F-35 fuel handling

[smsgtmac]

http://www.dailytech.com/Air+Force+Worries+Hot+Fuel+Could+Harm+F35+Proactively+Paints+Trucks+Shiny/article36985.htm
And the purported F-35 fuel problem keeps on spreading throughout the web.

Common "Dorkus Maxima Left Coastus" in its native habitat

Michael Hatamoto.jpg (20.52 KiB) Viewed 16684 times

Obviously a 'deep thinker' who should be taken seriously [/sarc]

From: https://plus.google.com/110843335283283802166/posts

And....
My Word! Have you seen the comment thread at Breaking Defense? They're unhappy with Colin Clark calling for sanity on this story and there appears to be a team fiction-writing project going on in the thread rewriting the story to suit their taste. They're making sh*t up you wouldn't believe!

[XanderCrews]

She is going to make some girl very happy one day

[sferrin]

She is going to make some girl very happy one day

I thought that was dude. That's one fugly chick. Or is it a dude? Definitely has a punchable face whatever it is.

[Corsair1963]

So far, however, "The jets are performing phenomenally...there's no problem."


"This is not an F-35 issue; there are no special restrictions on the F-35 related to fuel temperature. The F-35 uses the same fuel as other military aircraft. It can fly under the same temperature conditions as any other advanced military aircraft," the Pentagon's F-35 Joint Program Office told CNBC.



http://www.cnbc.com/id/102253195#.

[spazsinbad]

'zero-one' Pointed out same URL here earlier: viewtopic.php?f=22&t=26708&p=282616&hilit=Hasson#p282616

[Corsair1963]

Sorry, my mistake........don't have the time to keep up as much as I would like.

[spazsinbad]

No worries - just that it is easy for those experiencing deja vu to know that things were seen before and/or discussed elsewhere. Here is a good example how the FUD of Chinese Whispering gets around and distorted - but we knew that...

RAF's £150million stealth fighter jet could 'shut down' after overheating fears
15 Dec 2014 John Tmomey [2 mommies? so that is his problem]

"The RAF’s new £150m stealth fighter jet will “shut down” if the aircraft’s fuel becomes too hot, test pilots now fear...." [FUD = Fear Uncertainty Doubt]

...The problem emerged last week at Luke airforce base in the United States where the F-35 Lightning 11 aircraft is being tested.

The F-35, the most expensive aircraft ever produced, is designed to use its fuel as a cooling agent.

But if the fuel gets too hot the whole aircraft could shut down in mid flight causing the jet to crash, according to aviation engineers...."

Source: http://www.express.co.uk/news/uk/547086 ... ting-fears

[KamenRiderBlade]

Marine’s Construct Tactical Fuel System
https://www.youtube.com/watch?v=Qv7lWhOmFuc

Another forward thinking option that the USMC are doing.

With this kind of setup, they can have cold fuel ready to go.

[beepa]

Off topic a bit but interesting vid of F35b mid air refuel...

https://www.youtube.com/watch?v=bWcTJUDaYAE

[archeman]

Off topic a bit but interesting vid of F35b mid air refuel...

https://www.youtube.com/watch?v=bWcTJUDaYAE

That really is an interesting video.
What the heck are they doing up there (2nd half)?

From those perspectives, the 'B's neck muscles really stand out.

neck-muscle.jpg (32.17 KiB) Viewed 14199 times

ScreenHunter_06 May. 26 21.38.jpg (15.2 KiB) Viewed 14199 times

[Dragon029]

Sorry to bring up an old thread like this, but I'm looking for a particular chart / diagram plotting fuel temperature vs time in an F-35 sortie. It was only perhaps 1/6th of the page (relatively small), and it didn't have any units listed.

I'm pretty sure it was in a PDF, but I can't say for certain.

Anyone know of the chart I'm talking about and are able to link it?

[Lightndattic]

Off topic a bit but interesting vid of F35b mid air refuel...

https://www.youtube.com/watch?v=bWcTJUDaYAE

That really is an interesting video.
What the heck are they doing up there (2nd half)?

They're doing the same thing I do on my motorcycle when stuck behind slower traffic.

[Dragon029]

A post made by user Frostiken on Reddit, who has previously worked as (to my understanding) an avionics tech for the F-35, explaining the "hot fuel problem" to another user:

The F-35 uses fuel as a heatsink. The PTMS (power/thermal management system) system is fiendishly complicated and robust so I wish I had a block diagram to be a little more accurate here, but all you really need to know is this: under typical circumstances, avionics are cooled with PAO (polyalphaolefin, liquid coolant) which is pumped through heat exchangers to keep it below a certain temperature. The radar system and DAS especially are two of the hottest-running systems in the jet. Heat is dumped into fuel to keep the PAO cool. Fuel is subsequently cooled via the Fuel-Air Heat Exchanger (FAHX), which is fed with ram air. This heat exchanger and ram air duct are located above the right intake, opposite the gun.

The problem occurs when your fuel reaches thermal saturation. Now the F-35 carries tons of ****** fuel. The thing is a giant flying fuel tank. It carries more fuel than the F-22, and has half as many engines. It carries an F-15's plus an F-16's worth of internal fuel. If you asked me to describe the F-35 in one word it would be 'fuel'. So under typical flight (it's cold as **** in the air and the fuel-air heat exchanger works great) this isn't an issue.

