chuchoteur
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F35B Flights Suspended

Fri Jan 18, 2013 9:17 pm

http://www.defensenews.com/article/2...y=tab%7Ctopnews%7Ctext%7CFRONTPAGE

US Department of Defense decided to suspend F35B flight operations until hydraulic failure is analysed and understood.
 
ThePointblank
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RE: F35B Flights Suspended

Sat Jan 19, 2013 12:56 am

Far too early to pass judgement. Could be the fitting itself, bad metallurgy, chaffing, a loose clamp or a number of other things.
 
Powerslide
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RE: F35B Flights Suspended

Sat Jan 19, 2013 2:40 am

Every time the F35 has something go wrong in testing a new thread is started. People nitpick every single problem as if it's some sort of utter failure. Comical really. Perhaps its time to do the opposite, start a new thread whenever the F35 reaches a new milestone - that'd be what, one every week or so?
 
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Aesma
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RE: F35B Flights Suspended

Sat Jan 19, 2013 2:47 am

Well it's grounded, it's not nothing.

Can someone explain what is "fueldraulic", I figured it was using fuel as hydraulic fluid, but why ?
New Technology is the name we give to stuff that doesn't work yet. Douglas Adams
 
bilgerat
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RE: F35B Flights Suspended

Sat Jan 19, 2013 12:24 pm

Quoting Powerslide (Reply 2):
Every time the F35 has something go wrong in testing a new thread is started. People nitpick every single problem as if it's some sort of utter failure. Comical really. Perhaps its time to do the opposite, start a new thread whenever the F35 reaches a new milestone - that'd be what, one every week or so?

Go back and read the OP again. Neither the OP or the linked article passed any kind of negative comment, purely reporting the fact that the F-35B has been grounded after a hydraulic failure.

If anything in this thread is comical it's how quick you are to go on the defensive in the second reply to a thread in which nobody has yet criticised the F-35.

Quoting Aesma (Reply 3):
Can someone explain what is "fueldraulic", I figured it was using fuel as hydraulic fluid, but why ?

Correct. Fuel is used instead of hydraulic fluid to save weight. Not a bad idea but you'd better be pretty damn sure your system is tight and not going to leak fuel onto something hot.

Quoting ThePointblank (Reply 1):
Far too early to pass judgement.

Agreed.
 
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Francoflier
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RE: F35B Flights Suspended

Sat Jan 19, 2013 7:15 pm

Quoting BilgeRat (Reply 4):
Fuel is used instead of hydraulic fluid to save weight.

Strange design. Outside the potentially dangerous implications, I would have thought that Jet fuel makes for a pretty poor hydraulic fluid. It's very fluid, and it multiplies the risks of leak, which is bad news for two reasons now.

Is the whole hydraulic system powered this way (flight controls)? What's the backup system, cables, electric motors?

That must call for some pretty innovative engineering. I can't see that ever used on a civilian airliner.
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
ThePointblank
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RE: F35B Flights Suspended

Sat Jan 19, 2013 9:05 pm

Quoting francoflier (Reply 5):
Strange design. Outside the potentially dangerous implications, I would have thought that Jet fuel makes for a pretty poor hydraulic fluid. It's very fluid, and it multiplies the risks of leak, which is bad news for two reasons now.

Considering that regular hydraulic fluid is also highly flammable, it's not much of a trade off.

Quoting francoflier (Reply 5):
Is the whole hydraulic system powered this way (flight controls)? What's the backup system, cables, electric motors?

Only the F-35B uses a fueldraulic system for STOVL exhaust vectoring system. The rest of the control surfaces use electrohydrostatic actuators run by a power-by-wire flight-control system. The system is lifetime sealed with no maintenance required, compared to conventional hydraulic systems.
 
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kanban
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RE: F35B Flights Suspended

Sun Jan 20, 2013 12:22 am

Quoting ThePointblank (Reply 6):
The system is lifetime sealed with no maintenance required, compared to conventional hydraulic systems.

If it's lifetime sealed, the fluid could have been beer... so why put a lower flashpoint fluid in?
 
connies4ever
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RE: F35B Flights Suspended

Sun Jan 20, 2013 1:11 am

Quoting ThePointblank (Reply 6):
The rest of the control surfaces use electrohydrostatic actuators run by a power-by-wire flight-control system. The system is lifetime sealed with no maintenance required, compared to conventional hydraulic systems.

