F-35 accident Fort Worth 15/12/22 - pilot ejected ok

[treadigraph]

Interesting video... hope pilot is uninjured.

https://youtu.be/_gqczk-zdck

[NWSRG]

My (totally untrained) eye thought the descent was a bit quick...no idea what happened after the bounce though. And then the throttle seems to stay open?

[MPN11]

Good seat performance! Why the delay? Trying to shut it down, or waiting a couple of precious seconds for a better seat profile?

Oh well, sh1t happens, and a good human result.

[sandiego89]

Yikes, imagine the sudden loss of the lift fan (mechanical, software glitch, perhaps associated with the bounce) would look something like that, with a significant pitch-over. Still seems to be lift being generated by the rear nozzle.

[Stitchbitch]

Something went a bit squirrely. That's four F-35B pilot saves for that seat, nice bit of engineering.

[gums]

Salute!

Wow, I want of those seats for my truck after the initial crash on the highway.

Having seen many videos of the plane landing on the boats, something at last 2 or 3 seconds went awry and touch was not like I have seen.

Gums sends...

[Mogwi]

Going to be a heavy mess bill!

Mog

[NutLoose]

An F-35 jet from Lockheed Martin crashed during a test flight on Thursday morning.

That’ll be a fail then, glad he got out.


White Settlement police chief Chris Cook says the pilot safely ejected.

Images show the jet intact on the grass near White Settlement Road.



Well, bar the nose leg, the canopy, the seat etc etc etc..

:E
https://www.fox4news.com/news/f-35-jet-reportedly-crashes-during-test-flight-in-fort-worth

​​​​​​​

[B2N2]

If I’m not mistaken the F35B(?) Mavy version has an automatic ejection sequence if a certain sumthing sumthing happens with the vertical thrust.
This may have been the airplane ejecting the pilot.

[Arm out the window]

The pilot was probably frantically trying to press CTRL-ALT-DEL while it was squirreling around on the ground, before giving it up as a bad job!
Guess we will find out more in due course, but it certainly looked like a quick power cut would have settled things down quickly, if that were possible at the time.

[albatross]

Isn’t the F-35 supposed to be rated for very high vertical rates upon landing? The gear in this event doesn’t seem to “give” very much.
If he was testing high vertical rates on touchdown the results appear to have been suboptimal.
Mind you the video quality is not great on my Ipad.
Glad the pilot ejected safely.
His friends will probably be sending gag gifts of underwear for Christmas.

[gums]

Salute!

We have seen at least two nose gear collapses with the 35, and maybe there's a design flaw that can be fixed.

I was surprised the test pilot waited until the plane stopped rotating and then punched. And with the Eglin nose gear collapse in mind, he might have just decided to ride it out. Then the Japanese nose gear thing a few weeks ago.

Another attaboy for Martin Baker, and I don't think their system acted on its own...rather, the pilot pulled the handle.

Gums sends...

[tartare]

Holy freaking schmoley.
Have just given Mrs T a heads up - she'll get that on the TV News tonight down here in Oz!

[India Four Two]

Five seconds between ejecting and landing! That’s faster than climbing out after a normal shutdown. Well done MB.

[stilton]

Salute!

We have seen at least two nose gear collapses with the 35, and maybe there's a design flaw that can be fixed.

I was surprised the test pilot waited until the plane stopped rotating and then punched. And with the Eglin nose gear collapse in mind, he might have just decided to ride it out. Then the Japanese nose gear thing a few weeks ago.

Another attaboy for Martin Baker, and I don't think their system acted on its own...rather, the pilot pulled the handle.

Gums sends...


Looks like he waited until it was upright, I wouldn’t think ejecting sideways on the ground would end well ?

[MechEngr]

I think the Japanese nose gear failure is completely unrelated. There are long drag marks from the main gear indicating the brakes were locked to stop the wheels turning. I would not expect most nose gear to handle being pulled opposite to the braking direction while the main gear is skidding.

Edit: Excluding catapult launched aircraft, which this does not appear to be.

[SRMman]

It seems to me that this is not a gear related incident. After a relatively gentle bounce the aircraft is initially level, when it suddenly becomes unbalanced and pitches strongly nose down until it contacts the ground. At this point the nose gear fails but clearly there is still full thrust from the aft nozzle causing the aircraft to rotate on the ground. I would suggest that the forward LiftFan has failed in some way. Pleased to see the ejection working as advertised.

[BEagle]

The Martin-Baker Mk16-US16E ejection seat as fitted to the F-35B does indeed have an active automatic ejection system which fires the seat when certain criteria are sensed. These are low speed, low altitude and adverse pitch rate.

The same seat fitted to the F-35A and F-35C does not have this system.

[SpazSinbad]

Test Flying The Joint Strike Fighter by Graham Tomlinson 17 Jun 2011
"...In the unlikely event of the lift fan failing catastrophically the aircraft would pitch inverted in 0.6 seconds, and the pilot is protected by auto-ejection signalled by pitch rate and attitude...." http://myweb.tiscali.co.uk/hawkerassociation/hanewsletters/hanewsletter030nvu/testflyingjointstrikefighter.html

[melmothtw]

I think the Japanese nose gear failure is completely unrelated. There are long drag marks from the main gear indicating the brakes were locked to stop the wheels turning. I would not expect most nose gear to handle being pulled opposite to the braking direction while the main gear is skidding.

Edit: Excluding catapult launched aircraft, which this does not appear to be.

I think the point being made isn't that the nosewheel failures are linked, but that the nosewheel may have an inherent weakness that needs to be addressed.

The Martin-Baker Mk16-US16E ejection seat as fitted to the F-35B does indeed have an active automatic ejection system which fires the seat when certain criteria are sensed. These are low speed, low altitude and adverse pitch rate.

The same seat fitted to the F-35A and F-35C does not have this system.

Indeed, though I don't think the automatic ejection system is what sent the pilot skywards on this occasion, as whatever parameters would have caused the seat to fire automatically were present some seconds before it actually fired. Suspect the pilot made the choice and ejected himself.

[212man]

In the unlikely event of the lift fan failing catastrophically the aircraft would pitch inverted in 0.6 seconds
It appears that is what the aircraft was trying to do after the bounced landing, but the nose hit the ground first, and if he had been higher it might have been a less favourable outcome.

I think the point being made isn't that the nosewheel failures are linked, but that the nosewheel may have an inherent weakness that needs to be addressed.

​​​​​​​I don't think it's any surprise the nose gear failed in this incident - the impact is pretty severe!

[Video Mixdown]

What's the white smoke/vapour coming from the rear? I don't remember seeing that on any of the other vertical landing videos I've seen.

[uxb99]

So is the pilot aware there is going to be an auto-ejection (I suspect not) ? If no then how does the system protect against injury to arms and legs?

