Hybrid tilting aircraft

An airplane and a helicopter operate on some very different principles. This typically results in a plane of the same weight and having the same amount of fuel/energy covering a lot more ground, and staying in the air a lot longer (more efficiently) than a helicopter. In exchange, it has a less precise feedback cycle for positioning (relying on airflow subject it to wind turbulence), and it has to take off and land in a cleared runway. It is very attractive to try and split the difference, and create an airframe which can both hover safely to the ground, and efficiently glide. There are a number of experimental methods available to do this in UAVs.

This does *not* include aircraft which do not glide, such as pitch-control helicopters, bicopters, tricopters, electronically controlled multirotors, and coanda effect vehicles.

Full-size tiltrotors, tiltwings, and tailsitters

The V-22 Osprey manned tiltrotor and Eagle Eye UAV tiltrotor are fixed-wing, tilting-prop bicopters, which work like a traditional fixed-RPM cyclic/collective tandem helicopter in hovering mode.

The V-22 tiltrotor loses about 10% of its hovering lift to drag from the horizontal wing surface. In designs like the tilt-wing (never built on more than an experimental basis), the aerodynamic surface of the wing rotates with the prop.

In tail-sitters (never built on more than an experimental basis), the entire fuselage rotates and lands on its tail in hovering flight.

Variable Pitch and Fixed Pitch

Variable-pitch blades like a helicopter tend to be very inefficient compared to fixed-pitch blades, since they have to be optimized for a variety of lift conditions even within a single cycle of rotation (cyclic control). They're also mechanically complex and not very durable compared to simple fixed props and brushless motors. The advent of the RC multirotor is thanks to controllers which allowed multiple simple brushless motors to balance each other in flight with slight throttle corrections. These methods of using fixed-pitch control are simply not done on human-scale aircraft, because they require the fast response of a battery and electronic controller rather than an internal combustion engine, so fixed-pitch VTOL methods are still a rather novel area, largely specific to smaller models (although the growth of fuel cells will start to change this).

Examples

Tricopter Tiltrotor

These use three props in forward flight, and two throttle-controlled props as well as a throttle/roll-servo controlled prop in hovering flight. A pitch-servo is mounted to each motor for the transition, and may or may not serve as an active degree of freedom in hovering.

Here is the IAI Panther, which transitions from a V-tail sailplane to a tricopter by tilting all three of the fixed-pitch props and adjusting throttle. Props are mounted as pullers forward of the wing and pushers aft of the fuselage

Here is a model with two pushers mounted on both sides of a front canard, and one pusher rear-mounted.

Quad Biplane Flying Wing

Here is the Foxteam Hybrid, essentially a quadrotor with tilt-wings, except that there is no traditional fuselage, no tail, and no elevator / vertical stabilizer, all fixed-wing control is occurring using differential thrust.:

• link

Tractor Prop Tailsitter

Tailsitters may use a pair of tractor props on each wing, a coax tractor prop, or with a great deal of difficulty one traditional tractor prop and flapperon yaw stabilization.

Here is a student project that built a traditionally-styled tail-sitter, which flies vertically using control surfaces like in 3D flying.

Here are three examples of less plane-like trail-sitters, which use 2-d symmetry instead of 1-d symmetry and use what are essentially four wings. Four-wing tailsitters don't have to pay as much attention to hover-mode yaw (which is glide-mode roll) in hovering mode, since they behave identically in different orientations. Because of the amount of aileron / (?vertical aileron?) that these have to use to de-twist the single prop's airflow, these may be easier to fly at a higher level of abstraction through an IMU/autopilot rather than using the four dimensions of analog stick throw on a normal transmitter. A four-wing tailsitter bears more than a passing resemblance to a single-rotor coanda-effect helicopter which also uses flapped control surfaces, the difference is a matter of how well it can glide.

• Indoor UAV capable of fixed point flight and efficient forward flight

• VTOL mode testing with the UAV devboard / matrixpilot

• E-flite UMX Hyper Taxi

Quad Nacelle Flying Wing

The Quadshot uses a single wing, with four props mounted on above and below via vertical extensions.

The Quadshot now has its own page with video reviews.

Flexrotor

This unique arrangement uses helicopter-style collective and cyclic pitch on a large main rotor, with the unusual use of ailerons for roll control and small wingtip rotors for yaw. The entire fuselage is rotated between hovering and horizontal flight.

Droop-Wing Coax Tiltrotor

Baldwin is pushing this concept as a container skycrane:

Quad Tandem Tiltrotor

Two tandem wings with tilting props on the end.

Plane Quad Graft

A small quadrotor simply attached to a bigger fixed-wing plane. The quad does nothing during gliding flight, the plane's prop does nothing during hovering.

Coanda Pusher Tailsitter

Uses 4-vane vectored thrust of an oversized ducted fan for stabilization, despite being an inverted pendulum. Uses canard elevators and flapperons for forward flight.

This one sticks purely to flapperons in a swept flying wing:

Links

• Paparazzi-based Quadcopter/Biplane hybrid transitions to and from horizontal flight - a quad VTOL biplane, proof of concept for Booz project by Poin at ENAC
• FOX Hybrid V2 - another quad VTOL biplane, Foxteam UAV Clan
• cgvalant85's VTOL Tail Sitter Senior Project - twin engine, twin boom stabilized 3D plane with landing gear tail