GB2592063A

GB2592063A - VTOL Aircraft with contra-rotating fans

Info

Publication number: GB2592063A
Application number: GB2002091.3A
Authority: GB
Inventors: Mohammad Mohseni Seyed; David Richard Wijker Norman
Original assignee: Samad Aerospace Ltd
Current assignee: Arc Aerosystems Ltd
Priority date: 2020-02-14
Filing date: 2020-02-14
Publication date: 2021-08-18
Anticipated expiration: 2040-02-14
Also published as: GB2592063B; GB202002091D0

Abstract

A vertical take-off and landing (VTOL) aircraft comprising a pair of coaxial contra-rotating main lift fans 2 close to aircraft’s centre of gravity. The aircraft comprises one fan 5 on the vertical tailplane 11 for yaw control, one fan 7a, 7b on each outer wing for roll control, two auxiliary fans 4a, 4b on the horizontal tail and an optional additional nose fan for pitch control. Yaw control may be provided through differential power to main lift counter rotating fans. Separate thrusting engines 12a, 12b may be provided for forward flight. The fans may be closed with fan bay doors for forward flight. Preferably, upper and lower beams 1, 3 provide for mounting main fans, structural continuity in the fore-aft direction, attachment of landing gear and vertical tailplane. Main lift proportion may be generated within the fuselage width. Front and rear spars 8, 6 may form fan duct outer edge.

Description

VTOL AIRCRAFT WITH CONTRA-ROTATING FANS

The present invention relates to a vertical and take-off and landing (VTOL) aircraft, e.g. an aeroplane capable transitioning from powered lift (provided by vertical thrusting fans) and horizontal wing-borne flight where lift is generated aerodynamically from the aircraft's wings.

BACKGROUND

VTOL aircraft offer the prospect of door-to-door air travel eliminating the need for a runway. Helicopters currently perform this mission, however, helicopters are expensive and noisy and uncomfortable over long distances. The invention disclosed here works as a conventional aircraft in all modes except for take-off and landing.

The invention is therefore intended to provide the speed, comfort and safety of a conventional aircraft along with the operational flexibility of a helicopter in accessing remote landing sites or areas not served with airfields.

SUMMARY OF THE INVENTION

A need has been identified for a passenger civilian aircraft that incorporates VTOL features. The prior art consists of a wide range of VTOL/VSTOL aircraft that have been developed since the 1950s and 60s comprises VTOL aircraft, e.g. with three fans, providing vertical lift but this does account for thrust vectoring to control the dynamics of the aircraft around the pitch (transverse), roll (longitudinal) and yaw (vertical) axes. The prior art also does not allow for a failsafe operation were one of the fans to fail. This invention seeks to address the need for flexibility in air travel whilst considering the economy of more-electric design and greater consideration of occupant safety.

According to a first aspect of the present invention, an aircraft is provided according to claim 1. It comprises of a VTOL aircraft that transitions from powered lift (provided by vertical thrusting fans) and horizontal wing-borne flight where lift is generated aerodynamically from the aircraft's wings.

The aspects of lift and control are separated so that the main lift fan located near the aircraft centre of gravity does not play any part in the control of roll, pitch or yaw, or in any part of the forwards driving thrust of the aircraft.

The aircraft transitions between hover/vertical flight and horizontal flight via separate forwards thrusting engines (12a and 12b). In this way the functions of a) vertical lift, ID) forward thrust and c) control are all separated, providing simpler certification and higher safety margins.

The VTOL aircraft hovers by the power of fans located around the aircraft. The primary lift comes from the main lift fan (2) located close to the aircraft's centre of gravity. The centre of gravity will however vary depending on the loading of the aircraft. The aircraft will also need to be able to manoeuvre and maintain balance. To facilitate this, the aircraft is fitted with auxiliary fans on the horizontal tail, vertical tailplane and in the outer wing to control rotation in pitch, yaw and roll axes.

Pitch control is provided by fans in the horizontal tail (4a and 4b) -note that provision for an additional fan located in the nose of the aircraft may also be considered; Yaw control is provided by a fan in the vertical tailplane (5); or yaw control may be achieved through differential power to each of the contra-rotating fans (2) Roll control is provided by fans in the outer wings (7a and 7b); operating differentially The main lift fan (2) is a co-axial contra-rotating pair, with one fan mounted above the lower beam (1) and the other under the upper beam (3).

The advantage of this arrangement is that it allows the main proportion of lift to be generated within the width of the fuselage, and this enables the design to close off the lift fan in normal flight via articulating doors.

In a multi-rotor aircraft, the thrust from each engine must be modulated in order to control the aircraft, but this puts a significant challenge into the control systems as well as having to maintain fast response times in high power -high inertia systems. The single lift only fan must be contra-rotating in order to cancel torque effects, but also allows higher thrust from a given diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view of an aircraft according to an embodiment of the invention. Fig. 2 is a top plan view of an aircraft according to an embodiment of the invention.

Fig. 3 is a front elevation view of an aircraft according to an embodiment of the invention.

Fig. 4 is a side elevation view of an aircraft according to an embodiment of the invention.

Fig. 5 is a rear elevation view of an aircraft according to an embodiment of the invention. DETAILED DESCRIPTION OF THE EMBODIMENTS The following description presents embodiments of the present invention and, together with the drawings, serves to explain principles of the present invention. However, the scope of the invention is not intended to be limited to the precise details of the embodiments, with variations apparent to a skilled person deemed also to be covered by the description of this invention. Terms for components used herein should be given a broad interpretation that also encompasses equivalent functions and features. Descriptive terms should also be given the broadest possible interpretation; e.g. the term "comprising" as used in this specification means "consisting at least in part of" such that interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner. Directional terms such as "vertical", "horizontal", "up", "down", "upper" and "lower" are used for convenience of explanation usually with reference to the illustrations and are not intended to be ultimately limiting if an equivalent function can be achieved with an alternative dimension and/or direction.