Sounds like the line Boeing peddled to airlines regarding the original 737 rudder actuator: there was no backup actuator because the "two-in-one" design was "self-correcting". Two commercial accidents and about 150 lives later, Boeing had to admit they had got it wrong.

Lifetime ? Well, gives me a reason to live to 100.   
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ThePointblank
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RE: F35B Flights Suspended

Sun Jan 20, 2013 2:01 am

Quoting connies4ever (Reply 8):
Sounds like the line Boeing peddled to airlines regarding the original 737 rudder actuator: there was no backup actuator because the "two-in-one" design was "self-correcting". Two commercial accidents and about 150 lives later, Boeing had to admit they had got it wrong.

Lifetime ? Well, gives me a reason to live to 100.
Quoting kanban (Reply 7):
If it's lifetime sealed, the fluid could have been beer... so why put a lower flashpoint fluid in?

The two of you did not read the technical details carefully.

The fueldraulic system controls the STOVL exhaust thrust vectoring system. This system is unique to the F-35B variant, and only powers the exhaust thrust vectoring system.

The electrohydrostatic actuators control the primary flight surfaces for all variants of the F-35. The F-35 is the only fighter in production, the first combat aircraft developed, and the second mass-produced aircraft (the A380 is the first) in the world that uses electrohydrostatic actuators. Each unit is self-contained; for example a failure (or damage) to the actuator for the left wing controls will not affect flight controls for the rest of the aircraft. There is one EHA driving each flight control surface. For critical surfaces (Horizontal Tail and Flaperons), dual-tandem EHAs provide redundant actuation within a single line replaceable component. Only total power failure will result in the loss of flight control, and by then, in any fighter aircraft, you are looking to bail out anyways.

The electrohydrostatic actuators are simpler and easier to maintain, not to mention the weight savings, and reduced power consumption compared to regular hydraulic systems, which are more bulky, heavier, and require constant maintenance actuation equipment and the vehicle system.

The maintenance on the system is extremely simplified to simple replacement, rather than repairs, for example, on a F-16, for example, all your actuators are still hard-lined into the hydraulic system. The actuators on the F-35 are fully self-contained: four cannon plugs, some bolts, and it pops right out after you take your panels off.

On the F-16, you’d be four cannon plugs, eight bolts, two hydraulic lines, refuel or resetting the hydraulic systems, re-servicing those, bleeding and leaking them, and then doing the ops checks, not to mention if you had some kind of rigging you had to do for the actual actuator if it wasn’t just a straight swap, you’d had to go in and do all your rigging for that actuator. The F-35 system self-adjusts the flight controls, so once you go in and replace an actuator, you run auto-rig, and the system auto-rigs the actuator.

You can read up on the technical details of the system by reading this 170 page thesis on the topic someone did up:
http://cmht.mcmaster.ca/docs/McCullo...rostatic%20Actuator%20-%202011.pdf
 
KC135Hydraulics
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RE: F35B Flights Suspended

Sun Jan 20, 2013 2:05 am

I'd hate to have a hydraulic system powered by a fluid that is consumed as it flies!
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larshjort
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RE: F35B Flights Suspended

Sun Jan 20, 2013 2:32 am

I wonder what the reason for the detached fuel line is? Improper installation, design flaw or manufacturing defect?

Quoting KC135Hydraulics (Reply 10):
I'd hate to have a hydraulic system powered by a fluid that is consumed as it flies!

If you run out of fuel during flight you don't need to operate the trust vectoring system anyway 

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Legs
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RE: F35B Flights Suspended

Sun Jan 20, 2013 6:22 am

Quoting francoflier (Reply 5):
Strange design

Its certainly not a new design, fuel has been used as a hydraulic fluid to actuate engine nozzles as far back as the P&W TF-30, which has it's roots in the late 1950's.
 
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kanban
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RE: F35B Flights Suspended

Sun Jan 20, 2013 6:28 am

Quoting ThePointblank (Reply 9):
The two of you did not read the technical details carefully

Thanks for 170 pages of theory... now the simple question... why use fuel as a medium? if it's a closed system with minimal leakage any fluid would work .. one would think on an a/c replacing the Harrier envelope one would wanytt to minimize flammability if hit.

