F-35 Cancelled, then what ?
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Re: F135 engine fire incident story, version B.
Here is the story from the WSJ:
Note the absence of the words "fan blades", or any descriptive terms leaving one to wonder where the problem actually is…
Here is the story from the WSJ:
LONDON—The engine fire on a Lockheed Martin Corp. LMT +0.79% F-35 Joint Strike Fighter that has grounded the fleet might have been a somewhat isolated incident, the Pentagon's top arms buyer said Sunday.
"We don't see at this point what I call a systemic problem," said Frank Kendall, U.S. undersecretary of defense for acquisition, technology and logistics.
The grounding occurred after an F-35A jet suffered a fire on June 23 on the ground at Eglin Air Force Base in Florida.
The operational hiatus has kept F-35s from making a planned trans-Atlantic flight to the U.K. for participation at the Royal International Air Tattoo in England during recent days and means the plane will be a no-show when the Farnborough air show opens outside London on Monday.
Safety investigators have reviewed the fire, saying that excessive friction occurred among blades and other internal parts of an engine built by the Pratt & Whitney arm of United Technologies Corp. UTX +0.83%
When one of the blades failed, Mr. Kendall said, it sparked the fire.
Safety authorities are now discussing whether to allow the plane to return to flight. Mr. Kendall said he was "hopeful" the F-35 could still make an appearance at the air show in the coming days.
Some friction among components is acceptable.
For reasons that aren't fully known, the level of interaction exceeded design margins in the plane that caught fire.
Mr. Kendall said evidence so far suggests it was a unique incident, although it is too early to draw that as a final conclusion.
The grounding comes as the government and Lockheed Martin also are trying to ramp up efforts to reduce costs.
Lockheed Martin said on Thursday that it, along with partners, would spend $170 million to find ways to lower long-term costs.
Mr. Kendall said the initiative "is a positive step."
"We don't see at this point what I call a systemic problem," said Frank Kendall, U.S. undersecretary of defense for acquisition, technology and logistics.
The grounding occurred after an F-35A jet suffered a fire on June 23 on the ground at Eglin Air Force Base in Florida.
The operational hiatus has kept F-35s from making a planned trans-Atlantic flight to the U.K. for participation at the Royal International Air Tattoo in England during recent days and means the plane will be a no-show when the Farnborough air show opens outside London on Monday.
Safety investigators have reviewed the fire, saying that excessive friction occurred among blades and other internal parts of an engine built by the Pratt & Whitney arm of United Technologies Corp. UTX +0.83%
When one of the blades failed, Mr. Kendall said, it sparked the fire.
Safety authorities are now discussing whether to allow the plane to return to flight. Mr. Kendall said he was "hopeful" the F-35 could still make an appearance at the air show in the coming days.
Some friction among components is acceptable.
For reasons that aren't fully known, the level of interaction exceeded design margins in the plane that caught fire.
Mr. Kendall said evidence so far suggests it was a unique incident, although it is too early to draw that as a final conclusion.
The grounding comes as the government and Lockheed Martin also are trying to ramp up efforts to reduce costs.
Lockheed Martin said on Thursday that it, along with partners, would spend $170 million to find ways to lower long-term costs.
Mr. Kendall said the initiative "is a positive step."
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Engine Fire Cause Emerges
F-35 Latest: Engine Fire Cause Emerges 14 Jul 2014 Amy Butler and Guy Norris
F-35 Latest: Engine Fire Cause Emerges | Defense content from Aviation Week
""FARNBOROUGH - The blade rubbing that prompted a fire in an F-35A – leading to a fleetwide grounding July 3 – took place in the third-stage fan of the integrally bladed rotor (IBR) in the low pressure section of the F135 engine, according to Lt. Gen. Christopher Bogdan, program executive officer for the U.S.–led F-35 program.
