Altimeter inaccurate

Ron Rosenfeld wrote:

It is my understanding that in Canada there is a requirement to alter
minimums for certain approaches in very cold weather. No such requirement
exists (Part 91, at least) in the US.

I don't believe there have been any accidents in the US due to this
phenomenon.

You're correct about the Canadian regs, though I don't know how many
Canadian pilots remember to apply them. In any case, many parts of the
northern U.S. can see temperatures down to -35 degC or -40 degC just as much
as Canada can; when you combine that with the allowed +/-50 ft altimeter
error, you could be down below 100 ft when you think you're at 200 ft DH.

A more likely problem, though, would be early in an IAP, when you're still a
few thousand feet above the station elevation and have to clear a mountain
or a tower on a hill.


All the best,


David