F-35 accident Fort Worth 15/12/22 - pilot ejected ok
In the unlikely event of the lift fan failing catastrophically the aircraft would pitch inverted in 0.6 seconds
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.
Another superb save by MB and another addition to our exclusive Tie club !
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?
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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)
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)
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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
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
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
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
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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.
Whether it was pilot initiated or automatic it was an amazing escape.
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?
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?
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.
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?
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?
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?
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?
Last edited by 212man; 17th Dec 2022 at 17:20.
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.
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.
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.
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.
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?
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?
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.
From what I see, well done MB.
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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.
