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December 2022 Ft Worth F-35B Stealth Fighter ground ejection result of "harmonic resonance"
Vanity | Friday, Feb 24 | Stephen Losey

Posted on 02/28/2023 8:42:22 AM PST by Paal Gulli

First reported here (twice), complete with video, when it happened last December at NAS JRB Fort Worth. The mishap was remarkable because the pilot ejected while the a/c was on the ground.

The news reports that followed all spoke to the engine as the cause -- which would seem to indicate that neither the pilot nor other aspects of the aircraft were under suspicion -- and DoD ordered engine manufacturer Pratt & Whitney to stop delivering new engines for the F-35B until the problem was sorted.

Last Friday, a news source that may not be quoted here for copyright reasons reported that P&W had identified the cause of the mishap as "a rare system phenomenon involving harmonic resonance" (in the engine). Not stated directly but P&W must have told DoD the problem is fixed because they have approved resuming engine deliveries. However, for reasons the story does not address (possibly waiting on a retrofit of "the fix" to all F-35Bs already in the field), the a/c are still grounded, which means the Marines won't be getting any new F-35Bs for the timebeing.


TOPICS: Military/Veterans
KEYWORDS: aerospace; f35b; military
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To: T-Bird45

Galloping Gertie was a special case of induced resonance. (I am an EE not an ME.) The light poles on the roadway caused turbulence in the airflow around them, aeoli. When the roadbed tipped they shed the aeoli, which induced an aerodynamic impulse exactly in phase with the resonant frequency of the bridge. The tipping of the roadbed caused the impulse, which reinforced the tipping of roadbed, like the escapement on a pendulum in a clock, only a clock pendulum stabilizes when the energy dissipated on each cycle equals the energy supplied by the escapement. For poor Gertie, mechanical failure preceded stabilization.

https://www.youtube.com/watch?v=j-zczJXSxnw


21 posted on 02/28/2023 9:14:33 AM PST by Lonesome in Massachussets (Forsan et haec olim meminisse iuvabit.)
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To: jagusafr
Depends on who the pilot's father is...................
22 posted on 02/28/2023 9:15:16 AM PST by Red Badger (Homeless veterans camp in the streets while illegal aliens are put up in hotels.....................)
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To: smokingfrog
Seemed like shutting down the engine was the problem at the time,

That's what I thought. He was staying with it till it got back up on it's wheels. Couldn't throttle down so he thought it was going to keep going thru that fence.

23 posted on 02/28/2023 9:21:17 AM PST by TangoLimaSierra (⭐⭐To the Left, The Truth is Right Wing Violence⭐⭐)
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To: Cold Heart

Would the clip-on or the stick-on work better at 20,000 RPM?


24 posted on 02/28/2023 9:21:50 AM PST by Jeff Chandler (THE ISSUE IS NEVER THE ISSUE. THE REVOLUTION IS THE ISSUE.)
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To: the OlLine Rebel

Induced resonance:

https://freerepublic.com/focus/chat/4134559/posts?page=21#21


25 posted on 02/28/2023 9:23:27 AM PST by Lonesome in Massachussets (Forsan et haec olim meminisse iuvabit.)
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To: Red Badger

John McGriftCain


26 posted on 02/28/2023 9:25:06 AM PST by kiryandil (China Joe and Paycheck Hunter - the Chink in America's defenses)
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To: Lonesome in Massachussets

Picked up an Engineering class a few years ago where the instructor showed a clip of a CH-46 (chained down) and it just beat itself to pieces during ground runs.


27 posted on 02/28/2023 9:25:41 AM PST by Psalm 73 ("You'll never hear surf music again" - J. Hendrix)
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To: V_TWIN

From the link…

Initial assessments in the F-35B mishap investigation found a high-pressure fuel tube had failed.

They’re blaming the fuel tube failure on the vibrations, looks like.