The present description refers to embodiments with particular combinations of features; however, it is envisaged that further combinations and cross-combinations of compatible features between embodiments will be possible. Indeed, isolated features may function independently from other features and not necessarily be implemented as a complete combination.

In this arrangement, both the fan and the wing must be located close to the aircraft's centre of gravity. The key structural load paths are for the wing and the fuselage. The arrangement of upper and lower beams (1) and (3) provides for both the mounting of the main fans (2) and structural continuity in the fore-aft direction, allowing for attachment of nose landing gear (9), main landing gear (10) and vertical tailplane (11).

The wing spanwise loads cannot pass through the middle of the fan, therefore the load path is split to pass in front and behind the fan via a front spar (8) and a rear spar (6).

This structural configuration allows separation of drive to each of the contra-rotating fans, simplifying the design of the drive train. The lift force from the fans is passed directly to two large beams which form top and bottom booms carrying all fore-aft loads in the fuselage and allows easy installation of empennage and engines.

The vertical separation of the upper and lower beams provides space for the front and rear spars of the wing to pass through. At the intersection, the crossing members attach to provide an efficient load path for transferring wing bending and torsion loads between left and right wings and shear forces between wing and fuselage. This layout will provide a stiff, light structure whilst enabling a large hole in the centre for the passage of air through the main fan.

Advantageously, the present invention effectively provides a failsafe operation where any three vertical fans, during vertical motion, provide sufficient combined lift, should one of the four vertical fans fail. This advantage is provided by the distribution of the fans around the aircraft's centre of gravity and appropriate powering thereof. The configuration intends that, were one fan to fail, the aircraft would still have remaining points to provide lift about the centre of gravity. At the least such a configuration will enable safe descent in the event of one-fan-failure.

Further advantage of this fan layout over the multi-fan lifting arrangements is that the functions of lift and control are de-coupled. In "conventional" rotor-borne vehicles like quad-copters, the main lifting fans must be modulated in power/thrust in order to control the aircraft in roll, pitch and yaw. In small quadcopters, this is not an issue as the inertia forces are low and the response times are high; but as the vehicle is scaled up, the increased inertia of the rotors and the drive system mean that the motors need to be over-sized in order to provide the control functions. This adds to weight and system complexity. Having a single lifting point located close to the aircraft centre of gravity means that it may be sized simply for providing thrust to overcome the aircrafts weight plus a small margin.

The control functions come from the reaction control system, which is a group of fans that provide roll, pitch and yaw control. These fans may be made much smaller due to their distance from the aircraft cg, and in being smaller, they can have much lower inertia forces, which provides faster response times.

Another advantage associated with having a large fan located close to the centre of gravity is the structures must go around the hole in the airframe that is created by the fan duct. The principle load paths are lateral and longitudinal. The lateral loads come from the wing. In normal wing-borne flight, the weight of the aircraft is carried principally by the wing, which reacts the aircraft weight via shear forces at the wing root. In doing this the wing also generates bending moments which are balanced either side of the aircraft. The shear and bending forces are carried in the wing spars which pass in front and behind the fan duct.

In an embodiment the two contra-rotating fans lie within the depth of the wing, so the spar webs form the outer edge of the aerodynamic duct. The motors for the fans are located above and below the contra-rotating rotors. These motors are supported by longitudinal beams above and below the fans. During hover, the thrust from the fans is transferred to these beams which carry the aircraft weight via shear and bending to react aircraft weight. The loads are transferred at the points where the longitudinal beams and front and rear spars intersect. The advantage of this layout is that the upper and lower longitudinal beams may be extended fore and aft to provide an efficient structural load path connecting empennage, engines and landing gear.

The aircraft can take-off conventionally or vertically. A particular aspect of the invention is the vertical take-off that is provided by the main lift fan which powers up such that the thrust exceeds the weight, causing lift-off. The main lift fan lifts over 90% of the aircraft weight, the remainder is carried by the fans in the rear of the aircraft. These also provide pitch control.

Once in the hovering position, the aircraft accelerates forwards using the forward propulsion engines until it gains sufficient forward speed that the aircraft's weight is carried by aerodynamic forces from the wing. During the transition phase, the main lift fan thrust is steadily decreased, and once fully wing-borne flight is achieved, the fans are shut down and the fan bay doors are closed.

From this point the aircraft flies in a conventional manner.

Claims

Claims: 1. A vertical take-off and landing (VTOL) aircraft, comprising: A main pair of coaxial and contra-rotating lift fans located close to the aircraft's centre of gravity providing primary lift. The aircraft hovers by the power of fans located around the aircraft; The centre of gravity will however vary depending on the loading of the aircraft; The aircraft is fitted with auxiliary fans, to be able to manoeuvre and maintain balance: two on the horizontal tail, one on the vertical tail-plane and one on each of the outer wing to control rotation in pitch, yaw and roll axes.
2. The aircraft according to claim 1, wherein the arrangement of upper and lower beams provide for both the mounting of the coaxial contra-rotating main fans and structural continuity in the fore-aft direction; also allowing for attachment of nose landing gear, main landing gear and vertical tailplane.