I don't spot an answer to this question, so thought to re-post it here. Larger airplanes are heavier and would ostensibly be pushed less by the wind compared to a small airplane? Do larger airplanes have higher crosswind limits then?
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4$\begingroup$ A big difference is the landing speed at touchdown. A 747 touching down at, say, 150 kts needs far less correction than a 172 touching down at 50 knts. $\endgroup$– TerryJul 21, 2020 at 2:25
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2$\begingroup$ The relation between weight and side area is fairly constant regardless of size. What matters is landing speed. $\endgroup$– Guy InchbaldJul 21, 2020 at 6:17
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1$\begingroup$ you'd expect the square-cube law to be at work here: weight increases with volume, i.e. the third power of e.g. length, while side area only increases with the second power. $\endgroup$– HobbesJul 21, 2020 at 7:25
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2$\begingroup$ @GuyInchbald Statistically, wing loading goes up with absolute size, so that relation is not constant. $\endgroup$– Peter KämpfJul 21, 2020 at 9:01
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$\begingroup$ @PeterKämpf Yes it does but then statistically landing speed also goes up with absolute size. You can use statistics to prove anything, as the saying goes. There is no fundamental principle why wing loading should be linked to scale, but there very much is so when it comes to speed. $\endgroup$– Guy InchbaldJul 21, 2020 at 9:09
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2 Answers
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Generally yes, since a 20kt crosswind requires considerably less crab angle on final at 135kt compared to 70kt. The CRJ900 has a demonstrated max crosswind component of 32 kt (If I had those conditions in a 172 and had to put it down, I think I'd just land across the runway).
There is also a significant technique difference once you get above, say, 100,000 lbs, or depending on the engine location. On heavies where you only have a few degrees of banking margin when the gears touch before the nacelles hit, the technique is to fly wings level crabbing into wind into the flare, and give a large boot of rudder just prior to touchdown, and get it down before you start drifting off to the side (you are effectively in a skidding turn, but there is a delay before you start to actually change direction and you have to achieve ground contact in that delay period, so you make it snappy and don't work on teasing out a smooth touchdown).
On smaller aircraft it's more the traditional sideslip technique, wing low with opposite rudder maintained to keep runway alignment through the flare and touchdown. My jet time was on CRJs and I would land in crosswinds slightly wing low with rudder to keep aligned, similar to landing a glider in a crosswind (it took about 7-9 deg of bank to risk tip contact and a crosswind would never need much more than 3-5, although tip strikes do happen in the CRJ fleet from time to time when pilots have an oops on landing).
Transport airplanes generally don't have a maximum crosswind component as a published limitation, but will list a "demonstrated" crosswind component with the statement "not considered limiting". It means that it's only the maximum component demonstrated in testing, and you are free to land in stronger ones, but the manufacturer doesn't vouch for the ability of the plane to handle it.
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1$\begingroup$ Flying gliders, we always did what you describe in your second paragraph. $\endgroup$ Jul 21, 2020 at 14:22
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$\begingroup$ I fly gliders too and I usually use a bit of slip (why I said "slightly wing down"), but not as much as in a power plane. With the wings loaded and curving up, the tips are actually quite a ways clear of the ground and you have more bank margin than you'd think. But yeah you can do it that way if you don't want to lower the wing, but you can't delay the touchdown too long once the rudder is in unless you drop the wing a little. $\endgroup$– John KJul 21, 2020 at 17:33
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$\begingroup$ Of course. I was taught, and always taught myself, to kick the rudder at the precise moment of touching. $\endgroup$ Jul 21, 2020 at 19:24
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$\begingroup$ Another glider pilot chiming in here, I always use the wing-down slip method and try to keep fuselage fully aligned w/ runway centerline throughout the last part of the final. $\endgroup$ Jul 21, 2020 at 22:22
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$\begingroup$ @MartinArgerami: I thought you were supposed to touch down crabbed and then kick out the rudder. $\endgroup$– VikkiJul 21, 2020 at 22:54
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Flying and landing speed are a function of wing loading, airfoil, ... . The key issue is the landing speed versus the crosswind speed (apparent wind issue).
For gusting crosswinds, having a lot of dihedral (and/or low roll inertia) requires more compensation to handle.
