Re: External inspection

Date:         13 Feb 99 02:26:11 
From:         westin* (Stephen H. Westin)
Organization: Cornell University Program of Computer Graphics
References:   1 2 3 4 5
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JF Mezei <> writes:
> I do not understand. If the static pressure trapped inside the system
> were enough to show a V1 speed on the pilot's gauges, shouldn't pilots
> have noticed that the gauges were reading V1 while the plane was iddle?

No. There are two ports involved: one is a tube facing forward and
measuring ram air pressure, which depends (to first order) on
airspeed. This presumably wasn't blocked.

The second port is needed because planes don't stay at a constant
altitude: as outside static air pressure declines with altitude, the
ram air pressure (as absolute pressure) declines. To correct for this,
the airspeed indicator has a static port open to the non-pressurized
atmoshpere outside the plane and registers the pressure *difference*.

I believe that this static port was blocked, giving a normal airspeed
indication on the ground, but progressively stranger readings as the
plane climbed.

-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.