Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!att!cbnews!military
From: ps01%gte.com@RELAY.CS.NET (Paul L. Suh)
Newsgroups: sci.military
Subject: Re: SU-27 Angle of Attack
Message-ID: <8090@cbnews.ATT.COM>
Date: 10 Jul 89 04:20:12 GMT
Sender: military@cbnews.ATT.COM
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From: "Paul L. Suh" <ps01%gte.com@RELAY.CS.NET>
>From: Mark Nelson <nelson@udel.edu>

%A short article in the latest _Economist_ (July 3) discussed fighter
%maneuverability of the F-15, F-16, Rafale (sp?), and SU-27.  Apparently,
%the F-16 is capable of a 35 degree angle of attack, and the Rafale of
%45 degrees.  The article didn't mention the SU-27's sustained angle of
%attack capabilities, but it described the SU-27's "Cobra" maneuver:

%The plane, in level flight, with 0 degree aoa, pivots back to 110 degrees
%(beyond vertical!), and then returns back to 0 degrees, all the while
%travelling essentially horizontally.

%Anyone care to speculate on this?  Does it mean the SU-27 is incredibly
%maneuverable?  How could the plane maintain control?  How does it
%correlate to a sustained high angle of attack capability?

%As a related question, how does a high angle of attack translate into
%greater maneuverability?  My assumption is that it allows faster turns
%in the horizontal plane by effectively decreasing the apparent length
%of the fuselage perpendicular to the (vertical) axis of rotation,
%thereby decreasing the angular momentum of the plane.  Is this right?

%    |   /	Attempted diagram
%    |  /
%    | /
%    |/
%    |
%   /|		/ = Fuselage of plane, length = L
%  / |		| = Axis of rotation (vertical)
% /  |		) = Angle of Attack = A
%/)  |		- = Apparent length of fuselage normal to axis of
%---------	    rotation = L * cos (A)

%Mark Nelson                 ...!rutgers!udel!nelson or nelson@udel.edu


This is not terribly remarkable.  F/A-18's are capable of the same sorts
of stuff.  Test flights have taken the Hornet to an AoA of 110 degrees
in the vertical _PLUS_ 30 degrees of sideslip!  (F/A-18 Hornet, by Bill
Gunston, published by Ian Allan, Ltd., Shepperton, Surrey, UK (c) 1985)
This is one of the reasons why the F/A-18 is being used by NASA in their
high AoA test program (AvLeak, a couple of weeks ago)

While I have no direct sources, I would assume that the F-16 ATFI
demonstrator is capable of similar antics.  Other possible candidates
for aircraft capable of extreme AoA are the F-15 STOL and the X-29
Forward-swept wing testbed (I'm not sure that X-29 is the correct
designation).  

>From what I have read, this is unlikely to become a common manuver,
because it is very wasteful in energy.  You go in fast, make a quick
turn, and wind up going around 200 knots.  This leaves you being 
a sitting duck if anyone launches a missile at you immediately 
afterwards.  Not a bad thing if your fight is 1 vs 1, but in a
multiple ship furball, you're a goner.  VFFing in a Harrier has many of
the same problems.  


					--Paul
					ps01@gte-labs.com