Crosswind limits

[bookworm]

I've seen a couple of cases where crosswind limits have been quoted for commercial transport aircraft, for example 40 knots on a dry runway and 25 knots on a wet one.

What is the measurement/assessment/value that is required to be within those limits?

The ATIS wind?
The instant wind (when? do you go around if the wind goes out of limits on short finals?)
Some value from the TAF?
Something to do with the crew's assessment of what might be possible?

Are gusts accounted for?

Thanks

[Genghis the Engineer]

The value quoted is an actual, demonstrated limit - judged by the test team to be the maximum that an averagely trained pilot could reasonably be expected to handle using the recommended crosswind landing technique. A high ability pilot who knows their type well can usually handle more - somebody new to a type or low-hours probably needs to self-impose a lower limit.

There's no fixed standard but as a rule if the ATIS says 15 gust 26 - take the crosswind as 26 since that's what you may see and need to handle.

The go-around decision needs to be high enough to do a go-around IN TURBULENCE with the handling problems that may cause. What that figure is really depends upon the judgement of a commander who knows his aeroplane well.

G

[pesket]

If you have instant wind, use it and add half the gust factor.
the limits are set thru the test program and they are only demonstrated. many manufacturers won't set limits in the AFM anymore, they will just demonstrate them, they are scared of law suits I guess.

[Airbrake]

Genghis, and all.
The demonstrated cross wind limit in the aircraft manual must be taken as the aircraft AND pilot limit. If a test pilot tells me that the max demonstrated cross wind for my type of aircraft is 30kts I'm not going to give it a go at 35kts because I have been on the type a few years and think I'm better than my mates who stick to 30kts!
Besides, following an accident where you go off the runway due to loss of control when weather and crosswind may have been a contributing factor you could sell me tickets for your court case. Especially the day you try and convince the prosecutor for your dead pax that you were better than average and had high time on type!
This is a sore point because several Captains at my company blatantly disregard the demonstrated crosswind limit. Remember its not just keeping it straight with all the donks working you have to be able to do it at V1 with failure of the critical engine, and that I suggest would be a marginal exercise if your crosswind is out of limits.
We have some more gale force winds coming to the UK over the next 5-6 days, lets hope we don't see any aircraft stuck in the grass or worse.

[bookworm]

Thanks to those that have replied so far. The answers are not quite what I expected so let me try to clarify what I'm asking.

I'm a GA pilot and I'm familiar with the concept of the aircraft's maximum demonstrated crosswind component. In the sort of aircraft I fly the max dem xwind is governed by FAR 23.233. For transport category aircraft it's 25.233 and 25.237. I agree strongly with pesket that manufacturers tend to demonstrate non-limiting values: in the FAR 23.233 case it can be as low as 0.2 Vso. If I treated it as limiting (and it explicitly says in the manual that it is not) then I'd probably never be able to fly in this country!

It was my understanding that for public transport ops, company Operations Manuals set limits (not recommendations) for crosswind operations. If there are no such limits, please correct me. It was those limits that I was asking about. What value is compared with the limit to decide on whether or not a take-off or landing is permitted? Or is it always captain's discretion without hard limits as Airbrake's answer implies?

[Dan Winterland]

BEWARE! A demonstrated X-wind limit may be the average, but are you sure what the manufacturer of your type is really quoting. My leisure aircraft quotes a demonstrated limit of 17 knots. But the type I fly for a living quotes 28 knots. That is the absolute maximum based on the max aileron authority to counter the applied rudder. (Swept wing type).

Know your aircraft, and beware of the flight manual.