Coming out of London City Airport the other day, I was intrigued by two large signs instructing pilots to "CAUTION YOUR BLAST". Obviously this was the first thing I typed into Google when I got home, and it brought up many webpages with people asking what it meant. The answer I like best is the one that says it means not to accelerate too rapidly going onto the runway because you run the risk of blowing the ground crew over in the process.
(rab) How do you caution a blast? Do you say "OK, blast, you've committed an offence but we've decided not to prosecute this time provided you admit culpability"? Why don't these buggers speak English?
I think it might be due to limited sign space. I trust the interpretation of the message is part of a pilot's training, as being a native English speaker won't even help you with this one.
[rab] The turning points at LCY are very tight, and I suppose it must be to remind pilots to be wary of where their blast is directed. This video shows an example of people not cautioning the blast of a Airbus 340, where the pilot has no choice of where to direct his full throttle "blast".