74 votes
Accepted

Do helicopters use more fuel when hovering?

Yes it is correct that helicopters use more fuel when hovering: the engine needs to apply more power to overcome drag. Here is a graph of the engine power required for different airspeeds, from J. ...
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50 votes
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Why do helicopters have such limited range?

Helicopters are very inefficient in forward flight, for several reasons. Consider Glauert's high speed assumption, i.e. the helicopter can be represented as an aircraft with a circular wing during ...
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50 votes

Can a helicopter carry a large airplane?

If you look more closely, this "airplane" is only the husk of a Tupolev Tu-134, a rather small airliner, and the helicopter is a Mil-26, the heaviest helicopter ever to go into production. Not only ...
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40 votes

Do helicopters use more fuel when hovering?

Yes, it is correct, if the helicopter doesn’t fly too fast. A helicopter will produce the necessary lift most efficiently at a moderate forward speed. In a hover all the airflow which is available ...
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33 votes
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Can a helicopter really fly with rotors going this slow?

It's an illusion that the blades appear to be going slowly. It's actually a well known effect called the wagon wheel effect. Essentially the rotor is spinning at close to an even multiple of the ...
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33 votes

Would a helicopter with the blades on the bottom fly the same, if at all?

Yes that is possible, like the Hiller flying platform demonstrated. It had two counter-rotating propellers inside a shroud and the pilot controlled his craft by shifting his body weight, like on a ...
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30 votes

Why do helicopters have such limited range?

Because they are less efficient than fixed-wing aircraft. The rotor blades need to move significantly faster than the craft and therefore incur significantly more drag than fixed wings. More drag is ...
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  • 54.1k
27 votes

Do helicopters use more fuel when hovering?

Yeah, I'm not a physics student, but I work on Black Hawks. If you conceptualise a helicopter as just a main rotor disc producing lift, then Peter Kampf's answer about mass-flow through the rotor disc ...
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  • 271
27 votes

Why does a turbine helicopter need to spin a tail rotor?

Well, that’s complex. Where should I begin? The main job of the tail rotor is to use its long lever arm and directed force/thrust (horizontal lift) to counteract the torque of the spinning main rotor....
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26 votes
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Is it possible to fly with counterbalanced single blade engines?

Both Bo-102 and 103 were experimental aircraft, with Bo-102 more of a jig than an actual aircraft. They were used a testbed for various technologies and the single blade rotor is only one of them , ...
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  • 98.6k
24 votes

Would a helicopter with the blades on the bottom fly the same, if at all?

We spend all our weekends mowing lawn with these guys. Courtesy: Helifreak.com You can find thousands of Youtube videos showing how comfortably they can do that
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  • 5,951
23 votes

Why haven't quadcopters been scaled up yet?

Quadcopters are not an efficient design -- one large rotor is far more efficient than four smaller rotors. The reason quadcopters became popular is that they are mechanically simpler, safer (due to ...
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20 votes

Do you know the exact model and use of this rotorcraft?

It's a Bell TH-57, most likely a TH-57C, which is the Navy's variant of the Bell 206 JetRanger. It's used for VFR and IFR helicopter primary flight training for the Navy and Marine Corps. Most ...
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19 votes

Why haven't quadcopters been scaled up yet?

Advanced Tactics has also somewhat did it! A video of the first flight of the Black Knight Transformer has been released on Youtube.
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  • 2,415
19 votes

Do helicopters use more fuel when hovering?

The concept is known as "translational lift". When moving in forward flight, a helicopter's rotor disc acts a lot like an airplane's wing - it has a significant lift-to-drag ratio. The required ...
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  • 4,561
16 votes
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How do the Kaman K-225 rotor "planes" work?

These are a form of servo flap, commonly found on Kaman designs, but also on at least one early helicopter (namely, a coaxial rotor aircraft built by d'Ascanio (shown below): As opposed to ...
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  • 3,551
16 votes

Can a tiltrotor fly safely with one engine?

Short Answer: yes. If they could not, they'd likely not get certified One engine can drive both prop rotors. After digging into an old version of the V-22 flight manual, I find a whole pile of tables ...
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15 votes

Can a helicopter carry a large airplane?

One of the purposes of the Sikorsky CH-54 was to transport aircraft. Carrying a Chinook: Lifting a Caribou:
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14 votes
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How are folding wings managed?

The wing folding mechanisms (in aircraft) and rotor folding mechanisms (in helicopters) are different. The V-22 Osprey falls somewhere in the middle. In case of aircraft, the wing folding mechanism ...
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  • 98.6k
14 votes

Would a helicopter with the blades on the bottom fly the same, if at all?

One of the first helicopters that really flew (c. 1918) was the 'Petróczy-Kármán-Žurovec', intended to be used by the Austro-Hungarian Army as a tethered observation platform. The observer stood above ...
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  • 10.4k
14 votes
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Can a tiltrotor fly safely with one engine?

This concern was one of the major design challenges in the development of tilt-rotor VTOL craft. In every flying example I'm aware of, it was solved one of two ways: either the engines were embedded ...
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  • 14.3k
13 votes
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Would it be more effective to increase the length or chord of a rotor blade for better performance?

It's not so easy. The blade length, chord and engine power are connected in complex ways, and for each desired performance there is an optimal combination of those parameters. Rotors (and wings) ...
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  • 54.1k
13 votes

Can you help me to identify this helicopter?

The helicopter is a S-65C-3 Yas'ur (Albatross). It is a CH-53D version similar to USAF HH-53C Pave Low. Here is a photo of the same. The identification is based on the following: Six bladed main ...
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  • 98.6k
13 votes
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What causes hunting movement in helicopter rotors?

Lead lag is caused by the blades speeding up and slowing down as they flap up and down. The blade on the advancing side experiences an airflow equal to it's speed plus the forward speed of the ...
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  • 30.8k
13 votes

Why do helicopters typically have blades at the top?

Yes the answer is that simple, that mincer needs to be out of the way so it doesn't chop peoples' head or feet off, or slashes into a bit of concrete and shatters into 100 pieces scattered around like ...
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  • 57.8k
12 votes

Is it possible to fly with counterbalanced single blade engines?

The number of blades determine the solidity ratio of a propeller. If you need to limit tip speed and propeller diameter, the propeller will have a high solidity ratio by using many, short blades. Take ...
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12 votes
Accepted

What are the uses of gyroplanes?

Gyroplanes have quite a few applications, but the problem is that anything they can do, others (helicopters/fixed wing aircraft) can do better. The main advantage of a rotorcraft is that they can ...
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  • 98.6k
12 votes

Is it more efficient to have many or a few rotors?

Rotors need something to power them and the current generation of aircraft (once you get bigger than model size) burn hydrocarbons to get that power. If you want twelve rotors, then you either need ...
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12 votes

Is it more efficient to have many or a few rotors?

The problem with many propellers is that more of the propeller slipstream will flow around wings and tail. The higher local flow speed might be beneficial if you want blown flaps, but for regular ...
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12 votes
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Why do helicopter rotors have constant section and angle of attack?

Helicopter blades do have twist. The relative air speed increases from blade root to blade tip, and therefore on an untwisted blade lift would increase quadratically from root to tip. Or going the ...
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