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By: - 2nd January 2009 at 01:15 Permalink - Edited 1st January 1970 at 01:00
You can never have too much fuel (unless your airplane is on fire).
Fuel gives you:
- range, including the ability to use a non-direct axis of approach for attacking your target
- loiter time
- speed (can operate afterburner longer)
- reduces requirement for tanker support
By: - 2nd January 2009 at 14:43 Permalink - Edited 1st January 1970 at 01:00
Super Hornet seems high given that it's usually hauling around a centerline tank.
By: - 2nd January 2009 at 15:27 Permalink - Edited 1st January 1970 at 01:00
Super Hornet seems high given that it's usually hauling around a centerline tank.
Thats because FF isn't proportional to range.
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VOLCANO DIGIT VAPORIZER
By: - 2nd January 2009 at 15:36 Permalink - Edited 1st January 1970 at 01:00
Thats because FF isn't proportional to range.
I understand that. I guess what it says is that the Super Hornet is a "draggy" aircraft.
By: - 2nd January 2009 at 16:09 Permalink - Edited 1st January 1970 at 01:00
Yes FF is not proportional with range but I think it shows an advantage. Can we overgeneralize that the aircrafts with high FF rates needs less external fuel tanks?
And what about fuel consumption of the aircrafts?
By: - 2nd January 2009 at 16:15 Permalink - Edited 1st January 1970 at 01:00
No you cannot really generalise as so many factors are relavent to range. Lift to Drag ratio being one of the most important factors - as it essentially determines the altitude the aircraft operates and how efficiently it operates at that altitude.
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Kitchen Measures
By: - 3rd January 2009 at 03:18 Permalink - Edited 1st January 1970 at 01:00
F-35A: 38.9%（Empty weight: 13,170 kg，Internal fuel: 8,382 kg）F-35C: 38.5%（Empty weight: 14,548 kg，Internal fuel: 9,111 kg）
F-35B: 30.3%（Empty weight: 14,588 kg，Internal fuel: 6,352 kg）
Why do people continue to use PRE-WEIGHT REDUCTION numbers for the F-35?
PRODUCTION aircraft benefit from a 2+year weight reduction program...
F-35A
40.7%
Empty weight: 26,664 lbs (12,095kg)
Internal fuel: 18,307 lbs (8,304kg)
F-35B
31.1%
Empty weight: 29,695 lbs (13,470kg)
Internal fuel: 13,400 lbs (6,078kg)
F-35C
39.0%
Empty weight: 29,996 lbs (13,606kg)
Internal fuel: 19,145 lbs (8,684kg)
By: - 11th September 2009 at 20:10 Permalink - Edited 1st January 1970 at 01:00
Why do you keep using obsolete weights?
http://www.lockheedmartin.com/products/f35/f-35specifications/index.htm
Lockheed published "Weight Empty" as of August 2009
F-35C 34800 lbs
B 32000
A 29300
Are you still bullish on the F-35 now?
By: - 11th September 2009 at 21:12 Permalink - Edited 1st January 1970 at 01:00
How many of these aircraft have complete internal weapons carriage?
I would think this would change the "effective" internal fuel capacity due to the loss of drag.
By: - 11th September 2009 at 23:21 Permalink - Edited 1st January 1970 at 01:00
http://www.lockheedmartin.com/products/f35/f-35specifications/index.htmLockheed published "Weight Empty" as of August 2009
F-35C 34800 lbs
B 32000
A 29300Are you still bullish on the F-35 now?
I am not the one using obsolete weights. The numbers I posted are the official weights (as of Oct 2007 program review).
To believe that the numbers you posted are the correct empty weights the F-35 would have had to have GAINED weight OVER pre-weight reduction numbers (and that the production F-35A is HEAVIER than the non weight optimized AA-1)!
pre-weight reduction numbers (as of Sep 2006 program review)
F-35A: 29,036 lbs
F-35B: 32,161 lbs
F-35C: 32,072 lbs
I really do not know what the numbers you posted are (other than that they ABSOLUTELY ARE NOT CORRECT EMPTY WEIGHTS). The one for the F-35C at least is close to 'empty equipped' (as in armed weight). F-35C empty weight (29,996 lbs) + two '2,000 lb' JDAM (4072 lbs) + two AMRAAM (670 lbs) = 34,738 lbs.
