Thrust reverser credit
 

Do not take a thrust reverser credit on Wet/Slippery Rwy when crosswind component >15kt.

Why is this?

Thanks.

Thrust vector for reverse thrust tends to exacerbate downwind drift. In the extreme (icy runway), it will cause loss of control, and you will drift off the side of the runway.

Specific limitations will vary by airplane...

Landing on a slippery runway and using reverse thrust in a crosswind can increase the tendency to drift downwind and reduce the lateral control effectiveness. If the aircraft deviates significantly from the centreline then reverse should be reduced or cancelled until directional control is improved and the centreline regained.
Reduction or lack of reverse thrust's significant component to braking on a slippery runway may negate any credit given anyway.
The effect will be aircraft specific thus refer to the manufacturers advice / limitations.
See http://www.skybrary.aero/bookshelf/books/871.pdf ~ page 6.

Landing with a 15kt crosswind on a very wet/slippery runway, and particularly if contaminated, may well be the recommended maximum crosswind for landing in most aircraft, with or without thrust reverse.

And this is from the 737 800W preamble limitation.

Thanks, pretty much sums up my troubles!