F-35 internal fuel, range

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lbk000

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Unread post02 Jan 2020, 20:33

Su-27 operate downfueled because they simply can't fight on a large fuel load, while the F-35 doesn't give a damn.
The difference is much more operationally significant than the numbers look.
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mixelflick

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Unread post03 Jan 2020, 15:38

knowan wrote:
mixelflick wrote:In the F-35, we finally have a fighter that can rival the Flanker insofar as range.


The F-35 likely has significantly better range than the Flanker; note the range claims for the Flanker are exaggerated a fair bit.

Eg, Su-27 has 9.4 tons of internal fuel with twin engines, a large draggy airframe and external payload. F-35 has only 11% less fuel with a single engine, smaller airframe and internal payload.


I figured some of the Flanker's stats were exaggerated, but not range. It carries a LOT of gas (25,400lbs in the SU-35), and its engines have a stingy SFC. Nevertheless, external drag on a draggy airframe will bring that down, especially if flying at lower altitudes.

One thing I found interesting in the Flanker's development that originally, it carried only about 13,000lbs of fuel, like the F-15. However, later in its development the powers that be changed the requirement, and wanted a lot more range. This book on the Flanker BTW where I read it is probably the best/most comprehensive I've ever purchased - 720 pages! Excellent tome for those interested in a all things Flanker - https://www.amazon.com/gp/product/19108 ... UTF8&psc=1

Everything from the T-10 on up to Chinese Flankers and the SU-35.
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Unread post04 Jan 2020, 17:16

mixelflick wrote:
knowan wrote:
mixelflick wrote:In the F-35, we finally have a fighter that can rival the Flanker insofar as range.


The F-35 likely has significantly better range than the Flanker; note the range claims for the Flanker are exaggerated a fair bit.

Eg, Su-27 has 9.4 tons of internal fuel with twin engines, a large draggy airframe and external payload. F-35 has only 11% less fuel with a single engine, smaller airframe and internal payload.


I figured some of the Flanker's stats were exaggerated, but not range. It carries a LOT of gas (25,400lbs in the SU-35), and its engines have a stingy SFC. Nevertheless, external drag on a draggy airframe will bring that down, especially if flying at lower altitudes.

One thing I found interesting in the Flanker's development that originally, it carried only about 13,000lbs of fuel, like the F-15. However, later in its development the powers that be changed the requirement, and wanted a lot more range. This book on the Flanker BTW where I read it is probably the best/most comprehensive I've ever purchased - 720 pages! Excellent tome for those interested in a all things Flanker - https://www.amazon.com/gp/product/19108 ... UTF8&psc=1

Everything from the T-10 on up to Chinese Flankers and the SU-35.


Su-35 has about 22% more fuel than the Su-27 and Su-30, so it would have a fair bit more range.

The 1500 km combat radius claims for the Su-27 and Su-30 though? Basically propaganda; a realistic figure would be more like 1000 km.
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energo

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Unread post05 Jan 2020, 02:01

lbk000 wrote:Su-27 operate downfueled because they simply can't fight on a large fuel load, while the F-35 doesn't give a damn.


Negative. The F-35 also has limits on a comparably large internal fuel load. E.g. it doesn't have a full envelope on full internal fuel. The ORD specifically mentions "Manuevring Weight" at 60 percent internal fuel.
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Unread post05 Jan 2020, 02:55

energo wrote:
lbk000 wrote:Su-27 operate downfueled because they simply can't fight on a large fuel load, while the F-35 doesn't give a damn.


Negative. The F-35 also has limits on a comparably large internal fuel load. E.g. it doesn't have a full envelope on full internal fuel. The ORD specifically mentions "Manuevring Weight" at 60 percent internal fuel.

Please inform us of this 'new' F-35 limitation with a reference thank you - otherwise you will be bombarded with quotes to the contrary. The F-35 has full envelope maneuver with full fuel and internal weapons, explicated many times here IIRC.