Quoting legs (Reply 12):
Its certainly not a new design, fuel has been used as a hydraulic fluid to actuate engine nozzles as far back as the P&W TF-30, which has it's roots in the late 1950's.

Egads that's ancient technology.. at least 65-70 years old.    For those that don't know that smily identifies sarcasm.
 
ThePointblank
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RE: F35B Flights Suspended

Sun Jan 20, 2013 7:02 am

Quoting kanban (Reply 13):
Thanks for 170 pages of theory... now the simple question... why use fuel as a medium? if it's a closed system with minimal leakage any fluid would work .. one would think on an a/c replacing the Harrier envelope one would wanytt to minimize flammability if hit.

One reason: weight savings. Most conventional hydraulic fluid is flammable anyways. The only fluids that aren't are the specialized glycol water ones used in specialized applications like the steel industry. They're a PITA to work with since the are water based and at times corrosive.

Fuel is also used as a equipment coolant, and a component lubricant in the aircraft engine prior to combustion.

You can read up on the system here:
http://www.nap.edu/openbook.php?record_id=5871&page=61

Quoting legs (Reply 12):
Its certainly not a new design, fuel has been used as a hydraulic fluid to actuate engine nozzles as far back as the P&W TF-30, which has it's roots in the late 1950's.

Also, used on the Saturn V rocket as well to control the gimbals, as a random note.

[Edited 2013-01-19 23:05:03]
 
Legs
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RE: F35B Flights Suspended

Sun Jan 20, 2013 7:43 am

Quoting kanban (Reply 13):
why use fuel as a medium?

I'm not entirely sure. Im an avionics guy, not an engine/airframe expert so I can't say if they use fuel for the engine nozzles in order to preheat it before heading off to the combustion cans, or if the aircraft hydraulic systems can't deal with the heat it might pick up.

It may well be that the system designers dont want to have to bring another couple of pressure and return lines to the back of the engine for nozzles and whatever else, so they tap a high pressure line off the fuel pump.
 
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Francoflier
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RE: F35B Flights Suspended

Sun Jan 20, 2013 10:41 am

Is there a separate pump(s) that provide pressure to this system? Is the return fed directly to the tank, or is it used while on the way to the engine?
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
Legs
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RE: F35B Flights Suspended

Sun Jan 20, 2013 11:39 am

Quoting francoflier (Reply 16):

Dont know about the F-35, but the ones Ive worked with were self contained as part of the engine. At a guess, I'd say they take a high pressure line off the main fuel pump output for the pressure side, while the return is probably dumped just upstream of the pump inlet.

Edit: There is a simplified fuel system schematic on page 62 of the thesis ThePointBlank linked to, that shows a fairly typical fueldraulic system.

[Edited 2013-01-20 03:41:18]
 
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Francoflier
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RE: F35B Flights Suspended

Sun Jan 20, 2013 4:24 pm

Quoting legs (Reply 17):
There is a simplified fuel system schematic on page 62 of the thesis ThePointBlank linked to

Thanks!

It does seem a lot smarter than using a separate hydraulic system. Even if it does increase the chances of a fuel leak.
But then I imagine there is a way to isolate the system and just use a straight exhaust in that case...
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
rwessel
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RE: F35B Flights Suspended

Mon Jan 21, 2013 12:05 am

Quoting ThePointblank (Reply 14):
Also, used on the Saturn V rocket as well to control the gimbals, as a random note.

It's fairly common on liquid fueled rocket engines. In all of these cases the fuel is already being pumped under pressure - and a least for rockets, at very high volumes. You'd actually need a fair bit of incentive to introduce a whole different system to support those functions.
 
MD11Engineer
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RE: F35B Flights Suspended

Mon Jan 21, 2013 8:36 am

On civilian jet engines all the engine related actuators and valves are usually powered by servo fuel, which is being tapped off after the high pressure pump and controlled though electromgnetical valves.

