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PhillyGuy wrote:

The internal fuel figures are as followed.

F-22A - 20,650 lb
F-35A - 18,480 lb
F-35B - 14,003 lb
F-35C - 20,085 lb

The original ATF requirement was 700nm, due to supercruise and more internal fuel the F-22 should have longer legs than all the F-35 versions both with internal fuel and with external stores. Also, an A2A loaded F-22 will not weigh significantly more than some configurations of A2G loaded F-35's.

I am sorry but you are not making any sense here...

(1) I doubt your fuel figure for the F-22A is correct. In fact, I believe it is at least a ton or two short. But, in anycase, by your figures there is NO WAY an F-22A with 20,650 lbs of fuel will even come close to matching the range of an F-35A with 18,480 lbs of fuel .

(2) Supercruise does not make you more economical on fuel. It makes you LESS economical than if you go at Mach 0.95 or another aircraft which does. In anycase, for the purpose of estimating the limits of range, we are assuming that the F-22 is not supercruising and flying at its most economical speed which will be high subsonic.

(3) In order for you to believe that the F-22A will beat the F-35A on range -- by your figures -- you have to believe that an aircraft which weighs about 30% more empty, has higher drag due to its larger size and has twice as many engines of a comparable size (which also happen to be LESS efficient on fuel due to their lower bypass ratios) will burn less than 11.7% more fuel to go the same distance. I'll tell you this... its IMPOSSIBLE.

(4) In short, there is no way an F-22 is going to have longer legs than the F-35 on internal fuel. In fact, it is unlikely that it even matches the F-35A's range. I stand by my estimate that the F-22 is about ~15% shorter ranged than the F-35 on internal fuel. And, I am assuming that it carries about 25000 lbs of fuel internally not 20,650 lbs as you claimed. Unfortunately there is NO official figure on the internal fuelk load as it is stilll classified.

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dwightlooi wrote:

I am sorry but you are not making any sense here...

Well, lets try again...

dwightlooi wrote:

(1) I doubt your fuel figure for the F-22A is correct. In fact, I believe it is at least a ton or two short.

This (Technical Order 00-105E-9) is an official USAF safety DOC, the sectioned linked to below (page 12) deals with the F-22, as you can see the Raptor has 20,650 lb of internal fuel.

Link PDF

dwightlooi wrote:

(2) Supercruise does not make you more economical on fuel. It makes you LESS economical than if you go at Mach 0.95 or another aircraft which does.

Super cruise gives you more combat range, especially if you can sustain it over a long period of time (as the F-22 can).

dwightlooi wrote:

(3) In order for you to believe that the F-22A will beat the F-35A on range -- by your figures -- you have to believe that an aircraft which weighs about 30% more empty, has higher drag...

Where did you get your figures from? Currently the F-35A weighs 29,000 lb empty, the F-22 weighs about 32,000 lb. Trust me, the F-35 is no F-16 in the weight department. Shall I add a combat load? Because an F-35 with about 4K worth of bombs weighs only 6% less than an A2A configured Raptor. As for drag, look at the front profile of an F-35, then consider the fact that the Raptor cruises at 60K whereas the F-35 will cruise at much lower altitudes.

Enthusiast Joined: Jul 30, 2006 Posts: 49 Status: Offline

In response to PhillyGuy-

Weight gain occurs almost inevitably. 30000lb-class empty weight is an old figure; more likely than not, the actual weight is closer to 40000lb.

The following information is taken directly from the F-22 team website (www.f22-raptor.com).

Key Performance
Parameter Requirement Current Estimate Margin

Radar Cross Section (dB) X dB Favorable Favorable

Supercruise 1.5 Mach 1.72 Mach 15%

Acceleration (vs Time) 54 sec 53 sec 2%

Maneuverability (0.9M/30Kft) 3.7 g 3.7 g 0%

Combat Radius (NM)
Mission 1 (Sub+Super) 260+100nm 310+100nm 14%

Radar Detection Range 100% 105% 5%

Airlift Support 8 8.4 (0.4)

Mean Time Between
Maintenance (hrs) 3.0 3.0 Meets

410nm is a far cry from the original 700nm combat radius requirement but is consistent with the reported weight gain and fuel load reduction.

