Re: windshear warning systems

Date:         28 Dec 96 14:20:10 
From: (RD Rick)
Organization: Netcom
References:   1 2
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In <airliners.1996.3082@ohare.Chicago.COM> Andrew Weir
<100637.616@CompuServe.COM> writes:
>    The 1989 FAR requirement was for a windshear radar device which..
Correction:  I believe that should read windshear warning system.
Reactive warning systems rely on accelerometers and airspeed changes to
detect entry into a windshear.

>...those days only told the crew when they were in windshear already

What Continental did was to install a later version of weather radar
which, instead of merely telling you that you are in a windshear and
may hit the ground, gives approximately 30 seconds warning.  Some of
Continental's fleet has only the reactive system, and some has both.

Forward Looking Windshear Weather Radar (FLW) uses doppler shift of
returns from rainfall or blowing dust to detect microbursts, which are
downbursts of air that strike the ground and flow outward like an
inverted mushroom cloud.

>NASA would like the FAR redrawn so that the predictive system becomes
>the standard.  At the time the Black Box (Survival in the
>Sky in the US) films were compiled, Continental was the only airline
>with these predictive windshear radars installed.

Not quite so.  Six of Western Pacific's 15 737-300 are FLW equipped, as
are well over 100 others.

There is real economic incentive to install FLW, in addition to safety.
 Standard procedure for escape from a reactive windshear warning is to
firewall the engines.  By the time some windhears are escaped, the
engines are cooked, requiring expensive overhauls.