Re: Delta fuel / delta payload

Date:         07 Oct 98 02:49:14 
From:         "Philippe CHESNEL" <pchesnel@csi.com>
References:   1
Followups:    1
Next article
View raw article
  or MIME structure


Thomas Buro a écrit dans le message ...
>I am searching for the sensivity data of fuel burn to payload for
>aircraft. How much fuel (kg) is burned more, when one kg of payload is
>added to the aircraft. E.g. for a range of 1000 km, 5000 km and 10.000
>km. Has anyone this data for actual aircraft types.

That data is called K, the fuel transport coefficient ( translated from
french, maybe there is another english expression).
For example, when K=1.4, it means that you have to fuel 1.4 Tons (or Kg or
lbs etc.) at the gate, to get 1.0 Tons (or Kg ....) over the arrival
airport:
so, clearly, you burn 400 Kg to transport 1 Ton of fuel (or payload, cause
in that term, fuel and commercial payload is the same, some load to
transport).
I hope my explanation was clear !

Now a real example: for a B767, for a 7200Km flight, ( a 8H42 flight time),
the K is 1.357.
For an A340 (the aircraft I'm flying), I could have for you a lot of
accurate datas, but approximately, K=1.5 for a 13 hours flight, 11500 Km.
For a 1000Km range, K is about 1.050.

K is not linear to the range, but more probably parabolic, and is function
of the air distance (the ground distance corrected by the effective wind),
or the flight time.

In general, the consumption is not a linear function of the weight of an
aircraft.
But K, in fact, linearizes that function. So it MUST be used only locally,
after a complete computation of the trip fuel (with non-linear manufacturer
curves), to compute easily a SMALL variation of payload, or to get the
extra-fuel to take to have a given reserve at the arrival. That the common
use of that K in airlines operations.

Regards.