F-35 Cancelled, then what ?
It was described to me last fall as resembling "the guy in Alien when the thing bursts out of his chest". Not far off.
They must have known within about five minutes of the incident that the jet was a write-off, and it is no credit to anyone that they took until now to admit it in public.
They must have known within about five minutes of the incident that the jet was a write-off, and it is no credit to anyone that they took until now to admit it in public.
Join Date: Mar 2011
Location: Sussex
Age: 66
Posts: 371
Likes: 0
Received 0 Likes
on
0 Posts
What confuses me is that it has been said that this problem cost c$50m, hard to belive, a write off aircraft costing north of $100m, a program to develop a refresh for the F135 engine, including repairing /replacing all in service engines.
You have got to love accountancy 2+2= what do you want it to equal?
You have got to love accountancy 2+2= what do you want it to equal?
Join Date: Dec 2010
Location: Middle America
Age: 84
Posts: 1,167
Likes: 0
Received 0 Likes
on
0 Posts
You have got to love accountancy 2+2= what do you want it to equal?
Oh, wait, that is the write-off cost on a rather new F-15C/D, I brought the wrong insurance value book. We'll have to get back to you sometime on the F-35 write-off cost.
Really, Guys? An aircraft was lost during the development of a new type. That, of course, has never happened before, so I can see why, months after the event it's suddenly attracting as many rubber-neckers as M1 pile-up.
LO, as you know, nothing is written off until it's examined and evaluated. I agree, it looked like it at the time, but if all investigations were carried out by the likes of us from afar, watching a YouTube video, we probably wouldn't be as smart as we think we are.
As to what it costs, too late. Now go and add up the cost of all the other accidents, put all that money in a pot and donate it to the defence budget.
Why not do something constructive instead and guess how the actual problem is being fixed?
LO, as you know, nothing is written off until it's examined and evaluated. I agree, it looked like it at the time, but if all investigations were carried out by the likes of us from afar, watching a YouTube video, we probably wouldn't be as smart as we think we are.
As to what it costs, too late. Now go and add up the cost of all the other accidents, put all that money in a pot and donate it to the defence budget.
Why not do something constructive instead and guess how the actual problem is being fixed?
Join Date: Aug 2007
Location: London, New York, Paris, Moscow.
Posts: 3,632
Likes: 0
Received 0 Likes
on
0 Posts
Why not do something constructive instead and guess how the actual problem is being fixed?
Ah, that's more like it, Glad Rag. The temporarily permanent fix. Pre-trenching.
Now most of us don't know the answer to that, whether it will fix it or not.
I suspect the solution may just be as simple as that, for now. But, of course there are no details yet apart from a vague promise to come up with a permanent permanent fix if this one doesn't work.
Now, we're all guessing, maybe too early to do so, but I would be far more interested to understand more about what happened, how to fix it and what may be the future issues.
Now most of us don't know the answer to that, whether it will fix it or not.
I suspect the solution may just be as simple as that, for now. But, of course there are no details yet apart from a vague promise to come up with a permanent permanent fix if this one doesn't work.
Now, we're all guessing, maybe too early to do so, but I would be far more interested to understand more about what happened, how to fix it and what may be the future issues.
Join Date: Aug 2007
Location: London, New York, Paris, Moscow.
Posts: 3,632
Likes: 0
Received 0 Likes
on
0 Posts
Pre-trenching may [or may not be] the permanent solution, but there are plenty more issues that have been highlighted previously, that need addressing as well...
http://www.dodig.mil/pubs/documents/DODIG-2015-111.pdf
and that's just the WIP for the donkey....
Hmm.
http://www.dodig.mil/pubs/documents/DODIG-2015-111.pdf
and that's just the WIP for the donkey....
Hmm.
Join Date: Aug 2007
Location: London, New York, Paris, Moscow.
Posts: 3,632
Likes: 0
Received 0 Likes
on
0 Posts
You see, the problem was, this was a great aircraft on paper in the original specifications.
But as it stands at the moment it is anything but. Which is BAD news.
Saying that there are fixes coming is fine but, as I believe to be correct, the aircraft will never return to those original specifications for numerous reasons.
