Aeronautics and astronautics – Aircraft – heavier-than-air – Airplane and helicopter sustained
Reexamination Certificate
2002-08-26
2003-12-30
Dinh, Tien (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Airplane and helicopter sustained
Reexamination Certificate
active
06669137
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This patent is an improvement of my patent titled “Air Vehicle Having Scissors Wings” with U.S. Pat. No. 6,601,795B1 and Date of Patent Aug. 5, 2003.
FEDERALLY SPONSORED RESEARCH
Not Applicable.
REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX
Not Applicable.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to air vehicles such as manned and unmanned air vehicles and, in particular, to air vehicles that can fly both in helicopter mode and airplane mode to achieve vertical and/or short take-off and landing (V/STOL) and improve their flying efficiency at a wide range of speed and flying conditions.
2. Description of Prior Art
Various attempts have been made to combine helicopter's excellent capability of vertical and/or short take-off and landing and fixed-wing aircraft's ability of flying at a wide range of speed.
U.S. Pat. No. 5,454,530 “Canard Rotor/Wing” issued to J. W. Rutherford et al invents an aircraft utilizing a jet-propelled rotor/wing, preferably having two blades, to achieve V/STOL when it is in helicopter mode. During the conversion from the helicopter mode to airplane mode, the aircraft utilizes its canards and horizontal tail to generate most of the lift to offload the rotating rotor/wing. Afterwards, the rotating speed of the rotor/wing is slowed down and eventually stopped so that the aircraft is in airplane mode with the two blades of the rotor/wing become the left and right wing of the aircraft. When flying in airplane mode, the rotor/wing can operate like an oblique wing to maximize flight efficiency at different speeds.
A disadvantage of this invention is that different requirements to the canards and horizontal tail at different flying conditions force these aerodynamic surfaces to compromise their key parameters. The canards and horizontal tail should generate almost all the lift for the aircraft during the conversion between helicopter mode and airplane mode, but they are mainly used as control surfaces at other flying stages. As the canards and horizontal tail should be large enough to generate almost all the lift for the aircraft but they are mainly used as control surfaces at airplane mode, they make the aircraft inefficient at airplane mode.
U.S. Pat. No. 3,327,969 “Convertible Aircraft” issued to R. E. Head is an invention also utilizes a jet-propelled rotor/wing. During V/STOL, the rotor/wing rotates like a helicopter and generates lift with three stub blades installed on a big center body of the rotor/wing. During the conversion between helicopter mode and airplane mode, the big center body generates lift while the rotor/wing stops or begins to rotate. At airplane mode, the center body and two of the three stub blades generate lift for the aircraft.
This invention has a disadvantage of low flying efficiency. The relatively small and low aspect ratio stub blades are not efficient in generating lift at helicopter mode. In addition, the center body, which has a very small aspect ratio, has to generate almost all the lift during the conversion between helicopter mode and airplane mode. As the conversion should be made at a low speed, this low aspect ratio center body has to have large area to generate enough lift because its lift-to-drag ratio (L/D) is low. Furthermore, at airplane mode, one of the three stub blades is located with its long axis generally parallel with the longitudinal axis of fuselage, generating little lift.
Patent JP 404317891A “Aircraft For Vertical Take-Off And Landing” issued to H. Hatano is an invention utilizing two sets of rotor/wings that can convert between rotors and fixed wings. The two sets of rotor/wings are either mounted above the fuselage of an aircraft in tandem with one rotor/wing in front of another, or co-axially installed above the fuselage with one rotor/wing above another. During take-off, landing, and low speed flying, the rotor/wings rotate in opposite directions to make the aircraft fly like a helicopter. At high speed, both of the rotor/wings stop rotating to become fixed wings and the yaw angles of both fixed wings can be changed to fit different speeds.
One disadvantage of this invention is its complexity. When both of the rotor/wings are installed co-axially above the fuselage, the hub of the rotor/wings should contain mechanisms to control the collective pitch and cyclical pitch of the two counter-rotating rotor/wings at helicopter mode and the sweep angles of both of the rotor/wings at airplane mode. Having so many control mechanisms, the hub is not only complex but also difficult to have small size thus generates considerable drag during high-speed flights.
Another disadvantage is poor controllability and stability. During the conversion between helicopter mode and airplane mode, both of the rotor/wings have to keep generating lift to support the aircraft while they are being stopped or started to rotate, making the aircraft difficult to have good controllability and stability during the conversion.
X-wing configuration, as shown in U.S. Pat. No. 4,711,415 “X-Wing Helicopter-Scout Attack Configuration” issued to J. A. Binden, consists of a rotor/wing that can rotate as a rotor at helicopter mode and a fixed “X” shaped wing at airplane mode. The fixed sweep angles of the blades of the X-wing are affected by the requirements of helicopter mode, making them usually be a 45-degree sweep-forward angle for two blades and a 45-degree sweepback angle for the other two blades. These fixed sweep angles make a X-wing aircraft difficult to achieve efficient flying at a wide range of speed at airplane mode.
U.S. Pat. No. 2,879,013 “Convertible Aircraft” issued to G. P. Herrick is an invention utilizing a straight rotor/wing and a straight fixed wing. At helicopter mode, the straight rotor/wing rotates like a two-blade rotor of a helicopter. At airplane mode, the rotor/wing is stopped and together with the fixed wing, forming a configuration similar to a biplane. This invention cannot make an aircraft fly at high speed because the two straight wings can generate huge drag at high speed flying.
BRIEF SUMMARY OF THE INVENTION
The fundamental object and advantage of my invention is to build an air vehicle that can efficiently and effectively achieve V/STOL and fly at a wide range of speed up to supersonic speed. Specifically, the objects and advantages of an air vehicle based on my invention are:
1. Have V/STOL capability;
2. Can easily convert between helicopter mode and airplane mode;
3. Can efficiently and effectively fly at a wide range of speed up to supersonic speed;
4. Can fly at transonic and low supersonic speed without generating sonic boom.
A rotor/scissors wing configuration has been invented to achieve the above-mentioned objects and advantages. The invention has a fuselage, a rotor/scissors wing, and a scissors wing. The rotor/scissors wing is installed above the fuselage and the scissors wing is rotatably mounted on the fuselage. The following paragraphs explain how can the invention realize the above-mentioned four objects and advantages.
First, an air vehicle based on the invention can have V/STOL capability. At helicopter mode, the rotor/scissors wing rotates in a way similar to rotors of helicopters. There are two ways to drive the rotation of the rotor/wing. The first way is to direct the exhaust gas from at least one turbofan or turbojet engine to the jet nozzles located on the rotor/scissors wing to propel it to rotate. Another way is to transmit the shaft power generated by at least one turboshaft/turbofan convertible engine via a transmission system to drive the rotor/scissors wing to rotate. Tested on engines like the turboshaft/turbofan convertible engine based on a modified General Electric TF34 engine, turboshaft/turbofan convertible engines can work at both turbofan mode to provide thrust and turboshaft mode to provide shaft power.
When using the exhaust gas from turbofan or turbojet engines, the rotating rotor/scissors wing generates little, if any, torque moments on the a
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