why do helicopters need a stabilizer rotor but airplanes that use propellers don't?
Depends on the airplane. In a P57, if a pilot made the mistake of going full throttle on takeoff, it could lead to a crash; takeoff speeds are slow and the ailerons need a lot of throw to counter the torque from the prop, and just after the plane leaves the ground, the landing gear no longer supply a counter torque force, so suddenly it's up to the airlerons. Plus a lot of aileron throw can create adverse yaw, so then rudder inputs are required to compensate for that.why do helicopters need a stabilizer rotor but airplanes that use propellers don't?
Oh seriously? You didn't accidently happen to click those two links I gave below my post, did you?That was invented long before the helicopter: it's called a balloon.
Radio control helicopters can also push air upwards. In aerobatic mode the blades mostly rotate at constant speed, and the overall pitch (collective) can be changed from + 10 to +13 degrees to - 10 to -13 degrees depending on the power of the radio control helicopter. The high thrust to weight ratios (around 8 to 1 or so) allows these models to do impressive stunts. The model has seperate throttle and pitch control, but these are combined into a single programmable control on the transmitter, to maintain near constant rpm of the main rotor in aerobatic mode. In addition, the tail rotor control is also mixed in to prevent yaw reaction to pitch command inputs from the transmitter, but the tail rotor also has it's own control to allow the pilot to control the yaw axis.Helicopters work because they push air downwards fast enough to propel the helicopter upward.
No, too much momentum, instead the pitch angle is changed as described above.Can the pilot change the direction the blades are spinning?