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101

Wouldn't they be more stable and easier to control than helicopters? No, they would not. Quadcopters don't have any special inherent stability. When you increase power of one of the rotors to pitch, the increasing pitch will not do anything to the power difference and therefore the pitching moment. The advantage of quadcopters is that the rotors can be ...


72

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. Gordon Leishman, Principles Of Helicopter Aerodynamics: The line for total power goes down between 0 - 70 kts with increasing airspeed, this is caused by the line ...


50

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 high speed flight. Now, if you know anything about basic fixed-wing performance, you'll realize immediately that this implies an aspect ratio just over 1, ...


50

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 are the empennage and the outer wings missing, but also the engines, which helps to reduce the load considerably. Mil-26 lifting a Tu-134 carcass, seen from ...


40

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 for lift creation must be generated by the rotation of the main rotor. This means that a small amount of air must be accelerated by a lot. If the helicopter adds ...


32

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 camera's framerate divided by the number of rotors. This means that between frames the blades have moved a full quarter rotation (or a multiple of that). Creating ...


31

It has (sort of) been done: The company that did this is working on a more useful version. It's important to note that scaling up is extremely difficult in aviation. Model airplanes have performance numbers the full scale folks can only dream about.


30

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 caused by the suboptimal lift distribution. The centre of the rotor creates little lift because the blades are slow there and is shielded by the fuselage, which ...


29

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 Segway. There is no law of physics that prohibits a helicopter from flying upside down. The Hiller flying platform was one of several types built in the 1950s, ...


27

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 is the greatest factor. (Remember the disc is tilted forward as the helicopter moves forward). However, your question actually asked why do they burn less ...


26

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 , with the main thrust being in the development of (hinge-less) rigid rotor and (glass fiber reinforced) composite blades. The single blade rotor offers some ...


22

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


19

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 the smaller rotors) and far easier to control by software. That said, recent advances in machine learning have made so that helicopters can be controlled by ...


18

Advanced Tactics has also somewhat did it! A video of the first flight of the Black Knight Transformer has been released on Youtube.


18

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 thrust to maintain level flight is reduced by that ratio, and therefore necessary engine power and fuel flow are also reduced. In hover, the engine+rotor system has ...


15

One of the purposes of the Sikorsky CH-54 was to transport aircraft. Carrying a Chinook: Lifting a Caribou:


15

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 likely that picture you took was of a TH-57 out of Pensacola NAS on a training flight. They like to come out to KBFM and Jack Edwards in Gulf Shores to practice ...


14

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 the contra-rotating rotors... (Image source) http://www.aviastar.org/helicopters_eng/petroczy.php


13

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) generate lift by accelerating air downwards. The lift is proportional to the rate of change of inertia of the air. This, however, also changes kinetic energy of the ...


13

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 is usually made of high grade steel (or titanium in some cases) and actuated either hydraulically (or in recent cases) electrically. The outer wing rotates about ...


13

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 rotor The sponsons which hold the fuel The only variant of CH-53D with in-flight refueling probe in service is the Israeli version. All others (HH-53 and MH-53) ...


13

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 bullets. That is the main reason why the light 2-seater R22 has the rotor mounted on a pylon, at 2.7 m it is out of the way of most people. Image source ...


12

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 a ship's propeller: It needs to work in the space between the draft of the ship and the waterline, so it will have many stubby blades. If space allows, a ...


12

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 helicopter. The blade on the retreating side experiences airflow equal to the speed of the blade minus the forward speed of the helicopter. This causes dissymmetry ...


12

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 twelve engines or you need a smaller number of engines plus a bunch of heavy driveshafts and gearboxes. I assume from the fact that most contemporary aircraft ...


12

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 flight and especially in hover it will increase viscous and pressure drag without any benefit. This will reduce overall efficiency when the number of propellers ...


11

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 controlling blade pitch from the blade root using pitch links (which are, essentially, pushrods), as in a typical rotor head, the servo flaps allow for pitch to be ...


10

Yes, helicopters can be fitted with autopilots. Some are very simple, others are quite advanced. The more advanced ones can, for instance, follow a pre-programmed route, climb/descent to a pre-selected altitude, fly an ILS approach, perform a go-around automatically. They are not ordinarily found in small helicopters due to cost and lack of necessity. All ...


10

Four rotor copters were actually the first copters... Raúl Pateras Pescara, Buenos Aires, Argentina, 1916 Etienne Oehmichen, Paris, France, 1921


10

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 hover at a location; the gyroplanes are unable to do this, which is kind of a deal breaker. The main advantage of the gyroplane is that they cost less and are ...


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