28 posted on 02/28/2023 9:25:42 AM PST by smokingfrog ( sleep with one eye open (<o> --- )
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To: Lonesome in Massachussets

IIRC, harmonic resonance was tearing the wings off of early Lockheed Electras.


29 posted on 02/28/2023 9:31:54 AM PST by SIDENET (Whatever they're threatening, the vaxx is worse. Don't give in to coercion. )
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To: Paal Gulli

Looks to me like as soon as that cockpit was a bit more upright the pilot got the hell out of there intentionally.


30 posted on 02/28/2023 9:33:11 AM PST by TalBlack (We have a Christian duty and a patriotic duty. God help us.)
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To: smokingfrog

If that’s the case its lucky there wasn’t a fire


31 posted on 02/28/2023 9:34:38 AM PST by V_TWIN (America...so great even the people that hate it refuse to leave!)
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To: Paal Gulli
Yeah, sure. The pilot's rate of descent was too fast and he bounced when he hit and then the plane landed on its front landing gear leg and then broke it - the pilot didn't shut the throttle off.

You can hear the engine going at high thrust when he punched out.

Brain lock.

32 posted on 02/28/2023 9:51:59 AM PST by Chainmail (Harrassment, to be effective, must be continuous.)
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Comment #33 Removed by Moderator

To: Jeff Chandler

Depends on whether on the compressor or turbine blade. I would go with the stick on in the lower temperature and clip on for the higher temperature blades.

Lead substitute for environmental considerations.


34 posted on 02/28/2023 10:10:55 AM PST by Cold Heart
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To: Paal Gulli

FTA: ... while the a/c was on the ground

They cannot even spell aircraft.
The writer is texting too much.


35 posted on 02/28/2023 10:17:51 AM PST by minnesota_bound (Need more money to buy everything now)
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To: Sirius Lee
A Tech Sgt that I knew overseas had a Moto Guzzi with a sidecar.   He loved that bike.
36 posted on 02/28/2023 10:41:25 AM PST by higgmeister (In the Shadow of The Big Chicken!)
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To: Paal Gulli

“Remarkable” because he ejected while on the deck? Not exactly the first time that’s happened.
The plane was not under his control anymore, and was an instant from flipping. No good reason to burn to death at that point. Good decision...


37 posted on 02/28/2023 10:57:44 AM PST by DesertRhino (Dogs are called man's best friend. Moslems hate dogs. Add it up..)
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To: Red Badger

God only knows what demons are lurking in the 35B lift jet, driveshaft and main engine. It’s pretty intact so I’m guessing they have some good data inbound.


38 posted on 02/28/2023 10:59:26 AM PST by DesertRhino (Dogs are called man's best friend. Moslems hate dogs. Add it up..)
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To: Cold Heart

A balance issue cropping up with the engine or the fan itself would be almost impossible, unless one or the other threw a blade.

I’m thinking some sort of acoustic resonance. There’s a lot of very high energy airflows going on in and around around that fan. And there’s could be interesting stuff with that high-bypass engine. An acoustic resonance could drive mechanical vibration in turn.


39 posted on 02/28/2023 11:13:36 AM PST by Chad C. Mulligan
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To: Lonesome in Massachussets
"Harmonic resonance is the bane of mechanical engineers, and especially aircraft engines."

Ever hear of a phenomenon in helicopters called "ground resonance"?

https://en.wikipedia.org/wiki/Ground_resonance

It only happens to 'copters with articulated rotors and some sort of impact damping system on the landing gear (pneumatic wheels, oleo struts, or even thick rubber bushings on the saddle tubes of skids). The a/c enters a positive feedback loop and when it's pronounced enough to be noticeable, it's probably irreversible and the aircraft is going to shake itself to death.

https://www.youtube.com/results?search_query=ground+resonance

Frightening to watch, especially if you've ever been inside on of them thangs.

40 posted on 02/28/2023 11:40:59 AM PST by Paal Gulli
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