By: - 12th September 2009 at 00:07 Permalink - Edited 1st January 1970 at 01:00
I think the fuel fraction (definition see here) says significantly more than the absolute values. Can somebody post these?
Hmmm...
I stumbled over this when i was debating the two UB Flanker bought nd shipped to the US:
"But for comparison sake... (to the best of my resources)
AL-31F (as installed in early SU-27s)
MAX Thrust: 27,557 lbs
MIL Thrust: 17,305 lbs
Length: 194.7"
Max Diameter: 48.82"
Inlet Diameter: 35.8"
Weight: 3,373 lbs
MAX SFC: 1.96 lb/h/lb st
MIL SFC: 0.666 lb/h/lb st
F100-PW-229 (As available today @ $5M each!)
MAX Thrust: 29,100 lbs
MIL Thrust: 17,800 lbs
Length: 191.2"
Max Diameter: 46.5"
Inlet Diameter: 34.8"
Weight: 3,795 lbs
MAX SFC: 2.060 lb/h/lb st
MIL SFC: 0.762 lb/h/lb st
So while a pair of shiny new F100-PW-229s would physically fit into the engine bays of the SU-27 (almost exactly) and the -229 makes about the same power; the differences in gearbox placement would make the procedure cost prohibitive."
The AL-31F(early version) consume less fuel over the F100-PW-229s on full mill power.
Can anyone confirm this data?
If true, i guess the 117-S engine would gubble a lot more fuel vs the AL-31F(12.500kgf).
Sources: J@ne's stuff..
Thanks
By: - 12th September 2009 at 08:56 Permalink - Edited 1st January 1970 at 01:00
Many issues come to my mind when looking at the naked OEW and internal fuel numbers.
- The OEW figures are normally wrong, the Suchois are heavier, the "official" numbers often exclude some items. Cheating on OEW is due practice everywhere around the world.
- As was stated before, fuel carried is one thing. Fuel consumed is another. The fuel consumption depends on:
- basic airframe drag (which is largely the same for all 4th generation aircraft)
- normal mission layout, a fighter carries significantly less load than a bomber
- requirements on operational safety (aircraft carrier)
- As I said repeatedly, more internal fuel is not always better. An air combat fighter is designed to have lowest when entering combat. The F-16 was designed with requiring 9g performance at 50% internal fuel. A closer look at the numbers unveils that such low internal fuel would basically cut the burner time to one minute, assuming the pilot wants to eat dinner at his base instead of having a C-ration in the woods.
- internal weapons cut the drag, while that doesn't change the overall picture too much when looking at cruise ranges. The drag of externally carried missiles below ~M.85 is acceptable. Everythinh counts in large amounts though: look at a Suchoi 27 with full missile armament
http://commons.wikimedia.org/wiki/File:Su-27_armament.jpg ... sue is draggy - a clean aircraft at 30k ft and ~M.8 (optimum range Mach) will see the engine operating close to idle, especially aircraft with a clear supersonic ability. The SFC (specific fuel consumption) jumps up significantly. Carrying external tanks causes more drag, but the effect of operating in a more efficient engine regime compensates that to some extent. Generally the penalty in subsonic (up to M~.85) drag for drop tanks is quite low, about 10% of zero lift drag for a 300gal drop tank.
- the fuel burn also depends on type of engine (though quite similar for all considered aircraft) and altitude/speed profile. Though an F-18 might fly for 2 hours on internal fuel and cover over 1500km of distance, going into burner for a minute easily eats up 15 minutes normal flying time.
- when you wanna see the specifications of a true fighter, look up YF-16. Nothing ever came close, the Eurofighter maybe.
