flaps in crosswind

[teflon tiger]

Are flaps recommended in a crosswind landing considering both a high wing and low wing aircraft and the reasons why?

[Tinstaafl]

Up to the a/c's Max. Demonstrated. X/wind limit there isn't really any advantage to a semi-flapped landing.

The disadvantage of course is increased LDR.

If the conditions involve significant gusts/turbulance ie enough to make controllability/performance difficult than semi-flap gives an increase in excess power available.

If the x/wind component is large enough to exceed the control inputs needed to prevent drift & stay aligned with the runway then semi-flapped may make a difference.

The reduced amount of flap means that the approach/touchdown speeds will be faster, leading to increased control authority allowing a slightly higher x/wind component. It will also result in a reduced drift for the same x/w component or same drift & control input for a slightly increased x/w.

[invalid entry]

Totally agree. On a/c with a choice of flap setting, I always use less in a strong or gusty crosswind.
eg PA28 only 2 notches, 737 flap 30 rather than 40

[OnTheStep]

there's certainly something to be said for partial flap in strong xwd conditions.

while i don't make a habit of assuming the role of test pilot, the max demonstrated for the bonanza is 17kts but coming in flapless has shown that it can be brough in during *ahem* slightly higher winds with relative success in performing some semblance of a landing. the limiting factor being the rudder effectiveness, the added airspeed on the flapless approach gives a more solid 'on rails' feeling through the flare and touchdown.

[Tinstaafl]

Yes - my experience has been that it is always rudder authority that is the limiting factor (in a steady state crosswind).

Doesn't matter what method I use: crab, slip or combined.

If crab there's a limit to how much yaw rate I can induce to align just before touchdown

If slip the limit is how much yaw I can prevent with the in-to-wind wing down, to keep aligned during the approach & touchdown.

Similarly with combined only the limit varies between the two mentioned above depending on just where I choose to transfer method.

[OnTheStep]

and when in doubt, go to the poh/sops/et al!

don't get caught slipping for half a minute while the fuel port gulps like a fish for motion lotion with the fuel hiding on the other side of the tank. ;)

[beardy]

If, as is normal, the flaps do not extend along the full length of the trailing edge then when they extend they alter the lift distribution along the wing bringing the centre of pressure closer to the fuselage. This means that the increment of lift provided by the natural stability of the aircraft in roll to disturbance ( dihedral or sweepback ) is reduced, in other words the restoring moment is reduced when flaps are extended. To compromise, in turbulent conditions, it may be prudent to reduce the amount of flap extension and consequentially increase the roll stability. An alternative is to droop the ailerons.

[OnTheStep]

unless you happen to be in the twotter that day ;)

full span flaps/flaperons and all, i suppose you'd just as soon put her down across the width of the runway anyways :p