More details emerge on F-35 engine problems

On June 3rd, F-35 AF-27 made a routine maneuver while on a test flight over Florida. The result of this maneuver was the engine flexing two inches, allowing the third stage turbine blades to rub against the casing wall. This caused them to undergo temperatures as high as 1900 degrees, when they were designed for 1,000 degrees.

The higher than designed for temperatures caused micro cracks to occur in an adjacent turbine. Three weeks later, that turbine exploded, puncturing the aft fuel tank, and causing a fire, resulting in major damage to the aircraft.

The Pentagon has implemented a program of borescoping the engines every three to six flight hours, depending on airframe type. They have been quick to call this a one off engine problem, but five more engines have been removed with excessive early wear patterns, including one with less than 70 hours on it.

AvWeek

a reply to: Zaphod58

Question is, is this a long term solution, is there a long term fix for the F-35 or are they going to rewrite it?.

The F-35...

Good lord what problem are they going to find next? It seems every time I turn around there is some new complication with that bird.

Obviously, this must be related to your other thread about substandard titanium.

www.abovetopsecret.com...

a reply to: theabsolutetruth

Pratt and Whitney is working on the long term fix. The problem is that having to borescope the engine so often slows testing of the fix way down.

a reply to: CAPT PROTON

There were 140 engines delivered that used that titanium, so I'd be less than shocked if it was one of them.

Avoiding to Pratt & Whitney they think they understand what happened, and are currently testing a fix on the test rig, and on ground engines.

P&W statement

Should the military have to be checking these engines for cracks every five or six hours? What happened to reliable equipment that was trouble free till it's next scheduled inspections and rebuilds?

Gee, if Commercial jets had to do that maybe we wouldn't have so much air traffic, they would be in line for the repair shop every day.

originally posted by: Zaphod58


The Pentagon has implemented a program of borescoping the engines every three to six flight hours, depending on airframe type.
AvWeek

Jesus that sound like my Banshee. Hate two strokes.

Is this the same as the article I read yesterday about the engine "blowing up", which is likely linked to the titanium bought from Russia?

Do we have another conspiracy?

a reply to: rickymouse

They only are until the fix is installed. Once that's done they will go back to full envelope normal operations.

a reply to: Zaphod58

Seems to me, with the pricetag on these things, that most of the flaws would have been out of them before they are released. It is not supposed to be like a car where companies send them out with known flaws.

a reply to: Rosinitiate

It's not clear if this particular engine used that titanium or not.

originally posted by: rickymouse What happened to reliable equipment that was trouble free till it's next scheduled inspections and rebuilds?

It's a brand new engine in a brand new airplane. There are going to be lots of headaches. Foolishly, we defunded the alternative engine. Not that the F136 would have been problem free, but the competition would have left us with the best of options for engines after all was said and done. Not dissimilar to how the issues with the F100 weren't really fixed until the F101/F110 began to threaten contracts.

The engine flex occurred when the pilot did a ridge clearing maneuver. He flipped onto his back and arced over the top of the ridge, instead of climbing to a higher altitude. When he did, the particular pitch, roll, and yaw forces flexed the engine, allowing the stators to bite into the foam used to form a seal between the stators and IBR, as they hadn't carved a groove into it yet.

They have identified one of five areas being the cause, and should have it narrowed down by the end of the month, with a fix testing by next month. One possible fix is to precarve the channel that will eventually be worn into the foam before delivery of the engine. If they do that, there will be an expected performance loss, although they say it will be "a nit" of loss.

Six aircraft have had the envelope expanded again, and it's hoped that they can slowly allow others to expand theirs without a retrofit, depending on their engine wear. Full envelope is expected by the start of the year, which places the first carrier tests, and the B model IOC in jeopardy.

aviationweek.com...

This could be a reason for the unacceptable engine flexing during moderate to high G turns.

The F135 is the heaviest high-performance fighter engine ever built, weighing 70% more than the P&W F100 and measuring 24% larger in diameter, with consequently larger inertial and gyroscopic forces. The Pegasus engine in the AV-8B Harrier II, with a similar diameter to the F135, suffered from blade rubbing in the event of departures from normal flight, and those engines had to be removed for inspection and overhaul.

m.aviationweek.com...

Sounds like the Harrier has had similar problems. Stronger engine casing/frame/parts could lead to more weight.

a reply to: Zaphod58

When I first read it I thought it sounded pretty serious like an engine design fault which might need some engineering and strengthening to prevent the excessive flexing of the engine parts. But precutting of the foam which is what I understand happens anyway after the engine runs in sounds like a fairly easy fix and this might not be such a big problem at all.

a reply to: JimTSpock

The engine has a pretty high mean time between failure rate going, largely because so many engines were gently burned in doing envelope expansion testing. This was a case of a new airframe, with a low time engine performing a maneuver that led to the blades biting into the foam. It should be a pretty easy fix, depending on what the actual problem that caused it was.