What is interesting is that compared to the YF-22 the F-22 has a slimmer fuselage, but the F-22 weighs more. Perhaps some structural strengthening partly accounts for this.

Quote:

This (Technical Order 00-105E-9) is an official USAF safety DOC, the sectioned linked to below (page 12) deals with the F-22, as you can see the Raptor has 20,650 lb of internal fuel.

Well, thanks for the document. But, this document in fact proves my estimate and disproves yours! On Page 15 it states that the TOTAL FUEL load is 23,043 litres – that’s internal and external fuel. The external tanks are 2503 litres each. Hence, by substracting 2503 x 4 from 23,043 we arrive at an INTERNAL FUEL load of 13,031 litres. JP-8 is ~98% Kerosene which has a specific gravity of 0.81 kg/litre. Therefore, we arrive at an INTERNAL FUEL WEIGHT of 10,555 kg (23,270 lbs). As I have said before, I think you are a ton or two short and – as it turns out – you are 1.19 tons short.

Quote:

Super cruise gives you more combat range, especially if you can sustain it over a long period of time (as the F-22 can).

Supercruise gives you much better supersonic persistence and efficiency. In otherwords, if you are to fly at Mach 1.7, doing it by supercruising is a lot more efficient. But we are not talking about supersonic persistence here. We are talking about the limits of combat radius and range. And, the best range for both fighters WILL be achieved at high subsonic speeds. A Raptor flying without ever supercruising will go further than one which did at some point during the flight.

Quote:

Where did you get your figures from? Currently the F-35A weighs 29,000 lb empty, the F-22 weighs about 32,000 lb. Trust me, the F-35 is no F-16 in the weight department. Shall I add a combat load? Because an F-35 with about 4K worth of bombs weighs only 6% less than an A2A configured Raptor. As for drag, look at the front profile of an F-35, then consider the fact that the Raptor cruises at 60K whereas the F-35 will cruise at much lower altitudes.

The Raptor is currently estimated at 15,500kg (actual numbers classified) whereas the Lightning II AA-1 is 13,182kg. Between, 2004 and present they redesigned much of the aircraft to hack off weight and all the AF-1 is expected to be tangibly lighter. The current statistics pdf (updated 07/06/06) http://www.lockheedmartin.com/data/assets/12792.zip on Lock-Marts’s website gives a weight estimate as ~12,020 kg.

There is no reason to believe that the F-35 is restricted to low altitudes. Just as a rough estimate it’ll probably be most efficient between 40,000 and 50,000 ft – this is consistent with a 0.6:1 bypass engine and it’s not extreme by any measure as the 747-400 can cruise at 45,000 ft for instance even with its 4~5.5:1 bypass engines.

In anycase, my assertion is that with an approximately 29% higher weight (15.5 vs 12.5 tons) and 29% increase in fuel (10.5 vs 8.15 tons) -- plus the larger and draggier airframe, higher speed optimized airfoil (I think the F-22A uses some variation of the NACA 6 family) and twice as many less efficient engines – you are not going to get a longer ranged aircraft. In fact, you are going to get a shorter ranged one. And, I am actually giving the Raptor significantly more fuel and the F-35 slightly less than you did with my estimates; by your numbers it looks even worse.How much shorter? My estimate is ~15% shorter, but you are free to disagree. If you take the best assumptions for the F-22 and the worst assumption for the F-35 then they are at best equal in range, but that likelihood of that is pretty low and they will really have to screw up on the Lightning II which doesn’t appear to be the case as the current reports indicate that the F-35A is exceeding the range requirements outside the tripwire band.

Enthusiast Joined: Sep 27, 2006 Posts: 67 Status: Offline

There's something wrong with that PDF....

It says the total fuel load is 23,043 liters, or 5,450 US(or at least that's what it says) gallons...

but 23,043 / 5,450 = 4.228

and 4.228 liters IS NOT 1 US gallon. A US gallon is 3.785 liters. Shocked

So it depends on which one is right... If it is 23,043 liters of fuel, that comes out to roughly 6,088 US gallons, not 5,450.