[RetiredBA/BY]

So is the pilot aware there is going to be an auto-ejection (I suspect not) ? If no then how does the system protect against injury to arms and legs?
He is not, no time. Restraints are fitted to head and arms and legs, according to a brief I received at MB on a factory visit. Rather like the leg restraints fitted to earlier seats.
Another superb save by MB and another addition to our exclusive Tie club !

[Tango and Cash]

What's the white smoke/vapour coming from the rear? I don't remember seeing that on any of the other vertical landing videos I've seen.

I noticed the puffs of white smoke from the engine exhaust as well. It doesn't appear normal, at least not from the other F-35 vertical takeoffs/landings I've seen. Perhaps hydraulic or fluid leak from somewhere in the lift fan system? One of the gearboxes which run from the engine to the lift fan?

[arf23]

Five seconds between ejecting and landing! That’s faster than climbing out after a normal shutdown. Well done MB.

don't give Ryanair ideas....

[oldmansquipper]

Looking at the Japan incident…

Clearly, some bloody FLM brakeman in the cockpit putting the brakes on ‘to see what would happen’…🙄😉

(the ‘tramping’ before the NW leg collapses does suggest the brakes were applied for some reason)

[PDR1]

The SHAR had an engine "dump valve" which diverted fuel flow to filling a sump as soon as it got weight on wheels* to ensure that when it touched the deck it stayed firmly there rather than being light or bouncing regardless of what the pilot did on the throttle. From the look of that video F35 doesn't have a similar system, which surprises me. Lots of things in that video look a bit odd. The initial hover is stable, and the reconfiguration for vertical descent seems to be to schedule (tailplane trim change) - thedescent rate is a bit higher than I'd expect, although the attitude is constant suggesting it was under control. The touchdown was definitely on the firm side, but seemingly not beyond the energy dissipation range of the undercarriage. But the thrust seems to remain at the descent setting (ie thrust = weight) allowing the aeroplane to bounce where I would have expected it to be closed to a safe value.

Shortly after the bounce there then appears to be a complete failure of the forward lift fan with ensuing pitch-down, wiping out the nosewheel etc. But the think that REALLY surprises me is that the engine seems to be still running at a high-ish thrust setting right up to the point where the pilot bangs out, suggesting that engine wasn't responding to the throttle commands until the ejection sequence cut the fuel flow.

The lift fan failure is obviously a concern and its cause will need to be established. But for me the bigger concern would be why the engine continued to deliver thrust for so long. I can't believe the pilot didn't try to shut it down, so that could imply uncommanded throttle operation. That's a bit scary.

PDR

* not sure it operated through the WoW switch - I think it was a completely separate system but I've forgotten the details as it's been 20 years since I last thought about it

[oldmansquipper]

The SHAR had an engine "dump valve" which diverted fuel flow to filling a sump as soon as it got weight on wheels* to ensure that when it touched the deck it stayed firmly there rather than being light or bouncing regardless of what the pilot did on the throttle. From the look of that video F35 doesn't have a similar system, which surprises me. Lots of things in that video look a bit odd. The initial hover is stable, and the reconfiguration for vertical descent seems to be to schedule (tailplane trim change) - thedescent rate is a bit higher than I'd expect, although the attitude is constant suggesting it was under control. The touchdown was definitely on the firm side, but seemingly not beyond the energy dissipation range of the undercarriage. But the thrust seems to remain at the descent setting (ie thrust = weight) allowing the aeroplane to bounce where I would have expected it to be closed to a safe value.

Shortly after the bounce there then appears to be a complete failure of the forward lift fan with ensuing pitch-down, wiping out the nosewheel etc. But the think that REALLY surprises me is that the engine seems to be still running at a high-ish thrust setting right up to the point where the pilot bangs out, suggesting that engine wasn't responding to the throttle commands until the ejection sequence cut the fuel flow.

The lift fan failure is obviously a concern and its cause will need to be established. But for me the bigger concern would be why the engine continued to deliver thrust for so long. I can't believe the pilot didn't try to shut it down, so that could imply uncommanded throttle operation. That's a bit scary.

PDR

* not sure it operated through the WoW switch - I think it was a completely separate system but I've forgotten the details as it's been 20 years since I last thought about it

conjecture, I know, but if the aircraft had already ‘landed’ (the bounce) perhaps the auto-eject system ‘thought’ that was it, and switched itself off? My limited knowledge of the system says that auto eject is almost instantaneous (quicker that the human brain) and he took a while to go. Main engine still going and drove the jet round on the grounded wing tip. Good presence of mind to wait. Reminds me of Bill Langworthys Jaguar episode. Disconnenected PFCU led to rapid rolling on take off. He said after, he waited till he saw brown for the second time.

[Janner200]

If the lift fan drive fails forward of the LP compressor, the power from the LP turbine is no longer being absorbed by the lift fan and the excess power will instantaneously accelerate the LP compressor supercharging the core. The engine control will respond to the failure but even if it chopped the fuel immediately the exhaust nozzle thrust would take longer to respond.

Whether it was pilot initiated or automatic it was an amazing escape.

[Thrust Augmentation]

Is it not a bit early to be pointing the finger at the lift fan - for all we know this operated as expected, but the engine did not?

Since seeing the 1st images of shipboard testing on USS Wasp, I've always though the the front gear simply wasn't designed with consideration to the task in hand. It looks more like you would expect to find on a ground based aircraft, not from something that may have to dump itself onto a heaving & pitching deck with bringback (possibly). Is praiseworthy bringback a thing with VL or only SRVL?

[Auxtank]

So is the pilot aware there is going to be an auto-ejection (I suspect not) ? If no then how does the system protect against injury to arms and legs?

It's one of the first things - if not THE first - to happen in the ejection sequence. The arms and legs are brought in tight to the chair by restraints.

[oldmansquipper]

Is it not a bit early to be pointing the finger at the lift fan - for all we know this operated as expected, but the engine did not?

Since seeing the 1st images of shipboard testing on USS Wasp, I've always though the the front gear simply wasn't designed with consideration to the task in hand. It looks more like you would expect to find on a ground based aircraft, not from something that may have to dump itself onto a heaving & pitching deck with bringback (possibly). Is praiseworthy bringback a thing with VL or only SRVL?

conjecture….it’s what we do. 😉

[212man]

Is it not a bit early to be pointing the finger at the lift fan - for all we know this operated as expected, but the engine did not?

Since seeing the 1st images of shipboard testing on USS Wasp, I've always though the the front gear simply wasn't designed with consideration to the task in hand. It looks more like you would expect to find on a ground based aircraft, not from something that may have to dump itself onto a heaving & pitching deck with bringback (possibly). Is praiseworthy bringback a thing with VL or only SRVL?

Well, clearly soon after the bounce, there is a large dissymmetry of thrust between the front and rear, with the aircraft attempting to turn upside down. So discussion about the forward lift fan seems entirely reasonable. But I suspect that was a consequence of the hard impact.

