Re: External inspection

Date:         17 Jan 99 02:37:35 
From: (Jeff Meeker)
Organization: posted via:, Dallas, TX (214) 343-3333/(817) 461-8484 for info
References:   1 2 3
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On 29 Dec 98 03:12:29 , JF Mezei <> wrote:
>Rob Montgomery wrote:
>> At the risk of sounding the fool, and admitting not to be an expert,
>> wouldn't the prudent pilot abort the takeoff roll if airspeed
>> indications were severly off the mark (i.e. at the cross-check)? I
>> can't believe that any handling pilot would just eyeball the decision
>> and rotation speeds.
>Are V1 and V2 based on airspeed or based on a speedometer controlled by
>landing gear wheels ?

These are airspeeds.  How fast the plane travels across the ground
doesn't mean much.  You want to know how fast the air travels over the

>If controlled by airspeed, the above poster has a pretty damm good point: how
>come they would have been able to do the take off roll if their airspeed
>indicators were inop ?

It wouldn't appear to be inop.  If the static  pressure trapped inside
the system was the same as the current outside static pressure,
everything would appear normal.  You would only notice an invalid
reading when the static pressure changes from what is trapped inside
the system.

>I was under the impression that reaching V1 and V2 speeds is a critical phase
>of any takeoff. Is this really the case ?

yup.  V1 is the desicion speed.  It is calculated on various factors
such as runway length, airplane configuration, airport elevation,
temperature, pressure, and airplane weight.  If something bad happens
before this speed, take off is to be aborted.  Once you hit this
speed, you are COMMITTED to taking off.