How do aircraft tyres straighten themselves when landing in a crosswind?
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If the side slip (edited) is executed correctly, the wheels shouldn’t have to straighten, the ground track should be straight.
The upwind wheel should touch first, going straight, then the downwind wheel. There should be no side load on the wheels.
I might have misunderstood your question??
I’m fairly certain that they are built off centre. Similar to how office chair wheels are designed.
So the drag of the air, and then the tarmac will cause the wheel to align with the direction the plane is landing
When the aircraft is airborne in a cross wind, the plane is facing slightly off it’s travelled path so the the sum of forces acting on the plane pushes it in the direction it wants to go (Thrust from the engines, wind, push from control surfaces – ailerons, rudder etc). Once the plane touches the ground, the drag force from the rolling resistance one the wheels and braking once engaged starts to dominate. The wheels are much more able to resist lateral forces from the wind as they can act on the ground whereas the plane in the air has nothing to push against but you still have to control the plane to keep it from being pushed around.
All that said, the wheels don’t really push the plane to straight – the pilot uses the control surfaces to straighten the plane (I never finished learning to fly but [this page](https://www.boldmethod.com/learn-to-fly/maneuvers/how-to-make-a-perfect-crosswind-landing-every-time-touchdown/) goes over some of the ways you can land in a cross wind in fairly simple terms)
A pilot will apply rudder just before touching down, to ensure the wheels are pointed down the runway. An aircraft shouldn’t land in a sideslip.
For crosswind generally an aircraft can perform the approach (potentially all the way to landing) in two basic ways:
* Using a sideslip. The aircraft “dips” one wing towards the wind to offset the crosswind. Using this technique the aircraft wheels remain aligned with the runway and there are minimal side forces.
* Using a crab angle. The aircraft is turned sideways into the wind. If maintained until touch down, there will be some side forces on the landing gears. However, on large aircraft, the landing gears are engineered to withstand the side forces during crosswind landings.
Often pilots will land with a combination of sideslip and crab angle. E.g., use a crab angle during an approach but partially or completely de-crab (potentially with some sideslip) during flare and subsequent touchdown.
If fully landing on a crab, airplane will naturally straighten itself due to momentum and forces on the landing gear the. The pilot also provides control inputs (rudder & aileron) to control the direction of travel.
Note: sideslip is limited during landing due to wing clearance from the ground. Crab angle is usually limited by the amount of crosswind and the condition of the runway.
For small, high-wing planes like Cessnas, sideslip is probably the preferred method. The high-wing gives plenty of sideslip angle to work with and the landing gears on small planes don’t take well to a lot of side forces.
On the opposite spectrum, some very large aircraft have [main gears that can be steered / swiveled](https://www.youtube.com/watch?v=nhVD3E0-0Wc)so they can land crabbed even in very high crosswind conditions.
It’s not that complex OP. Either A) pilot aligns the center line of the aircraft with the runway using rudder input, or B) it touches down and naturally aligns itself by friction. Just like your car in a slight skid from water/snow/mud etc. it will naturally try to “right” itself.
Although far from standard (in fact, this may be unique to the B-52), the B-52 has the ability to slew its landing gear to the heading direction of the runway. This allows the bomber to land while crabbing through touchdown and rollout in high-crosswind conditions. Other aircraft are built with more robust landing gear that can easily take the loads associated with crosswind landings. As I understand it, the B-52, due to other unique aspects of its design, just couldn’t accommodate beefier gear (notice that the plane’s gear are all attached to the fuselage and grouped tightly).
One interesting exception to what everyone else has said is the B52 bomber. Its wheels can all be set at an angle for crosswind landings. So after touching down, the plane continues rolling down the runway facing sideways.
I use the low wing method. (I did majority of my training in Pipers, so it’s what’s natural to me) You approach the runway as normal, then when you flare, you control the nose with the rudder, and your direction of flight with the ailerons. This is also basically the same thing as a slip. So if you have a crosswind from the left, you’d use left aileron, while also using right rudder. This keeps your aircraft flying straight, while also being aligned with the runway. But keep in mind that this will also drop you like a rock, which can be countered by pulling back on the yoke a bit to keep you from slamming the wheels on the runway.
It sounds like a lot, but it’s about the same as standing on a basketball. It’s a balancing act that eventually just comes natural. Edit- it’s also way easier to deal with a left crosswind, than a crosswind from the right. It’s natural to pull back and turn left, while using right rudder. Not so much the other way around lol
In a semi-related question. Anytime I see video of these tyres they start to rotate upon striking the ground. How do these tyres survive more than a few landings? Do any plane make them spin before landing or would that not make a difference?
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