[JohnDixson]

212, I read that the 35B is the stol/vertical landing version, hence one would assume the gear is designed to 12 fps, and looking at the video, I’m going to guess it was 6-8 fps. The bounce might have resulted as a result of either the design of the gear oleo valving, or the pilot not reducing power at touchdown or a mix-hard to say definitively. Example of what some other vertical lift aircraft do:
1, At design weight, and 10 fps ( design for this aircraft ) the Army UH-60 will bounce just like this F-35B video. ( No power ( i.e. collective stick ) reduction at touchdown.
2. At design weight and 12 fps. The Navy SH-60B will not bounce, but “squash” down on the gear ( good design too- as the USN had us doing that on a 9 degree slope to replicate a tossing frigate situation ). This gear has very different oleo porting than the Blackhawk.
So, that this 35B bounced may/may not be a factor in dissecting what happened and why.

[212man]

212, I read that the 35B is the stol/vertical landing version, hence one would assume the gear is designed to 12 fps, and looking at the video, I’m going to guess it was 6-8 fps. The bounce might have resulted as a result of either the design of the gear oleo valving, or the pilot not reducing power at touchdown or a mix-hard to say definitively. Example of what some other vertical lift aircraft do:
1, At design weight, and 10 fps ( design for this aircraft ) the Army UH-60 will bounce just like this F-35B video. ( No power ( i.e. collective stick ) reduction at touchdown.
2. At design weight and 12 fps. The Navy SH-60B will not bounce, but “squash” down on the gear ( good design too- as the USN had us doing that on a 9 degree slope to replicate a tossing frigate situation ). This gear has very different oleo porting than the Blackhawk.
So, that this 35B bounced may/may not be a factor in dissecting what happened and why.
I agree the vertical speed does not look to be outside of certification criteria, but the dissymmetry event appears after the bounce so it’s hard to imagine they’re not related. Unless, the pilot was aware something was going awry higher up and trying to land more quickly than usual.

[SATCOS WHIPPING BOY]

Is it not a bit early to be pointing the finger at the lift fan - for all we know this operated as expected, but the engine did not?

Since seeing the 1st images of shipboard testing on USS Wasp, I've always though the the front gear simply wasn't designed with consideration to the task in hand. It looks more like you would expect to find on a ground based aircraft, not from something that may have to dump itself onto a heaving & pitching deck with bringback (possibly). Is praiseworthy bringback a thing with VL or only SRVL?

But the nosewheel survived the heavy landing, it was the nose down crash that wiped it out.

[212man]

But the nosewheel survived the heavy landing, it was the nose down crash that wiped it out.
exactly. Totally outside of any design/envelope criteria

[SATCOS WHIPPING BOY]

Importantly, have we heard if the pilot is OK. Judging by the timings (11 seconds from nose in to eject) I say he made the decison to leave rather than the computer, so hopefully he was correctly braced to eject.
From what I see, well done MB.

[Arm out the window]

I can't figure out why there wasn't an immediate throttle chop once it started pushing itself around on the ground. I'd reckon it'd be the instinctive and sensible thing to do, a bit like dumping the collective in a helicopter at the onset of ground bounce. Anyway, pilot report to come and no doubt some interesting insight on what actually happened and what options were apparent and available.

[megan]

Being reported - Lockheed Martin’s F-35 production line is located at Air Force Plant 4, an Air Force-owned facility adjacent to Naval Air Station Joint Reserve Base Fort Worth. The accident aircraft, which Lockheed Martin has not yet transferred to the U.S. government, was reportedly being flown by a government employee on a test flight.

[SpazSinbad]

FkCO8elWIAAAjue.jpeg (1362×923) (usni.org) (https://news.usni.org/wp-content/uploads/2022/12/FkCO8elWIAAAjue.jpeg) & F-35B Joint Strike Fighter Crashes in Texas, Pilot Safely Ejects - USNI News (https://news.usni.org/2022/12/15/f-35b-joint-strike-fighter-crashes-in-texas)
"...The pilot ejected safely, according to the statement. The pilot was a U.S. government employee, Pentagon Press Secretary Brig. Gen. Patrick Ryder said during a Thursday press conference. The plane had not yet been transferred to the U.S. government, Ryder said...."
https://cimg6.ibsrv.net/gimg/pprune.org-vbulletin/1654x1020/f_35boffpiste16dec2022_557007a4987c652d5e637f822549120500dd8 105.jpg

[trevelyan]

Looks like he waited until it was upright, I wouldn’t think ejecting sideways on the ground would end well ?

With you on that - wings level and pull. Not always that simple but worked well in this instance. Glad the seat did its job, incredible piece of engineering.

[PDR1]

Is it not a bit early to be pointing the finger at the lift fan - for all we know this operated as expected, but the engine did not?

Simple observation. The aeroplane bounces and is in a stable hover when suddenly it pitches violently nose-down, rotating about the rear nozzle. The engine is clearly still producing thrust and the rear nozzle stays at the same height (not rising or descending) until other factors intervene. This is extremely unlikely to be a reaction controls issue. The sudden removal of support from the lift fan is the explanation which fits the observed dynamics. Whether this is due to a transmission failure (clutch, shaft, gearing etc) or some misadventure in the control shuttering is something the investigation will discover. There was no sign of mechanical distress from the fan prior to or during the pitch-down - no thrown debris etc, so it's unlikely to be mechanical break-up in the fan itself. The high pitch rate would (in my view) tend to point to the transmission failure because I don't think even full uncommanded shuttering could achieve that sort of response.

The inability to shut down the engine is possibly a separate, and more concerning, issue. AIUI in the hover the F35B only has digital throttle due to the need to maintain synchronisation between nozzle and fan thrust - there is no "manual fuel control" option. This would tend it suggest the software was still commanding thrust even after we assume the pilot had closed the throttle, right up until the ejection sequence cut the fuel. Why this happened needs to be understood as quickly as possible as it has other ramifications[IMHO].

PDR

[Saintsman]

It's one of the first things - if not THE first - to happen in the ejection sequence. The arms and legs are brought in tight to the chair by restraints.

It's been while since I've seen a modern ejection seat, so is it the case that the arms are now retrained upon ejection?

[PPRuNeUser0211]

It's been while since I've seen a modern ejection seat, so is it the case that the arms are now retrained upon ejection?
Has been for quite a while depending on the type - faster types normally had them previously (Tornado being an example)

[Mogwi]

The SHAR had an engine "dump valve" which diverted fuel flow to filling a sump as soon as it got weight on wheels* to ensure that when it touched the deck it stayed firmly there rather than being light or bouncing regardless of what the pilot did on the throttle. From the look of that video F35 doesn't have a similar system, which surprises me. Lots of things in that video look a bit odd. The initial hover is stable, and the reconfiguration for vertical descent seems to be to schedule (tailplane trim change) - thedescent rate is a bit higher than I'd expect, although the attitude is constant suggesting it was under control. The touchdown was definitely on the firm side, but seemingly not beyond the energy dissipation range of the undercarriage. But the thrust seems to remain at the descent setting (ie thrust = weight) allowing the aeroplane to bounce where I would have expected it to be closed to a safe value.