Such restriction MAY have been in the past but not today - for example: 26 PDF page report attached below
"...Under previous versions of software, the JSF was restricted in maneuvering based on fuel weight and, under the best of conditions, the F-35A was limited to seven gravitational force equivalents (G-forces), simply called “Gs.” This forced pilots to artificially pad or limit their turns, so as not to “over-G” the aircraft. In a defensive engagement for example, pilots looking over their shoulder at the aircraft prosecuting them would underplay their “G” loading to ensure that they did not place too much stress on the jet (“over-G”) and force an untimely end to their sortie.

Those restrictions are now completely gone, and even with a full internal weapons load-out and fuel, pilots can pull back as far as the stick will go and let the jet limit loadings to nine Gs anytime the jet is capable of generating that kind of turn. As discussed below (under “The Weapons School Standard”), that same finesse is what fighter pilots have always referred to as energy management, and it can only be learned through multiple, regular air-to-air training repetitions..." John Venable 14 May 2019 https://www.heritage.org/node/13072063/print-display
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F-35A Fighter Most Dominant & Lethal Multi-Role Weapons System BG3406 pp26.pdf
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Unread post05 Jan 2020, 09:29

spazsinbad wrote:Please inform us of this 'new' F-35 limitation with a reference thank you - otherwise you will be bombarded with quotes to the contrary. The F-35 has full envelope maneuver with full fuel and internal weapons, explicated many times here IIRC.

Such restriction MAY have been in the past but not today - for example: 26 PDF page report attached below


Spaz,

I think we had this covered many years ago. Recall the Bowman report and my talks with LM. And what would be the rationale in claiming *no* performace degredation at take off? The F-35 is designed to take off with full internals, burn some off and then fight. Surely not the other way around.

Quote from LM following my visit at the plant in 2008, specifically asking about this:
CTOL is 9g with 60% internal fuel (60% = about 5,000kg of fuel, or about 1,600kg more than a fully fueled F-16) and two internal AIM-120s. The internal weapons stations are 9g. Also 9g with external A-A missiles.

F-35 roll performance is comparable to F-16. F-35 maximum AOA capability is much greater than F-16. F-35 can reach 50 deg AOA, which is nearly twice the F-16 capability. The F-35 aircraft has instantaneous turn-rate capability better than F-16.


Note: The stores 9G reference is independent of fuel: i.e. the F-35 can pull 9Gs with a full internal weapons load, but not both. I think that is where the confusion originates.
Last edited by energo on 05 Jan 2020, 09:41, edited 1 time in total.
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spazsinbad

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Unread post05 Jan 2020, 09:38

Some perspective please. The date for your quote is 2008? My quote was recent. Can you concede that in the meantime - a decade - things have improved? That is clear from my quote. There are many other quotes about the F-35 having the full performance envelope with full fuel/internal weapons. Sure the aircraft has to taxi and take-off but these days it can be refuelled inflight to have FULL FUEL and still have a full internal weapon load. Many quotes support this F-35 factoid.
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Unread post05 Jan 2020, 09:46

spazsinbad wrote:Some perspective please. The date for your quote is 2008? My quote was recent. Can you concede that in the meantime - a decade - things have improved? That is clear from my quote. There are many others about the F-35 having the full performance envelope with full fuel / internal weapons. Sure the aircraft has to taxi and take-off but these days it can be refuelled inflight to have FULL FUEL and still have a full internal weapon load. Many quotes support this F-35 factoid.


I don't think so as LM was refering to the final designed performance. And I don't think AR was part of the design missions. At least I've never seen or heard about such, for any aircraft.
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Unread post05 Jan 2020, 10:00

You have added a NOTE: which is interesting. However you will have to explain more about what was quoted to you some eleven years ago now. I'm looking at my documents for more quotes that will probably point to the same quotes in this forum. Meanwhile I came across this AIRSHOW quote which is perhaps tangential but it interested me: [more on way] And yet you are not able to concede that 'things have changed since 2008'? Remarkable indeed.