By: - 12th September 2009 at 09:10 Permalink - Edited 1st January 1970 at 01:00
How many of these aircraft have complete internal weapons carriage?I would think this would change the "effective" internal fuel capacity due to the loss of drag.
When making trade-offs in aircraft design and looking at it from the flight performance perspective (disregarding stealth), internal carrying is very ****ty.
"Huh? But it has lower drag ..."
Sure, but it increases the empty weight significantly and the volume of the aircraft, causing issues in transonic speed. Generally, when air2air combat is concerned, putting missiles externally and combat fuel internally is best choice. The fuel needed to cruise into combat and probably to accelerate should be put into drop tanks. This configuration is the agreed standard all over the world.
Very efficient missile arrangement can be found on the Eurofighter, the F-14 (when carrying AIM-7), the F-4 and some other. Wing-tip missiles are very efficient, basically cutting drag.
Although the F-18 seems not to be very famous on these forums (which doesn't mean much, as these fora have no minimum qualification standards), its layout is very efficient.
By: - 12th September 2009 at 09:16 Permalink - Edited 1st January 1970 at 01:00
The AL-31F(early version) consume less fuel over the F100-PW-229s on full mill power.
Can anyone confirm this data?
Confirmed as rubbish.
@Everyone: disregard such numbers!
Jane's charges lots of money and that somehow makes their numbers bullet-proof. Actually, citing single point SFC numbers is complete bullock, so many factors come into play.
Flight performance isn't so terribly complicated, at least when compared to other aeronautical engineering disciplines like structural analysis or full aerodynamics, but still there are always several factors in one equation. Just picking one and neglecting the other is as helpful as a dead horse.
By: - 12th September 2009 at 09:18 Permalink - Edited 1st January 1970 at 01:00
No you cannot really generalise as so many factors are relavent to range. Lift to Drag ratio being one of the most important factors - as it essentially determines the altitude the aircraft operates and how efficiently it operates at that altitude.
When LoD of 9-11 you make a good guess for 4th generation aircraft when not carrying heavy a2g loads. I once posted numbers about that issue. Getting numbers and putting them into a reasonably useful model is work, I think I spent quite some time on it last year.
By: - 12th September 2009 at 09:59 Permalink - Edited 1st January 1970 at 01:00
Confirmed as rubbish.
@Everyone: disregard such numbers!Jane's charges lots of money and that somehow makes their numbers bullet-proof. Actually, citing single point SFC numbers is complete bullock, so many factors come into play.
Flight performance isn't so terribly complicated, at least when compared to other aeronautical engineering disciplines like structural analysis or full aerodynamics, but still there are always several factors in one equation. Just picking one and neglecting the other is as helpful as a dead horse.
I think this was related to engine fuel consumtion only, test bench data perhaps!
Not the whole fuel fraction regime with drag, etc etc..
Sooo.. Schorsch, why don't you put out some correct numbers on those engine in my example?
So we all can see how wrong Jane's specs really are.
Strange way to downplay Jane's..
Everyone understand that Jane's don't have all the specs from the manufactors, but still its some of the best stuff i've come across compairing to other sources..
If you have more usefull data, pls post it.
Thanks
By: - 12th September 2009 at 10:04 Permalink - Edited 1st January 1970 at 01:00
I think the fuel fraction (definition see here) says significantly more than the absolute values. Can somebody post these?
That depends.
Fuel fraction numbers may vary by a wide margin and still be true. FF of 0.3 is generally considered optimal for fighter performance/size aircraft. However, this generalization has been made by NATO and its engine's fuel consumption standards, which at that time mostly converted to high bypass turbofan engines. So an FF of 0.3 proved to be the optimum for such an aircraft.
If you go higher with FF, you get a tanker (higher drag, proportionally less range) and if you go lower you get Mig-21.