Shortly after the bounce there then appears to be a complete failure of the forward lift fan with ensuing pitch-down, wiping out the nosewheel etc. But the think that REALLY surprises me is that the engine seems to be still running at a high-ish thrust setting right up to the point where the pilot bangs out, suggesting that engine wasn't responding to the throttle commands until the ejection sequence cut the fuel flow.

The lift fan failure is obviously a concern and its cause will need to be established. But for me the bigger concern would be why the engine continued to deliver thrust for so long. I can't believe the pilot didn't try to shut it down, so that could imply uncommanded throttle operation. That's a bit scary.

PDR

* not sure it operated through the WoW switch - I think it was a completely separate system but I've forgotten the details as it's been 20 years since I last thought about it


Well, this is news to me! No one ever mentioned a “dump valve” in the Harrier fuel system in all the 2000+ hours I spent flying it. The only “dump valves” to my knowledge were those used in the fuel jettison system - and one pilot proved that those were not wired through the weight-on-wheels switches - oops!

Perhaps I didn’t pay enough attention in groundschool.

Mog

[Droop Snoot]

Salute!

We have seen at least two nose gear collapses with the 35, and maybe there's a design flaw that can be fixed.

Gums sends...

Gums...

Great to see you here!

The nose gear sees a big load a a fairly odd angle... perhaps 10 degrees nose down. Could it be that the component of that load is not within the design limits of the gear?

DS

[Ridger]

Well, this is news to me! No one ever mentioned a “dump valve” in the Harrier fuel system in all the 2000+ hours I spent flying it. The only “dump valves” to my knowledge were those used in the fuel jettison system - and one pilot proved that those were not wired through the weight-on-wheels switches - oops! Perhaps I didn’t pay enough attention in groundschool. Mog

As an ex Harrier engine guy, this also surprises me! I'd be interested to see a schematic if one exists - it doesn't appear here: https://www.dowtyheritage.org.uk/content/dowty-group/dowty-fuel-systems/fuel-system-for-rolls-royce-pegasus-engine

[SpazSinbad]

Blue Sky OPS 26 Apr 2012 Mark Ayton "Mark Ayton spoke with Peter Wilson, a former Royal Navy Sea Harrier pilot and now STOVL lead test pilot at NAS Patuxent River... ...Some of the [test] vertical landings required extreme nose-down attitudes on the aircraft at various weights and phenomenal descent rates. Recounting the landings, Peter Wilson told AIR International: “I was trimming nose down to make the nose gear hit first rather than the main gear coming down as fast as I could, given the control law of the aeroplane. When the nose gear (underneath the pilot’s seat) hits first at that sort of descent rate it gets your attention because it’s a pretty heavy landing and a remarkable experience in the cockpit.”..." AIR International F-35 Lightning II http://militaryrussia.ru/forum/download/file.php?id=28256

[stilton]

I think the point being made isn't that the nosewheel failures are linked, but that the nosewheel may have an inherent weakness that needs to be addressed.



Indeed, though I don't think the automatic ejection system is what sent the pilot skywards on this occasion, as whatever parameters would have caused the seat to fire automatically were present some seconds before it actually fired. Suspect the pilot made the choice and ejected himself.


One other thing that’s apparent is the aircraft does touch down with some forward speed, not sure if that was intended by the pilot or perhaps a by product of a systems failure

[Fonsini]

My bit of pure speculation.

When the F-35B flight control system detects weight on wheels it immediately commands a series of vanes to close off the airflow to the lift fan thus cutting thrust immediately, this can be clearly seen in videos of the lift fan in operation. So there is no “throttling back”, the intake side of the fan (i.e. the top) simply cuts off the airflow.

That bit is established fact, now for the conjecture.

When the aircraft bounced 2 things would have happened, firstly the aforementioned vanes closed on contact, but when the flight control system almost immediately then detected weight being taken off the wheels (the bounce) it reverted to flight mode and throttled up the engine. The vanes on the lift fan would still be closing and couldn’t cycle that quickly. Thrust asymmetry, nose down pitch, wheel collapse, ejection.

That would be my guess, we could have a problem with the FCS being unable to adequately interpret a condition where the aircraft bounces on landing.

[hulahoop7]

Maybe PoW loosing a shaft was a blessing in disguise. Reading through this interesting thread, we might be seeing a situation emerge where a number of design issues need to be looked at in order to make the F35b sufficiently robust for CVRL. Perhaps now we will see an investigation that properly sorts issues and CVRL can proceed. Whereas if there had been a catastrophic incident this summer, CVRL might have lost backing.

[Uplinker]

On the video the sequence is:
~ descent
~ touch
~ bounce
~ aircraft ascends to about 5'
~ aircraft still in controlled horizontal hover - power clearly feeding to both fans
~ aircraft suddenly pitches nose down
~ nose hits ground

The newscaster states "the nose gear appears to snap off, sending that jet spinning out of control", but it was nothing to do with the nose gear - it obviously broke, but that was well after thrust from the front fan had gone.

Or maybe, thrust from the rear nozzle suddenly increased to cause the pitch down. Could that happen? There are white vapour emissions from the rear nozzle area during the descent - are these normal or possibly a hydraulic leak from the nozzle actuators?

Does the F-35 have an afterburner?

[H Peacock]

I’m tending towards a software issue where the bounce has confused the lift-fan shutter system! 😬

[Tarnished]

The puff of smoke out of the back end at about 15 feet leads me to conject that it may have ingested (there is a lot of sucking going on) a bird which has cause a partial loss of lift fan thrust, but insufficient loss of thrust to trigger the auto eject which is triggered on a sensing of high rate negative pitch. The pitch rate we see is not as high as I have been led to believe we would see if for example the lift fan drive shaft disintegrated. Maybe a bird did some damage.
In regards to the arm restraint question earlier, the Mk16US seat has arm, leg and head restraint (to protect from neck injuries while wearing the HMD)

[meleagertoo]

Playing the video in slomo shows that vapour/smoke is emanating from around the exhaust nozzle durng the last several metres of descent and increases considerably during the bounce which initially appears to be fully controlled. But then as the nose drops savagely and the aircraft rolls and yaws the really big burst of vapour/smoke appears instantly from under the rear fuselage roughly in line with the stbd main gear. However it does this before (only just before) that tyre touches the ground so is not rubber smoke, and is surely far too immediate intense to be tyre smoke anyway?
Something was coming apart in a big way in the power train imho, and was doing so some time before the first touchdown.

It would not surprise me in the least if next week we don't see all F35s grounded indefinately pending further investigation of the front fan/gearbox/driveshaft systems.

[gums]

Salute!

The F-16 net, sub section F-35, has excellent descriptions of the FLCS and the engine/fan logic depending upon 'mode" the pilot selects and then the "mode" that HAL selects, heh heh.

I highly recommend the King's subjects, that dominate posts here, dare to visit the F-16 net, f-35 forum. Some of the other forums are worth exploring, as well. Mog and other Harrier folks will enjoy the description of the vertical landing mode.

