On 6 Mar 2004 17:09:52 -0800, (Jake McGuire) wrote:

My attempt at rough range calculation snipped

Sadly, this is not how one calculates range for aircraft. The "liters
per mile" is not constant, but rather a function of specific fuel
consumption (fuel consumption / thrust), lift/drag (dependent on
speed, altitude, and weight), speed, and weight fraction (wet weight /
empty weight).

According to aerospaceweb.org, the Eurofighter has a dry weight of
9750 kg and an internal fuel capacity of 4000 kg (weight fraction of
1.41)

The numbers have changed a lot since then, the Empty weight of the
Typhoon is 11,000kg, quite a hike isn't it.
But then again the fuel load is now at 4996kg, as confirmed by a pilot
to me personally and from a cockpit picture showing the fuel load
as 4992kg.
So the weight fraction now is as follows
Using the updated figures 15996/11000=1.45

while the F-22 has a dry weight of 34000 lb and an internal fuel
capacity of 25000 pounds (weight fraction of 1.68).
Now some of these figures seem very suspect to me...

Usual T/O weight 60klbs???
Max T/O weight 62klbs??

If you look at the empty weight of 34klbs and add 25klbs
you get 59klbs, Hmmm, add 2500lbs for 6 Amraam 120C and two Aim 9X
your at 61.5K, now add Cannon shells??? Ooops you just bust the Max
T/O weight.... what you going to take off so the pilot can get in...?
The max T/O weight looks very wrong, and I bet the Empty weight has
crept up too,( I think this because the figures quoted predate the
mutterings about weight gain)....


OK using the your figures the Raptor is 59klbs/34klbs is 1.73

But using the more likely figures you get 53klbs/34klbs=1.55


Now the second set of figures seem much more likely to me.


Range is
proportional to the logarithm of weight fraction, so assuming that
lift/drag are fairly similar and that the engines are of comparable
technology, the F-22 should be able to cruise 50% further on internal
fuel than the EF2000.

Its a bit closer than that!


Using 2x1000L drop tanks raises the EF2000's weight fraction to 1.55,
so the F-22 should still be able to cruise 17% further disregarding
its lift/drag advantage (no external tanks).

The conformal fuel tanks that are slated for tranche 3 look better
value they have a capacity of approximately 1,500 litres each could
extend the range of the aircraft by 25%, with 'surprising little
aerodynamic effect'.

Cheers


-jake

John Cook

Any spelling mistakes/grammatic errors are there purely to annoy. All
opinions are mine, not TAFE's however much they beg me for them.

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