So – clearly quadcopters are more stable (see all the drones), so why aren’t actual helicopters all quad copters?
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Drones are much lighter and don’t require as much power to lift up. Personal use drones also don’t go anywhere near as fast as larger scale helicopters. All this is to say that a standard helicopter generally has much more powerful fuel-based engines that cost more money to build, maintain and operate. It is just not practical to build *all* helicopters as quadcopters because of this.
Drones are much lighter and don’t require as much power to lift up. Personal use drones also don’t go anywhere near as fast as larger scale helicopters. All this is to say that a standard helicopter generally has much more powerful fuel-based engines that cost more money to build, maintain and operate. It is just not practical to build *all* helicopters as quadcopters because of this.
You have to remember that in physics things change along with size. The design which works best for something small will be far worse for something large. Just look at how different the bodies of different sized animals are.
You have to remember that in physics things change along with size. The design which works best for something small will be far worse for something large. Just look at how different the bodies of different sized animals are.
A single large rotor doesn’t have to spin as fast as 4 smaller ones to provide the same amount of lift. Quad copters that need to move significant mass would be extraordinarily loud even by helicopter standards
Four small rotors are also very complicated to control without computer assistance to ensure all the torques and thrust levels are balanced. On a drone with a fancy computer this is easy because the software can tweak the power to each motor thousands of times per second and you have no idea. In the late 1940s none of that existed, you needed to be able to control the aircraft with levels that pushed rods and levers which pushed through a hydraulic system to push on other rods and levers that do the controlling. Helicopters existed and were in combat service for over a decade before the first plane to use electrical (fly by wire) controls
There’s still a lot of industry and experience around building single rotor helicopters so they’re going to keep making them until someone builds the industry and experience to make powerful, cost effective, reliable, and safe quad copters of a usable size.
A single large rotor doesn’t have to spin as fast as 4 smaller ones to provide the same amount of lift. Quad copters that need to move significant mass would be extraordinarily loud even by helicopter standards
Four small rotors are also very complicated to control without computer assistance to ensure all the torques and thrust levels are balanced. On a drone with a fancy computer this is easy because the software can tweak the power to each motor thousands of times per second and you have no idea. In the late 1940s none of that existed, you needed to be able to control the aircraft with levels that pushed rods and levers which pushed through a hydraulic system to push on other rods and levers that do the controlling. Helicopters existed and were in combat service for over a decade before the first plane to use electrical (fly by wire) controls
There’s still a lot of industry and experience around building single rotor helicopters so they’re going to keep making them until someone builds the industry and experience to make powerful, cost effective, reliable, and safe quad copters of a usable size.
The biggest advantage of a quadcopter is stability. For a cheap (or expensive) toy, it makes sense to quadruple the parts so users can enjoy it out of the box with little to no training. With a very expensive functional tool, you can expect serious training for the operator and can get the same stability with lower costs of production and maintenance in addition to fewer points of failure.
The biggest advantage of a quadcopter is stability. For a cheap (or expensive) toy, it makes sense to quadruple the parts so users can enjoy it out of the box with little to no training. With a very expensive functional tool, you can expect serious training for the operator and can get the same stability with lower costs of production and maintenance in addition to fewer points of failure.
1) Helicopters have variable pitch. That’s how change direction, speed up, and basically fly. Drone quadcopters don’t. Variable pitch allows the helicopter to autorotate in the event of an engine failure, instead of crash like a drone.
2) Four rotors isn’t four times the redundancy, it’s four times the chance for failure. Quadcopters don’t fly well on 3 rotors.
3) The ‘heavy lifting’ is done by the outer parts of the rotor, because they’re moving faster than the inner part of the rotor. This favors one (CH-53) or two (CH-47) large rotors over four smaller rotors.
4) Likewise, to compensate for the smaller rotor diameter, quadcopter blades spin faster. This has the advantage of helping with retreating blade stall (the retreating blade is also going forward into the relative wind as the aircraft goes faster, until it’s not going fast enough to work). But it also means the advancing blade is going faster and is limited by the speed of sound (blade tips going supersonic causes a host of problems). And the blade has to be stronger (and hence heavier) to compensate for the higher forces that come with higher RPM.
Drones are not built that way because the are more stable. The design is because it is a cheaper way to build them if you power them with batteries.
Quadcopters drones work because they have electric motors that quickly can control the rotational speed of a fixed rotor.
Regular helicopters have one or more internal combustion engines usually gas turbines. They do not change the rotational speed fast. Helicopters usually operate them at a constant rotation speed for the flight
So the control system of a helicopter is a https://en.wikipedia.org/wiki/Swashplate_(aeronautics) that controls the angle of attack of all blades. There are both changes for them all if you want more or less lift to go up and down. It also has directional control so you then have a higher angle of attack on now side to provide more lift there and to move around. To that add a tail rotor.
A quadcopter also needs a structural part that keeps the rotors apart and the weight compared to strange do not scale in a way that is advantageous for a large helicopter. The square cube law is in effect
there are helicopters with multiple rotors that provide lif like a https://en.wikipedia.org/wiki/Boeing_Vertol_CH-46_Sea_Knight , https://en.wikipedia.org/wiki/Bell_Boeing_V-22_Osprey etc. They have a mechanical connection between the rotors so they rotate at the same. A V-22 has one engine just below each rotor, they are still connected because you do not what a single engine failure to result in a crash.
The reason they have multiple rotors is to provide enough lift for a CH-46 and similarly designed. A single-rotor would be very large. A V-22 have two so you can fly like an airplane with them tilted forward and the lift is provided by the wing. A single-rotor ontop is cheaper for most helicopter requirements.
For drones, it is ok if a single engine failure results in a crash but that would not be ok for a crewed helicopter.
So what is a cheap and good design for a small electrically powered front that does not carry humans is not a cheap or good design for an internal combustion engine power helicopter with humans onboard.
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