The three-stage IBR sits behind the front fan in the F135 and compresses the air before passing it into the high-pressure core. Each stage is separated by a stator and rotates within the casing, which is lined with an abradable strip to maintain tight clearances between the blade tips and the inner wall of the compressor casing. This enables tight tolerances while reducing pressure loss and some rubbing is acceptable. In the engine for AF-27, the blades were rubbing far in excess of the design, creating excessive heat and microcracking in the blades. The resulting high cycle fatigue failure forced the section to “come apart,” Bogdan says, prompting the fire June 23 at Eglin.
The pilot safely egressed and the flames were extinguished with foam.
Senior Pentagon officials say the problem thus far appears isolated; officials have inspected all 98 Pratt & Whitney F135 engines in service, Bogdan says. “All 98 of the other engines did not indicate the same phenomena as the one that failed,” he said. “We have created a body of evidence now that we think is ample enough to fully understand what happened.”...
...Meanwhile, “there is a growing body of evidence that this is not a systemic, major design problem,” Kendall said.
“This is not related to any incident in the past,” said Pratt & Whitney President Paul Adams.
Pratt engineers were already in the midst of a redesign to the first stage fan in the IBR, embracing a solid bladed design over the hollow design. A ground-based test engine “blew” late last year, Bogban said, owing to cracking in the hollow blades. The second and third stage fans –- the area in question for the June 23 fire -– are both constructed of solid blades. Pratt has submitted plans to Bogdan’s office for approval of plan to produce solid blades in the first stage and they are under review. This work is unrelated to the June fire incident, Adams said.""
The three-stage IBR sits behind the front fan in the F135 and compresses the air before passing it into the high-pressure core. Each stage is separated by a stator and rotates within the casing, which is lined with an abradable strip to maintain tight clearances between the blade tips and the inner wall of the compressor casing. This enables tight tolerances while reducing pressure loss and some rubbing is acceptable. In the engine for AF-27, the blades were rubbing far in excess of the design, creating excessive heat and microcracking in the blades. The resulting high cycle fatigue failure forced the section to “come apart,” Bogdan says, prompting the fire June 23 at Eglin.
The pilot safely egressed and the flames were extinguished with foam.
Senior Pentagon officials say the problem thus far appears isolated; officials have inspected all 98 Pratt & Whitney F135 engines in service, Bogdan says. “All 98 of the other engines did not indicate the same phenomena as the one that failed,” he said. “We have created a body of evidence now that we think is ample enough to fully understand what happened.”...
...Meanwhile, “there is a growing body of evidence that this is not a systemic, major design problem,” Kendall said.
“This is not related to any incident in the past,” said Pratt & Whitney President Paul Adams.
Pratt engineers were already in the midst of a redesign to the first stage fan in the IBR, embracing a solid bladed design over the hollow design. A ground-based test engine “blew” late last year, Bogban said, owing to cracking in the hollow blades. The second and third stage fans –- the area in question for the June 23 fire -– are both constructed of solid blades. Pratt has submitted plans to Bogdan’s office for approval of plan to produce solid blades in the first stage and they are under review. This work is unrelated to the June fire incident, Adams said.""
Last edited by SpazSinbad; 14th Jul 2014 at 22:58. Reason: Unintentional Misdirect undone with now highlighted parts
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SPAZ so this is good news? Hollow, lighter, blades get replaced in all future production engines with heavier solid blades.
I was under the impression that there was a weight problem with the F35..... So when/if this change in specification is approved, all engine testing goes back to zero hours for the system.
When will there be enough engines with the new blades to continue/start engine testing?
Just a thought...
I was under the impression that there was a weight problem with the F35..... So when/if this change in specification is approved, all engine testing goes back to zero hours for the system.
When will there be enough engines with the new blades to continue/start engine testing?
Just a thought...
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Just a thought? I read recently I think that the turn back to solid blades (there in original engine I believe) would add 6 pounds weight. I'm not an employee of anyone to know anything other than public information available on the internet etc. So you would know what I know - except perhaps flying in the RAN FAA some forty years ago now.
