AOPA - Career Pilot

Turbine Aircraft Technology

Turbine Technique: As the Tiller Turns

Steering by hand

BY THOMAS A. HORNE (From AOPA Pilot)

Nosewheel steering is something that most pilots of lighter airplanes (say, under 20,000 pounds maximum takeoff weight) don't think too much about. After an initial period of awkwardness in primary training, we learn how to use our feet to steer on the ground. In most cases, airplanes from the smallest piston single up to turboprops and light jets use either rudder pedal-operated nosewheel steering linkages, differential main-gear braking, or hydraulically powered steering systems to help keep them pointed in the direction we want.

It's different with heavier jets. Because they weigh so much, differential braking isn't always the best way to get around. And pedal-operated nosewheel steering would take too much leg power to muscle around a nosewheel holding up several thousand pounds of airplane. Also, coping with the momentum generated by residual thrust at idle, and the braking required after application of breakaway thrust (the shot of power needed to move away from a standing stop), is hard enough on the brakes — let alone using them again and again as an aid in ground steering. Ride the brakes too much and they could heat up and wear out quickly.

Enter the nosewheel steering tiller. This device, located on the captain's side panel, can look somewhat like a sailboat tiller, although some are shaped like a large knob. Depending on the airplane's system design, the tiller steers the nosewheel through a mechanical linkage, a dedicated hydraulic system, or an electronic steer-by-wire system. Because of the peculiarities of each system, tiller feel and operation can take some getting used to. Some hydraulically operated tiller knobs, for example, require that you constantly hold pressure in the direction of the turn. Release your grip on the knob and hydraulic pressure sends it — and the nosewheel — back to the centered position. With some other systems, the nosewheel stays turned after a tiller deflection. Until you make peace with a tiller, your steering can be jerky as you learn how much to lead or lag your inputs. The back-seaters will wonder as the airplane zigzags out the ramp and down the taxiway.

Tiller steering is great for maneuvering in and around tight spots because it can pivot the nosewheel about a wide radius of motion. It's also very precise, and makes tracking centerlines a snap.

Things become a little bit more complicated during takeoffs. Crew coordination is essential. During the first part of the takeoff the captain controls nosewheel steering via the tiller. At the same time, the copilot/first officer applies aileron inputs to correct for any crosswinds. Once there's enough airspeed for the rudder to take effect (this varies, but can be as high as 80 knots), the captain shifts his grip from the tiller to the control yoke, and the copilot makes any final adjustments to the takeoff power setting. To make sure everybody understands what's going on, the captain says something like "my yoke" when he takes control. That's the signal for the copilot to let go of his yoke.

As for landings, the process is reversed. Rudder steering is used during the first part of the landing roll, and the tiller comes into play after speed bleeds off.

To some pilots, tiller steering is a sure mark of a "real" airplane, along with overhead panels, windshield wipers, foot warmers, and redundant flight control systems. But just like the rest of a heavy airplane's systems, using this type of steering becomes second nature after a little bit of practice.