Aircraft do not steer on the ground the same way they turn in the air. During taxi, takeoff roll, and landing rollout, the nosewheel helps point the airplane along taxiways and runways at low speeds. Nosewheel steering matters because a small steering input at the front gear can move the whole aircraft safely around tight turns.
Pilots use cockpit controls such as the tiller and rudder pedals to command these ground turns.
Key Facts
- Turning radius depends on steering angle: smaller radius requires a larger nosewheel angle.
- Arc length for a ground turn is s = rθ, where θ is in radians.
- Lateral tire force helps turn the aircraft: F = mv^2/r.
- Yawing moment from the nose gear can be estimated as τ = Fd, where d is the distance from the center of mass.
- At very low taxi speeds, the tiller usually provides large nosewheel angles for tight turns.
- Rudder pedals usually provide smaller steering angles and are useful for runway centerline control.
Vocabulary
- Nosewheel steering
- Nosewheel steering is the system that turns the aircraft nose gear to change direction while the aircraft is moving on the ground.
- Tiller
- A tiller is a cockpit hand control that commands relatively large nosewheel steering angles during taxi.
- Rudder pedals
- Rudder pedals are foot controls that move the rudder in flight and often provide limited nosewheel steering on the ground.
- Free-castoring nosewheel
- A free-castoring nosewheel swivels freely and is steered mainly by differential braking, engine thrust, or aerodynamic forces.
- Powered steering
- Powered steering uses hydraulic, electric, or mechanical assistance to turn the nosewheel in response to pilot input.
Common Mistakes to Avoid
- Using the tiller at high speed, because large nosewheel angles can create excessive side loads and make the aircraft hard to control.
- Assuming rudder pedals and the tiller give the same steering authority, because pedals usually command only small angles while the tiller is designed for tighter taxi turns.
- Forgetting that a free-castoring nosewheel is not directly steered, because it pivots freely and the pilot must use braking, thrust, and speed control to guide the aircraft.
- Turning too sharply while stopped or nearly stopped, because twisting the tire against the pavement can increase wear and stress the nose gear.
Practice Questions
- 1 An aircraft taxis through a turn of radius 18 m at a speed of 6 m/s. What lateral acceleration does it need? Use a = v^2/r.
- 2 A nose gear produces a lateral force of 4200 N at a point 5.5 m in front of the aircraft center of mass. What yawing moment does it create? Use τ = Fd.
- 3 A pilot is taxiing a small aircraft with a free-castoring nosewheel toward a tight turn. Explain why differential braking may be needed and why a tiller command would not directly point the wheel.