Pentagon suspends F-35 flights due to crack in engine blade

Pentagon suspends all F-35 flights due to crack in engine blade 22 Feb 2013 ANDREA SHALAL-ESA, Reuters

http://www.banffcragandcanyon.com/2013/ ... gine-blade

"WASHINGTON - The Pentagon on Friday suspended the flights of all F-35 fighter planes after a routine inspection revealed a crack on a turbine blade in the jet engine of an F-35 test aircraft in California.

The F-35 program office said it was too early to know the fleet-wide impact of the engine issue, but it was suspending all flights until an investigation into the issue was completed.

It said it was working closely with Pratt & Whitney, the United Technologies Corp unit which builds the engine for the fighter, and Lockheed Martin Corp, the prime contractor for the radar-evading warplane, to ensure the integrity of the engine and return the F-35 fleet to flight as soon as possible."

That is it.

Entire F-35 fleet grounded over engine issues By Aaron Mehta - Staff writer 22 Feb 2013

http://www.navytimes.com/news/2013/02/d ... again-mil/

"...On Feb. 19, 2013, a routine engine inspection revealed a crack on a low pressure turbine blade of an F135 engine installed in a [conventional takeoff] test aircraft at Edwards Air Force Base, Calif,” wrote Kyra Hawn, Joint Program Office spokeswoman, in a statement.

“Engineering teams are shipping the turbine blade to Pratt & Whitney’s Engine Facility in Middletown, CT, to conduct more thorough evaluation and root cause analysis. It is too early to know the fleet-wide impact of this finding, however as a precautionary measure, all F-35 flight operations have been suspended until the investigation is complete and the cause of the blade crack is fully understood,” Hawn wrote....

...Matthew Bates, a P&W spokesman, wrote in an email that following the test flight, "maintainers conducted a routine boroscope engine inspection and discovered the crack."

"A routine boroscope visual inspection provided an indication there was a crack, and a subsequent Eddy Current Inspection, or ECI, appears to corroborate the results of the boroscope inspection. However, additional testing will be required to fully understand the cause," he wrote.

Bates added that the engine with the crack has 700 total engine operating hours, with 409 of those accrued in flight. He believes the engine analysis should take "roughly" a week...."

Pretty much it at moment.

Helmet on for all the nay-sayers complaining that this will be the end of the F-35...

A week eh? Good as time as any to have one of them them furloughs everyone's talking about.

I'm wondering if the 'engine health management' kicked in for this incident?

spazsinbad wrote:I'm wondering if the 'engine health management' kicked in for this incident?

I thought it was a "routine inspection."

Depends.

Can the PHM system give them items to check during a "routine" inspection?

Routine engine borescope inspections are generally carried out after a predetermined number of hours. Inspections like that are carried out even if all systems say everything is OK. Small cracks in turbine blades usually don't affect engine performance but if they go unnoticed and keep growing things can get ugly very quickly. An EHM system will not discover problems like that in time. And if they do... well my guess you're already in serious trouble or about to find out.

I remember hearing about a F/A-18F Hornet took a bird to the engine, and because of the use of blisk technology in F414s, the engine appeared undamaged from the outside, and the engine was still running normally, but borescope inspection revealed a crack, so the engine was removed, fully inspected and repaired. This was considered Class B damage (< $1m), and no fleet wide stand-down was required.

It would be possible that a small pebble could get sucked in and dent/crack a blade without being noticed until scheduled borescope inspection. The F135 engine is likely to be even more durable than the F119 or F414 engines.

neurotech wrote:I remember hearing about a F/A-18F Hornet took a bird to the engine, and because of the use of blisk technology in F414s, the engine appeared undamaged from the outside, and the engine was still running normally, but borescope inspection revealed a crack, so the engine was removed, fully inspected and repaired. This was considered Class B damage (< $1m), and no fleet wide stand-down was required.

It would be possible that a small pebble could get sucked in and dent/crack a blade without being noticed until scheduled borescope inspection. The F135 engine is likely to be even more durable than the F119 or F414 engines.

I doubt they take any chances with the F-35 considering what a big whoopsie in the air would do to the program.

neurotech wrote: [...]
It would be possible that a small pebble could get sucked in and dent/crack a blade without being noticed until scheduled borescope inspection.

That is possbile, but unlikely in this case as the report only mentioned a crack in a low pressure turbine blade. FOD on a single low pressure turbine blade is very rare as the object would have gone trough the Fan (3 stages) Compressor (6 stages), Combustor, High Pressure Turbine (single stage) without causing any other damage.... as I said, could be possible in theory but in reality very unlikely.

Cracks in turbine blades are usually the result of heat and stress on the blades.

SpudmanWP wrote:Depends.

Can the PHM system give them items to check during a "routine" inspection?

Standard aircraft maintenance practice specifies routine inspections on all aircraft -- take your pick. Edwards = test jet = more 'routine' inspections, including engine borescope looks.

m582 wrote:

neurotech wrote: [...]
It would be possible that a small pebble could get sucked in and dent/crack a blade without being noticed until scheduled borescope inspection.

That is possbile, but unlikely in this case as the report only mentioned a crack in a low pressure turbine blade. FOD on a single low pressure turbine blade is very rare as the object would have gone trough the Fan (3 stages) Compressor (6 stages), Combustor, High Pressure Turbine (single stage) without causing any other damage.... as I said, could be possible in theory but in reality very unlikely.

Cracks in turbine blades are usually the result of heat and stress on the blades.

Yes, you are right. The comment about the pebble applies more to the fan stages, not the LPT. My bad.

@bigjku: That and a F/A-18F is a twin-engine aircraft. The jet should be recoverable on one engine. In reality, a single-engine recovery is far from certain, especially on a carrier.

For the F-35, the test pilots have successfully completed engine-restart tests, and would know what the recovery envelope is for a glide landing. I'm not sure if they'll ever attempt a real glide landing, but an engine failure on take-off without empty dry lake to land on, would almost certainly be a Martin-Baker event. The political fallout of loosing a $150m LRIP jet would not be good for the program.

Won't the Edwards testers create a deadstick landing procedure if they haven't already?

I mean sooner or later it's gonna happen to somebody who probably not a test pilot under controlled conditions....

BTW - what is best glide for the A model?

Something similar happened several years back with the B jet. The recent
Incident was for the A variant.
http://www.flightglobal.com/news/articl ... ht-221423/