Ultralight coaxial rotor aircraft

Abstract

An ultralight coaxial dual rotor helicopter having a substantially L shaped frame. Attached to the back of the frame is a vertical shaft engine, and a pair of yaw paddles for controlling yaw of the craft. The drive shaft connects to a belt drive at the top of the frame, which transmits the engine power to a transmission and coaxial drive gear for driving the rotors. Crank actuators are provided for tilting the rotor axis to control the pitch and roll of the craft. A pilot seat and ballast tank are attached to the front of the frame. The ballast tank may be filled with a volume of water to balance the craft for the weight of the pilot. The fuel tank is located behind the pilot seat on the centerline of the helicopter, such that as fuel is used and the weight of fuel in the tank changes, the balance of the craft will not be affected.

Description

[0001] This application is a divisional of U.S. patent application Ser. No. 10 / 077,169, filed Feb. 14, 2002, which claims priority to U.S. Provisional Application Ser. No. 60 / 268,978, filed Feb. 14, 2001, both of which are incorporated herewith by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to coaxial helicopter systems. More particularly, the present invention relates to an ultralight coaxial helicopter system. [0004] 2. Discussion of the Related Art [0005] Coaxial helicopters were first developed, in the form of small devices used as toys and curiosities, centuries ago. The earliest attempts at designing a practical helicopter focused on coaxial rotors and dual counter-rotating arrangements. Later, what has come to be thought of as conventional helicopter designs were developed. These were single-rotor helicopters, and it was found that they needed a long tail boom having a tail rotor at the end rotating in a plane roughly p...

AI Technical Summary

Benefits of technology

[0019] In a further more detailed aspect, a pair of yaw paddles extend from the back of the airframe for controlling yaw of the craft as mentioned. These yaw paddles can be configured so as to provide drag during forward flight to limit airspeed, and to improve directability and controllability of the helicopter. In addition, two or more paddles can be provided. Providing a pair of paddles allows their plan form area to be reduced, reducing their susceptibility to yawing the aircraft in cross-winds, while maintaining the same surface area to interact with rotor set downwash.

[0020] In another more detailed aspect, a pilot seat and a provision for removable ballast are attached to the lower front of the L-frame. One means of providing ballast is to provide a fluid ballast tank at the front of a short boom attached to the frame. The ballast tank may be filled with a selected volume of water to balance the craft and account for differences in the weight of different individual pilots. A fuel tank is located behind the pilot seat, and on or adjacent to a center of gravity of the helicopter, and substantially directly below the rotational axis of the rotors. This is done so that as fuel is used and the weight of fuel in the tank changes, the overall weight balance of the craft will not be noticeably affected.

[0022] In another more detailed aspect, the control system can be configured to keep the pilot aware of altitude and to keep the forward speed of the aircraft below a threshold value, so that the aircraft stays low to the ground and relatively slow in relative speed to mitigate harm to the operator from a crash. Furthermore, an emergency power system can be provided to provide temporary power to the rotors for landing in the event of sudden loss of engine power. This system can be powered by stored compressed air, or by another gas generated rapidly from a chemical gas generator triggered by a power failure. Further, additional safety provisions can include providing pontoons with blow-out plugs to mitigate a hard landing in a crash, providing a ground echo location capability and one or more explosive charges to slow the helicopter just prior to impact to mitigate a crash, and to program the control system to automatically take control of the aircraft in an emergency to provide for a relatively soft upright landing. The helicopter can be configured for carrying one or two persons, in the latter case for providing an ultralight trainer.

Problems solved by technology

Without the tail rotor to provide the counter-moment, the airframe could rotate uncontrollably once airborne due to these reaction forces.

While, as mentioned, coaxial helicopters have been known for many years, development of this type of aircraft has heretofore been limited because of complexities involved in arrangements for control of the rotor blades to give roll, pitch and yaw control.

The control arrangements are necessarily complex, and relatively high forces must be transferred by the swashplate assemblies and control links, so they must be robust, and accordingly, heavy.

This arrangement does not allow differential collective to be applied for yaw control, and so a further means for yaw control is typically provided.

The power output of the engine may also be varied, albeit within a fairly narrow operational power band, and this can affect lift and yaw.

However as noted above, there is a trade-off for these advantages, in that providing for the control of coaxial rotor helicopters presents additional complexities and increased swashplate, linkage, and rotor weight and increased maintenance concerns.

Such known ultralight helicopters essentially mimic full-size conventional helicopter propulsion and control systems, and tend to be expensive.

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