Although every aircraft is designed to fly, there is a specific system that should be incorporated into the project of any flying machines that will provide ground maneuvers.
That is the Steering System!
Basically, this text describes in a simple manner two different concepts that are widely used on old and modern aircrafts.
The objective here is to show some details that make these two projects unique. They are both commanded by a tiller on the cockpit and actuates hydraulically through a set of valves and manifolds.
Of course small aircrafts also do have steering features, but the focus here is on large aircrafts.
The first picture shows the Push and Pull Steering System.
The fluid in the actuators and system is always under pressure and the steering actuating cylinders can function as shimmy damper.
One point to observe is the necessity of a quick disconnect pin between the upper and lower torque links since the pressurized actuators does not provide the self-disengagement of the steering system.
The second picture shows the Rack-and-Pinion Steering System.
Although it is a gear type steering system, its actuation is also done through pressurized hydraulic cylinders. The internal piston on each cylinder pushes the rack-and-pinion left and right.
Since there is the possibility to mechanically disengage the rack from pinion, it is important to set the maximum steering angle on both sides (left and right) in order to do not damage the internal parts in case of steering overtravel operation while connected to the towing vehicle.
One point to observe is the necessity of a towing light indication box that is manually operated by the ground crew while moving the aircraft from/to the ramp.
Of course there are some other differences and peculiarities on each system, but let them for the experts.
Hope this brings some cool information for your knowledge.
Regards from Brazil!
https://www.linkedin.com/in/marcelogerin
Ps. Some pictures and/or details may differ from the real aircraft type. They were used as illustrative only.
RACK-AND-PINION STEERING SYSTEM
PUSH AND PULL STEERING SYSTEM