In truth this question may depend on your own company policies, or SOP's.
In the good old days my lot clearly stated it was SOP that the gust value was used to calculate crosswind component, and the situation described by SentryIP would apply.
Lately however we've had new types enter service with specific 'mean' and 'gust' limits on crosswind, and both have to be within limits now! The diff is about five knots extra for the gust.
I recently queried one of our fleet captains on this and he advised that the old policy of using the gust as the sole value for calculating crosswind (on types with no 'gust' limit stated) is now discontinued. Therefore he suggests that only the mean wind is considered in this scenario.
He did add that it's up to the skipper...etc.
So you could interpret what he was saying to mean that "25 gusting 80" is within limits...but on your own head be the consequences of attempting it (and I 'spose your pax too, eh). I'll bet he'd deny everything if we had a whoopsie!
Err on the safe side I always say.
I've no idea if JAR OPs has modified the principles here. Any offers?
[This message has been edited by CaptSensible (edited 16 December 2000).]