ThePointblank From Canada, joined Jan 2009, 1386 posts, RR: 0 Reply 1, posted (9 months 2 weeks 5 days 22 hours ago) and read 5928 times:
The issue is a defect in the low pressure turbine blades of one of the engines. Possible that it is due to a casting issue or a similar story to UA 232 where the original ingot had defects in it, but that's conjecture. Nothing to be too terribly concerned about unless it is a traceable quality control issue, so this is a grounding for safety's sake and to cover all of the bases. I expect that once inspections are complete, the jets will resume flying.
I will also note that F-35 is still a fighter in testing, and since this occurred at Edward AFB, there will be more 'routine' inspections, including engine borescope looks, just to see how the fighter ages with use.
Quote: Matthew Bates, a spokesman for Pratt & Whitney, which supplies the engines for the planes, said the Pentagon's F-35 program office had decided to rescind the grounding order after extensive tests and analysis of the cracked turbine blade, which was discovered on February 19 during a routine inspection conducted after every 50 hours of flight time.
Bates said Pratt engineers had been working around the clock with Pentagon experts to determine the cause of the crack in the engine blade, including a "destructive" test that cracked open the blade.
The tests showed that the crack resulted from the "unique operating environment" in flight tests -- many of which tested the engine's powerful after burners -- rather than a high-cycle fatigue crack, which would have required a design change.
Bates said the engine in question had operated at high temperatures for more than four times longer than a typical F-35 flight, which led to a separation of the "grain boundary" of this particular blade.
The Navy order rescinding the flight ban, or so-called "red stripe," said that engine had experienced the most "hot engine time exposure" of all the engines in the developmental program. It said it would now require reports to monitor and limit similar damage after every 25 flight hours.
Aesma From France, joined Nov 2009, 5704 posts, RR: 9 Reply 7, posted (9 months 1 week 5 days 1 hour ago) and read 4404 times:
The CNN "journalist" has obviously no idea of what he's talking about since he implies there is a big fleet of F-35 and that the grounding means a loss of defense capability when in fact the airplane is far from being in service.
New Technology is the name we give to stuff that doesn't work yet. Douglas Adams
Oroka From Canada, joined Dec 2006, 875 posts, RR: 0 Reply 8, posted (9 months 1 week 1 day 3 hours ago) and read 4185 times:
But it doesnt matter that it wasnt a design defect. Being an engine that was subjected to 4x its designed operational levels has no bearing to the fact that the F-35 is horrible and wasnt perfect right off the drafting table (I know, computer aided design).
It is a good thing for the F-35 that it wasnt a design problem, or even a quality control problem, but good things for the F-35 are non topics.
Quote: The analysis indicates that the Lockheed Martin F-35 engine blade cracked despite being made correctly according to the blueprint for making the part, Croswell says. That finding points to a flaw in the casting process itself.
"There may be features in the castings that are allowed by the blueprint, but now we've learned that those features we should not allow," Croswell says.
P&W can either change the process used to make the casting of the turbine blade or simply throw out any blade that shares similar features of the one that cracked.
"It may be as simple as culling those blades that have that feature," Croswell says.
P&W is finalising an analysis of which option would be most affordable, and that report will be submitted to the joint programme office at the end of June.
Add the unusual operating perimeters of the engine in question, and you have a crack.