A few of us have posited that HAL got confused with the bounce, reverted to "flight" sub-modes, the fan had shut down and finally, the pilot initieated the ejection. A few of us have been looking at the WoW switch logic, but we all felt something did not work as expected.

Gums sends...

[Uplinker]

......Something was coming apart in a big way in the power train...........

Brilliant phrase ! :ok: :)

Could this, (abrupt and uncontrollable pitching down), happen to a Harrier, just out of interest?

[212man]

Brilliant phrase ! :ok: :)

Could this, (abrupt and uncontrollable pitching down), happen to a Harrier, just out of interest?
I stand to be corrected, but I doubt it. The Harrier forward nozzles use LP air whereas the F-35 uses a fan driven by a shaft. So anything affecting the thrust of the Harrier forward nozzles would probably be affecting the whole power unit. The F-35 could have front lift fan failure modes that still allow the deflected exhaust to produce significant thrust. My take on a simple understanding of the two power systems.

[Mogwi]

Correct! Thrust is equally distributed between front and rear (cold and hot) nozzles in the Harrier. Donk stops and you go straight (and level!) down +/-. A failure of one reaction control can give a hard-over in pitch or roll, with fatal results but has only (to my knowledge) happened once.

All 4 nozzles are connected by very large bicycle chains which lock them in sync, so that differing nozzle angles are not possible. Simple but very effective system. No effin great intake doors, whizzing fans or bendy rear ends sight.

Mog

[H Peacock]

The Harrier has certainly suffered from nozzle failures in the past, although not sure if it was whilst in the hover. I believe initially the front nozzles were fibreglass before being redesigned. The Harrier’s nozzles are also much nearer to the CofG, so any change of moment from an individual nozzle failure is likely to be less than the F35; however, the loss of a 1/4 of the summed lift vector is probably still going to result in an accident!

[212man]

All 4 nozzles are connected by very large bicycle chains which lock them in sync, so that differing nozzle angles are not possible. Simple but very effective system. No effin great intake doors, whizzing fans or bendy rear ends sigh

I was going to use the phrase “agricultural” but feared it might cause offence!

I also noted the C of G element but tired eyes tapping an iPhone drove me to brevity.

[PDR1]

I may be wrong, but IIRC the GRP front nozzles were only used on the P1127/Kestral; one came off while exploring supersonic dives so they were replaced with metal nozzles from the Harrier GR1.

PDR

[gums]

Salute!

All of the Harrier technology and procedures and such are not relevant to the F-35 when it is landing in one of the modes where the fan is running and all those doors are open and the engine nozzle has swiveled to provide upward thrust.

Great to hear a revue of all the Harrier stuff, but the F-35 is in another universe. I personally know a Harrier pilot, and have been briefed about landing the beast, so not a pure armchair commentator.

Go to the F-35 forums on F-16 dot net and others to get a good understanding of how the thing is supposed to work.

Gums sends...

[Jhieminga]

I haven't been able to read up on the F-35's systems, but doesn't it use some convoluted control laws that have the stick controlling altitude in hover mode or something like that? In that particular mode... what can you actually do with the throttle to influence a situation such as this? Can you shut the engine down quickly if needed? The only relevant Harrier is the VAAC one I guess...

[NoHoverstop]

I haven't been able to read up on the F-35's systems, but doesn't it use some convoluted control laws that have the stick controlling altitude in hover mode or something like that? In that particular mode... what can you actually do with the throttle to influence a situation such as this? Can you shut the engine down quickly if needed? The only relevant Harrier is the VAAC one I guess...

The experimental (rear) cockpit (RC) in XW175 didn't have authority to shut down the engine; flight idle was the min the experimental FCS could do, based on the physical limit of travel of the throttle servo. We had a debate once about how to shut down the engine in the case where the aircraft Captain (Safety Pilot in the front cockpit) couldn't do it. Following earlier debates, we'd added a wire-locked (copper wire) switch in the rear cockpit that told the FCS "Independent Monitor" (IM) hardware/software to ignore all the carefully set-up limits. This was so that if the SP was out of action, whoever was in the RC (not always a pilot and frequently not a Harrier pilot) could have a bash at landing using whatever assortment of software and hardware was set-up for the RC at the time, without the IM suddenly deciding to disengage the FCS at an inconvenient moment. If the SP came round, he could always take control (front cockpit disengage switches didn't use software), but otherwise the heroic RC occupant would land it, get the engine to idle and then worry about how to stop the engine. The view was that this could be a job for the airfield fire service.

Not relevant to this F-35B incident, in which it isn't really possible to say from the video what happened except that something went wrong. It's fun reading all the (wrong) theories though. :ok:

[gums]

Salute!

PLEASE, go to the f-16 net I referenced and read two or three descriptions of the flight control laws once the pilot hits the landing mode button.

In short, the throttle doofer does not have a cutoff...engine shuts off with a switch.

Second, in the vertical landing mode the throttle thing, aka cow pie, works like this: push forward to move plane forward, move back to slow or go in reverse. The side stick commands up and down and left right movement of the plane.

Please go read all the details at the other forum.

Gums sends...

[SpazSinbad]

F-35B STOVL Control & VLs Explained

https://www.youtube.com/watch?v=1JMNWQQfMM8

[Jhieminga]

Thanks, that refreshed my memory on the unified control concept. Getting into speculation about what the computer or the stick actuator did or did not do will not get us anywhere but I wonder what will emerge from the investigation in due course.

[Thrust Augmentation]

Is a vertical touch & go even possible in the aircraft?

I'm struggling to see another video of an F35B hitting the deck & then becoming airborne again, everything I see follows the same sequence of touchdown & throttle down, the process seems so consistent that it may be automated after WOW. Sensor, processing or software glitch possibly "Fan - start the shutdown sequence" & "Engine - give it plenty"?

[Timelord]

But was it a vertical landing? It looked to me as if it had some forward in it leading to a bit of a rolling landing which I presume is slightly different for the software sequences.

[mickjoebill]

How far away is an ejection seat which can activate at angles close to horizontal at low level and then steer itself to a safe parachute deployment altitude?
​​​​​​

Mjb

[OK465]

How far away is an ejection seat which can activate at angles close to horizontal at low level and then steer itself to a safe parachute deployment altitude?

about 3500 miles:


https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/590x350/russia_map_london_moscow_1266620_f05e48c98dd21b7dfc45eb4c2b5 1b423c57b66fd.jpg

​​​​​​​

[gums]

Salute!

Yeah, Okie, those Russian seats have shown in more than one airshow how good they are. I also felt very comfortable in the ACES2 seat in the Viper.

Gums sends...

[stilton]

Thanks, that refreshed my memory on the unified control concept. Getting into speculation about what the computer or the stick actuator did or did not do will not get us anywhere but I wonder what will emerge from the investigation in due course.


