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In an aircraft, headwind slows it down, and tailwind speeds it up. But it does not steer the flight off course.

But when there is extreme crosswind, how does the pilot handle the situation? And what does crosswind do to the aircraft structure?

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    $\begingroup$ This article provides a lot of basic information on crosswind landings: en.wikipedia.org/wiki/Crosswind_landing $\endgroup$ Nov 16, 2021 at 20:23
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    $\begingroup$ "crosswinds make pilots crabby" $\endgroup$
    – Criggie
    Nov 17, 2021 at 8:35
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    $\begingroup$ Some airports have multiple runways at right angles to each other, and will direct landings onto the one that has a more favorable angle to the wind at any given time. $\endgroup$ Nov 17, 2021 at 15:00

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The pilot compensates, depending on the phase of flight the compensation will be different.

On takeoff rudder and aileron corrections are used to keep the airframe in line with the runway as it executes its ground roll. This mitigates side loads on the gear and ensures the airplane does not swerve on takeoff and right after lifting off.

En route you generally fly a given ground track, either towards a VOR (or other such beacon) and/or a GPS path. When flying VFR you might even fly to known landmarks and locations. If there is a crosswind at altitude then you need to point your plane such that the resulting vector keeps you on course. The extents of this are nicely illustrated with the FAA's ground reference maneuvers. Keep in mind that the lower the cross wind component and the higher the aircraft's airspeed the shallower the angle too correct will be.

Most modern autopilots (and even plenty of older ones) are capable of tracking beacons and GPS courses and will fly the correction for you.

On approach and landing the corrections are a bit different. The approach to the runway is flown much like an en-route correction, pointing the plane such that the resultant course is inline with the runway. In order to land the aircraft it must be inline with the runway so rudder is used at the end to yaw the airframe in line with the runway for touchdown. Unless you're flying a B52...

Here is a good presentation on the matter. More good info here.

En route, the crosswind does not do anything to the structure, you are simply flying through the air and subject to its movement. On landing you are limited by the rudder and aileron authority to actually correct for crosswinds. The biggest dangers from crosswinds on landing are excessive side loading on the landing gear, tail or wingtip strikes, and simply running off the runway.

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  • $\begingroup$ En route, flying IFR, you can also ask for a different altitude if the time/fuel savings from having tailwind offset the time/fuel expenditure of the altitude changes. $\endgroup$ Nov 17, 2021 at 9:55
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    $\begingroup$ Maybe to elaborate on the "En route the crosswind does not do anything to the structure, [..]" part: the aircraft is pointed a bit 'sideways' so the combination of headwind and crosswind (as seen from an observed on the ground) is just headwind for the airplane (the airplane itself does not perceive any crosswind, just headwind). $\endgroup$
    – Klaws
    Nov 17, 2021 at 14:28
  • $\begingroup$ Could perhaps add pod strikes or prop strikes to the list of risks, for planes with wing-mounted engines. $\endgroup$ Nov 17, 2021 at 15:15
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But when there is extreme crosswind, how does the pilot handle the situation?

extreme crosswind means you don't go flying or divert to a safer destination. What is extreme to C152 is nothing to A320, so degree of how extreme the wind is is relative.

to cope with crosswind, pilot introduces WCA (wind correction angle) and flies heading that is different from ground track by the value of WCA. You fly into the wind, and in VMC your next fix that you are flying to will not be right ahead of you but slightly (or not very slightly) aside.

landings are done either slipping or crabbing, or variation of both.

And what does crosswind do to the aircraft structure?

nothing. Up there, there is no crosswind, there is no wind at all in that sense that airplane moves in the air mass which moves relative to ground, and this movement of air mass relative to ground is called wind.

Very strong wings, however, are more often than not associated with windshear, microbursts, strong turbulence etc. Windshear is particularly dangerous if happens at low height.

on touchdown, extreme crosswinds can cause accidents, because airplane has control surface movement limitations. If full control inputs are insufficient to compensate for crosswind, airplane can be blown off the runway. Microbursts and windshears can lead to rapid loss of altitude and very hard landings if no immediate action is taken. One must be complete idiot to go flying in such weather conditions.

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It might be added that if you are flying a tail-wheel airplane, a tail wind can make the final segment of the rollout uncontrollable. When the airspeed of the airplane is zero the ruder and alerions have no effect. Between the time when the airspeed hits zero and the groundspeed hits zero, you are at the mercy of the wind and inertia.

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    $\begingroup$ Is differential wheel braking not usable to control things during this timeframe? $\endgroup$
    – Ralph J
    Nov 23, 2021 at 23:58

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