crosswind

[alfaman100]

If you are conducting a precision approach in either CAT II or CAT III conditions, are you likely to encounter any significant crosswind (below 200ft)?

Difference of opinion needs settling if anyone can help!

Thanks

[BOAC]

The expression '40kt fog' is well known in aviation circles

It does not need to be far off the runway at 40kts to make a significant x-wind component.

[Old Smokey]

And the problem then is that most Auto-Land Cross-Wind limits are less than the normal limit for the aircraft.

Thankfully (at least in my experience) the most common "REAL" Auto-Lands are in thick foggy conditions with little or no wind, I hope that my good luck keeps running

Regards,

Old Smokey

[alfaman100]

Thanks for your responses
Regards
Alfa

[alf5071h]

There can be some significant crosswinds in Cat 2, but wind strength generally decreases in thicker fog (Cat3). However, some auto land systems might have to cope with blowing snow or dust which could result in ‘Cat 3’ visibilities.

Auto pilot certification has to meet stringent requirements (JAR-AWO) to achieve a reliable touch down in an acceptable landing box. Some of the data originates from flight testing, but most is provided by simulation of the autopilot performance in a wide range of variables, which are based on the flight tests.
I flew a 35 kt crosswind auto land to certificate an AFM limit of 15kts. The auto land appeared to be very capable, if not more than I could achieve in the conditions. In my experience the auto land limits are conservative, rightly so for systems where human intervention is either not required (Cat3b), or not guaranteed.