I remember John Farley discussing the differences between the Harrier and the F35B, he seemed impressed with the pilot friendliness and simplicity of the vertical landing system in the latter but concerned about the mechanical complexity of the system and it’s vulnerability to failure

[SpazSinbad]

Did the magnificent John Farley fly the F-35B? He flew the VAAC Harrier version? Anyhoo this is how it goes ashore. Complexity is the job of the computer flight controls while the pilot positions the F-35B accurately according to F-35B pilot reports with failure modes in STOVL flight also taken into account but what caused the accident under discussion - I have no idea. F-35B Vertical Landings FCLP USMC

https://www.youtube.com/watch?v=HKSMtnx31oo

[SpazSinbad]

A V/STOL FLIGHT CONTROL JOURNEY ENABLED BY RAE SCIENTISTS John Farley 2006
"...it was clear to me [John Farley] that the eventual aim of the scientists was to hand over control of the aircraft to a computer leaving the pilot just to tell that computer what manoeuvre he wanted it to fly. If this happened it would mean the Harrier pilot’s nozzle lever would no longer be needed because control of the nozzle angle – as well as everything else that the pilot hitherto controlled – would be left to the computer...."
&
“…UNIFIED. Unified was the most radical mode. Here the pilot pulls back on the stick to go up and pushes to go down, regardless of airspeed. At all speeds above 40 kt ground speed the stick commands flight path rate and so relaxing it to the centre position when the aircraft is flying level maintains height. If the aircraft is in a climb or a dive, relaxing the stick maintains the existing climb or dive flight path angle. As the aircraft decelerates through 40 kt the stick response blends to become a height rate control by 30 kt ground speed so, in the hover, with stick centre commanding zero height rate, it appears to the pilot as a height hold.

When flying up and away lateral stick commands roll rate. This blends between 130 and 100 kt to become a closed loop roll attitude control, so that relaxing the stick to centre below 100 kt commands wings level. Above 40 kt ground speed the rudder pedals command sideslip. Decelerating below this speed the pedals blend to a yaw rate command by 30 kt, providing a heading hold in the hover with feet central. A throttle-type left hand inceptor, incorporating two detents, commands longitudinal acceleration.

Putting the inceptor in the centre detent holds the current speed. Acceleration or deceleration is selected by moving the lever forward or aft of the detent, with full travel demanding maximum available performance. Decelerating through 35 kt ground speed starts a blend and below 25 kt the aft detent commands zero ground speed. Either side of the aft detent gives the pilot a closed loop control of ground speed up to 30 kt forwards or backwards. In summary, if the pilot centres both the stick and throttle when flying on the wings, the aircraft holds the existing speed, bank attitude and climb or dive angle. In the hover, centralising everything maintains the existing hover height, position and heading. Such hover characteristics are the stuff of dreams for every Harrier pilot at the start of their conversion.…”
http://www.rafmuseum.org.uk.nyud.net/documents/Research/RAF-Historical- Society-Journals/Journal-35A-Seminar-the-RAF-Harrier-Story.pdf
______________

VERTICAL LEAP Richard Scott Feb 2020 "...JOHN FARLEY AND VAAC...
...the first thing you have to decide is what you want to put your hands and feet on in a ‘jump-jet’ — and various other changes. What they finished up with, which has now gone into the F-35, is a left-hand inceptor which slides backwards and forwards and looks a bit like a throttle. It isn’t a throttle; it tells the aircraft, ‘I want to go slower or faster’. Put it in the detent in the middle, and it says, ‘Hold the speed I’m at’. Put it in the detent in the middle, and it says, ‘I want you to hover’. The right hand is operating a little sidestick, and with that you’re indicating whether you want to go left, right, up or down”. As Farley concluded admiringly, “It completely deskills the whole operation.”
Ben Dunnell AEROPLANE Magazine February 2020, Issue No 562, Vol 48, No 2

[SpazSinbad]

"The US16E Seat interfaces with Lockheed Martin's auto-eject system (F-358 STOVL) which caters for low-altitude, low-speed and adverse pitch attitude escape conditions" MB PR

Synopsis of Lecture to RAeS Loughborough Branch on 08 Mar 2011 - Martin-Baker: the JSF story so far by Steve Roberts, JSG IPT Lead, Martin-Baker Aircraft Company Ltd http://homepage.ntlworld.com/john.ollerhead/RAeS/Past_lectures_files/110308%20JSF%20seat.pdf

“...The ejection seat was required to be common to all three aircraft variants. It was also required to have superior ejection performance to all previous seats, meet new neck injury criteria and provide an auto-ejection capability when used in the F-35B (STOVL) aircraft. The last requirement demanded early firing of the ejection seat in the event of an aircraft malfunction in a manner similar to that used in the Russian YAK 36, 38 and 141 aircraft....

...The F-35-B (STOVL) aircraft has additional failure modes associated with Lift Fan, Vane Box, Lift Fan Drive Shaft, Roll Duct and Turbine failures. A typical pilot takes two seconds to react to the ejection klaxon or one second if warned in advance of a likely failure. In the case of a STOVL related failure, ejection must take place within 0.6 seconds. Hence it was necessary to install smart failure sensors on the aircraft to automatically fire the ejection circuit mounted in the back of the seat....”

[safetypee]

For those who wish to read more on VAAC and FBW in general, there is very good book by Gerry Shanks (RAE) - "The Challenges of Fly-By-Wire", the role of the Royal Aircraft Establishment (Bedford and Farnborough).
Starting with the 'Flying Bedstead' though to VAAC leading to the F35.

There is a good description of the principles of the Two-Inceptor control system, Unified and Fusion concepts. It is interesting to note the the final choice was biased by pilots viewpoint, particularly Harrier vs non Harrier. As JF noted above, flying an (old) aircraft, or controlling a computer which flys the aircraft. There were similar debates about VTO aircraft from the SC5 onwards.

There is complementary book by Brian Weller 'The History of the Fly-By-Wire Jaguar'. It's technical views relate to the design of a FBW system without any manual reversion, and thence control of an highly unstable aircraft; including pilot viewpoints.


Wrt the F35 accident it appears that there was a lack of 'up' thrust from the fan.
Seeking more understanding, does the F35 hover control have pitch-attitude stabilisation, if so by what means; can the attitude be adjusted manually (slew / trim) or it is it pre programmed. Thence with a fan thrust malfunction, the stabilisation would attempt to apply more fan thrust to counter the nose down pitch change - maintain attitude, but not necessarily increase nozzle thrust.

and / or;

with perhaps natural pilot reaction, with Unified control - back stick would demand more thrust from both fan and nozzle, but only enough able to raise the rear end.

[SpazSinbad]

Boring vertical landings. :} USMC F-35Bs Vertical Landing aboard JS Izumo 03 Oct 2021

https://www.youtube.com/watch?v=u_s2wpqj6xo

[safetypee]

Spaz, the video illustrates my question above.

If the 'stick' controls up and down - 'throttle' controls fore and aft; then how is the constant pitch attitude maintained.

