Re: Birgenair 757 crash - A&C article

From:         gsmoff@Mcs.Net (gary)
Organization: MCSNet Internet Services
Date:         02 Jun 96 16:23:51 
References:   1
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> What I do not understand is if a pitot probe is blocked. the indicated
> speed must be lower than the air speed, not highter ?

Airspeed indicators, or in this case Air Data Computers, are also vented
to static pressure in order to compensate for changes in air density due
to changes in altitude.  If you block a pitot port and decrease static
pressure the indicated airspeed will in fact rise.  The confusing part is
why the crew would have ignored the other two airspeed indications in the
cockpit.  Those being the alternate airspeed indicater on the center
instrument panel and the First Officer airspeed indicator which would have
been driven by the number two air data computer, both of which were
sourced from their own pitot probes and should have been reding correctly.

Gary S. Moffitt