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From: jabusch@osiris.cso.uiuc.edu (John Jabusch)
Newsgroups: sci.military
Subject: Re: Persian Gulf Combat Aircraft--The A-4 Skyhawk
Message-ID: <1990Oct11.050803.29068@cbnews.att.com>
Date: 11 Oct 90 05:08:03 GMT
References: <1990Oct8.030359.11680@cbnews.att.com> <1990Oct10.000404.29790@cbnews.att.com>
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From: jabusch@osiris.cso.uiuc.edu (John Jabusch)

>From: henry@zoo.toronto.edu (Henry Spencer)
>>From: jfb@ihlpm.att.com (Joseph F Baugher)
>>	.  Israeli Skyhawks have been upgraded over the years, notably by the
>>	   addition of extended jet tailpipes for infra-red suppression ...

>Minor quibble:  the extended tailpipes don't do a lot to suppress IR
>emissions, as it is pretty hard to do much about a jet engine's IR,
>especially against modern heat-seekers (which home on the exhaust, not
>the hot engine parts).  The extended tailpipes come from experience
>with shoulder-launched-SAM hits:  those simple little missiles tend
>to hit in the tailpipe area, and they don't have a very big warhead,
>so if the tailpipe is nice and long, all they do is dent the sheet
>metal.

Most of the extended tailpipes have an external open cowling which deflects
cooler air from the airstream into the exhaust.  As a result of the dynamics,
a hot spot is created behind the jet, but not right at the end of the pipe.
In some cases, for example the A-7's later mods, the hot spot is more than
a few feet back!  Enough in practise to alter the effects of even a 
Sidewinder or Sparrow, which direct most of their blasts sideways.

Anyway, as you pointed out, the simple little missiles from shoulder-
launched SAMs are most effected by this.  Of course, this is the primary
threat for a close-support fighter in today's military, since they are
frequently too close to the mud for a larger unit to track effectively.
If they can suppress small-SAM effects, they can stay lower longer,
and avoid the large SAM sites and their tracking systems.

John W. Jabusch
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--
John W. Jabusch
INTERNET: jabusch@cerl.cecer.army.mil    MILNET: jabusch@osiris.arpa        
US Mail: USA CERL, PO Box 4005 Newmark Drive, Champaign, Il 61824-4005
Voice/Phone: Commercial (217) 352-6511