Why is that obviously not true? There is no legal limit and we know why a demonstrated limit is not really a limit.
Let’s say you are flying an aircraft which flies final at 60kts and Fb =1 and a POH max demonstrated crosswind of 18 kts.
If you have a crosswind of 18knts and Vw x Fb = 18 x1 = 18 do you still say you would not land in that crosswind?
I have never said you can’t set your own or lower limits and I have never claimed you should use a particular technique. I have said that you need to perfect that technique through training so that it becomes 2 nd nature. But that is just an opinion. There are probably pilots out there who are just naturals.
gallois wrote:
Touching down at 25kts – 30kts should not be a problem with higher crosswinds than 18knts even without full aileron deflection.
How on earth are you going to do that? Let’s say 20 kts crosswind and 30 kts airspeed. This means:
42 degrees crab angle
Your speed along the runway is 22 knots
At that air speed, if you rotate in yaw 42 degrees in one second, your inside wing looses at least 1/2 of the lift, while your outside wing almost doubles. The inner wing tip will have almost zero air speed. No aileron that I know will compensate that. Even if you happen to have that rudder authority, you will have to rotate in yaw much slower. You cannot rotate faster than your ailerons can compensate.
With a wing down approach, you have already rotated the aircraft to the correct touchdown heading. No more rotation needed. You land on one main wheel. The remaining problem is getting the other wheel down without blowing to the side due to little very little weight on the wheels, and wind catching the inner wing when the when both wheels are on the ground. It’s doable, but not without skidding several meters while at the same time weathervaning. That’s my experience at least. It’s definitely not something I will deliberately do many times, and hope to get away with it without destroying something on the aircraft. There are better and safer ways (like actively using the width of the runway to your advantage).
The main problem is not the crosswind. The main problem is low air speed and low weight. Higher air speed (but equally higher cross wind) will solve the “helicopter situation”, but since aircraft are designed the way they are, your rudder authority is not likely to improve.
gallois wrote:
There is no legal limit and we know why a demonstrated limit is not really a limit.
Which is what I wrote, wasn’t it? But the interesting thing here are not the legalities but the practicalities.
If you have a crosswind of 18knts and Vw x Fb = 18 x1 = 18 do you still say you would not land in that crosswind?
But now you’ve set Fb=1 so the “effective crosswind” is the same as the actual crosswind! Then there is obviously no issue. The interesting cases are when Fb≠1. The limits in the POH are what they are. Whether they are demonstrated or legal or aerodynamic limits doesn’t matter. The point is that they refer to actual crosswind, not some “effective” crosswind, so it doesn’t make sense to compare them to something other than actual crosswind.
I have never said you can’t set your own or lower limits and I have never claimed you should use a particular technique.
And I have never claimed that you said that. I’m simply trying to understand the use of “effective crosswind” during landings. It still doesn’t make sense to me.
Good stuff:
@LeSving we were talking of actual wheels touching down at 25 -30knts not Vr.
As you slow heading down the runway centre line you are adding more into wind aileron. But your wheels are not skidding they are rolling down the centre of the runway. It will be the into wind aileron which will stop you from skidding across the runway or pirrouetting into the wind.
Unless of course you get it wrong.
@Airborne_again I really don’t know how to be any clearer. Demonstrated crosswind is just that, what crosswind could be demonstrated during testing. If they had only very little wind they will put that minus a margin for error. It’s why some aircraft have very low demonstrated crosswind Let’s just say X = Vw x Fb is a quick bit of mental arithmetic to decide whether something is a go or no go without getting the wizzy wheel or calculator out. X × 1 (sin a) = the maximum crab angle you are going to need.
In practice If you use the crab method you don’t need further calculation all you need is to keep the nose on the centre line as you descend. Then decrab at your usual point.
But if you do find you are crabbing at more than Xx1 the wind is greater than you have been given and maybe you will need to think of a go round if you are not totally comfortable with crosswind landings in the aircraft you are flying.
gallois wrote:
It will be the into wind aileron which will stop you from skidding across the runway or pirrouetting into the wind.
Well, in many ULs, you have a hard time taxying with 20 kts cross wind without weathervaning into the wind. In the Savannah you can fly at 20 kts (barely, but still) 
Hence a better method is to simply land straight into the wind with zero ground speed I mean seriously.
You are right it I better to land straight into the wind, but it’s not always possible.
The Super Guépard 1.3 VSO is 80km/h.
Because of its lack of inertia you run the risk of it plopping down at that speed and for a kiss landing most of us prefer to use 100km/h to 110km/h.
But landing across a runway into wind is a very good crosswind technique if the runway is wide enough.
Chaps, at some of the crosswind speeds you’re discussing here the question is not how to land the airplane, but rather: after you’ve landed, now what? I’ve been in a situation once (at LEMG) where I needed wing walkers to get to the tiedown. Cessna 172RG, impossible to taxi in 40-50kt winds.
How true but that applies to all winds and directions in a taildragger and you have to keep your wits about you until you’ve got the aircraft in the hangar. And yes sometimes that means wing walkers.
Thanks for that video @hazek, indeed a good refresher.
I like his recommendation to actually do a long (very) low pass in a heavy and gusty x-wind to practice.
As to running out of rudder, twins have the advantage of using differential power. I have only done that once and it was quite effective. On final at Reus LERS I ran out of rudder, did a go-around and tried next time with a bit more power on one engine. To be honest it felt a bit like an experiment but that rwy is so wide that I took the chance.
@Emir have you ever had to do that?
