Airbus Is About To Build A Self-Flying Electric Robo-Taxi (fastcompany.com)

Airbus said today it is building a prototype of an electric self-flying plane for a single passenger, which it is calling the Vahana. The autonomous plane can fly a single passenger on trips of around 50 miles. From a report on FastCompany: Airbus teased two possibilities for the Vahana on December 14: an electric helicopter and a plane with wings that tilt up to enable vertical take off and landing, or VTOL. After its engineers ran the numbers on both types, Airbus today announced that it's building a prototype of the sci-fi looking tilt-wing plane, which will begin test flights before the end of the year. "The vehicle is being built. Parts are being made as we speak," says Airbus chief engineer Geoffrey Bower. The company's goal is to get air taxis in service in about 10 years, possibly partnering with ride-hailing companies like Uber. "We would love to see what that kind of partnership might evolve into," says Maryanna Saenko of Airbus Ventures.

Comments

Rotary wings are not very energy efficient.

[140Mandak262Jamuna]

[I am leaving auto gyros out, though they are technically rotary wing a/c]

In fixed wing aircraft the thrust from the jet or propeller equals the drag, and the lift produced by the wings. The lift to drag ratio for most aircraft will exceed 10. Thus the plane needs to produce one tenth of its weight as thrust. There are specialized aircraft gliders/sailplanes etc that can push this ratio up to 20. I vaguely recall something called Eppler airfoil that has a lift/drag ratio of 40 for a narrow range of Reynolds number.

But a helicoper needs to produce thrust equal to weight. Thus it can hover and take off and land vertically. But it consumes a lot more fuel than fixed wing aircraft. So much so that it is uneconomical even to serve as air taxis between a metro hub and the suburban airport.

People with deep pockets, military, has been trying various formats to get vertical take off and fixed wing efficiency. The tilt wing aircraft like the Osprey (C22?) have lots of stability issues during the transition. Vectored thrust aircraft like Harrier also suffers from fuel efficiency issues. I do not see how changing the energy source from combustion to electro chemistry is going the change the physics of the problem.

Re:Rotary wings are not very energy efficient.

[joe_frisch]

Agreed. Hovering requires thrust > weight. Power goes as mass/time * velocity^2, while thrust goes as mass/times * velocity. So to have efficient thrust for lift you need to move a lot of air slowly, not a little air quickly. This is why helicopters have enormous swept disk areas. Any design that uses less area will be less efficient than a helicopter - already a very inefficient device.

Less efficiency means less range (already a problem with an electric), heavier motors and batteries, AND more noise and down-wash damage.

Tilt rotor sounds great, but adds a lot of additional weight and complexity on an already very marginal system. It allows high cruise speeds, but it takes time to climb and accelerate / decelerate, while navigating crowded airspace. Cruise speed tends to be an issue mostly on much longer trips than 50 miles.

So, how is this better than a single person helicopter?

Then, even if it works, where can it be used? No way noise ordinances will let someone use it from their back yard or city street At least in the US aircraft need to carry a half hour of spare fuel for safety. There are air traffic control issues if there are more than a few of these.

I just don't see a use case that wouldn't be better served with a conventional (but autopilot controlled) helicopter.

Looks like marketing silliness to me. I'll believe it when I see a working prototype

Re:Good design

[ASDFnz]

My only quibble is the design relies on differential torque of the propellers for pivot rotation. I think it would be better to arrange for thrust vectoring for this. Also thrust vectoring would allow you to run identical propellers because the thrust vectoring can eliminate the torque.

Differential torque is far more efficient than thrust vectoring. To alter your angle of trust you need a minimum of one extra motor that does nothing but provide the function (and weight, and battery draw).

Since your props are already spinning in a counter rotation function (to stop it taking off like a spinning top) the extra function of providing yaw is just about free in terms of weight and battery life.