Why shouldn't we? If there are good reasons not to then I'd appreciate knowing about them before we do any damage!
Water pentration into joints, seals, bearings etc. The airframe is designed to shelter bits like this from the worst effects of water carried in the slip stream whilst flying. With a pressure washer you can back flush bits that the airflow can't normally get at.
Pressure washers are fine for cleaning tractors, excavators and cows! But best avoided for aircraft.
A point to remember is that any form of detergent or cleaner will degrade the lubricants in hinges, cables etc so once you've finished washing get round with the grease gun and or WD40 to prevent corrosion setting in.
Don't use washing up liquid either it's loaded with salt.
