units of measurement on altimeters

(Pat Norton) wrote:

Do all commercial aircraft that fly in and out of North America have
dual unit altimeters (hPa and inHg)?

I don't know about that, but as regards to the metric system, I would
like to mention that using hPa is _not_ the recommended way. Although
the "h" prefix is formally part of the SI system, it's regarded as
unsuitable by many, including NIST.

In practice, using hPa means being just _nominally_ metric, i.e. using
actually millibars but under a different name. The odd thing is that
the correct kPa would be more practical.

--
Yucca, http://www.cs.tut.fi/~jkorpela/