Navy instructor pilots refusing to fly

a reply to: Arbitrageur

They could get a good start on replacing the filters if that's what they're going to try. They couldn't get all 197 done, but if they do it right, they'll start flying them as they are done and do a rolling start bask to flying status.

But if it's more than just the filter, another 48 hours won't do a lot, no.

Decent air is a tough thing to provide. It's easier in aircraft than it is in spacecraft, though. Spacecraft atmo systems are hell on wheels, more complex even than nuclear sub systems, which are a treat in themselves.

Zap, have they done carboxyhemoglobin tests on affected crew immediately after landing?

a reply to: Bedlam

I haven't heard everything they've done, but judging by the condition of some of the pilots after flying, they SHOULD have.

They had to pull a guy out of the cockpit the other day because he couldn't even climb out on his own.

originally posted by: Zaphod58
a reply to: Bedlam

I haven't heard everything they've done, but judging by the condition of some of the pilots after flying, they SHOULD have.

I'm not in those loops. If any of the guys in your extended contact group know, I'd be interested.

We had a few big issues with..um..self contained environment air, let's say, that caused non-stop problems. It's a different thing with an OBOGS setup but still, I'm wondering if there's a similar fix, especially considering they're probably using bleed air as a feed stock.

Navy contrives to fix some of these on subs by essentially 'incinerating' the air and then filtering the residue, that SORT of works, but causes other issues with the residue. For both space systems and the sub fleet, a lot of residual problems were solved by catalytically breaking VOCs, CO, and higher order oxygen allotropes. There was another issue with nitrogen oxides of various types, another catalyst stage for that, the whole thing ended up fairly compact although you need power and some heat sinking - one stage needs UV and another works better hot than room temperature. It was contrived to use the waste heat from the UV generator to provide some of the heat for the other stage but you still have to keep the temperature fairly stable for optimal function.

eta: the issues fixed included CO poisoning, you can spot that with a carboxyhemoglobin test, but oddly enough you need to do the draw RIGHT THEN or it'll look normal after - if you're in an environment where they're keeping the pressure low but the O2 level high to reduce nitrogen saturation issues, you'll see oxygen deprivation looking symptoms that resolve unusually quickly and don't leave a trace. Most medics think the CO will hang around because at STP it does, but the carboxyhemoglobin in space systems can leave the bloodstream faster than you expect because the environment ISN'T STP when you're breathing O2 mix and juggling the pressures up and down.

VOCs, nitrogen oxides and higher order oxygen allotropes can cause temporary alveolar changes that reduce gas exchange either by edema or by altering membrane chemistry, and they, too, can resolve faster than you'd expect although they tend to last longer. It's also mission duration dependent.

Are they seeing problems with wound healing with people on OBOGS systems using bleed air yet? That'll be an issue. The longer the flight, the worse the problem.

etaa: did they change the mask or hose design just before the issues started?

The Navy has extended the grounding indefinitely. They're allowing time for engineers to determine the cause and a fix.

www.foxnews.com...

a reply to: Bedlam

I'm still trying to find out about the tests. How immediate does it have to be?

I don't think they changed the mask or hose any. The concentrator and other parts of the system were changed, but there shouldn't have been a requirement to change the mask or hose on it.

I heard about a few problems along the lines of healing with the F-22s when they were having the big OBOGS problems. The biggest issue they thought they had was acceleration atelectasis.

a reply to: Zaphod58

Yeah, but why would you get AE on OBOGS but not O2?

Just idle curiosity about the mask design, you get dead air or too much blow by you can screw up the co2 levels.

They can instrument the ETCO2 to better spot when it occurs. A problem with this sort of thing is catching exactly when it starts.

a reply to: Zaphod58

Funny that this comes up now. jimstone has run an article about a training flight where an instructor was shot down by someobdy following him.

He makes the point that live amo is never used on training flights and witnesses on the ground say a flash and streakes of light go from the plane behind to the on in front and it immediately caught fire and crashed.

Link

a reply to: Azureblue

Yeah, that's BS. First, they DO use live rounds in training. Second, the F-16 wasn't shot down, it suffered a failure on takeoff, which happens.

a reply to: Bedlam

They think it was because the F-22 flies so high, pulling high Gs.

They are taking at least two aircraft to Pax River to tear them down and let the engineers take a look at them.

originally posted by: hutch622
a reply to: Zaphod58

Do these planes have any sort of warning system for contaminated air , seems to me that it would be pretty easy to have one .

yeah, and how about a separate small tank of oxygen built into the flight suit for when the main system fails.

a reply to: Bedlam

The dead air issue is a big one. I'm honestly shocked that modern masks don't have some sort of dual-lumen air supply tube with an intake/exhaust valve to prevent the pilot from re-breathing previously-exhaled CO2.

On a long enough circuit, that happens all too easily, especially when you talk about higher respiratory rates and lower tidal volumes, aka precisely what you'd expect to see in a pilot who is under either physiological or psychological stress.

a reply to: Zaphod58

I'd be more inclined to believe that explanation if we saw similar situations arise in earlier fighters operating at similar altitudes (the F-15, the Lightning) or at similar G-loads (any of the later Sukhoi's).

Even the atelectasis issue would be preventable with a system that is maintaining good CPAP/PEEP throughout the flight envelope.

My money would be on an issue with the ventilator circuit design or the pressurized air supply that was essentially un-replicatable outside of the altitude/temperature/G-load conditions in which it typically arose, making it essentially impossible to isolate and identify on the ground.

a reply to: Barnalby

The others didn't fly that high. They were at 60,000 feet pulling 7+ Gs. Nothing else went anywhere near that altitude.

originally posted by: Barnalby
a reply to: Bedlam

The dead air issue is a big one. I'm honestly shocked that modern masks don't have some sort of dual-lumen air supply tube with an intake/exhaust valve to prevent the pilot from re-breathing previously-exhaled CO2.

It also (more complexity!) needs to change depending on what's going on with the pilot in terms of METS at the time. In a closed system you need to have CO2, but not too much. Your capnic state can cause all sorts of ca-razy issues that look like weakness/disorientation. It's not so hard if you're in an open environment - you evolved for that - but when you're on a closed system like a Draeger rebreather or a flight O2 system where you're bottled up, it can cause subtle issues.

originally posted by: Barnalby
...making it essentially impossible to isolate and identify on the ground.

Um, 'someone I know' found it possible to play Spot The Issue by monitoring the ETCO. It gives you sort of summary data, but "the guy is no longer exchanging gases properly" is useful by itself, even if it doesn't give you the cause.

a reply to: Bedlam

When I hear "monitoring the EtCO2 readout" I feel uncomfortably close to my real work.

The data that waveform capnography gives you is so fantastic that it almost feels like cheating. When a "DURR, me fix patient!" critical care paramedic can tell you what you're doing wrong by reading a shark fin looking squiggle on a screen, it's just a testament to how powerful the tool is.

a reply to: Bedlam

We had a few big issues with..um..self contained environment air, let's say, that caused non-stop problems.

Mmmm... Do tell I'm listening with all ears Mr Bedlam.

originally posted by: thebozeian
a reply to: Bedlam

We had a few big issues with..um..self contained environment air, let's say, that caused non-stop problems.

Mmmm... Do tell I'm listening with all ears Mr Bedlam.

It's the same thing with nuclear subs. Incredibly nasty funk after a bit.