Sponsor Message:
Military Aviation & Space Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
F35B Flights Suspended  
User currently offlinechuchoteur From France, joined Sep 2006, 763 posts, RR: 0
Posted (1 year 7 months 6 days 19 hours ago) and read 5373 times:

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.

27 replies: All unread, showing first 25:
 
User currently offlineThePointblank From Canada, joined Jan 2009, 1691 posts, RR: 0
Reply 1, posted (1 year 7 months 6 days 15 hours ago) and read 5211 times:

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

User currently offlinePowerslide From Canada, joined Oct 2010, 569 posts, RR: 1
Reply 2, posted (1 year 7 months 6 days 14 hours ago) and read 5162 times:

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?

User currently offlineAesma From France, joined Nov 2009, 6594 posts, RR: 9
Reply 3, posted (1 year 7 months 6 days 14 hours ago) and read 5162 times:

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
User currently offlineBilgeRat From United Kingdom, joined Dec 2006, 214 posts, RR: 1
Reply 4, posted (1 year 7 months 6 days 4 hours ago) and read 4940 times:

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.


User currently offlinefrancoflier From France, joined Oct 2001, 3741 posts, RR: 11
Reply 5, posted (1 year 7 months 5 days 21 hours ago) and read 4717 times:

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.



Looks like I picked the wrong week to quit posting...
User currently offlineThePointblank From Canada, joined Jan 2009, 1691 posts, RR: 0
Reply 6, posted (1 year 7 months 5 days 19 hours ago) and read 4670 times:

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.


User currently onlinekanban From United States of America, joined Jan 2008, 3483 posts, RR: 27
Reply 7, posted (1 year 7 months 5 days 16 hours ago) and read 4577 times:
Support Airliners.net - become a First Class Member!

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?


User currently offlineconnies4ever From Canada, joined Feb 2006, 4066 posts, RR: 13
Reply 8, posted (1 year 7 months 5 days 15 hours ago) and read 4552 times:

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.   



Nostalgia isn't what it used to be.
User currently offlineThePointblank From Canada, joined Jan 2009, 1691 posts, RR: 0
Reply 9, posted (1 year 7 months 5 days 14 hours ago) and read 4521 times:

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


User currently onlineKC135Hydraulics From United States of America, joined Nov 2012, 298 posts, RR: 0
Reply 10, posted (1 year 7 months 5 days 14 hours ago) and read 4519 times:

I'd hate to have a hydraulic system powered by a fluid that is consumed as it flies!

User currently offlineLARSHJORT From Denmark, joined Dec 2007, 1445 posts, RR: 0
Reply 11, posted (1 year 7 months 5 days 14 hours ago) and read 4498 times:

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 

/Lars



139, 306, 319, 320, 321, 332, 34A, AN2, AT4, AT5, AT7, 733, 735, 73G, 738, 739, 146, AR1, BH2, CN1, CR2, DH1, DH3, DH4,
User currently offlinelegs From Australia, joined Jun 2006, 239 posts, RR: 0
Reply 12, posted (1 year 7 months 5 days 10 hours ago) and read 4428 times:

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.


User currently onlinekanban From United States of America, joined Jan 2008, 3483 posts, RR: 27
Reply 13, posted (1 year 7 months 5 days 10 hours ago) and read 4425 times:
Support Airliners.net - become a First Class Member!

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.


User currently offlineThePointblank From Canada, joined Jan 2009, 1691 posts, RR: 0
Reply 14, posted (1 year 7 months 5 days 9 hours ago) and read 4406 times:

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]

User currently offlinelegs From Australia, joined Jun 2006, 239 posts, RR: 0
Reply 15, posted (1 year 7 months 5 days 9 hours ago) and read 4399 times:

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.


User currently offlinefrancoflier From France, joined Oct 2001, 3741 posts, RR: 11
Reply 16, posted (1 year 7 months 5 days 6 hours ago) and read 4354 times:

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?


Looks like I picked the wrong week to quit posting...
User currently offlinelegs From Australia, joined Jun 2006, 239 posts, RR: 0
Reply 17, posted (1 year 7 months 5 days 5 hours ago) and read 4335 times:

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]

User currently offlinefrancoflier From France, joined Oct 2001, 3741 posts, RR: 11
Reply 18, posted (1 year 7 months 5 days ago) and read 4252 times:

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...



Looks like I picked the wrong week to quit posting...
User currently offlinerwessel From United States of America, joined Jan 2007, 2342 posts, RR: 2
Reply 19, posted (1 year 7 months 4 days 16 hours ago) and read 4139 times:
Support Airliners.net - become a First Class Member!

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.


User currently offlineMD11Engineer From Germany, joined Oct 2003, 13985 posts, RR: 62
Reply 20, posted (1 year 7 months 4 days 8 hours ago) and read 4052 times:

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


User currently offlinejollo From Italy, joined Aug 2011, 213 posts, RR: 0
Reply 21, posted (1 year 7 months 4 days 1 hour ago) and read 3958 times:

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)


User currently offlinesebolino From France, joined May 2001, 3681 posts, RR: 4
Reply 22, posted (1 year 7 months 4 days 1 hour ago) and read 3945 times:

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 ...  


User currently onlinekanban From United States of America, joined Jan 2008, 3483 posts, RR: 27
Reply 23, posted (1 year 7 months 3 days 21 hours ago) and read 3845 times:
Support Airliners.net - become a First Class Member!

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 ..


User currently offlinechuchoteur From France, joined Sep 2006, 763 posts, RR: 0
Reply 24, posted (1 year 7 months 3 days 18 hours ago) and read 3778 times:

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.


User currently offlinePowerslide From Canada, joined Oct 2010, 569 posts, RR: 1
Reply 25, posted (1 year 7 months 3 days 16 hours ago) and read 3798 times:

I wouldn't know of any modern fighter that allows flying in/around/near thunderstorms in their SOP's.

User currently offlineGeezer From United States of America, joined Aug 2010, 1479 posts, RR: 2
Reply 26, posted (1 year 7 months 2 days 23 hours ago) and read 3634 times:

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 and over again and expecting a different result; Albert Einstein
User currently offlineThePointblank From Canada, joined Jan 2009, 1691 posts, RR: 0
Reply 27, posted (1 year 6 months 3 weeks 3 days 8 hours ago) and read 3171 times:

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.


Top Of Page
Forum Index

Reply To This Topic F35B Flights Suspended
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Military aviation related posts only!
  • Not military related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Safety Of Handcuffed Pax On Extradition Flights? posted Tue Apr 10 2012 16:45:18 by BuyantUkhaa
U S Military Charter DC-10 Flights posted Thu Sep 15 2011 13:14:18 by bigbird
End Of An Era, Last UK Harrier Carrier Flights posted Thu Nov 25 2010 06:44:02 by keesje
Choose Wakeup Songs For Last Space Shuttle Flights posted Tue Aug 24 2010 15:23:41 by L410Turbolet
AMC Charter Flights posted Sat Aug 21 2010 15:39:10 by ChopChop767
MoD Ascension Island/Falklands Flights posted Tue Dec 29 2009 03:56:04 by Edina
Boeing Test Flights posted Thu Dec 17 2009 18:58:05 by Cubsrule
Jannet Flights From Vegas posted Mon Dec 15 2008 04:38:13 by Rutankrd
Space Shuttle Flights Beyond 2010 posted Wed Dec 19 2007 03:44:24 by Michlis
Question About MAC Or Charter Flights posted Thu Aug 30 2007 07:23:24 by Mike89406

Sponsor Message:
Printer friendly format