This invention relates in general to an aircraft having a rotor for providing lift for take off and landing, and wings for providing lift at cruise flight speeds, the aircraft having an electric motor for selective rotation of the rotor.
A type of slowed rotor aircraft, sometimes called a gyroplane, is illustrated in U.S. Pat. No. 5,727,754. The aircraft has a rotor similar to a helicopter blade rotor. The aircraft has a propeller that provides forward thrust, and wings for providing substantially all of the lift in cruise flight. The rotor blades have weighted tips to create inertia. The aircraft in the '754 patent will perform a jump takeoff by rotating the rotor at a speed higher than that needed for steady state flight while the collective pitch is at zero and the landing gear brakes on. The propeller is also rotated prior to takeoff. The collective pitch of the rotor and propeller are then increased to a takeoff level and the brakes released, which causes the aircraft to lift. A clutch disengages the engine from the rotor at the moment of takeoff, but the inertia of the rotor continues spinning the rotor after liftoff.
As the aircraft accelerates forward and the rotor rpm decays, the rotor is tilted back relative to the airstream, causing the rotor to auto-rotate. The auto-rotation of the rotor occurs due to the airstream passing through the rotor blades. As the aircraft gains forward speed, the wings will begin providing a greater portion of the lift required to maintain the aircraft in flight. As the aircraft forward flight speed increases further, the wings will provide substantially all of the lift, at which point the rotor collective pitch will have been reduced to at or near zero. The rotor rpm will be maintained at a slow rate by tilting the rotor relative to the fuselage.
The rotor aircraft described herein has an engine and a propeller driven by the engine to provide forward thrust to the aircraft. Wings provide lift while in forward flight. A rotor having a rotor drive shaft is mounted for selectively providing lift. An electric motor selectively applies torque to the rotor drive shaft. At least one rudder is positioned within a prop blast region of the propeller. The rudder is sized to counter torque applied by the electric motor to the rotor drive shaft while the aircraft is airborne.
The electric motor may comprise the sole source for applying torque to the rotor drive shaft. Alternately, a clutch may be connected between the engine and the rotor drive shaft for selectively engaging and disengaging the engine from the rotor drive shaft. The clutch is located such that the electric motor is able to supply torque to the rotor drive shaft while the clutch is disengaged.
The electric motor may be sized to supply all of the torque to pre-rotate the rotor to a selected liftoff rotational speed prior to liftoff of the aircraft. If so, a clutch between the engine and the rotor drive shaft may not be needed. Alternately, the electric motor may be sized to pre-rotate the rotor prior to lift off to a selected fraction of a pre-rotation liftoff speed while the clutch is disengaged. When reaching the selected fraction, the clutch may be engaged to enable the engine to apply torque to the rotor drive shaft to reach the pre-rotation liftoff speed.
The aircraft has sensors for sensing flight conditions of the aircraft. A controller controls the electric motor while the aircraft is airborne in response to input from the sensors. The wings are capable of providing substantially all of the lift required during forward flight at a cruise speed. The rotor is capable of being positioned to provide substantially zero lift and auto-rotate due to air flowing through the rotor at the cruise speed. The controller may cause the electric motor to cease applying torque to the rotor drive shaft during autorotation at cruise speed. The controller may cause the electric motor to apply torque to the rotor drive shaft during flight if the sensors indicate additional rotor speed is needed.
Referring to
Aircraft 11 also has a pair of vertical stabilizers 19, each of which has a moveable rudder 21. Each vertical stabilizer 19 is mounted on a separate boom or tail portion 23 extending aft of fuselage 13. An elevator 24 extends between vertical stabilizers 19.
A rotor mast 25 extends upward from fuselage 13 and supports a rotor 27, which comprises at least two blades. Preferably, rotor mast 25 may be tilted in forward and rearward directions relative to fuselage 13. The blades of rotor 27 are weighted at their tips by weights for increasing stiffness at high rotational speeds and for creating inertia. Each blade of rotor 27 may have a shell that encloses a longitudinal twistable carbon fiber spar (not shown). The spar is continuous through the shell and attaches to the shell at approximately 40 percent of its radius. Other rotor constructions are possible. Each blade of rotor 27 is pivotal to various collective pitches about a centerline extending from rotor mast 25.
