Planes with propellers normally have one or two propellers in front, facing forward, helicopters have one on top facing up and one facing the side, and drones have four on top facing up.

How do the propeller positions and number effect flight dynamics such as speed and stability, and why do each of these use what they do?


closed as off-topic by Aaron Stevens, Qmechanic May 30 at 6:09

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  • 2
    $\begingroup$ "helicopters have one on top facing up and one facing the side" - to be sure, there are Tandem rotors helicopters. $\endgroup$ – Alfred Centauri May 30 at 0:07
  • $\begingroup$ We want drones to hover and airplanes to travel longer distances. Given the same size battery both with fly for about the same duration. $\endgroup$ – PhysicsDave May 30 at 0:30

traditionally, a helicopter tilts its lift vector so it can propel itself laterally by cyclically varying the pitch of its main rotor blades. This requires a complex mechanical system manufactured to close tolerances which also has to withstand the stresses imposed on it which arise from its rapid rotation. It also requires a tail rotor to counteract the torque which the engine applies to the main rotor.

A quadcopter drone can tilt its lift vector simply by slowing down one rotor and speeding up the opposite rotor, so it dispenses altogether with the cyclic pitch mechanism and instead uses electronic control to vary the speed of each of its main rotors. the motors and control systems which make this possible are now sufficiently inexpensive that the earlier designs of radio-controlled helicopter camera platforms, which used cyclic pitch control just like the big boys, are obsolete.


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