dear friends and followers welcome back to my channel today I'll be talking
about a question I have received ever so often: "Joe, how do pilots steer the plane
on ground?" That is a great question so let's get started!
ok let's quickly look on how a little Cessna or a
piper cadet steers around the apron to get to the runway. The nosewheel on a
Cessna is mechanically connected to the rudder pedals which you use to move the
rudder attached to the vertical stabilizer but the nose wheel only moves
by a few degrees so if you wanted to perform a 90 degree turn to enter a
taxiway for example you would apply a brake pressure on either side of the
main landing gear and use the propeller airstream to more or less pull yourself
around the corner. The disadvantage is obviously our tire abrasion and a lot
of stress on the nose wheel strut. So airplane manufactures had to come up
with an idea. Now, using asymmetric thrust would do
the job but the torsion forces on the nose wheel strut would severely damage the
construction; so again the nose wheel is linked to the rudder pedals like in your
little Cessna but another additional mechanism was installed: the so called
nose wheel steering which is powered hydraulically. You could compare it like
your power steering in your car. Now next to your side stick? you have this little
tiller which you can turn left and right. So let's imagine you've just vacated? the
runway and you have to make a few turns from one taxiway to another. As you
turn the tiller hydraulic fluid is forced into this cylinder. Within the cylinder
sits a cog rail which can be moved in either direction depending on your input.
The cog rail passes along a cog wheel which is directly connected to the nose
wheel so as you move the tiller to either side you more or less control a
valve which opens up and hydraulic fluid pushes the cog rail which turns the cog
wheel and then turns the nosewheel. Now the maximum
deflection you can apply with the tiller is 75 degrees which is ideal for turning
into the gate position or lining up on the runway, but, as you perform your
takeoff roll the tiller inputs become smaller with increasing speed. You then
transition from the tiller to the rudder pedals to steer the aircraft on the
runway as they are also interconnected with the nose wheel steering. The maximum
deflection is six degrees to either side and again with increasing speed the
possible deflection angle gets less and less until reaching a speed of 130 knots
where the nose wheel steering is then deactivated and you maintain the plane
on the runway centerline by using the rudder of the vertical stabilizer as
the speed is high enough to control the plane with aerodynamic forces. As we lift
off the nose wheel then fully extends and slips into a centering cam which centers
the nose wheel before it gets retracted and stowed. Now as you know, airplanes
need to be pushed back out of their gate position and in order to do that
operations will send you a push back truck which either will lift up your
entire nose wheel or is connected via a push bar at the front of the nose wheel.
Now either way the pushback driver has to insert a so-called steering pin. As
soon as the pin is inserted, the nose wheel then can move freely to either side
by a maximum of 95 degrees as it is then disconnected from the hydraulic system
because as you commence pushback you also start your main engines applying
hydraulic pressure to the system. Now once the engines are running you have to
perform a flight control check including the rudder of the tail fin with the
pedals and as you can do that check during taxi your plane would swerve back
and forth during your rudder check as the pedals are connected with the nose
wheel. To avoid that you press the nose wheel steering disconnect button which
deactivates the linkage to the rudder pedals but you can still use the tiller
to maneuver your plane during the flight control check. It's fairly
simple to be honest. So let's recap, so you can steer the nosewheel by either
using the steering tiller on either side of the pilot side stick until reaching
80 knots or the rudder pedals until reaching 130 knots and there's one more
option: the autopilot. As you come in for an auto-land landing, after touchdown
the autopilot controls the nose wheel to maintain the runway centerline by using
the signals of the ILS localizer antenna. So once you reach taxi speed you
disconnect the autopilot and the auto brake system and use either the rudder
pedals or the steering tiller to vacate the runway. Now how do you know as a
pilot if you're on the taxiway line? Now the perspective from the cockpit onto
the taxiway is pretty good as you are sitting relatively high, so as long as
you have the perspective that your vertical axis of your body is in line
with the taxi line you're spot on or if you can feel a bump every now and
then your nose wheel has just rolled over a taxiway light which is embedded
into the tarmac and to be on line at your gate position you either have a
marshall guiding you with hand signals or, if available, via the avgds -the
advanced visual docking guidance system. To sum up, the nose wheel steering
system is a great help to steer and navigate the plane around long taxi
routes, lining up on the runway, and to enter the gate position but the minor
the inputs the better and smoother it will feel for the passenger while
taxiing. And by the way, the Boeing 777 can also move its rear axle of
the three on the main landing gear to perform closer turns, reduce tire wear,
and stress on the structure so it's similar to a bulldozer. So that was it
for today I hope you enjoyed the short video about the nosewheel steering on
airplanes. Make sure to perform a touch-and-go at my Instagram account, the
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See you next week! All the best, -your captain, Joe