A forward thrust device, which in this example is a single propeller 29, is mounted on a rear portion of fuselage 13 and faces rearward. Rudders 21 are positioned aft of propeller 29 in a region that receives a discharge or prop blast from propeller 29. Even when aircraft 11 is not moving forward, part of the airstream from propeller 29 flows past each rudder 21. Propeller 29 may have a continuous carbon fiber spar (not shown) that runs from blade tip to blade tip. The carbon fiber spar is twistable inside a shell of propeller 29 to vary the collective pitch. Other devices and arrangements to provide forward thrust to aircraft 11 are possible.
A rotor drive shaft 35 extends upward from fuselage 13 within rotor mast 25 (
In the embodiment of
A controller 41 controls electric motor 37, such as by controlling the power provided from battery 39. A number of flight condition sensors 43 are linked to controller 41. These sensors 43 may include ones that sense the following: airspeed; angle of attack of wings 15; torque applied to rotor drive shaft 35; lift provided by rotor 27; and rotational speed of rotor drive shaft 35. Other conditions may also be sensed. Controller 41 includes a processor that computes a desired rotational speed or torque to be applied to rotor drive shaft 35 by electric motor 37 depending upon the flight conditions sensed.
In operation of the embodiment of
While torque is being applied to rotor drive shaft 35 by electric motor 37 a counter torque is generated against fuselage 13. There is no tail rotor in the embodiment shown. The pilot will orient rudders 21 to prevent fuselage 13 from spinning in an opposite direction to rotor 27. While still at slow forward speed, the prop blast over rudders 21 resists this counter torque.
At a steady state cruising speed, the collective pitch of rotor 27 will be at or near zero and the tilt of rotor mast 25 placed so that rotor 27 will be auto-rotating at a slowed speed, such as 100 to 200 rpm. Controller 41 may control electric motor 37 so that it will not be supplying any torque to rotor drive shaft 35. Under these conditions, rotor 27 supplies very little of the lift for aircraft 11.
Occasions may arise during flight that require rotor 27 to rapidly increase its speed, without significantly increasing its collective pitch. For example, turbulence encountered during cruise flight may result in a loss in some of the lift provided by wings 15. Increasing the collective pitch and tilt of rotor 27 would increase the speed of rotor 27, however, these steps could result in excessive flapping of the blades of rotor 27. Instead, when sensing a need for more lift to be provided by rotor 27, controller 41 will cause electric motor 37 to begin applying torque to rotor drive shaft 35, rapidly increasing the rotational speed of rotor 27. Controller 41 may decrease and completely cut off the torque supplied by electric motor 27 once the conditions merit. A similar need for a rapid increase in the rotational speed of rotor 27 would occur in the event engine 31 fails.
During a short landing, as the forward airspeed of aircraft 11 declines, wings 15 will supply less lift. Rotor 27 may be tilted and the collective pitch increased to provide more of the lift. If desired, controller 41 may cause electric motor 41 to apply torque to rotor shaft 35 during landing to augment the rotational speed caused by auto-rotation and control the rotor speed.
In the embodiment of
In the
Once the pilot initiates liftoff, clutch 49 disengages engine 31 and the rotational speed of rotor 27 begins declining. Controller 41 may continue to cause electric motor 37 to apply torque until steady state forward flight conditions occur. Controller 41 may control the torque input of electric motor 37 to rotor shaft 35 in the same manner as in the embodiment of
The first embodiment eliminates a need for a clutch between the engine and the propeller. If the engine is an internal combustion type, a gear box may be eliminated. In the second embodiment, the electric motor pre-rotates the rotor to a selected fraction of the liftoff rotational speed, at which time the engine will be engaged to complete the pre-rotation. In both embodiments, the electrical motor can be used during flight for increasing the speed of rotation rapidly if needed.
While the disclosure has been shown in only two of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.
This application is a continuation-in-part of Ser. No. 13/305,441, filed Nov. 28, 2011.
Number | Date | Country | |
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Parent | 13305441 | Nov 2011 | US |
Child | 13445594 | US |