"C J Campbell" wrote in message
...
Modern airliners have multiple static ports, but they do not have one like
your 172. The alternate static port in your 172 uses cabin air. Airliners
are pressurized, so an alternate static port like on the 172 would be
worthless.
I wonder. After all, the time you'd really need the alternate static port,
you'd be low enough for the cabin to be left unpressurized. More than
likely, the pilots would notice the need for alternate static reference
before they climbed above an altitude where pressurization is required.
I can believe that pressurized transport category airplanes don't bother
with a cabin-vented alternate static port, as a matter of the designers not
bothering to provide that. But I don't see any reason why that wouldn't be
a feasible safety feature.
Just select the cabin-vented alternate static port, and allow the cabin to
climb to ambient pressure altitude.
Pete
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