I don't know but I presume hollow blades are apparently hard to make and that there was a reason for trying to do it. The extra expense was somehow considered worthwhile.
It might only be 6 pounds but it's 6 pounds in something that spins very fast so there must be a lot of momentum stored. Presumably this makes the engine respond more slowly to throttle changes, for example. I don't know for sure because I'm far from an expert.
If the blades were hollow for the sake of cooling then that might mean that some other measure will have to be taken to prevent them from melting - with other undesirable trade-offs.
It might only be 6 pounds but it's 6 pounds in something that spins very fast so there must be a lot of momentum stored. Presumably this makes the engine respond more slowly to throttle changes, for example. I don't know for sure because I'm far from an expert.
If the blades were hollow for the sake of cooling then that might mean that some other measure will have to be taken to prevent them from melting - with other undesirable trade-offs.
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6 lbs static I take it...
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pounds weight/heaviness - not thrust of engine:
Perhaps not the exact same situation but analogous perhaps anyway: [March 2014]
F-35 Engine Part to be Redesigned | Defense News | defensenews.com
Perhaps not the exact same situation but analogous perhaps anyway: [March 2014]
"...
The company had already begun a redesign for the IBR as part of a movement to reduce overall engine costs, according to both Bogdan and Pratt spokesman Matthew Bates. The new design replaces the current hollow blade design with solid blades, which allow the company to use simpler, and hence cheaper, manufacturing techniques.
That redesign will add roughly six pounds to the engine; although the engine in question was a STOVL F-35B model, the IBR redesign will impact the engines for all three JSF variants. While weight is closely monitored on the F-35, Bogdan did not seem concerned about the extra weight....
The company had already begun a redesign for the IBR as part of a movement to reduce overall engine costs, according to both Bogdan and Pratt spokesman Matthew Bates. The new design replaces the current hollow blade design with solid blades, which allow the company to use simpler, and hence cheaper, manufacturing techniques.
That redesign will add roughly six pounds to the engine; although the engine in question was a STOVL F-35B model, the IBR redesign will impact the engines for all three JSF variants. While weight is closely monitored on the F-35, Bogdan did not seem concerned about the extra weight....
Last edited by SpazSinbad; 14th Jul 2014 at 22:59. Reason: Earlier Redesign Hollow to Solid NOT related to June Fire
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Yes, yes most have already read about the slight weight increase from the links you have previously shown us the WHOLE POINT is where do they shave the resulting 6 lb,s off the airframe OR do they notch the 190F up to 195?
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So now we know, the cause was excessive rubbing of the 3rd stage fan blisk at the front end of the engine. This is certainly an unusual problem in that the diameter of a blisk can be carefully controlled during the machining operation. It will be interesting to learn of the corrective action, it might not be that the blisk is the problem, but the casing surrounding it.
Relative to the actual fan :
Fan blades are made hollow to save weight not for cooling purposes. Hollow fan blades are more expensive to produce, but weight savings is a huge driver. Think of the fan of the engine, the shaft which connects it to the low pressure turbine and the low pressure turbine, as a bar bell. The higher the weight of the fan rotor and the LPT rotor, the higher the pressure is on shaft to bend. The shaft bearings and the bearing structural supports keep shaft bending from happening. So increased weight of rotating components can result in additional weight being added to structural support components, a mushrooming situation.
Relative to the actual fan :
If the blades were hollow for the sake of cooling then that might mean that some other measure will have to be taken to prevent them from melting - with other undesirable trade-offs.
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What is the status of the redesigned engine with solid blades? Rather a major change in the thermal balance of the engine I would have thought, so does all reliability and thermal stress have to be restarted? Interested to know what time delay this will put into the program? IOC delayed for the USMC?
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Some more tidbits for youse to speculate upon: [Earlier we got off on the wrong foot about 'hollow back to solid blades' - impression corrected above I hope?]
