Wait a minute: Demonstrated X-wind Velocity

[Goose Egg]

Have you guys noticed that when you land with a windspeed over the demonstrated value that you start running out of rudder?

Not quite yet... That 22 knot crosswind, I had to use a lot of rudder, but I didn't have to use all of it. And that's the most I've ever been in.

But then again, I do fly also fly a Grob G109B motorglider, which is set up with a conventional gear configuration. With that long wingspan, you can't do a lot of banking close to the ground, and I can see how you could run out of rudder real quick. Crosswind technique for the Grob is touch down with the upwind wheel first, then use opposite aileron to allow the downwind wheel to touch, then use divebrakes to kill all the lift, then add aileron back into the wind. It can get a little crazy.

Oh, and I should probably mention that I like to land Cessnas with full flaps in a lot of wind. I've noticed that I like to have the extra drag--otherwise it just seems like it floats forever. This is contrary to what I've heard a lot of instructors say--that minimal or no flaps is better in a strong crosswind. I've tried it both ways; I like a lot of flaps better.

-Goose

 

[midlifeflyer]

The "maximum demonstrated cross-wind" is not the highest wind that the super-duper-test-pilot-type can manage. I don't know what it is.

Some say it is just whatever wind was blowing that day and the test pilot could handle it, others say different things and I don't recall any official publication that defines it. It is another source of OWT. Old Wives' Tales.

But it isn't the strongest crosswind that the airplane is capable of.

I also think the aircraft company has 'liability' in mind when establishing this number.

My guess is that it's a cross between liability and marketing. Between "look how good our airplane is in a crosswind" and "opps, better not make it sound =too= good." Although it probably is a factor, I think the liability reason tends to get overblown a bit - mostly because I think these numbers have historically been pretty consistent since before the "liability crisis." My 1958 Comanche shows 20 mpg (17 kts) and that was back in the days when "strict liability" for product defects was only a glimmer in a tort lawyers eye.

 

[mattpilot]

About a month ago i landed a 152 at a nice little airport that had winds blowing directly across it at 22 Gusting 29.

It was a very... uhh... challenging experience.

 

[PURPLEHAZE21]

It's a pre calculated number based on a formula. Essentially its a percentage of your stall speed in the landing configuration. Lets be real...do you think they paid a test pilot to sit in an airplane and wait for a Xwind day... The number is derived so you can theoretically land within "safe limits". If you exceed the crosswind and crash, the manufacturer says your an "idiot" and there not responsible. If you crash prior to the limit, it's pilot error.

 

[UndauntedFlyer]

Have you guys noticed that when you land with a windspeed over the demonstrated value that you start running out of rudder?

I am thinking the manufacturers don't want to tempt people into sideloading their planes.

I have never noticed this. There is usually a good bid of rudder left on most light aircraft at 17k of crosswind if the airplane is flown onto the runway. The max demonstrated crosswind is a really no where near the max possible crosswind if the airplane is flown onto the runway wing low, followed by flying the nose-wheel onto the runway to further prevent weather-cocking along with opposite runner. One thing to understand is that the max demonstrated crosswind is not a limit. It is only a figure that is usually the same for most light aircraft (around 17K) and it is a product of the manufacturers’ legal department. It says that any properly certified student pilot or higher should be able to handle crosswinds up to that figure.