Russian fighters, on the other hand, with their leaky engines and FF of 0.3, often came out short legged. Mig-21 was notorious for being unable to use the last 1/5 of its fuel at all, since its CG would move so far that the pilot couldn't fly it anymore. That reduced combat radius of early Fishbeds to 200km, or so. Obviously, such Mig wasn't competitive against NATO fighters in terms of sheer endurance. Hence Tu-128 super long range interceptor, with high FF.
Modern Russian fighters follow that logic. While Mig-29 is a short range interceptor (by PVO specification), the Su-27 is a long range one and has a FF of 0.35, similar to Tu-128. However, many NATO aircraft with smaller FF are able to match its range, due its lower bypass engines (leaky turbojet).
I think, knowing FF gives you a general role and operating profiles of an aircraft (tactical, strategic, low/subsonic, high/supersonic, etc...), but only the altitude/speed/consumption table can provide you with accurate reading and performance assessment.
By: - 12th September 2009 at 10:17 Permalink - Edited 1st January 1970 at 01:00
Yeah Schorsch, would you care to give us the correct numbers then? You can't just come here and say "rubbish". The numbers Jane's is giving for the AL-31F is reported by other sources as well. So do you mean they got the wrong numbers for the P&W or what are you talking about?
By: - 12th September 2009 at 10:25 Permalink - Edited 1st January 1970 at 01:00
Adittional data:
Maximum dry:
AL-31F 17,305 lb st
Later versions 17,857 lb st
SFC MAX thrust 1.96 lb/h/lb st
Maximum dry:
AL-31F 0.666 lb/h/lb st
AL-31FP 0.67 lb/h/lb st
AL-31FN 0.705 lb/h/lb st
AL-31F:
Mass Flow 247lbs/s, BPR 0.571, OPR 23.5 MAX SFC 1.96lb/h/lb st
F100-PW-229:
Mass Flow 254lbs/s, BPR 0.36, OPR 32.4, MAX SFC1.94 lb/h/lb st
I do imagine the better MIL SFC has to do with the engines' respective BPR, one also has to consider the OPR. The PW-229 has LOTS more compression.
And the fact that the F100-PW-229 has smaller fan blade diameter and higher flow mass due to more compression vs the AL-31F, would suggest that those fuel consumption data aren't to far off.
Thanks
Posts: 992
By: toan - 2nd January 2009 at 00:48
Su-35BM: 39.6% ~ 41.1%（Empty weight: 16,500 ~ 17,500 kg，Internal fuel: 11,500 kg）
MIG-31: 39.4%（Empty weight: 21,825 kg，Internal fuel: 14,200 kg）
F-35A: 38.9%（Empty weight: 13,170 kg，Internal fuel: 8,382 kg）
F-35C: 38.5%（Empty weight: 14,548 kg，Internal fuel: 9,111 kg）
Su-30MK: 34.9%（Empty weight: 17,700 kg，Internal fuel: 9,500 kg）
Rafale: 31.4% ~ 33.6%（Empty weight: 9,500 ~ 10,220 kg，Internal fuel: 4,680 ~ 4,800 kg）
F-18E: 32.2%（Empty weight: 14,288 kg，Internal fuel: 6,780 kg）
EF-2K: 30.9%（Empty weight: 11,150 kg，Internal fuel: 4,996 kg）
JAS-39NG: 30.6%（Empty weight: 7,100 kg，Internal fuel: 3,130 kg）
F-35B: 30.3%（Empty weight: 14,588 kg，Internal fuel: 6,352 kg）
F-22A: 29.3%（Empty weight: 19,660 kg，Internal fuel: 8,165 kg）
MIG-35: 28.6%（Empty weight: 12,000 kg，Internal fuel: 4,800 kg）
Tejas: 27.0%（Empty weight: 6,500 kg，Internal fuel: 2,400 kg）
JF-17: 26.3%（Empty weight: 6,450 kg，Internal fuel: 2,300 kg）
JAS-39C: 25.0%（Empty weight: 6,800 kg，Internal fuel: 2,268 kg）
F-CK-1A: 24.5%（Empty weight: 6,492 kg，Internal fuel: 2,111 kg)