[Fortissimo]

If the 'stick' controls up and down - 'throttle' controls fore and aft; then how is the constant pitch attitude maintained.

Based on the previous descriptions in the thread, the pitch attitude will be commanded by the FBW system and achieved by managing the output from one of the two downward thrust sources. It would be a reasonable guess that the attitude will be aimed at putting all 3 wheels on the deck at the same time. Perhaps an F-35 driver can enlighten us if this is wide of the mark.

[SpazSinbad]

Spaz, the video illustrates my question above.
If the 'stick' controls up and down - 'throttle' controls fore and aft; then how is the constant pitch attitude maintained.
POST 69 Video Wizzer Wilson explains the aircraft computer controls the F-35B in hover with the pilot just accurately positioning it.

https://www.youtube.com/watch?v=1JMNWQQfMM8

[SpazSinbad]

Eleven [out of 33] F-35 fighters grounded after US crash 25 Dec 2022 https://www.jpost.com/breaking-news/article-725763 "...the IDF (https://www.jpost.com/opinion/article-725711) and Lockheed Martin, who manufactures the F-35, pointed out that it is not certain that the Israeli F-35A has the same problem. Rather, they emphasized that the grounding, which only applies to 11 aircraft out of a much larger fleet of F-35s and other planes, was taken as a precaution...."

[gums]

Salute!

To answer the question about pitch attitude, I'll describe short as I can what I saw here when the Bee did a go around from an approach with all the doors open and what looked like normal pitch maneuvering. Was #3 behind an A and a C. So my guess is the flight was a demo for some brass.

The A and C landed and the Bee went up to downwind just like a normal plane with all doors open. It turned base and flew to the runway just like basic planes do, and at 100 feet or so leveled, slowed and went into a hover. Plane maintained perfectly level and the pilot rotated the heading 90 deg one way then back. Once more go around after it gained speed and this time came in a bit slower than I suspect a normal landing would be and with minimal flare plopped onto the runway, then turned off after about 300 feet or so.

So the part about the control laws blending in and out according to the speed seems to describe what I saw that day.

Gums sends...

[SpazSinbad]

Pentagon grounds some F-35s after ejection on Texas runway

Pentagon grounds some F-35s after ejection on Texas runway (defensenews.com) (https://www.defensenews.com/air/2022/12/27/pentagon-grounds-small-group-of-f-35s-after-ejection-on-texas-runway/) 28 Dec 2022
"...A source familiar with the program, who spoke on the condition of anonymity because they were not authorized to discuss details of the incident, said the JPO’s initial assessment found that a propulsion system issue led to the Dec. 15 crash of the hovering F-35B, which has now led to broader groundings in the fleet. The source said that, in guidance to the services, the JPO said a failure of a tube used to transfer high-pressure fuel in the fighter’s F135 engine prompted the office to update its safety risk assessments. The JPO also told the services that jets with fewer than 40 hours of flying are affected, this source said...."

[Stuff]

Israel have apparently grounded their F-35As as a result of the Fort Worth crash so whatever went wrong might not be isolated to the B model.

https://eurasiantimes.com/us-israel-grounds-f-35-stealth-fighters-after-f-35b-crash-in-texas/

[gums]

Salute!

Rumor on the street over in the States is a problem with a fuel line or other component that is pressurized and has several functions. Remember, this is "rumor network". So could be a component they are looking at that is common on the engine, regardless of the A,B or C.

Gums sends...

[tdracer]

Salute!

Rumor on the street over in the States is a problem with a fuel line or other component that is pressurized and has several functions. Remember, this is "rumor network". So could be a component they are looking at that is common on the engine, regardless of the A,B or C.

Gums sends...
Seeing the same reports as gums - high pressure fuel line on the engine (likely part of the fuel control - e.g. FADEC).
BTW, saw an article yesterday that said the "aircraft ejected the pilot". Now, given the accuracy of reporting, I'm inclined to take that with a grain of salt. But if it is in fact correct, it would suggest the ejection was automatic, not commanded by the pilot.

[RAFEngO74to09]

Lots of new still photos in this video F-35s Grounded Again Following Ft. Worth Crash - YouTube

[megan]

Interesting cloud of smoke at 1:50 in the above video, wonder what it might infer.

[SpazSinbad]

Reason for the swift descent? :} Smoke gets in your eyes.

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/1095x699/f_35bhoversmokecrashlater_f4643409c0298e446cd188dec57e27cb8a fa05cd.jpg

[Compass Call]

Never realised that the canopy was built in two pieces.

[SpazSinbad]

Probably not here now but anyway: http://www.flightglobal.com/blogs/the-dewline/Birdstrike%20Impact%20Studies.pdf

https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/1624x1050/f_35variantscanopydesign_07c2a886d5a8debd5efdb3ba5f46faeaa43 e2310.jpg

[Compass Call]

SpazSinbad
Thanks for the info.

[Video Mixdown]

Never realised that the canopy was built in two pieces.
I thought it was a one-piece moulding that is cut in half (by MDC?) during the ejection sequence.

[tdracer]

Reason for the swift descent? :} Smoke gets in your eyes.


Not familiar with the specifics of the F135 engine, but it's standard design practice on jet engines that the high-pressure fuel doesn't only go into the burner - it's used as muscle for various actuators such as variable vanes and bleeds, etc. - so lots of fuel lines snaking their way around the engine. Typical pressure downstream of the fuel metering unit is around 300 psi - so any crack in a fuel line is going to result in a large fuel leak - not only do you have a big risk of fire if a line fails, you lose muscle pressure to the various actuators. In other words, bad things are likely to happen.
Smoke (or flames) is a pretty common indicator...

[SpazSinbad]

I thought it was a one-piece moulding that is cut in half (by MDC?) during the ejection sequence.
Pictures always better than words that are not specific enough probably. Pic no longer at this URL so posted here to show canopy with MDC on the F-35A. There is the canopy metal bowframe [that is integrated with the canopy - I guess this is a cause for confusion - X-35A had a TWO piece canopy] in front of the pilot and the canopy as visualised in the previous - above - image graphic. http://www.jsf.mil/images/gallery/sdd/f35_test/a/sdd_f35testa_100.jpg

Quote from previous graphic: F-35 Canopy Design Description 2009 LM
- Transparency is Single Piece Formed & Stretched Acrylic
- Thick Windscreen is Fwd of the Bowframe & Transitions to Thinner Transparency Section Aft
- CTOL & CV Canopy Designs are Common & Windscreen Design is Tri-variant Common
- Flexible Linear Shape Charge Bonded to IML [Inner Mould Line] to Facilitate Pilot Escape
http://www.flightglobal.com/blogs/the-dewline/Birdstrike%20Impact%20Studies.pdf [no longer there]

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/1680x1050/f_35acanopyabove_40a9377f0bb231fe2aa9664f5fee52e1b9e99f13.jp g

[Rigga]

Reason for the swift descent? :} Smoke gets in your eyes.

