Hi,
Just to throw in a little humor here as the 'lift' thread heats up:
Assume you're gliding in a Piper Warrior or Archer doing 80 knots in no wind
conditions with the engine at idle. If you try open that little air vent on
the pilot's left, it is forcibly sucked outwards. Makes sense until you
think that the air outside is standing still while the air inside is doing
100 knots and should therefore have a lower pressure!
Hilton