3 ms·

Air suspension? Helicopters are aerodynes just like fixed-wing aircraft, deriving lift from aerofoil speed. They are just less efficient because in traditiona

Air suspension? Helicopters are aerodynes just like fixed-wing aircraft, deriving lift from aerofoil speed. They are just less efficient because in traditional single-rotor designs only part of the rotor disk is generating lift at any one time ( and part is stalled ) and of that part needs to be directed as propulsive thrust. Some helicopters have employed short wings to offload the rotor. A wingless VTOL aircraft such as the Flying Bedstead, or the Lunar Lander testbeds, is a non-aerodyne and is even less efficient because it relies on a small volume of highly-accelerated air for lift versus displacement of a large quantity of slow ( roughly speaking ).

11thEarlOfMar 10y ago
Ok, thanks for the explanation. Still wondering if electric powered flight is commercially viable for general purpose human transport.
Gravityloss 10y ago
I guess you could think of a hovering helicopter vs a circling aircraft, both having the same weight and hence same lift. Both have to accelerate some air mass downwards. The lift comes from the velocity x mass = momentum of air, which has to be the same with both. Since the airplane wings affect a larger air volume than the helicopter blades, the airplane accelerates a larger air mass, but to a lower speed. The helicopter: smaller air mass, higher speed. Since energy required is proportional to the second power of speed, the helicopter requires more power for the same lift. You could create a helicopter that was quite efficient in hover, with really big blades. It would then have some other problems, like limited speed.
dragonwriter 10y ago
> Air suspension? Could be a reference to ground effect, and a mistaken belief that helicopter lift is driven by ground effect (ground effect does play into helicopter low-altitude behavior, but as you mention they are aerodynes.)

11thEarlOfMar 10y ago

Ok, thanks for the explanation. Still wondering if electric powered flight is commercially viable for general purpose human transport.

Gravityloss 10y ago

I guess you could think of a hovering helicopter vs a circling aircraft, both having the same weight and hence same lift. Both have to accelerate some air mass downwards. The lift comes from the velocity x mass = momentum of air, which has to be the same with both. Since the airplane wings affect a larger air volume than the helicopter blades, the airplane accelerates a larger air mass, but to a lower speed. The helicopter: smaller air mass, higher speed. Since energy required is proportional to the second power of speed, the helicopter requires more power for the same lift. You could create a helicopter that was quite efficient in hover, with really big blades. It would then have some other problems, like limited speed.

dragonwriter 10y ago

> Air suspension? Could be a reference to ground effect, and a mistaken belief that helicopter lift is driven by ground effect (ground effect does play into helicopter low-altitude behavior, but as you mention they are aerodynes.)