NOSE GEAR STEERING
Hal Stoen, June 9, 2000
There has been considerable discussion of late on nose wheel steering. Perhaps this input will help- and, perhaps not. I'm going by memory as I don't have any reference material at hand. This pertains only to General Aviation, not to Transport Category aircraft..
There are exceptions, but most GA aircraft have the nose gear interconnected with the rudder. There are some that have free castering nose gear, but these are few in number. To my recollection all Cessna singles and twins have interconnected rudder/nose gear, as do all Piper aircraft.
This interconnection between the nose gear and the rudder is done with springs, although I understand some kit aircraft use bungee cords. If you are sitting still on the ground and push a rudder pedal full in to the stops the rudder will deflect accordingly- the nose wheel will not turn. As soon as the aircraft starts to roll, the nose wheel will start turning in the appropriate direction.
On retractable gear aircraft there is a link that disengages with the nose gear steering mechanism so that the nose gear assembly may retract into the nose bay in a non-castered position. When the gear is extended this link re-engages to allow nose gear steering.
When taking off into a cross wind the ailerons are turned into the wind as necessary to prevent the wing on the cross wind side from lifting too early in the take off roll. Let's use a take off with a strong cross wind from the right for example. As the aircraft rolls down the runway, the stronger flow of air from the right side creates more lift on that side making the wing want to become airborne before the rest of the aircraft is ready. To counter this the pilot turns the wheel to the right as necessary. This action lowers the left aileron and raises the right one. The end effect is to place more downward pressure on the right wing. This helps to prevent the wing from rising too early, and also places more weight on the right gear to help the aircraft remain on the ground until a "positive" lift-off is made.
All this time the nose gear is tracking down the center of the runway and the rudder is centered. Just prior to lift-off, usually at an increased speed, the ailerons are centered, the wheel is brought back a little more smartly than normal (to prevent any side loading on the gear as the weight is removed), and as soon as the aircraft breaks ground a slight turn (coordinated) is made into the wind.
On landing in a crosswind, there are two basic styles: "crabbed into the wind", and "cross-controlled, wing down into the wind":
"Crabbed into the wind"
In this approach the aircraft is headed into the crosswind
at the appropriate angle to prevent the aircraft from drifting.
The aircraft arrives over the end of the runway in coordinated
flight with the rudder and ailerons in the neutral position. The
aircraft is at an angle with the runway, pointing into the crosswind
as necessary to prevent drifting. While not pointing down the
runway, the aircraft is _tracking_ down the runway. Just before
touchdown the aircraft is aligned with the runway. At touchdown
the nose gear is centered. Right after touchdown the ailerons
are once again rolled into the wind to keep the upwind wing from
This type of landing requires split-second timing, lest the aircraft make surface contact in a crabbed position and heads off to the boonies, perhaps losing some landing gear fittings, tire rubber, and collecting some runway lights in the process. Personally, I could never master this type of timing.
"Cross-controlled wing down into the wind"
In this approach the aircraft is aligned with the runway using cross-control operation to keep the aircraft from drifting (uncoordinated flight). With a crosswind from the right, the right wing is lowered as necessary to prevent drifting to the left. Lowering the right wing of course makes the aircraft want to turn that way, so left rudder is added as necessary to keep the aircraft from turning. This "cross-controlling" is adjusted as the airspeed dissipates. Also, this type of operation raises the stall speed, so a greater than normal approach speed is used. With the right wing down, and left rudder applied, the nose gear is pointing to the left prior to touchdown. The aircraft is tracking and pointed down the runway. Touchdown is done with the right main gear first. Then the ailerons are rolled so that the left main makes contact. Then the rudder is centered and the nose lowered more smartly than normal. Because the rudder is centered, the nose gear is centered and the aircraft rolls down the center of the runway.
I hope that my mind didn't develop any "memory leaks" and I that recalled all of this correctly. I mainly hope that this may clear things up a little bit on rudder/nose wheel steering.
This narrative, along with aditional content, is available as a CD or an eBook.
For CD information click here. For eBook information click here.
click to return to the index