Re: Air France Concorde crashes after departing Paris CDG

Date:         27 Mar 2001 16:05:25 
From:         "matt weber" <mattheww50@home.com>
References:   1 2 3
Followups:    1
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----- Original Message -----
From: "Malcolm Weir" <malc@gelt.org>
To: <airliners@chicago.com>
Sent: Wednesday, March 21, 2001 6:33 PM
Subject: Re: Air France Concorde crashes after departing Paris CDG

> On 16 Mar 2001 05:56:29 , Wolfgang Keller <w_keller@gmx.de> caused to
appear
> as if it was written:
>
> [ Snip ]
>
> >Question to the more competent people here: How 'flyable' would a
Concorde
> >with two failed engines (on one side) be. I thought I've read somewhere
> >that during the original trials, the manufacturers had to make the
> >experience that the loss of one engine already made the aircraft yaw
quite
> >lot. So with both engines on one side lost, I guess there might have been
> >problems with the other two no longer getting enough air in the intakes?
>
> All indications are that the thing was flyable in the sense that it was
> above the control speeds for its configuration.  It lacked the speed to
> climb, though.

Flyable only in a very narrow sense of the word.  Concorde is a strange
airliner in that minimum drag at MGTOW on most aircraft is pretty close to
V2, on Concorde it is at 415kt.  The full thrust of 2 engines on Concorde is
roughly equal to drag at 275kt.  Below 275kt, drag exceeds thrust,
consequently flight at speeds below 275kt on 2 engines is a black hole in
the flight envelope. If you get into it, unless you can somehow get the
speed above 275kt, or get another engine going, the outcome will be fatal.
You cannot remain in the air for very long..   At low altitude, it is in
fact a death trap.

The emergency operations procedures recognize this, in that in the event of
an engine failure, the priority on departure changes from climb rate to air
speed, to get beyond the 275kt problem ASAP.  At speeds below 275kt, the
drag slows the aircraft, forcing the pilot to raise the angle of attack to
maintain lift, which creates still more drag, slowing the aircraft still
further until it finally falls out of the air...