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/1095x699/f_35bhoversmokecrashlater_f4643409c0298e446cd188dec57e27cb8a fa05cd.jpg

The smoke also appears forward of, and external to, the jet pipe - so could come from anywhere inside the airframe. I would suspect the fan drive system from the meagre evidence so far.

[SpazSinbad]

Not familiar with the specifics of the F135 engine, but it's standard design practice on jet engines that the high-pressure fuel doesn't only go into the burner - it's used as muscle for various actuators such as variable vanes and bleeds, etc. - so lots of fuel lines snaking their way around the engine. Typical pressure downstream of the fuel metering unit is around 300 psi - so any crack in a fuel line is going to result in a large fuel leak - not only do you have a big risk of fire if a line fails, you lose muscle pressure to the various actuators. In other words, bad things are likely to happen.
Smoke (or flames) is a pretty common indicator...
F-35 Air Vehicle Technology Overview 2018 LM people
"...The F-35B 3BSM consists of a STOVL LOAN and a three-bearing swivel mechanism. The mechanism can deflect the exhaust flow through 95 degrees in the pitch axis and ±12.25 degrees in the yaw axis as a function of pitch angle. The 3BSM can vector up to 23,900 pounds of thrust at the maximum rearward thrust split. The 3BSM forward (No. 1) bearing is powered by twin fueldraulic actuator motors through a gearbox and drive train. The middle (No. 2) bearing is likewise powered by a twin fueldraulic actuator motor and gearbox/drive train system. A transfer gearbox links the middle and aft (No. 3) bearings with an efficient, compact, epicycle gear train. The twin actuator motors on the No. 1 and Nos. 2 and 3 bearings, respectively, are designed with a fail-degraded capability (full torque, half rate).This is one of the key differences between this design and that of the X-35B. In the X-35B, the Nos. 2 and 3 bearings were braked following a first failure, with no ability to continue vectoring the aft thrust post. This did not satisfy operational requirements requiring an ability to perform a shipboard vertical landing following a first failure. The dual redundancy on the fueldraulic motors enabled that fault tolerance on the F-35B...."
https://www.lockheedmartin.com/content/dam/lockheed-martin/eo/documents/webt/F-35_Air_Vehicle_Technology_Overview.pdf

[SpazSinbad]

03 Jan 2023 John A. Tirpak | "...An Air Force spokesperson said that a “small number” F-35As in USAF service are grounded until a technical compliance/technical directive is completed. While she did not provide details, a TC/TD usually means that a part or system must undergo inspection, and if a problem or faulty part is found, be replaced. A government source said the problem seems to be engine-related, and so far, only jets with “a few dozen” flying hours or less are being inspected for the problem. “The scope and duration” of the effect on the USAF F-35A fleet “are to be determined based on additional ongoing analysis,” the Air Force spokesperson said. She did not say how many F-35As are affected, or whether they are in a single unit or dispersed across the combat air forces.” https://www.airandspaceforces.com/30-billion-f-35-deal-will-see-prices-rise-deliveries-dip/

[SpazSinbad]

New F-35 engine deliveries suspended amid ongoing investigation 05 Jan 2023
"WASHINGTON — The U.S. military and defense contractor Pratt & Whitney have suspended deliveries of new engines for the F-35 fighter in the wake of a December mishap on a Texas runway. The F-35 Joint Program Office said in an email to Defense News that the delivery of new F135 engines was paused Dec. 27, after what the JPO described as a “mutual agreement” involving itself, the Defense Contract Management Agency and engine-maker Pratt & Whitney....
...The JPO said in a statement last week to Defense News it had issued guidance restricting some higher-risk aircraft from flight operations while the investigation continued. The JPO later revised its statement to say it had recommended the flight operation restrictions until procedures are developed for their return to flight...." https://www.defensenews.com/air/2023/01/04/new-f-35-engine-deliveries-suspended-amid-ongoing-investigation/

[SpazSinbad]

Fix coming for F-35 engine problem that froze fighters’ deliveries 11 Feb 2023
https://www.defensenews.com/air/2023/02/10/fix-coming-for-f-35-engine-problem-that-froze-fighters-deliveries/

[megan]

From Aviation Week

The F-35 Joint Program Office (JPO) has issued a directive recommending that all Pratt & Whitney F135s powering the global fleet of Lockheed Martin F-35s be retrofitted within 90 days with a fix for a vibration problem that caused an aircraft to crash on Dec. 15.While no flight restrictions are included, the JPO Time Compliance Technical Directive (TCTD) instructs immediate compliance “for the small number of aircraft that were restricted from flight.” No details have been released about what the retrofit involves, although the JPO says it can be performed “at the operational level and can be completed in 4-8 hr.”

Pratt & Whitney developed the retrofit procedure to mitigate harmonic resonance that was uncovered as the likely cause of the December mishap, which involved an F-35B during a predelivery check flight at the company’s Fort Worth production site.

Described by the engine-maker as an extremely rare phenomenon, the vibration problem is potentially common to the F135 variant powering the F-35B short-takeoff-and-vertical-landing model as well as the versions powering the conventional-takeoff-and-landing F-35A and F-35C models. Jennifer Latka, vice president for F135 programs, says there were no differences in the build standard of the engine involved in the accident or in that of the other small population of aircraft affected. “And we can all say with certainty that it was not a manufacturing or quality issue,” she adds.

While only a small number of aircraft were affected by the harmonic resonance, “the plan is to retrofit the entire fleet, because the retrofit is inexpensive, nonintrusive and supports the JPO’s desire to maintain and manage a single configuration across the entire fleet,” the program office says. “The JPO will work with the military services and international partners to ensure understanding of the TCTD. The safety of flight crews is the JPO’s primary concern.”

The JPO said Feb. 24 that it had cleared Pratt & Whitney to resume delivering engines, but Lockheed Martin has yet to resume deliveries of new F-35s. More than 850 F-35s have so far been delivered globally.

[SpazSinbad]

It's been while since I've seen a modern ejection seat, so is it the case that the arms are now retrained upon ejection?
Graphics from from PAGE 25 & 26: Emergency Responder Familiarization Training - F-35 LIGHTNING II 2010
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/1680x1050/f_35ejectionseatarmrestraints_bd2409e2b1af68f3b81c176edfb188 2308ab4c5a.jpg


https://schultzairshows.com/wp-content/uploads/2020/05/usaf-f-35-emergency-extraction-card-2019.pdf (3.6Mb)

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/1680x1050/f_35ejectionseatlegrestraints_d1a27ba18426fd714fae597e6ed9d1 2213980c12.jpg

[Just This Once...]

The Martin-Baker arm restraints entered service in the early 1970s and were standard equipment on the Tornado from first flight (1974?). They have been adopted to many other types since then, including the current RAF fleet of Hawk T2, Typhoon and the aforementioned F-35.

You have to respect the forceful summer breeze:


https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/1200x800/tornado_no_canopy_7838c50c653dde658591b0c0d4b4dc783464f2a0.j pg