More F-35 Engines Show Signs of Blade Rubbing 14 Jul 2014 Brendan McGarry
More F-35 Engines Show Signs of Blade Rubbing | Military.com
More F-35 Engines Show Signs of Blade Rubbing 14 Jul 2014 Brendan McGarry
"...The incident is the second in less than a year to affect a part of the engine known as the integrally bladed rotor, or IBR. The component contains three sets of fans to help compress air into the engine. A first-stage fan made of hollow titanium blew apart during ground testing in December and is undergoing redesign, while a third-stage fan made of solid titanium disintegrated during the June takeoff.
Officials said the two cases aren't related.
A review of almost 100 engines in the fleet didn't find evidence of the same problem affecting the third-stage fan, though several showed signs of mild rubbing, Bogdan said. The extent of the problem appears to be isolated to that particular aircraft,..."
Officials said the two cases aren't related.
A review of almost 100 engines in the fleet didn't find evidence of the same problem affecting the third-stage fan, though several showed signs of mild rubbing, Bogdan said. The extent of the problem appears to be isolated to that particular aircraft,..."
Last edited by SpazSinbad; 14th Jul 2014 at 23:00. Reason: Rong Trou
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F35 might still make it to the UK now that it is flying again,
U.S. lifts grounding order for Lockheed F-35 fighters: sources By Reuters
U.S. lifts grounding order for Lockheed F-35 fighters: sources By Reuters
FARNBOROUGH England (Reuters) - U.S. military officials have lifted a fleetwide grounding order for Lockheed Martin Corp F-35 fighter jets, but will maintain some operating restrictions on the jets given an ongoing investigation into a massive engine failure last month, sources familiar with the situation said on Tuesday.
Discussions are still under way about whether the decision will clear the way for the newest U.S. warplane to travel to Britain to make its international debut at the Farnborough air show
Discussions are still under way about whether the decision will clear the way for the newest U.S. warplane to travel to Britain to make its international debut at the Farnborough air show
https://www.f35.com/news/detail/f-35...r-admiral-john
One could wonder just what flight restrictions might help the engine. No more than 90% rpm? No flying all the way across the Atlantic? If they still thought (at the time of that statement that they still don't have the full answer, I wonder if they're feeling to get the thing in the air again.
that's OK then!
One could wonder just what flight restrictions might help the engine. No more than 90% rpm? No flying all the way across the Atlantic? If they still thought (at the time of that statement that they still don't have the full answer, I wonder if they're feeling to get the thing in the air again.
Safety remains the overriding priority.
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Two US fighter jets were due to make their international debuts this week at the year's most important aerospace event, the Farnborough Airshow. At the moment, only one of them is here.
The F-35 may be the world's most expensive, most advanced military jet programme, but it was a cheap and cheerful budget aircraft that managed the trans-Atlantic crossing to Farnborough.
The Scorpion costs about $20m (£12m) a throw, is built from off-the-shelf components, and went from drawing board to first flight in 23 months.
The F-35, costing three times as much and conceived in the early 1990s, is still in the US while engineers figure out what caused a fire that has grounded the entire fleet.
OK, making comparisons is unfair; the Scorpion and F-35 are lightyears apart in specification and functionality. But it is still slightly ironic
The F-35 may be the world's most expensive, most advanced military jet programme, but it was a cheap and cheerful budget aircraft that managed the trans-Atlantic crossing to Farnborough.
The Scorpion costs about $20m (£12m) a throw, is built from off-the-shelf components, and went from drawing board to first flight in 23 months.
The F-35, costing three times as much and conceived in the early 1990s, is still in the US while engineers figure out what caused a fire that has grounded the entire fleet.
OK, making comparisons is unfair; the Scorpion and F-35 are lightyears apart in specification and functionality. But it is still slightly ironic
BBC News - Farnborough Airshow: The Scorpion in search of a customer
