Re: Southwest Airlines 737-700

Date:         19 Feb 98 01:34:36 
From:         "Chris Dahler" <dahler@iglobal.net>
Organization: All USENET -- http://www.Supernews.com
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>Speaking of B-737-700...  I've heard that some carriers make it a
>practice to disable the RTO safety features (auto brake, etc) on B-737
>aircraft so equipped as a concession to training standardization...
>
>Would any Bluecoater care to explain the pros and cons of such a
>policy... and discuss these in light of considerations such as
>uncertainty about take-off weight (carry-on baggage, etc.), reduced
>power take-offs, higher gross weights, possibly higher V1, Vr and
>Vlof, etc.

Deactivating RTO is a practice used by a few airlines, Southwest probably
being the largest.  The degradation of reaction time from the onset of an
emergency to the application of full braking by the pilot is taken into
account when computing balanced field length and the resulting maximum
allowable takeoff weight.  There is a weight and V1 penalty for not using
RTO, and any airline with this feature deactivated takes this penalty.  The
thinking is that the expese of maintaining the autobrake system is greater
than an expense incurred in the rare instance where the airline would have
to limit freight or pax to accommodate a weight restriction.  In any case,
activating the autobrake system does not actually provide an additional
margin of safety when viewed in this light, because with this system, the
aircraft may take off heavier and have a higher V1, which will result in
more runway used during the emergency stop.  Balanced field computations
will by definition result in maximum performance in either situation, which
means a minimum necessary runway length for stopping to allow the maximum
weight for takeoff.  Autobrakes just allow the airline to squeeze a few more
pax or a little more freight onto the aircraft.