Re: External inspection

Date:         01 Feb 99 02:37:09 
From:         "R.R.B.777" <Richard.RECLUS@wanadoo.fr>
Organization: Wanadoo - (Client of French Internet Provider)
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Jeff Meeker a écrit dans le message ...
>On 29 Dec 98 03:12:29 , JF Mezei <jfmezei.spamnot@videotron.ca> wrote:
>>Rob Montgomery wrote:
>>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
>wing.

I partially agree: in the calculation of takeoff speeds there are air
speeds and ground speeds. However they are all converted to airspeeds as
it's the primary indication.

>>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.

As you said V1 is a decision speed but it's even more an action speed:
you're supposed to take appropriate maneuvers at V1 and not above.  So
only critical events should lead you to an aborted take off close to V1
(5kts or less) like engine critical failure,fire etc....However you are
not commited to an aborted takeoff before V1.  For the case of airspeeds
in case of the complete loss of indications (primary and stanby) I would
perform an aborted takeoff if that happens early enough (lets say 10kts
before V1 or earlier) or else I would continue taking off based on the
procedures without anemometric indications. Note that it's my own
opinion and somebody might consider the contrary is safer. But on my
part I always considered aborted takeoffs (near V1) more critical than
any non critical events (fire, engine severe damage) i.e even an engine
shutdown should lead to an aborted takeoff at V1 only very carefully
(you have to have in mind what brought the choice of V1: obstacle
limitations or runway length)

R.R.B777