BTW I get tired of finding quotes that are not from my memory 11 years ago. I usually only quote what I can quote:
The F-35’s High Angle of Attack Explained 12 Jul 2016 LM [this is a quote from LOCKHEED MARTIN hisself]
https://www.f35.com/in-depth/detail/the ... -explained
-
“...The F-35 was also designed to turn at nine Gs, with a full load of internally-stored fuel & weapons...”
-------------------------------------------------------
Inside the F-35 Lightning II - the invisible fighter jet 29 Oct 2015 Erica Elkhershi
http://www.telegraph.co.uk/news/2016/03 ... ghter-jet/
“...The F-35 has a 43,000 pound thrust class engine which pushes the aircraft to 1.6 times the speed of sound and 700 nautical mph. It pulls 9G - “& it does all of that full of bombs, full of fuel, full of missiles”, Mr Flynn added.

Fourth generation fighter jets, which the F-35 is replacing, need external fuel tanks to fly long distances in combat, and they carry bombs and missiles on the exterior of the aircraft. “When you do you create drag, you slow the aeroplane down. It can’t go super sonic anymore, it can’t pull at maximum G and it can’t accelerate quickly,” Mr Flynn said. “My aeroplane [F-35] does all of that full of bombs, full of missiles, full of fuel.””
--------------------------------------------------------
The F-35’s Race Against Time Nov 2012 John A. Tirpak
http://www.airforcemag.com/magazinearch ... ghter.aspx
“...Lockheed Martin Vice President Stephen O’Bryan, the company’s point man for F-35 affairs, declared that the fighter meets requirements. A former Navy F/A-18 Hornet pilot, O’Bryan said... ...Stealth also permits (and requires) internal fuel and weapons carriage. The Air Force F-35 variant, fully loaded for combat, can pull nine-G turns with a full load of fuel and missiles. This cannot be done by fighters lugging along external weapons & fuel tanks...”

"...2. Aircraft configuration and Fuel Requirements. The profile is flown in a standard configuration aircraft. Taking off with less than full fuel is authorized. Fuel load considerations include: divert requirements, cable availability, and density altitude. Typical fuel loads at engine start are: full fuel for a staged show, 14,500 pounds for a high show, and 12,000 pounds for a low show. All nose low maneuvers were designed to recover above 500’ AGL even in the event of a jet malfunction that relegates the aircraft to only 4Gs, 20° AOA, and mil power. 4Gs and 20° AOA are available even with an FCS POWER LIMIT Caution...." [Yes virginy no armaments are mentioned] 2019 USAF F-35A MANEUVERS PACKAGE https://www.faa.gov/about/initiatives/a ... ackage.pdf

USAF completes F-35A modifications required for IOC 18 Jul 2016 STEPHEN TRIMBLE
"...The USAF restricted the delivered F-35A fleet to 3g maneouvres when carrying a fuel load of fuel. Only when more than half of the fuel tank was empty could the F-35A perform manoeuvres up to 7g’s, the maximum allowable for USAF variant with Block 2B software. The Block 3F version scheduled for release next year will allow the F-35A to operate the full flight envelope with manoeuvres up to 9gs.…" https://www.flightglobal.com/news/artic ... oc-427568/
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Unread post05 Jan 2020, 13:49

Well. that's pretty clear now isn't it!?!

Remarkable really. I assume the Raptor is the only other aircraft capable of such. So we know the F-35 is a 9g capable airframe with full internal fuel and weapons, whereas it seems the Flanker needs to be at 60% internal fuel or less. I have to hand it to both aircraft really. Their design teams broke new ground in both cases...

The difference of course being the F-35 is much newer. Whatever the case, its an incredible advantage for the F-35 vs. all other 4th/4++ etc. jets...
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Unread post05 Jan 2020, 18:19

mixelflick wrote:Well. that's pretty clear now isn't it!?!

Remarkable really.


Absolutely!

