Vehicle: Aircraft: Rotation
Tiltrotor Autogyro Quadcopter Hybrid   (+4, -1)  [vote for, against]

An autogyro flies via autorotation of the unpowered main rotor.

A quadcopter allows simple, stable control without the need for varying the rotor pitch.

A tiltrotor can face its rotors horizontally or vertically for speed or lift. The aircraft has fixed wings to provide lift when the rotors are facing forwards.

This invention at first looks just like a quadcopter and is easily capable of vertical take off and landing. However, when at an acceptable altitude, two of the rotors tilt forwards, and the other two disengage from the engine.

The front facing rotors provide thrust while the freewheeling rotors provide lift via autorotation.

No fixed wings means greater efficiency for vertical takeoff.

Lift like an autogyro means safe landings are possible in the case of engine failure.

Top speed should be (at least slightly) greater than a quadcopter. Probably best suited for intercity travel and rescue missions.
-- mitxela, Feb 01 2011

// A quadcopter allows simple, stable control without the need for varying the rotor pitch. //

What? Maybe you mean without individual cyclics, but it sounds like all of them are fixed-pitch rotors, and you are doing pitch control by RPM varying, which is hard to do in full-size and non-electric (turbine would be worst). Fixed pitch is very impractical when switching from lift to autogyro, or lift to thrust.
-- baconbrain, Feb 01 2011

I think his point is that helicopters are less efficient and slower than autogyros (of comparible sizes) and therefore the suggestion isn't to fix the pitch of the blades, but to have fully articulated rotors which can be free-wheeled or tilted.
-- TomP, Feb 01 2011

Rotary wing = very bad.
-- 8th of 7, Feb 01 2011

//Rotary wing = very bad//

Not at slow speeds, and at high mu ratios, autorotation can be quite efficient. As long as this is not for trans-continental high speed flight, this isn't bad.

I think this idea is looking to replace helicopters rather than aeroplanes, in which case, this can fly in and out of small spaces, hover, fly very slowly (therefore good camera platform) and fly faster than a most current helicopters more efficiently - i.e. //for intercity travel and rescue missions// and camera work.

Only problems are that more rotors => more drag at high speeds, and the hover requirement means that a higher power engine is needed.
-- TomP, Feb 01 2011

random, halfbakery