with an old caravan, use a claw hammer, just treat the screws as old nails, after all, you're not wanting to use the screws again.
.....Don't waste money on screw extractors as they don't work that well, particularly on small diameter screws.
....drill the heads off, or as Robbi says treat them as nails and use a claw hammer, but use a thin piece of metal or wood underneath the pivot point of the hammer to protect whatever part you are removing......
At least they are Philips head and not slotted. Spray the screw heads with some WD 40 or similar just to clean them.( and leave for a few minutes) Place your screwdriver in the cross( if they are really badly corroded scrape out the cross with a needle or other sharp item so the screwdriver fits) and tap the back of the handle with a hammer whilst at the same time turning the screwdriver anti clockwise. This usually works on most seized/rusty screws, if not then drill the heads off, or as Robbi says treat them as nails and use a claw hammer, but use a thin piece of metal or wood underneath the pivot point of the hammer to protect whatever part you are removing.
Don't waste money on screw extractors as they don't work that well, particularly on small diameter screws.
Santababy i think you're missing the point mate, Tengu wants to keep the alluminium sheeting, thats all. The screws hold the sheeting to the frame ( timber ), a claw hammer or crowbar with a nail lifter at the end will either pull the screws out or snap the heads off......either way the sheeting will have minimul damage.
it doesn't matter that the screws are left in the timber frame
Fair enough. Missed that bit. I'm thinking of screws stuck in mechanical parts she might have wanted to salvage.
Sounds like you've got your old USAF head on there buddy !.
As Robbi says use a claw hammer, its just wood & probably rotten underneath or a van only fit for scrap so no harm done.
Rob