Half a croissant, on a plate, with a sign in front of it saying '50c'
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Who needs a runway? Every airplane wing can be a helicopter blade

Yet another blend of helicopter and fixed-wing aircraft
  [vote for,

Start with two surfaces facing opposite directions like the blades of a helicopter.

Connect them together with a rod that prevents them flying apart or getting too close, but doesn't resist twisting motion. Instead, to control the pitch of each blade/wing, each has a separate elevator behind it like on the tail of an aeroplane. Also, instead of centrally driving the rotor like on a standard helicopter, have a propeller on each blade/wing (again like it's an aeroplane), to pull it around the central point.

Start up the propellers and the wings spin around like helicopter blades.

Normally (in helicopter mode) the wings point in different directions, but if you tilt them both all the way up to vertically up or all the way down to vertically down, they're both pointing in the same direction. This is aeroplane mode, where together they function like an aeroplane instead of a helicopter. You'd keep them pointing mostly the same direction, adjusting both together to pull up or down, or pointing them slightly differently to roll/bank the pair of wings (rotating it much slower than you'd spin the blades of a helicopter)

The propellers are not expected to have enough power to maintain vertical flight upwards in aeroplane mode - attempting this would risk a stall.

Say both blade/wings are pointing straight down, you can then pull up so the combined aeroplane is flying horizontally instead of downward. In lieu of a rudder, turning is done by banking.

Also while in helicopter mode, you can adjust the wing angles to tilt the virtual helicopter rotor away from pointing vertical - you can tilt it to horizontal before transitioning to aeroplane mode if you want.

There could also be an intermediate mode where the wings are spinning at a moderate rate but it's more like a spinning aeroplane than a helicopter.

Control: This should have some sort of computerised control translating the pilot's intentions into elevator movements, rather than just having the pilot directly control the two elevators. There could be two sets of controls, one for aeroplane mode and one for helicopter mode.

Carrying a central load: As a small-scale remote control toy this isn't needed, but two more rods or cables can be added to the blade-connecting rod, to connect a central load to each point where the connecting blade-connecting rod attaches to the blades (making a triangle). There is a bearing to allow the blades and triangle of connectors to spin freely without the load spinning, and then further joint mechanisms to allow the the load.

Comparison to other aircraft:

Compared to a helicopter it can fly better at high speed (by going into aeroplane mode).

Compared to an aeroplane, it can do vertical takeoff and landing (I haven't specified any landing gear, but it could be attached the same way as a central load).

When I went to put this idea on the halfbakery there were two similar ideas already (so I've used a similar name) but they didn't quite match my vision.

Compared to the aircraft in "Who needs a runway? Every airplane can be a helicopter II", the wings are mounted more like helicopter blades, so there is not a central fuselage that has to spin around together with the blades when in helicopter mode. Also the wings aren't symmetrical front- to- back as they each have the elevator behind them to control their pitch.

Compared to "Who needs a runway? Every airplane can be half a helicopter" the two halves do not need any mechanism to separate and reconnect, and they can be simpler as they do not need to function independently (each separate wing has no left-right steering, and probably no landing gear, though we could add that to eliminate load on the connecting rod during takeoff and landing)

Autogyro: unfortunately the craft has no autogyro mode. It can auto-rotate like a helicopter though, if it runs low on power to run the propellers. I'd been kind of obsessed with autogyros when I was thinking of this idea.

caspian, Jun 06 2013

Similar to what you describe http://www.youtube....watch?v=w0AWUgnVZHo
NASAs Samara concept. I like it! [neutrinos_shadow, Jun 07 2013]

Illustration http://karma.neocit...opter-aeroplane.png
Showing how it could transition from helicopter to aeroplane via a dive [caspian, Oct 14 2016]


       The transition from rotary wing to fixed wing mode would be somewhat umm... exciting!   

       Given the mass of engines, fuel, etc. involved, it would take time to stop rotating and flip one wing around to be facing in the direction of travel and, during that time, lift would be dropping to effectively nil. (If you allowed lift from one wing during the other's transition, you'd also be doing a yawing roll, adding to the fun of falling out of the sky!)   

       Mind you, if done at sufficient altitude, that's not an actual safety issue, and one that's really only an issue if there's a passenger/pilot on board. Cameras and other inanimate cargo don't get motion sickness!
ian_mackereth, Jun 15 2013

       I added an illustration. It should be able to transition from a helicopter to a plane without either wing in particular flipping all the way, each only flips 90 degrees. It may however end the transition in a vertical dive, which the plane then has to pull out of.   

       [Edited to clarify]
caspian, Oct 15 2016

       I suppose you have thought of making the wings out of some adjustable shape polymer to make the aerodynamics better. stringy custard winged helicopter plane with autoadjusting wing profile
beanangel, Oct 15 2016

       [beanangel] standing near a custard winged helicopter plane sounds a bit like standing next to a wet dog, but maybe it could hold together. Is the stringiness for reinforcement?
caspian, Oct 15 2016

       If the aircraft is made from an adjustable super strong polymer then it should stall to land and flap to take off.
wjt, Oct 16 2016


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