Where problems arise is when the aircraft land after flying a sortie. Because they land with very little fuel, it means that the fuel has diminished ability to sink the PTMS heat. Less fuel = heats up faster. Furthermore, without the ram air and with the substantially hotter atmospheric temperatures at ground-level, the FAHX has to rely on the substantially less powerful (compared to ram air) suction of the IPP (integrated power package, basically the beating heart of the aircraft) to move air across the FAHX. (Sidenote: remember that I said the PTMS system is fiendishly complicated? There's something like eight different modes of operation for the system all for various states of thermal saturation or failure. In the event that the IPP can't draw air across the FAHX, there's a little fan in there that will kick on in a last-ditch effort to help keep the fuel cool. It looks like a huge heavy-duty version of the heatsinks you put on a PC CPU). When the fuel gets too hot the jet enters Thermal Management mode and shuts down the hotter avionics to avoid damage. Like I said, not an issue when flying, but an issue when they're at 1,000 pounds of gas or less and landing after a day of flying. This means that the post-flight Vehicle Systems test (VSBIT) is going to fail, which is a code-3 grounding situation. But it's a recognized problem so not much thought is put into it.

The problems are exacerbated when you fuel them up from a fuel truck, however, and they already have fuel in them. Air Force fuel trucks are a dark evergreen color which absorbs a lot of thermal radiation from the sun, which makes the fuel in the truck heat up. You pump all this hot fuel into a jet that already has lots of hot fuel in it, and simply put, you aren't going to be able to run the jet until that fuel radiatively cools down enough to adequately sink avionics heat. Until that fuel is cool enough (remember that the larger the difference in temperatures, the faster and more efficiently heat can be swapped), you can't get the jet off the ground because it won't pass its preflight VSBIT.

This is where the story about the Air Force painting the fuel trucks white came from, in order to keep the fuel in the trucks as cool as possible to help the jet cool down and be able to quick-turn it if need be. It's a problem in-work, and it's simply because the F-35 avionics are so advanced and powerful that they generate a lot of heat. This actually is a rather interesting problem and I would therefore hazard a guess and say that if other fifth-gen-plus aircraft that are still in development (like the T-50) aren't having thermal management issues, it reflects that the avionics are substantially less powerful than what the F-35 has at its disposal.

Even the F-22 had thermal management issues and the military-hating media was all over that too, so this isn't a new problem. All that said, personally I haven't seen a single jet miss its second sortie of the day because it was still too hot from its first flight.

So basically we're dealing with Mechwarrior-style heat issues. Bottom line: thermodynamics ain't noone's fool.

Is there not some way to put heat sinks, all finned and ribbed, on trailing parts of the airframe to bleed excess heat, in conjunction with controls already in place? Or would this severely compromise its stealth capabilities?

You may have caught my post before I added some more at the beginning. The jet doesn't have any problem keeping fuel cool when it's flying. There's a ram air duct above the right intake that feeds the primary fuel-air heat exchanger. All the thermal issues happen when the jet is very low on fuel and mostly caused by heat buildup once its on the ground. Air temperature at ground level is scorching compared to at altitude, and without that delicious ram air, it has to rely on the IPP to pull air across the heat exchanger, which isn't as good.

Honestly even then, it doesn't happen very often. Maybe once or twice a week out of a full flying schedule, and this is in July in ****** Florida. I suspect that the 'white fuel truck' thing is specifically only going to be for 'hot-pit' refueling, where the aircraft lands, is refueled, and takes off again without shutting down.

Point is that more heat sinks isn't going to really do much, and wouldn't be worth it for the minor issue that the hot fuel is causing. Not only would that add weight, but since I believe (I don't know really anything about the stuff) the RAM coatings function as an insulator, it simply wouldn't really work.

This is a problem that could be solved with software, as the 'problem' is really entirely caused by the jet not wanting to pass its VSBIT when it is in TMS mode. There already are some workarounds used on the ground for various VSBIT failures.

Really I think if we were looking for a 'solution' regarding the fuel trucks, the best long-term solution (which I don't doubt may actually end up being the Air Force's ultimate idea) is to just upgrade the fuel trucks to cool the fuel as it comes down the fuel line.

Oh, so more than this being a genuine weakness of the aircraft, this is more a "We get that these conditions produce circumstances that look frightening, but really aren't" situation that the testing/diagnostic protocols and logic haven't been modernized to account for?

That's basically exactly it. That's why I said it is a real issue, but it's definitely not what it sounds like. You have to understand how the cooling system of the F-35 works to make sense of how 'white fuel trucks' and 'hot fuel' aren't really problems that are as stupid as they sound.

But even, the issue still isn't really that big of a deal. It's an irritating inconvenience more than anything, and it only really is ever going to affect one aspect of the aircraft - hot-pit refuels from a fuel truck. Which considering I've never seen that actually done in any warzone I've been in, is pretty low priority in the big picture.

[cantaz]

We use fuel as heat sinks even in legacy Hornets, both "scoops" one sees right behind the fuselage stations are fuel/heat exchangers.

Heck, these days it's probably easier to list off aircraft that don't use fuel for some form of cooling.