Which kinda makes you think the original specifications must have been completely unrealistic from the beginning.......<scratchchin>
However, with the news that both F15/16 lines may be closing, the US could well be in the horse manure if someone, somewhere, doesn't take an executive decision....
meanwhile the freight train keeps on rolling ...
But as it stands at the moment it is anything but. Which is BAD news.
Saying that there are fixes coming is fine but, as I believe to be correct, the aircraft will never return to those original specifications for numerous reasons.
Which kinda makes you think the original specifications must have been completely unrealistic from the beginning.......<scratchchin>
However, with the news that both F15/16 lines may be closing, the US could well be in the horse manure if someone, somewhere, doesn't take an executive decision....
meanwhile the freight train keeps on rolling ...
Join Date: Dec 2010
Location: Middle America
Age: 84
Posts: 1,167
Likes: 0
Received 0 Likes
on
0 Posts
Courtney,
What happened was a titanium fire, rare in modern day jet engines when it occurs forward of the HP compressor area, but in the colder area of the LP fan. The phenomena of a titanium fire involves subjecting a titanium part to a temperature above 1,600ºC (2912℉) and within 4 to 20 seconds a white hot fire starts which reaches a temperature of 3,300ºC (5972℉). The energy destroys surrounding materials by burning and melting. You can see in the photos provided by kbrockman how it has burned a hole or holes in the aircraft skin. The fire once started is nearly impossible to put out. Common extinguishing agents don't work and some make the fire worse as well as their usual quantity being inadequate. An argon blanket type gas coverage in place of normal air that contains oxygen works the best. Titanium fires behave like magnesium fires, it is why there are no magnesium gearboxes on jet engines provided to the Navy for carrier operations.
Titanium is used in the front end of the engine where possible because of its high strength-to-weight ratio verses steel or nickel-base alloys. So what causes titanium fires in the case of a rotating inner seal?
- Bearing failure
- Rotor unbalance, or
- (rarely) high g-loading and flexing under certain flight maneuvers
BTW, these reasons were known in the 1960s and were published in 1979 in a report for the FAA by the National Engineering Laboratory. There is no guessing and the reason given by USAF General Bogdan was the third item above. So what do you do to avoid the problem?
Proper design processes:
- Mechanical stacking determination between stationary and rotating components
- Heat transfer and deflection analysis
- Transient heat transfer and deflection analysis under burst and chop conditions in both radial and axial directions
- Determination of transient stresses so LCF of the part can be assessed.
- Analysis of out of round instability caused by local rubbing
- Frequency analysis to prevent resonance to determine the acceptable margin
- Determination of damping requirements
- Determination side-slip instability of the rotor stator at low speed affecting fan and LP compressor seals.
But, if the design proves to not work, what do you do to fix it?
- Open up seal tolerances (performance loss and potential adverse affect on bearing life)
- Configuration and material changes (probable added weight)
- Strengthening support structures (added weight but preserves performance)
glad rag quote:
I suspect most of this applies to the engine as well.
Now, we're all guessing, maybe too early to do so, but I would be far more interested to understand more about what happened, how to fix it and what may be the future issues.
Titanium is used in the front end of the engine where possible because of its high strength-to-weight ratio verses steel or nickel-base alloys. So what causes titanium fires in the case of a rotating inner seal?
- Bearing failure
- Rotor unbalance, or
- (rarely) high g-loading and flexing under certain flight maneuvers
BTW, these reasons were known in the 1960s and were published in 1979 in a report for the FAA by the National Engineering Laboratory. There is no guessing and the reason given by USAF General Bogdan was the third item above. So what do you do to avoid the problem?
Proper design processes:
- Mechanical stacking determination between stationary and rotating components
- Heat transfer and deflection analysis
- Transient heat transfer and deflection analysis under burst and chop conditions in both radial and axial directions
- Determination of transient stresses so LCF of the part can be assessed.
- Analysis of out of round instability caused by local rubbing
- Frequency analysis to prevent resonance to determine the acceptable margin
- Determination of damping requirements
- Determination side-slip instability of the rotor stator at low speed affecting fan and LP compressor seals.
But, if the design proves to not work, what do you do to fix it?
