors.

Where ground-based power supply is not available, battery packs can provide the impetus for pre-rotating the rotor 10. The battery packs can be charged separately with additional connectors when charging is available. An advantage of this arrangement is that the operation of the aircraft 1 is versatile and can be run with both on-board and off-board systems.

The aircraft 1 of the present invention comprises a fully articulated rotor head providing 3 degrees of freedom; flapping, teetering and blade pitch. The flight controls are linked mechanically and/or electrically to the rotor control system.

The rotor 10 of the present invention is a single rotor with a variable pitch arrangement. In a preferred embodiment, rotor blade pitch is controlled by a feathering hinge.

The rotor blade 10 may have additional blade pitch control devices. The rotor hub has a typical control rod and swash plate arrangement for collective pitch control.

The arrangement of the present invention permits variation of rotor blade 10 pitch angle. The pitch angle may be adjusted such that the rotor lift profile can be adjusted to generate sufficient lift for vertical take off using a minimum power threshold for pre-rotation.

In a preferred embodiment, to achieve vertical take-off and a no roll landing of the aircraft 1, the pre-rotation system requires a collective pitch control in which blade pitch angle is initially set to zero. The rotor spin is initiated; once the rotor speed reaches close to 150% of the typical speed, the blade pitch angle can be manually or automatically increased to initiate the gyroplane to lift off the ground.

This arrangement typical requires a less complex rotor head as compared to that of a fixed-pitch rotary system. As a result, the maintenance costs should be significantly lower.

The embodiments disclosed herein may relate to manned and unmanned aircraft of any size. In further embodiments, various parameters will be optimised for a gyrocopter or compound aircraft prepared and configured for take-off, such that, as a result of pre-rotation system with collective pitch control, no runway is required for take-off. Although described in relation to gyrocopters/compound aircraft, it will be appreciated that the present invention could equally be employed with eVTOL aircraft, or for the charging/recharging of batteries/battery packs in battery electric or hybrid electric aircraft. The principles of the invention could equally be applied for the charging of ground-based vehicles such as electric cars or trucks, with vehicle-mounted connectors being mounted to project or arranged to deploy from the front and rear wheels, or from underneath and/or the sides of the vehicle as it approaches a ground-based charging unit. In such an electrical connection system, between a vehicle on the ground and a ground-based electrical system, where the vehicle has at least two rear wheels and a steerable front wheel, the connection system comprises a ground-based connector unit associated with each wheel and adapted to engage with a wheel when the vehicle is driven in a forward direction towards the connector unit, at least one male connector being provided on one of the wheel and the associated connector unit and at least one female connector being provided on the other of the connector unit and the associated wheel, the male and female connectors of a wheel and an associated connection unit being adapted to engage mechanically and electrically as the wheel rolls in the forward direction onto the connector unit, the male and female connectors associated with the front wheel being adapted to engage mechanically and electrically after the male and female connectors associated with the rear wheels have engaged. Those skilled in the art will understand how each of the preferred features of the present invention described above in relation to an aircraft would be equally applicable to a ground-based electric vehicle.

In the present application, a system has been described using DC supply from the take-off pad 33 to the aircraft 1 and an AC or DC motor within the aircraft 1, fed via an inverter if necessary. In such an arrangement, the power source connection has a positive and a negative connection. An AC supply from the take-off pad 33 is also possible, in which case references to "positive" and "negative" connections should be interpreted as either "live" and "neutral" connections, or appropriate connections to a three-phase supply, as necessary.

It will of course be understood that many variations may be made to the above-described embodiment without departing from the scope of the present invention. For example, some or all of the male and female connectors could be mounted the other way round. The landing gear wheels might be replaced by skids. The tricycle undercarriage, instead of having a nose landing gear may instead have a tail landing gear, in which case the sequences of engagement and disengagement of the two types of landing gear would be reversed.

Where different variations or alternative arrangements are described above, it should be understood that embodiments of the invention may incorporate such variations and/or alternatives in any suitable combination.

