I believe that when washing demineralised water is supposed to be used, which doubtless contributes to the costs involved.
At LGW, the 2 companies involved use Best Gatwick Tap; I've not heard of a requirement for demineralised water. They also use pretty strong detergent. I asked them to wash my vehicle one day and it finished up matt yellow! (but nice and clean)
We have 2 areas of a couple of stands each where the runoff is intercepted rather than allowed down the normal drainage system. When we scrub all the other stands we use soap, rather than detergent, as it's considered more environmentally friendly.
Contaminated drainage is a nightmare, especially in the winter, what with Skydrol, lubricants, fuel and de-icing fluids. The Environment Agency won't accept our drainage water until the Biochemical oxygen demand (BOD) meets a certiain standard, so we have to provide large storage facilities (big ponds) to cope with the heaviest rainfall.
I certinly wouldn't have thought that flying through cloud would have had any effect on the dirt. Apart from boundary layer considerations, it takes heavy mechanical brush action to scrape the dirt off.
the_flying_cop
I think I sent the rest of them to the land of nod!
Cheers,
The Odd ONe