It's not imperial gallons either because they are 4.55 liters.

Neotopia wrote:

There's something wrong with that PDF....

It says the total fuel load is 23,043 liters, or 5,450 US(or at least that's what it says) gallons...

but 23,043 / 5,450 = 4.228

and 4.228 liters IS NOT 1 US gallon. A US gallon is 3.785 liters. Shocked

So it depends on which one is right... If it is 23,043 liters of fuel, that comes out to roughly 6,088 US gallons, not 5,450.

It's not imperial gallons either because they are 4.55 liters.

This is why the metric system is a far superior system, avoids confusion and every unit is a factor of 10 of another unit. Just look at Hubble, a lot of money was spent correcting that confusion with unit measurements.

Well, some of us have not given up on his majesty's English Imperial Units! :p

I stuck with liters because it was easier to do the math. 1 liter is 1.0 kg of water or 0.81 kg of Kerosene.

Enthusiast Joined: Dec 07, 2006 Posts: 28 Status: Offline

[quote="PhillyGuy"]

dwightlooi wrote:

Where did you get your figures from? Currently the F-35A weighs 29,000 lb empty, the F-22 weighs about 32,000 lb. Trust me, the F-35 is no F-16 in the weight department. Shall I add a combat load? Because an F-35 with about 4K worth of bombs weighs only 6% less than an A2A configured Raptor. As for drag, look at the front profile of an F-35, then consider the fact that the Raptor cruises at 60K whereas the F-35 will cruise at much lower altitudes.

Yep, the F-35 is quite the turkey in the a2a department. Don't try and argue aerydynamics here - no one wants to hear about simple obersaervations of frontal profiles and wing shapes. You're talking to the "insiders" here who some of which have a vested interest in calling everyone a "troll" who points out the huge flaws in the F-35 program/design. No one also wants to hear about t/w ratios, wing loadings, ect ect. Never mind that with 18K pounds of internal fuel, that the F-35 is going to be working itself into a sweat to keep pace with other planes like the F-16, F-15, F-22, Eurpofighter, ect. The F-35 will be expending much of its 18k pounds of JP just for the thrust enough to cruise along at a respectable high subsonic. Also no one wants to hear that we're spending 275 billion dollars for a plane which carries *2* aams and *2* bombs - subsonically - being dragged along by a force of KC tankers. A plane designed for all missions, all branches, all nations, it is wound up to be a turkey from the day the egg is fertilized. Cheers!

P.S. Don't ya know that with todays computers that therefore the F-35 is more aerodynamic than anything flying today - never mind frontal cross sections and humps sticking out of every part of its airframe.

Cheers again!

About the empty weight and internal fuel capacity of F-35:

http://www.jsf.mil/downloads/documents/ ... t%2006.pdf

An official document of USAF published in 26 September, 2006:

Page 8:

F-35A: Weight empty 29,036 Ib (13,170 kg) and Internal fuel capacity 18,480 Ib (8,382 kg).

F-35B: Weight empty 32,161 Ib (14,588 kg) and Internal fuel capacity 14,003 Ib (6,352 kg).

F-35C: Weight empty 32,072 Ib (14,548 kg) and Internal fuel capacity 20,085 Ib (9,111 kg).

http://www.0x4d.net/files/AF1/R11%20Segment%2012.pdf

Page 15:

Personally, I think the number of gallons should be the correct ones, since the external tank that F-22 uses today should be around 2,270 liter class, which is roughly equal to the 592 gallon fuel.

Therefore, I think the internal fuel of F-22A today is around 5,450 - 592*4 = 3,082 gallons = 11,667 liters = 9,042 ~ 9,800 kg JP-8 fuel (Density of JP-8: 0.775~ 0.840).

