Why are quadcopters not flown by human pilots yet?
Wouldn't they be more stable and easier to control than helicopters?
Scaling up the quadcopter design would make them very large. Only having one (or even two) rotor allows the helicopter to be smaller and even fold up the rotors and remain fairly compact. Since by definition helicopters are supposed to get into more difficult landing areas, increasing the footprint is generally undesirable.
Also, the power system would be complicated. RC quadcopters use an electric motor on each rotor for independent control. A larger version would probably use turbines like most helicopters, and they would either need 4 turbines or a way to gear fewer turbines to 4 rotors. This just adds complexity to the system.
The Chinook is an example of a helicopter that uses two rotors, but the added complexity makes it undesirable unless the added lifting power is needed.
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 only effect that can make quadcopter stable is having centre of gravity below centre of lift just like normal helicopter.
The advantage of quadcopters is that the rotors can be fixed pitch while single (or double) rotor helicopter needs complex control mechanism. While this is huge advantage for the small scale devices where each rotor can be powered by its own simple electric motor, the complexity of either additional engines or long transmission shafts would outweigh any advantage from the simpler rotors in full-scale vehicle.
And why can't full-scale helicopters use electric motors like the small ones? The reason is that when you scale an airfoil up, the lift it produces increases with its area, which grows with the second power of size, but its weight increases with volume, which grows with the third power of size. Therefore models have much more lift for weight and can afford simple but relatively heavy batteries while full-size aircraft need propulsion systems with higher power density.
And then there is also the factor of safety. In case of power failure, helicopters can still glide to the ground and still land vertically using autorotation. But since the rotor rotating speed can't be changed without power, controlling the helicopter during such manoeuvre requires variable pitch rotor. So there goes the main advantage of quadcopters.
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 software. I'd expect to see a resurgence in helicopter-style drones because of this.
Finally, I'm not an aeronautics engineer but I suspect there's considerable merit in combining attributes from a quadcopter and a helicopter. Imagine one large fixed-pitch rotor driven by an electric motor. A few small additional electric-motor driven rotors could provide the needed pitch, yaw, and roll control. Electricity would be generated by an efficient gas engine spinning at near constant speed. Enough backup power to land could be provided by small batteries. This design would be extremely reliable due to the greater reliability and simplicity of motors and fixed pitch rotors.
Advancements will come, but slowly since the costs and dangers of human-carrying vehicles are so high.
The reason quadcopters are chosen as platforms for small, computer controlled flying machines is because they are by design more agile and simpler to move in and around all three axes. This is because they are by design very very unstable.
It is in fact impossible for a human to control a quadcopter (that can move in and around all three axes) without the aid of a computer or some other kind of artificial stabilizer. The reason computers can control quadcopters is because they are fast enough to produce control input that counters any small destabilizing forces that act on the frame.
One way to imagine the inherent stability of a flying platform is to consider what would happen if you would let go of the controls. Normal airplanes and helicopters will tend to just keep flying to the same direction. If you let go of the controls of a quadcopter (and have no stabilizing mechanism installed) the quadcopter will very quickly just chaotically tumble towards the ground. This means that in a helicopter or an airplane the design "helps" you and forces the frame to fly in a stable manner (forwards.) In a quadcopter there is no such help but there are also no forces that hinder you from moving towards any direction you want.
This principle is also deliberately on frames such as the F-117. The F-117 is impossible to fly without the help of computers (it was designed to be unstable), but this has made it a much more agile airplane than its frame would normally have allowed.
The other (bigger) reason quadcopters have not been scaled up is because they consume (a lot) more fuel than other types of aircraft. Why would anyone build a quadcopter when a helicopter or an airplane does the job using less fuel. They are also slow and noisy.
Keep in mind that the "job" for scaled up airframes is usually to move stuff from point A to point B while the "job" for small, computer controlled quadcopters is to be agile.
legal reasons, not speculation about why we haven't attracted any controllers yet (that I'm aware of).
, but could not understand why he directed me West (remaining in Class B for 13 more miles) instead of having me climb 1,500 feet or angle back North or North-West to exit Bravo more quickly. I was given... with the remedial training option the FAA may offer, but what did he mean by "counseling session"? The controller implied it would be handled by phone. I'm not freaking yet, just concerned. I told everything
So everyone knows that carb heat decreases engine performance. Yet when we check the heat during run-up, the manifold pressure increases. Why is that? Shouldn't adding carb heat cause the intake air to become hotter and therefore thinner, and cause the manifold pressure to decrease?
At the club I fly at, there is an older Cessna 172 that has a manual "Johnson Bar" that is used to put the flaps down. In the newer 152, and I believe the rest of the planes (I have yet to fly them), the flaps are controlled via a electronic (or hydraulic?) lever. It appears to me that the manual flaps are more reliable, more maintainable, and a hell of a lot more fun in my opinion. Additionally, the manually flaps don't require a lot of strength to operate IMO. Does anyone know why the automatic design is favored over the manual counterpart? Same question applies to car transmissions...
This is related to the recent disappearance and the fact that some claim the plane's black box to be deeply under water and that's why it cannot be located
Can someone explain why the aircraft would fly in an arc using the satellite as a reference point? Have I missed something?
As I understand, there are two black boxes on-board an aircraft. One black box, the Cockpit Voice Recorder holds the cockpit conversations and the other, the Flight Data Recorder holds essential flight parameters. But why are the two black boxes holding separate data? Why don't both black boxes hold copies of both the FDR and the CVR data for extra redundancy in case the other box goes missing or is completely damaged by the crash? Are there any technical reasons for why this isn't possible or hasn't been attempted yet? Is there any benefit of having the CVR and FDR in separate boxes?
out? It seems like a somewhat practical solution, yet I have never heard of anyone doing it. Why do pilots often try to find a road to land on or a lake to ditch in when trouble strikes instead...There was another question that asked why commercial flights don't have parachutes. The almost ubiquitous response was that the parachutes would be useless because: Most accidents with commercial airliners happen on take off and landing, and there is no time to parachute. In order to get to a position where 100+ people can successfully jump out, you'd most likely need to descend some 20,000 ft
that radio beacon. We have not yet picked up anything, but that's typically what those black boxes contain." I was under the (potentially incorrect) impression that flight recorders, by nature...? If so, why? I know that flight recorders are equipped with underwater locator beacons. Are they also equipped with radio beacons (either an active transmitter or a some passive device like a corner
What can I do if my not-so-newly issued temporary pilot certificate is about to expire and I haven't gotten my permanent certificate yet? Is there any way that I can keep flying while waiting for it, and is there a way to check on the status of the permanent certificate?