Re: Convair CV990 "Coronado"

Date:         22 Jul 99 23:30:15 
From:         ehahn@mitre.org (Edward Hahn)
Organization: The MITRE Corporation
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In article <airliners.1999.734@ohare.Chicago.COM>, "Anthony Rassias" <anthrass@ozemail.com.au> wrote:
>Recently I read that, until the advent of the Concorde, the Convair CV990
>was the fastest civil aeroplane. I am now curious and looking for any
>information on the type - performance and specifications, production
>numbers, dates etc. Were the strange fairings on the upper surface of the
>wings used to break up shock waves created by flying at high subsonic
>speeds - or did they serve some other purpose?

The Convair 990 was designed to cruise at 990 km/h (hence the name).  I
don't have other specs handy, but it was supposed to compete with B707s
and DC8s.  Something like 40 total were produced (obviously a major
commercial failure).

The fairings on the trailing edge of the wing were known as "Kuechemann
Carrots" - and were added on to reduce unacceptable wave drag in the
original design.

A trans-sonic aircraft like the CV990 generates wave drag due to
compressibility effects.  It contributes to total drag, but is separate
and distinct from parasitic drag ("skin friction") and induced drag
(caused by lift).

The shape which has the least theoretical wave drag is a double-ogive
shaped body (i.e. looks like two .22 caliber rifle shells back-to-back).
As it turns out, this theoretical minimum can be approached by an
arbitrarily shaped body which has the same cross-sectional area as the
double-ogive.  This is known as the "Area Rule".

The original design for the CV990 had a normal shaped wing and fuselage.
Unfortunately, it was designed before the area rule was well-understood.
When the CV990 has poor performance due to excessive wave drag, the
"Kuechemann Carrots" were added to bring the aircraft cross-section
profile in-line with the Area Rule.

Aircraft designed after the Area Rule was worked out have incorporated
this shape in a much more graceful manner.

ed

----
Ed Hahn / ehahn@mitre.org / +1 703 883-5988
The above statement is solely an opinion of the author, and
does not express a position or implied warranty by the MITRE
Corporation.  Really.