Rotorcraft Rookie: In control

November 27, 2013

The collective with a twistgrip throttleI’ve always been captivated by people who can play the drums. Their arms and feet all moving on different beats at a different pace. It’s as if their brains have disconnected from their limbs and they are working only with some rudimentary brain function. It’s been said that flying a helicopter involves a similar detachment of hands and feet, but thankfully it’s not quite that hard.

Helicopters use three primary controls—the cyclic, collective, and anti-torque pedals. Each has a distinct function, and like an airplane, can be used either independently, or more likely, in concert with the others.

The cyclic will be the most recognizable to an airplane pilot. This is usually held in the right hand, and takes the form of a stick either coming out of the floor, or in the case of the Robinson R22, out a central pillar that either pilot can manipulate. Moving the cyclic changes the rotor blades independently, which changes the angle of the disc that’s created when they spin. Pushing forward causes the nose to pitch forward, turning right causes a right turn, and so on.

Anti-torque pedals are also a fairly familiar control to most fixed-wing pilots, although they aren’t rudder pedals in the true sense. Both control yaw, but whereas rudder pedals actually push a control surface, anti-torque pedals change the angle of attack of the tail rotor blades, which increases or decreases the amount of “lift” it produces. The result is the same yaw motion, but it’s much quicker and much more touchy than a rudder input. At first I thought my tailwheel experience would translate well to the helicopter, but now I’m thinking it might actually be a negative influence. Tailwheel flying wakes up one’s feet, but I usually do a sort of light dance on the rudder pedals during takeoffs and landings. A light dance on anti-torque pedals would translate to quick left and right yaws in a helicopter because of the sensitivity. So I’ve been trying to keep my feet more still, while also making sure they’re still awake.

The control most unique to helicopters is the collective. This is the lever pilots manipulate with their left hand that looks sort of like a parking brake. The name comes from the fact that manipulating it changes the pitch of all the blades simultaneously, or collectively. Pull up on the collective and the angle of attack on the main rotor blades increases, and the helicopter goes up. Push down and the opposite happens. The throttle remains relatively constant, and is controlled with a twist grip on the collective. In the R22 there’s both a mechanical linkage and an electronic governor that change the power setting when the collective changes.

It’s all pretty straight forward until you realize that each control can be used in any sort of combination. Take the example of a standard takeoff. An airplane pilot mashes the throttle all the way forward, holds the centerline with the rudder pedals, and pulls back when he hits rotation speed. Many helicopter takeoffs begin from a hover, where the controls are in a state of general equilibrium. To start the takeoff, the cyclic comes forward gently to get some forward airspeed. But without more lift, the helicopter would hit the ground. So you have to pull with your left hand. The cyclic comes forward more, the collective is pulled some more. It becomes a dance of slowly nosing over to gain airspeed with the cyclic, but with the added sensation of actually pulling the helicopter along with the collective. And takeoffs are easy.

Next time: Run-on takeoffs and landings

You can read all the stories in the Rotorcraft Rookie series online.