- Open up seal tolerances (performance loss and potential adverse affect on bearing life)
- Configuration and material changes (probable added weight)
- Strengthening support structures (added weight but preserves performance)
glad rag quote:
Saying that there are fixes coming is fine but, as I believe to be correct, the aircraft will never return to those original specifications for numerous reasons.
Which kinda makes you think the original specifications must have been completely unrealistic from the beginning.......<scratchchin>
Which kinda makes you think the original specifications must have been completely unrealistic from the beginning.......<scratchchin>
Last edited by Turbine D; 7th Jun 2015 at 21:08. Reason: word corrections
Thank you kbrockman for posting the pictures- she looks "well-done" indeed. Actually I am surprised with a fire burning that hot and so deep, the fire did not spread to the rest of the aircraft, and all we would normally see is a burnt out blob in the rough outline of a F-35 on the runway. I seem to recall she was about to fly, so would likely have had a good amount of fuel aboard. Wonder how quick the foam/fire trucks were on scene.
Could this say anything positive (not sure we are allowed to say anything postive about the jet in this thread
) about fire not spreading to fuel tanks and other structures? Not trying to downplay the engine fire and problem at all, but the logs books are full of ramp fires for many aircraft types, and it often results in a total burn out- not a partially burnt aircraft still sitting on it's gear.
Could this say anything positive (not sure we are allowed to say anything postive about the jet in this thread
) about fire not spreading to fuel tanks and other structures? Not trying to downplay the engine fire and problem at all, but the logs books are full of ramp fires for many aircraft types, and it often results in a total burn out- not a partially burnt aircraft still sitting on it's gear.
Turbine D,
A good recount of the physics of titanium fires. Thank you. It takes something serious to make the stuff burn and once it's going, forget the built in fire extinguisher.
I would take issue with one of your statements,
It's not just the fire risk, it's the way it reacts with salt. Generally, the salt wins. You are right that magnesium and titanium fires can't be extinguished with water. Pour water onto a magnesium fire and it aggressively reacts with it, releasing hydrogen, which then causes an even more energetic reaction. If you deprive it of all sources of O2, magnesium reacts with nitrogen - hence the need for noble gasses to suppress it.
But the intensity of titanium and magnesium fires are, as you have suggested, very energetic, release lots of heat.
And that's interesting when you consider Sandiego's point about the state of the airframe after the fire.
Please excuse me for paraphrasing you, Sandiego.
A good recount of the physics of titanium fires. Thank you. It takes something serious to make the stuff burn and once it's going, forget the built in fire extinguisher.
I would take issue with one of your statements,
Originally Posted by Turbine D
is why there are no magnesium gearboxes on jet engines provided to the Navy for carrier operations.
But the intensity of titanium and magnesium fires are, as you have suggested, very energetic, release lots of heat.
Originally Posted by Turbine D
The phenomena of a titanium fire involves subjecting a titanium part to a temperature above 1,600ºC (2912℉) and within 4 to 20 seconds a white hot fire starts which reaches a temperature of 3,300ºC (5972℉). The energy destroys surrounding materials by burning and melting.
Originally Posted by Sandiego
the fire did not spread to the rest of the aircraft, and all we would normally see is a burnt out blob in the rough outline of a F-35 on the runway. I seem to recall she was about to fly, so would likely have had a good amount of fuel aboard.
And
the logs books are full of ramp fires for many aircraft types, and it often results in a total burn out- not a partially burnt aircraft still sitting on it's gear.
And
the logs books are full of ramp fires for many aircraft types, and it often results in a total burn out- not a partially burnt aircraft still sitting on it's gear.
Last edited by Courtney Mil; 7th Jun 2015 at 23:11.
Was about to make the same comment about magnesium - I believe it was once said that "on contact with salt water, magnesium-based alloys demonstrate the structural qualities of Alka-Seltzer".
That is also one of many reasons why we will never see a restored B-36 in the air...
That is also one of many reasons why we will never see a restored B-36 in the air...
Do a Hover - it avoids G
Join Date: Oct 1999
Location: Chichester West Sussex UK
Age: 91
Posts: 2,206
Likes: 0
Received 0 Likes
on
0 Posts
LO
Agreed re magnesium and salt water. That is why we had to take it all out of the RAF engine and airframe when sorting the Sea Harrier.
