I hadn't done takeoffs with a crosswind before but, as I now try to do them with 90° crosswinds from both left and right and with direction confirmed by the windsock, the aircraft consistently veers into the wind during the takeoff run. It doesn't matter whether it is an FSX or payware aircraft. What am I missing?

There's an 'autorudder' checkbox in the options-Realism. Is this unchecked? 

That's basic aerodynamics at work: http://en.wikipedia.org/wiki/Weathervane_effect

Think of the rudder as a sail. As the wind pushes it, the nose will turn into the wind.

That is why aircraft have crosswind limits specified... the rudder is good up a point, but light

aircraft can typically not handle crosswinds above 15-20 knots.

During taxiing and takeoff with a crosswind, the wind pushes on the side of the rudder and causes the plane to turn ("weathervane") into the wind.  It's normal to have to use rudder (in a downwind direction) to keep the plane going straight.  Also, full aileron should be held INTO the wind during taxiing and on takeoff until the airspeed indicator comes alive.  Then the aileron input should be decreased as the plane accelerates, but some aileron should continue to be held into the wind.

 

Aileron control held into the crosswind not only helps prevent the wind from lifting the upwind wing, the "adverse yaw" (yaw effect in opposite direction to the aileron roll input) of the ailerons helps prevent the crosswind from turning the plane into the wind.  During the takeoff roll you should anticipate the need for lots of rudder input in a direction away from the wind.

Have a look at this very nice informative video:

 

https://www.youtube.com/watch?v=I96s0VLB_rU

 

That SF260 is a classic, a Real joy to fly!

Now it all makes sense. Thanks.

 

 

Now it all makes sense. Thanks.

 

(Attention: humor needed! B)  )

 

...Sense yes, but there is also:
Prop wash

Propeller torque effect

P-Factor

Gyroscopic Precession

 

According to the motto "the more we learn, the less we know"

 

 

http://wiki.flightgear.org/Understanding_Propeller_Torque_and_P-Factor

According to the motto "the more we learn, the less we know"

At my age, it's "The more we learn, the less we remember."

yep, the effect is called "weathercocking".  The aircraft wants to turn into the wind because of the forces upon it's shape.

 

That's why you need to use the rudder to counteract it.  You can't really fly fsx properly unless you have rudder pedals.

 

IAN

90 degree crosswind = death wish, use a different runway.

Echofox

Not every airport has multiple runways. Direct crosswinds are a fact of life and can be easily managed as long as you know your limits and the aircraft capabilities.

 

Corrected spelling and grammar errors. Thanks stupid cell phone spellchecker.

I set 90° and 15kts just to see the effect and at least I didn't crash.

Agree with oracle..

 

Problem is most planes handle crosswinds very poorly. Try a nice addon like RealAir Legacy or A2A Cherokee to work on those crosswinds