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By: - 19th January 2016 at 17:21 Permalink - Edited 1st January 1970 at 01:00
it depends on how much drag each one has (airframe aerodynamics, combined with the loadout and so on)
in the end, while the specific consumption is in the same ballpark, you don't know what power settings (so, what consumption) each one will have to use for best range
By: - 19th January 2016 at 17:46 Permalink - Edited 1st January 1970 at 01:00
Rafale's M88-4e engine fuel consumption isdry : 0.78 lbm/lbf·h
wet : 1.72 lbm/lbf·hTyphoon's EJ200 engine fuel consumption is
dry : 0.74–0.81 lb/lbf hr
wet : 1.66–1.73 lb/lbf hrAlso Rafale can carry 4.7 t internal fuel + 6 t external fuel (3 2000L tanks) = 10.7t fuel
Typhoon can carry 5 t internal fuel + 3 t external fuel (3 1000L tanks) = 8 t fuelNow both have roughly the same fuel consumption .. But Rafale has better fuel capacity
Why their combat radius is nearly equal ?
Fuel weight isn't 1 kg per litre! The actual fuel weight depends on the type of fuel used and its density. As such the weight of 1 litre fuel can vary. Commonly the density is about 0.8 kg / 1 l of fuel. You can do the math yourself. As far as the combat radius is concerned there are a lot of factors that need to be taken into account. The public data suggests a 750 nm combat radius for Typhoon and 1000 nm combat radius for Rafale in a hi-lo-hi attack mission profile. That doesn't tell you much about the loadout however. It's sufficient to say that Rafales vastly superior external fuel capacity translates into a better range and endurance for many mission profiles.
By: - 19th January 2016 at 18:20 Permalink - Edited 1st January 1970 at 01:00
Fuel weight isn't 1 kg per litre! The actual fuel weight depends on the type of fuel used and its density. As such the weight of 1 litre fuel can vary. Commonly the density is about 0.8 kg / 1 l of fuel. You can do the math yourself. As far as the combat radius is concerned there are a lot of factors that need to be taken into account. The public data suggests a 750 nm combat radius for Typhoon and 1000 nm combat radius for Rafale in a hi-lo-hi attack mission profile. That doesn't tell you much about the loadout however. It's sufficient to say that Rafales vastly superior external fuel capacity translates into a better range and endurance for many mission profiles.
About the fuel weight I knew that but for a simple comparison I assumed so (it is actually slightly more than 0.8 .. and if we added the empty fuel tank weight it will nearly compensate the difference)
about the combat radius thanks for that .. but could u give me sources for those numbers :) (specially rafale combat radius in hi-lo-hi)
By: - 19th January 2016 at 19:18 Permalink - Edited 1st January 1970 at 01:00
TSFC isnot a constant value , it varied with altitude and speed
For example
By: - 19th January 2016 at 19:32 Permalink - Edited 1st January 1970 at 01:00
TSFC isnot a constant value , it varied with altitude and speed
For example
Different in fuel consumption due to altitude is enormous
By: - 19th January 2016 at 21:44 Permalink - Edited 1st January 1970 at 01:00
As already noted that specific fuel consumption does not tell us very much
It tells us how much fuel is burnt to generate an amount of thrust (force) at a given altitude, air temperature and air density
But it does not tell us how much thrust (force) is required to overcome the drag of the airframe to accelerate
Or how much is required to match air resistance and maintain a crushing speed
An example a typical car travelling at 50 mph burns about half the fuel it is burning in order to overcome air resistance
Now drill down into the unknown variables
How much air resistance does an actual car have?
How much rolling resistance?
With our warplanes we have even more variables
What altitude is the 'lo(w)' part of the mission. What air resistance there? How efficient is the gas turbine at that altitude?
Same for the 'hi(gh) part?
How much air resistance do those stores have?
The simplest possible analysis comes if the OP's assertions are all correct (and they might be, I just don't have the facts to judge) AND (this is my assumption) both fly at same speed at same altitude in same conditions for whole of the mission
Raf has more fuel, very similar fuel consumption but flies about the same range. Why?