There is something I do not understand, but I hope that someone will be kind enough to explain to me why I do not understand Wink

: some people here seem to be concerned by the fact that the F-35 can carry a huge (and heavy) load of fuel internally. But I do not see why it is a problem. I mean that the F-35 does not have to carry all that much fuel for every mission, it is only the maximum fuel load it can carry. In the same manner, the Su-27 may carry a lot of fuel internally, so much that the Russian air force has not even cared about trying to get jettisonable fuel tanks to extend range. However, on most missions, the Su-27 does not carry a full load of fuel, it only carries what is deemed to be necessary for the mission.
If the plane is not too much draggy overall (because of the volume needed to get so much fuel internally), it may be seen as an advantage for range, as having all the fuel carried internally will bring less drag that carrying big tanks under the wings.
The only problem remaining is: when it carries, say, half-full fuel load, is the F-35 as good as any other fighter?

Am I missing something?

In order to establish Ranges for the F-35 and f-22 has anyone bothered looking at each aircraft engines specific comsumption at high altitude? and each of these planes cervice ceiling?

The Raptor engines have 40% of bypass while the one on the F-35 has 12%. Anyone?

Pilotasso wrote:

In order to establish Ranges for the F-35 and f-22 has anyone bothered looking at each aircraft engines specific comsumption at high altitude? and each of these planes cervice ceiling?

The Raptor engines have 40% of bypass while the one on the F-35 has 12%. Anyone?

Actually, the F-22A's F119 engine has a bypass ratio of 0.2:1, whereas the F35's F135 engine is 0.57:1.

Both engines have essentially the same core (high pressure spool). However, the F135 engine has a larger fan stage and a higher power yield low pressure turbine (single stage). The F135 also incorporates a larger number of bladed disks, newer materials and has a higher turbine inlet pressure. As a result of the larger fan and bypass the F135 is a larger diameter engine (~51" diameter vs ~47").

By conventional wisdom, a larger bypass ratio yields better efficiency all else begin constant. However, this increase is not linearly proportional to the bypass ratio. For instance, the F100 engine (0.36:1 bypass) has a specific fuel consumption of 0.76 whereas a typical commercial airliner turbofan (~5.0:1 bypass) is in around 0.35. When you go to the latest "super-duper-fans" like the 9.5:1 bypass GEnx or 11.0:1 R-R Trent 1000 you are looking at about 0.29~0.30 hourly specfic fuel consumption. No numbers have been released for the F119 or F135. But, I remember reading that the target for the F135 is 0.70.

Lower bypass engines have the advantage of higher power density. If you have are going to have a 40" engine, one with zero bypass (a turbojet) will give you more dry power than one with some bypass simply because for that give diameter you can fit a larger core if you have no bypass ducts. However, today pure turbojets have fallen out of favor because it is actually necessary to have a little bit of bypass air for exterior cooling purposes. The F119 is one such engine. With a 0.2:1 bypasss it is essentially a turbojet. A very low bypass engine also tends to perform better at extreme altitudes because more of the available ingested air is used to support combustion. However, it is not demonstrated that this is a significant advantage until you are talking about U2 and ASR-71 altitudes. And most of the time you have control problems and wing stall problems on the way there before your engine gets air starved.

A higher bypass engine has the benefit of better cruise efficiency. It also has the advantage of being able to create more A/B thrust simply because there is more unburnt airmass available to support afterburning. You also tend to have slightly lower exhaust temperatures even though at fighter class bypass ratios it probably doesn't amount to much. You pay for it however in terms of lower power density with respect to weight and with respect to diameter. You also get worse performance at extreme altitudes. However, this is probably not a big issue for most jet fighters because higher bypass engines in the 0.6 or 0.4 class will probably not run into their bypass caused limitations at the altitudes which the fighter's aerodynamics can support. We know this because we know that MUCH HIGHER bypass engines work at very high altitudes just fine. For instance, the Boeing 747 is certified to fly at 45,000 ft and it does it with engines in the 5.0:1 bypass bracket. The Cessna Citation X is certified to fly at 51,000 ft and it has 4.4:1 bypass RR AE3007 engines. And these are not the absolutel ceilings of these aircrafts, this is the ceiling they are certified to fly up to in passenger service. If somebody wants to break the rules and set some record, I am sure they can go higher.

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