Jan
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jollo
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RE: F35B Flights Suspended

Mon Jan 21, 2013 3:16 pm

Quoting kanban (Reply 13):
if it's a closed system with minimal leakage any fluid would work

I think there's a misunderstanding here:
* EHAs (electro-hydrostatic actuators) are sealed, self-contained closed systems but they *do not* use fuel as hyd fluid
* the F-35B's thrust vectoring system uses fuel as hydraulic fluid, but is definitely *not* a closed system (high pressure fuel is tapped on it's way to combustion)

These two technologies coexist on a F35B, but they are two distinct and very different items.

On a side note, Italian press today echoes UK newspapers (see here for example), reporting that F-35B are banned from flying "near thunderstorms" because of faults found in the "fuel tanks". Is this the same fuel leak issue, creatively misreported by journalists, or a new, separate problem?

(Italy ordered a couple dozens F-35B out of a total of 90, and the buy - and related expense - is a loudly disputed political bone in the upcoming elections)
 
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sebolino
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RE: F35B Flights Suspended

Mon Jan 21, 2013 3:36 pm

Quoting kanban (Reply 7):
If it's lifetime sealed, the fluid could have been beer... so why put a lower flashpoint fluid in?

Because if it was beer, the pilots would drill in the plane all the time to have a drink ...  
 
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kanban
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RE: F35B Flights Suspended

Mon Jan 21, 2013 7:04 pm

Quoting jollo (Reply 21):
I think there's a misunderstanding here:

Thanks for clearing that up in layman's terms...

Interestingly there is a new thread in Tech that talks about hydraulic fluids leaking into fuel ..
 
chuchoteur
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RE: F35B Flights Suspended

Mon Jan 21, 2013 10:45 pm

Quoting jollo (Reply 21):
On a side note, Italian press today echoes UK newspapers (see here for example), reporting that F-35B are banned from flying "near thunderstorms" because of faults found in the "fuel tanks".

There were some reports of a weakness in the centre fuel tank systems that could be critical in a lightning strike. Not really a huge problem, they are modifying some of the components and retrofitting them, the "no fly in thunderstorms" thing is just pending the fix being implemented, from what I could gather.
 
Powerslide
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RE: F35B Flights Suspended

Tue Jan 22, 2013 12:01 am

I wouldn't know of any modern fighter that allows flying in/around/near thunderstorms in their SOP's.
 
Geezer
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RE: F35B Flights Suspended

Tue Jan 22, 2013 5:10 pm

Quoting BilgeRat (Reply 4):
Correct. Fuel is used instead of hydraulic fluid to save weight. Not a bad idea but you'd better be pretty damn sure your system is tight and not going to leak fuel onto something hot.

I wonder how much weight they save.......about a pound ?

[quote=francoflier,reply=5]Strange design. Outside the potentially dangerous implications, I would have thought that Jet fuel makes for a pretty poor hydraulic fluid. It's very fluid, and it multiplies the risks of leak, which is bad news for two reasons now.

Great point........I was thinking the exact same thing.....

[quote=connies4ever,reply=8]Lifetime ? Well, gives me a reason to live to 100.   

Yeah, it's the same thing I'm trying to do........(only 20 more years to go now!)

[quote=ThePointblank,reply=9]On the F-16, you’d be four cannon plugs, eight bolts, two hydraulic lines, refuel or resetting the hydraulic systems, re-servicing those, bleeding and leaking them, and then doing the ops checks, not to mention if you had some kind of rigging you had to do for the actual actuator if it wasn’t just a straight swap, you’d had to go in and do all your rigging for that actuator. The F-35 system self-adjusts the flight controls, so once you go in and replace an actuator, you run auto-rig, and the system auto-rigs the actuator.

Sounds like a true "modern marvel" of engineering doesn't it ?
Stupidity: Doing the same thing over and over again and expecting a different result; Albert Einstein
 
ThePointblank
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RE: F35B Flights Suspended

Thu Jan 31, 2013 8:14 am

Update: The issue that caused the grounding was a defective part. The part was not built to spec by a subcontractor:

http://www.reuters.com/article/2013/...heed-fighter-idUSBRE90R0PE20130128
http://www.flightglobal.com/news/art...b-fueldraulic-line-failure-381574/

The part was improperly crimped by the supplier, and will be replaced.

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