Helicopters are the ugly ducklings of the aerospace world. They are noisy, suffer from high vibrations and are much slower than fixed-wing aircraft. They have a shorter range and have higher maintenance costs. In short, people use helicopters when they have to, since they can land almost anywhere, but whenever there is is choice, fixed-wing aircraft are still the transport of choice.
Is it Time for Something New?
At the same unmanned rotorcraft have advanced greatly in recent years, such that consumer drones can now be purchased for the same price as a bicycle. Military drones such as the Northrop Grumman Fire Scout and Boeing Hummingbird have also pushed the limits for what full scale and autonomous rotorcraft can achieve.
Given the inherent discomfort for people flying in helicopters, and the success of unmanned rotorcraft drones, perhaps now is the time to revisit unmanned rotorcraft for a clean sheet design that avoids any human-associations from the beginning.
An arrangement where the entire rotorcraft spins without a joint between the rotor and body would be no problem for modern fly-by-wire control systems to deal with, and could bring a cleaner and simpler design with several advantages:
- No need for a tail rotor, removing a power drain of 5-10% on conventional helicopters (and the associated weight).
- No movement between the main rotor and fuselage, no swash plate and no interface machinery between the fuselage and rotor leading to reduced drag and reduced vibrations (and a weight saving).
- More variability in rotor speed allowing for efficient flight at a greater range of speeds, better altitude performance and reducing noise and vibration.
How would a Flying Rotor Work?
An all moving body and rotor combination requires powering the rotation with rotor tip jets. There are several way to achieve this:
- Compressed air or reactive chemicals stored in the body provide a compressed gas supply that is released at the rotor tips. This design is simple, relatively quiet and safe but has lower energy density.
- Fuel stored in the body could be pumped to the rotor tips, where it would be burned. This would be also be relatively simple but very loud and not so fuel efficient.
- Fuel stored in the body could be used to power a gas turbine, with the exit gases then in turn being routed to the rotor tips. This is the most complicated setup, but produces the best balance between noise and efficiency.
Control of the aircraft could be achieved by vertical tip jets or tip jet deflectors operated by the flight control computers. These would, for example, only activate on one side of the rotor, in order to turn the rotor towards the intended direction of flight.
Normal skid landing gear seen on helicopters would not work, since there is no part of a flying rotor that is not moving relative to the ground. Therefore a new wheeled landing gear design would need to be developed.