The USAirways A320 accident last night has prompted a lot of interest in Airbus' so-called ditching switch. Courtesy of a guy called Andy Tracy, who is apparently a Cathay Pacific A330/340 captain, here's some detail on just what it does.
ON - The following valves close; (Lt White)
- outflow valves. Will not close automatically if under MAN control.
- emergency ram air inlet
- avionics ventilation overboard valve
- cargo compartment isolation valves
- pack flow control valves
- cabin fans stop
Caution: If the ditching pb is put ON, on ground, with low pressure ground cart connected and all doors closed, a differential press will build up.
I'm not absolutely sure it's "unique" as is being stated (though maybe). I believe there is something similar in the BAE Ssytems RJ series, though perhaps with different functionality. And I read that Boeing 727s at least had a snorkel-like system which used floats to close off external air valves if an aircraft sank into water.