Spaz's last post is definitely cristal clear on the subject: The F-35A is 9G/full envelope capable with FULL internal FUEL and FULL internal weapons load.
“Active stealth” is what the ignorant nay sayers call ECM and pretend like it’s new.
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Unread post05 Jan 2020, 20:44

energo wrote:
spazsinbad wrote:Some perspective please. The date for your quote is 2008? My quote was recent. Can you concede that in the meantime - a decade - things have improved? That is clear from my quote. There are many others about the F-35 having the full performance envelope with full fuel / internal weapons. Sure the aircraft has to taxi and take-off but these days it can be refuelled inflight to have FULL FUEL and still have a full internal weapon load. Many quotes support this F-35 factoid.


I don't think so as LM was refering to the final designed performance. And I don't think AR was part of the design missions. At least I've never seen or heard about such, for any aircraft.


It's been stated on numerous occasions, that F-35As with full fuel, and full internal payload (i.e. >5000lbs) have 9G/50° AoA/M1.6 envelope. It's not even subject to debate at this point.
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Unread post06 Jan 2020, 00:20

spazsinbad wrote:You have added a NOTE: which is interesting. However you will have to explain more about what was quoted to you some eleven years ago now. I'm looking at my documents for more quotes that will probably point to the same quotes in this forum. Meanwhile I came across this AIRSHOW quote which is perhaps tangential but it interested me: [more on way] And yet you are not able to concede that 'things have changed since 2008'? Remarkable indeed.


I don't follow you here. Why is it remarkable that I adhere to the source itself? Did requirements suddenly change after 2008? Was there a sudden huge improvement in performance that LM did not predict in 2008? Where is the logic in taking off with full fuel and go directly into a 9G battle? Where is the mission?

Your airshow quotes states that a reduced fuel load is used, so it does not conflict with LMs tatement.

The Flynn comment can be interpreted several ways, he is not specifically saying "full internal fuel". "Full of fuel" can simply refer to "Lots of fuel". I graced over the subject with Flynn at FIA14 and although I can't remember the specifics there was certainly nothing new that stood out. But I guess that is conjecture at this point.

The o'Bryan comment is more compelling, but its is still contrary to what LM clearly stated back then.

However, I found the replies to my followup questions:

BB: What is the g-limit with internal 2000-pund class weapons?
LM’s Answer: The CTOL F-35 has full (9g) capability with 2000 lb class internal weapons up to Basic Flight Design Gross Weight.


So now you can trade fuel with ordnance up to the Basic Flight Design Gross Weight. This is also in line with the Bowman report and its analysis of performance requirements in the JORD.

I will see if I can get more confirmation on this, but I'm not too optimistic.
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Unread post06 Jan 2020, 00:38

wrightwing wrote:
It's been stated on numerous occasions, that F-35As with full fuel, and full internal payload (i.e. >5000lbs) have 9G/50° AoA/M1.6 envelope. It's not even subject to debate at this point.


Clearly it's debatable, but your source is? On a general note, isn't it common for fighters to have AOA restrictions simply due to to the fact that CG is changing as weight is changing during the mission? Give me all yer best. :mrgreen:
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Unread post06 Jan 2020, 00:46

Firstly: which copy of the JORD do you refer. AFAIK it has been changed. Do you have a copy of whatever JORD?

Secondly: please specify 'Basic Flight Design Gross Weight' and why refer to BOWMAN which is now old & speculative? AND to what BOWMAN document do you refer? Some links to your assertions would be great otherwise you rely on notes & memory from 11 years ago.

Now tell me why requirements cannot be surpassed. We are told plenty of times that the performance of the F-35 is better than expected/required/whatever. In 2008 the aircraft may have been designed but then surpassed what you say.

O'Bryan is an LM spokesperson. How do you account for the LM PR quote:
The F-35’s High Angle of Attack Explained
12 Jul 2016 LM PR

"...The F-35 was also designed to turn at nine Gs, with a full load of internally-stored fuel and weapons, far outclassing any enemy jet with their externally-mounted missiles and fuel tanks. The F-35 is designed to be comparable to current 4th Generation tactical fighters, such as the F-16, F/A-18, and F-15, in terms of maneuverability, but the Lightning II’s design is optimized for stealth, allowing it to operate in contested airspace environments where they could not survive latest current and emerging threats...."

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