We had a titanium fire in a Dunsfold crash in 1968. We could not put it out. Mind you I am sure there have been many developments in fire fighting media since then.
Agreed re magnesium and salt water. That is why we had to take it all out of the RAF engine and airframe when sorting the Sea Harrier.
We had a titanium fire in a Dunsfold crash in 1968. We could not put it out. Mind you I am sure there have been many developments in fire fighting media since then.
Do a Hover - it avoids G
Join Date: Oct 1999
Location: Chichester West Sussex UK
Age: 91
Posts: 2,206
Likes: 0
Received 0 Likes
on
0 Posts
I forgot to mention that the USMC AV-8s were just like the RAF aircraft of the day. So when they landed on a ship they taxied to a fire hose and the whole thing was very well rinsed before the engine was shut down.
I do like this wording from the USAF press release:
.......The engine failed when the third stage forward integral arm of a rotor fractured and liberated during the takeoff roll.......(my bolding)
Guess that's a nice way to say it...makes it seem it was set free to lead a better life
F-35 Accident Investigation Complete > Air Education and Training Command > News Article
And given the below, I am indeed surprised there was not a total burn out as I mentioned in post #6217....:
"Pieces of the failed rotor arm cut through the engine's fan case, the engine bay, an internal fuel tank, and hydraulic and fuel lines before exiting through the aircraft's upper fuselage. Damage from the engine failure caused leaking fuel and hydraulic fluid to ignite and burn the rear two thirds of the aircraft"
As for the $50 million, this editors note says: (EDITOR’S NOTE: The “in excess of $50 million” is a reporting category, and is not a true estimate of the cost of the damage.) http://www.defense-aerospace.com/art...stigation.html
.......The engine failed when the third stage forward integral arm of a rotor fractured and liberated during the takeoff roll.......(my bolding)
Guess that's a nice way to say it...makes it seem it was set free to lead a better life
F-35 Accident Investigation Complete > Air Education and Training Command > News Article
And given the below, I am indeed surprised there was not a total burn out as I mentioned in post #6217....:
"Pieces of the failed rotor arm cut through the engine's fan case, the engine bay, an internal fuel tank, and hydraulic and fuel lines before exiting through the aircraft's upper fuselage. Damage from the engine failure caused leaking fuel and hydraulic fluid to ignite and burn the rear two thirds of the aircraft"
As for the $50 million, this editors note says: (EDITOR’S NOTE: The “in excess of $50 million” is a reporting category, and is not a true estimate of the cost of the damage.) http://www.defense-aerospace.com/art...stigation.html
Last edited by sandiego89; 8th Jun 2015 at 15:31.
Join Date: Oct 2001
Location: UK
Posts: 1,136
Likes: 0
Received 0 Likes
on
0 Posts
CM,
The compressor washes were done with fresh water and not from a fire hose in my time. They were done on Sea Jet and plastic pig alike.
Bloke in yellow surcoat would form an intake shape with one arm and using his other hand point into it and transcribe a circle. This was usually timed perfectly to coincide with having your hands on your head whilst weapons were made safe.
Once you'd secured the air con, anti g and one other thing that I've forgotten you gave the thumbs up and some mate fired a few gallons of water down each intake.
The compressor washes were done with fresh water and not from a fire hose in my time. They were done on Sea Jet and plastic pig alike.
Bloke in yellow surcoat would form an intake shape with one arm and using his other hand point into it and transcribe a circle. This was usually timed perfectly to coincide with having your hands on your head whilst weapons were made safe.
Once you'd secured the air con, anti g and one other thing that I've forgotten you gave the thumbs up and some mate fired a few gallons of water down each intake.
Now that makes more sense, Orca. I did't recall the RN using desalinated water for fire-fighting. I knew what John meant, but couldn't resist a bit of mischief. Sorry, John.
That said, I'm very grateful for your description of the process. The way you described it made me wonder if water ingress into other systems (e.g. Anti-g) produced problems later on. Or even for the next pilot?
That said, I'm very grateful for your description of the process. The way you described it made me wonder if water ingress into other systems (e.g. Anti-g) produced problems later on. Or even for the next pilot?