Claims

CLAIMS1. An electrical connection system between a gyrocopter or compound aircraft and a ground-based electrical system, the aircraft having at least two main landing gears and a nose landing gear, each landing gear including a wheel, the connection system comprising a ground-based connector unit associated with each landing gear and adapted to engage with a wheel when the aircraft is driven in a forward direction on its landing gear towards the connector unit, at least one male connector being provided on one of the landing gear and the associated connector unit and at least one female connector being provided on the other of the connector unit and the associated landing gear, the male and female connectors of a landing gear and an associated connection unit being adapted to engage mechanically and electrically as the wheel rolls in the forward direction onto the connector unit, the male and female connectors associated with the nose landing gear being adapted to engage mechanically and electrically after the male and female connectors associated with the main landing gears have engaged.
2. An electrical connection system according to Claim 1, in which the male and female connectors of a landing gear and an associated connection unit are adapted to disengage mechanically and electrically as the wheel rolls in the forward direction off the connector unit, the male and female connectors associated with the nose landing gear being adapted to disengage mechanically and electrically before the male and female connectors associated with the main landing gear have disengaged.
3. An electrical connection system according to Claim 1, in which the connection unit associated with the nose landing gear is located a greater distance in the forward direction away from the connection units associated with the main landing gear than the distance between the nose landing gear and the main landing gear in the forward direction.
4. An electrical connection system according to Claim 1, 2 or 3, in which the male and female connectors when engaged form a linkage having a first rotatable joint at one end mounted to the connection unit and a second rotatable joint at the other end mounted to the landing gear, so that the linkage may pivot as the aircraft moves in the forward direction, the vertical distance of the second rotatable joint associated with the main landing gear above the ground being greater than the vertical distance of the second rotatable joint associated with the nose landing gear above the ground.
5. An electrical connection system according to any preceding claim, in which each ground-based connection unit comprises an open-ended channel shaped to receive, guide and align a wheel as it rolls onto the connection unit and into the channel.
6. An electrical connection system according to any preceding claim, in which at least some of the connectors are for conducting electrical power from the ground-based electrical system to the aircraft.
7. An electrical connection system according to Claim 6, in which the at least some connectors for conducting electrical power are provided on the main landing gears.
8. An electrical connection system according to any preceding claim, in which at least some of the connectors are for conducting data and/or control signals between the ground-based electrical system and the aircraft.
9. An electrical connection system according to any preceding claim, in which the connectors provided on the landing gears are retractable.
10. An electrical connection system according to any preceding claim, further comprising a control unit adapted to receive and transmit data signals from and to the aircraft, and to activate and deactivate a power supply to selectively provide electrical power to the aircraft.
11. An on-board pre-rotation system for a gyrocopter or compound aircraft, comprising: an electrical connection system according to any preceding claim for connection to a power supply, an electric motor, and a controller.
12. An on-board pre-rotation system according to claim 11, further comprising a power supply, wherein the power supply is a battery pack.
13. An on-board pre-rotation system according to claim 11, further comprising an off-board power supply.
14. An on-board pre-rotation system according to any one of claims 11 to 13, wherein the electric motor is an AC motor.
15. An on-board pre-rotation system according to claim 14, wherein the connector is adapted to connect to a DC current, the on-board aircraft power supply system further comprising an inverter.
16. An on-board pre-rotation system according to any one of claims 11 to 15, further comprising a reverse current relay.
17. An aircraft comprising the on-board pre-rotation system of claims 11 to 16.
18. An aircraft according to claim 17, further comprising a variable pitch rotor and a rotor head connecting the variable pitch rotor and the on-board aircraft power supply system.
19. An electrical connection system between a vehicle on the ground and a ground-based electrical system, the vehicle having at least two rear wheels and a steerable front wheel, the connection system comprising a ground-based connector unit associated with each wheel and adapted to engage with a wheel when the vehicle is driven in a forward direction towards the connector unit, at least one male connector being provided on one of the wheel and the associated connector unit and at least one female connector being provided on the other of the connector unit and the associated wheel, the male and female connectors of a wheel and an associated connection unit being adapted to engage mechanically and electrically as the wheel rolls in the forward direction onto the connector unit, the male and female connectors associated with the front wheel being adapted to engage mechanically and electrically after the male and female connectors associated with the rear wheels have engaged.