In article ,
"Ron Natalie" wrote:

"Bob Gardner" wrote in message
news:cLmIb.79193$VB2.159840@attbi_s51...
I have no direct knowledge of how big an airliner
outflow valve is, but I am going to guess three inches in diameter

I think this is a good guess. It sort of looks like the top of a can of
parmesan cheese.

Parmesan cheese comes in *cans*?! Maybe I've lived in the Bay Area too
long :-).

Hamish