[simpits-tech] LVDT's Anyone ? (New Projects)

[Roy Coates]

On Wed, 1 Jul 2009, Rick Davis wrote:

> One thing you may be able to clear up, because I've been told this but don't
> know how much credence to apply to it, that the Concord actually flew by
> shifting fuel (weight) from forward to rear, and right wing to left wing?
> Any truth to that? Theory being that it flew so fast ailerons were
> ineffective (or prone to being blown to bits) so when you turn the Yoke
> left, pumps transfer fuel from the right wing to the left wing.
>
> Sounds bizaar, but possible?


I think that would take far too long. However...

"the centre of gravity (CoG) on Concorde it critical to it being able to
maintain supersonic speeds and also fly successfully at low speeds. The
centre of lift of the aircraft, when flying at Mach2, can move by some 6
feet. On a traditional subsonic aircraft the control surfaces (or entire
tailplane) would be moved to trim the aircraft correctly, but on Concorde
this would be unacceptable due to the drag it would cause and also leave
very little movement left to control the aircraft.

The way the change in the centre of lift from the wings is trimmed out on
Concorde is to compensate by moving the weight distribution, or CoG, by
pumping fuel from the forward trim tanks to the rear trim tanks and vice
versa. The trim tanks make up around 33 tons of fuel that can be moved
around the aircraft. (the main tanks hold 95 tons).

Before take off and during the acceleration through Mach1 to an eventual
Mach 2, fuel is pumped out of the forward trim tanks to the rear trim
tanks and the collector tanks in the wings. Around 20 tons of fuel is
moved in the process and results in a rearward shift of the CoG by 6ft (2
meters.)

At the end of the Cruise during the deceleration fuel is pumped forward to
the wing transfer and even the forward trim tanks is necessary thus moving
the CofG forward again as the centre of lift moves reward. Once on the
ground it is standard practice to then pump more fule into the forward
trim tanks to correctly balance the aircraft, so it can be unloaded
without any stability problems and the chance of it becoming a
"tailsitter"

The Movement of fuel also provides additional benefits at lower speeds: By
making the aircraft rearward heavy during take off and landing, this
causes the elevons control surfaces to move downwards to counteract this
weight and in so doing so increases the camber of the wing generating more
lift at slower speeds. Another feature is the ability to move fuel across
the aircraft between tanks 1 and 4. This allows the aircraft roll trim to
be set without having slightly different deflection on the elevons, which
again adds drag and reduces performance.

The full transfers on Concorde are carried out by the flight engineer from
his fuel control panel. On Concorde this is one of the most important and
time consuming jobs for the engineer. The panel allows the engineer to set
up the transfers to be carried out automatically and stop when the
relevant quantities of fuel have been moved to the correct tanks."


--

Roy Coates.
Dept of Engineering.
Liverpool University.
E-Mail: r.coates at liv.ac.uk
Tel: 0151 794 4862
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Lord, If I must have an instrument failure, please let it be the Hobbs meter.
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