# Why does a helicopter float motionless but still consume gas?

• fxdung
In summary, a helicopter consumes energy even when it is floating motionless because the blades are still doing work to push the air down.
fxdung
When a helicopter float motionless the work done on it is zero.But why does it still consume energy?A similar question is why when we hold still a weight, we must consume energy(we feel fatigue)?

It is not true that no work is being done. The rotor blades do a LOT of work pushing air down and thus causing the helicopter to accelerate upwards at 9.80665 m/sec/sec in a gravitational field that is causing it to accelerate downwards at the same rate. So ... helicopter stays motionless, air moves. From the frame of reference of the air, the helicopter is moving quite a bit and is doing a lot of work.

I think the aerodynamics of it all may be a bit more complicated than that simple explanation, but you get the idea ...

The exact same question was asked recently in the form of "if I push a box across the floor against friction, I am doing work, but in MY frame of reference the box isn't moving so I'm actually NOT doing any work. What gives?" In his frame of reference he is doing work moving the floor under him. In both his question and yours, you can't get rid of the work being done just by changing frames of reference.

FactChecker, russ_watters, davenn and 1 other person
fxdung said:
When a helicopter float motionless the work done on it is zero.But why does it still consume energy?A similar question is why when we hold still a weight, we must consume energy(we feel fatigue)?
Both are inefficient ways to generate a static force. The energy goes into moving air and heat.

fxdung said:
When a helicopter float motionless the work done on it is zero.But why does it still consume energy?
They don't always consume energy when floating motionless...

http://avia-proekt.ru/img/ch7_9.jpg

sophiecentaur, russ_watters, davenn and 5 others
phinds said:
I think the aerodynamics of it all may be a bit more complicated than that simple explanation, but you get the idea ...
Due to the nature of the question, the aerodynamics are unimportant and the Newton's 3rd law + definition of work (power) explanation is all that is needed.

If I had a quibble it would be on the need to discuss reference frames here. To me it's about the proper definition of the system being analyzed. A helicopter is not a book sitting on a table, it's a fan sitting on a table. The fan does work because it's a fan!

FactChecker
Why does a helicopter float motionless but still consume gas?

If you turned the engine off, would it continue to float?
If not, why not? (Please write a sentence for that and not a one-word answer)

davenn
fxdung said:
When a helicopter float motionless the work done on it is zero.
Helicopters dont float, They hover

russ_watters
A.T. said:
The energy goes into moving air and heat.
Yup, that description couldn't be much closer. . . as to how the real deal works .

.

## 1. Why does a helicopter need to consume gas to stay afloat?

Helicopters use fuel to power their engines, which in turn rotate the blades and create lift. Without this lift, the helicopter would not be able to stay in the air and would eventually crash.

## 2. How does a helicopter stay motionless while in the air?

Helicopters have a complex system of rotors and control surfaces that allow them to hover in one place. By adjusting the pitch and angle of the rotors, the helicopter can counteract gravity and stay in one spot.

## 3. Can a helicopter stay motionless without consuming gas?

No, a helicopter needs to constantly consume gas to maintain its position in the air. Even when hovering, the rotors are still spinning and using fuel to maintain lift.

## 4. Why does a helicopter consume more gas when flying than when hovering?

When a helicopter is flying, it needs to use more power to move forward and maintain lift. This requires more fuel consumption compared to when it is hovering in one spot.

## 5. How does the weight of a helicopter affect its ability to hover?

The weight of a helicopter directly impacts its ability to hover. Heavier helicopters require more power and fuel to maintain lift, while lighter helicopters can hover more easily with less fuel consumption.

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