Originally Posted by
Kiwiguy
The 737 is limited to 19 knots crosswind with minimal flaps and 23 knot crosswinds with 40 degrees flap. The limit applies to aircraft which are not de-crabbed. The limit is set not by the aerodynamic limit of the aircraft but rather by the strength of the undercarriage to resist hitting the runway sideways.
If the aircraft is de-crabbed to align with the runway in the flare then the risk is removed and theoretically if you use proper technique there is no limit.
I landed a Gulfstream Cheetah at Wellington's runway 16 in 45 knot winds gusting 55 knots from 240 degrees once. The crosswind limit on a Cheetah was 11 knots, but if you land properly it will handle that. The limit is on the undercarriage strength and not aerodynamic factors.
Originally Posted by
Kiwiguy
...The inference I took however was that if you de-crab in effect limit is not an issue. My humble opinion. Anyway you can take it from my equally humble efforts as a test pilot that this aeroplane (Cheetah) handles a damn sight more than the placarded limit.
...
That is, the crosswind limits on most aircraft are only the demonstrated limits and not the actual aerodynamic limits. Thing is FAA or CAA certifiers can not conjure up 50 knot crosswinds to test an aircraft. They demonstrate the aircraft to the maximum crosswinds they can find and then certify that as a demonstrated limit.
If you read the document you quoted carefully, you'll see that the terminology is
maximum demonstrated crosswind component. This is not a
limit and should not be considered limiting -- it would also be unusual to see it "placarded".
It is not set by "the strength of the undercarriage to resist hitting the runway sideways". Certification requires at least a certain minimum value to be demonstrated, and some manufacturers stop there. For light aircraft the value is 20% of the stall speed in landing configuration, which probably explains the 11 knots for the Cheetah.
There are both theoretical and practical limits on crosswind landing capability. For example if "the aircraft is de-crabbed to align with the runway in the flare" then the maximum achievable yaw rate will contribute to a limit.