Coz more of its fuel is in big draggy* drop tanks, so it has more air resistance at each point in the mission, so it has to generate more thrust for each section of the mission in order to maintain the same speed
If not all of the variables are the same (and I'd GUESS but its only a guess that they are not) then there could be lots of different reasons
Al
*Which is not me having a pop at the designers of French drop tanks, I'm sure that those tanks have the lowest possible co-efficient of drag. Its just that a big tank provides a big surface area and a large amount of air resistance
By: - 20th January 2016 at 04:25 Permalink - Edited 1st January 1970 at 01:00
Roughly the same range? Could be true, but better start your demo with that.
By: - 20th January 2016 at 08:57 Permalink - Edited 1st January 1970 at 01:00
Its just that a big tank provides a big surface area and a large amount of air resistance
Then what about two big engines and a big fuselage ?
More to the point, what about empty weight and Breguet range equation ?
Scorpion82 got it right, as usual. Cheers.
By: - 26th January 2016 at 20:55 Permalink - Edited 1st January 1970 at 01:00
Then what about two big engines and a big fuselage ?
More to the point, what about empty weight and Breguet range equation ?
Scorpion82 got it right, as usual. Cheers.
I LOVE it when someone does not bother reading the whole of my post but just cherry picks the bit they want to argue with
LOVE it
By: - 26th January 2016 at 21:38 Permalink - Edited 1st January 1970 at 01:00
I LOVE it when someone does not bother reading the whole of my post but just cherry picks the bit they want to argue with
This bit sums it up. I just don't feel the need to cherry pick every bit of your post, and I certainly don't care whether you love it or not.
By: - 27th January 2016 at 13:16 Permalink - Edited 1st January 1970 at 01:00
About fuel density, take a look of this image (Rafale fuel trapdoor):
[ATTACH=CONFIG]243560[/ATTACH]
4750 Kg is the internal fuel
1000 Kg equal to an 1250L fuel tank
7750 Kg = internal fuel + three 1250L EFT
Typhoon:
5000 Kg internal Fuel + three 1000L EFT (3*800 Kg) = 7400 Kg
So even with supersonic EFT the Rafale carry more fuel than a Typhoon.
Question: Why FAF still use 2000L EFT if they are "too draggy"? My guess is that the range is better with 2000L EFT than with 1250L EFT.
By: - 27th January 2016 at 17:43 Permalink - Edited 1st January 1970 at 01:00
About fuel density, take a look of this image (Rafale fuel trapdoor):[ATTACH=CONFIG]243560[/ATTACH]
4750 Kg is the internal fuel
1000 Kg equal to an 1250L fuel tank
7750 Kg = internal fuel + three 1250L EFTTyphoon:
5000 Kg internal Fuel + three 1000L EFT (3*800 Kg) = 7400 Kg
So even with supersonic EFT the Rafale carry more fuel than a Typhoon.Question: Why FAF still use 2000L EFT if they are "too draggy"? My guess is that the range is better with 2000L EFT than with 1250L EFT.
What type of tank is being used and how many are carried depends on the particular requirements for the mission. I.e. how distant is the target or target area, what are the transit altitudes, are tanker assets available, is there any loitering required and how long, where is the nearest alternate at various stages of the mission etc. For QRA and most AA missions Rafale most likely carry 1250 l drop tanks, for AG they typically carry 2000 l tanks. That doesn't exclude the possibility to use them vice versa, but it's also a question of maintenance work load. You don't remove the tanks after each and every flight.
Posts: 17
By: house-13 - 19th January 2016 at 17:08
Rafale's M88-4e engine fuel consumption is
dry : 0.78 lbm/lbf·h
wet : 1.72 lbm/lbf·h
Typhoon's EJ200 engine fuel consumption is
dry : 0.74–0.81 lb/lbf hr
wet : 1.66–1.73 lb/lbf hr
Also Rafale can carry 4.7 t internal fuel + 6 t external fuel (3 2000L tanks) = 10.7t fuel
Typhoon can carry 5 t internal fuel + 3 t external fuel (3 1000L tanks) = 8 t fuel
Now both have roughly the same fuel consumption .. But Rafale has better fuel capacity
Why their combat radius is nearly equal ?