How do Airplanes Steer on the Ground?
Ailerons, speed-brakes, the rudder, we’ve all seen those in action in the air. However, how do aircraft steer on the ground? These control surfaces will have no use because there won’t be any incoming air allowing the surfaces to redirect the aircraft.
Nose Wheel Steering
Tillers
Large commercial aircraft are equipped with tillers. Two tillers are present in the cockpit, one for the captain and one for the first officer, which are used to steer the nose wheel of the aircraft. Tillers can vary in shape and size, as seen below:
Tillers allow the aircraft to make very sharp turns, thus enabling it to navigate the complex taxiway systems at any airport.
Rudder Pedals
Smaller general aviation aircraft turn the nose wheel by pushing the rudder pedals. Connecting the rudder pedals to both the rudder and the nose wheel is only feasible on aircraft with a fixed landing gear, such as the Cessna 152. This eliminates the use of an extra functionality to steer the aircraft as all of the yaw is be controlled through one system, making it easier for trainee pilots to operate.
Differential Breaking
The concept of differential breaking is fairly easy to understand. Pilots can apply different amounts of braking for each of the main gears, pivoting the aircraft around the wheel and towards the side with a harder braking. This is generally done by small aircraft on tight turns, even if the aircraft is equipped with steering by rudder pedals.
Differential Thrusting
The concept of differential thrusting is easy to understand as well! Only applicable to multi-engine aircraft, this technique involves throttling the engine(s) on one side of the aircraft to a higher thrust than those on the other side. This pivots the aircraft towards the side with lower thrust. Intuitively, differential thrusting is less useful than differential breaking for tight turns but is highly applicable for high-speed exits.
Conclusion
In addition to these techniques, the rudder (the most classic method) is used for slight adjustments due to crosswinds when rolling down the runway. Each of these methods has its own usages and functions: if you’re rolling down the runway and you try to use the tiller, your nose gear will collapse :)
