Hornet physiological issues increasing

The recent plague of physiological problems being seen by F-18 pilots is getting steadily worse. The problem was originally reported in 2010, as hypoxia events, similar to those that plagued the F-22 as it entered service. There has been no commonality found in the events to this day.

The Navy has a 62 person task force investigating the problem, which has spread to all models of F-18. The problem has gotten so bad that at least two carriers have installed hyperbaric chambers for crews that are exposed to a decompression incident.

The problem appears to be related to decompression incidents with the legacy Hornet fleet, and hypoxia events in Super Hornets and Growlers. Of 383 incidents investigated, 113 were related to contamination, 114 involved an ECS component failure, 91 were human related, and 50 involved an OBOGS component failure.

theaviationist.com...

a reply to: Zaphod58

Can you elaborate on what "contamination" is?

a reply to: introvert

It could be just about anything. Under certain conditions when they refuel in flight jet fuel can get into the system, a hydraulic or oil leak could get into the system, bleed air, etc. That's why it's so hard to track down.

a reply to: introvert

I am no expert, but I would assume that contamination refers to hydrocarbons or other poisonous elements ending up in the air supply to the pilot by some means.

a reply to: TrueBrit

Exactly. And there are a few dozen things that could do it.

a reply to: introvert

Basically, the way that a fighter's air-supply system works is like a fancier version of the CPAP mask that your uncle uses to sleep at night (more realistically, it's probably closer to the acute in-hospital CPAP system that your grandmother is hooked up to after she goes into flash pulmonary edema on Monday because she ate a bit too much ham at Easter lunch).

Like any CPAP system, there's an inlet through which it takes in air to compress and send to the facemask. I'd imagine that on an aircraft, especially an old one with leaks and such, that that inlet and the filters involved with it are
1: More prone to randomly clogging, at which point the pilot starts feeling lightheaded and turning the color of the girl who ate the bad bubblegum in Willy Wonka And The Chocolate Factory. This is that much more likely if the system uses chemical filters to concentrate Oxygen, as those are just as likely to clog at the Brita in your fridge.
and
2: More prone to start taking in various hydrocarbons that are leaking from elsewhere inside the aircraft as its fuel and hydraulics systems inevitably start to shed fluid after a quarter century worth of use. This also makes the pilot lightheaded for a bunch of much nastier reasons (have you ever smelled Sevoflurane, Desflurane, Isoflurane, or any other anaesthesia gas as it spills and starts vaporizing? It smells EXACTLY like brake cleaner or throttle body cleaner, because it's just another VOC. Volatile organics do nasty things to the brain, which is why they can zonk you out so hard that you have no recollection whatsoever of your surgeon digging around in your chest for three hours during your quadruple-bypass procedure. It's also why gasoline smells so good...). Furthermore, it also clogs up those filters and makes #1 that much more likely to happen.

So yeah, either of those aren't something that you want to have happen when you're behind the wheel of a $50 million aircraft the size of a tennis court with as much horsepower as a midsize airliner.

Looking at this issue and the F-22's problems, methinks there might not be as much medical oversight of pilot air-delivery systems as there probably should be.

a reply to: Barnalby

One of the less known problems with the probe and drogue refueling system is environmental contamination. With a boom, the probe is on top of the aircraft, while the probe is on the side of the aircraft, near the nose.

When you disconnect, regardless of system, there's a puff of fuel released. On a probe equipped fighter, that puff goes straight down the #2 engine intake. Then it goes into the environmental system.

What makes it worse is that it's not very hard to break the drogue and snap it off the hose. If that happens, fuel sprays out of the hose until the boom operator shuts the pumps off. All that fuel is going right down the intake.

a reply to: Zaphod58

I find it difficult to accept that there is not a better way to keep the air fed to the pilot, from EVER being anything less than perfectly clean. This is the twenty first century for goodness sake!

a reply to: TrueBrit

We almost never had issues when we just used LOX bottles. The problem is that you're limited to how much the bottle can hold, and have to have specialized equipment on hand to replenish each bottle.

a reply to: Zaphod58

Of COURSE they power it off of bleed air...

Especially on a pre-stealth design like an F-18, you would think the system would have its own dedicated air intake, though using bleed air probably saves weight.

And yeah, that sounds like bad news bears across the board. I'm still honestly pretty surprised that there were never plans to build a fighter-sized flying boom tanker out of the S-3 or the C-2.

a reply to: Barnalby

It saves weight and complexity to run it off bleed air.

The philosophy was that the Air Force needs a boom, because they have to pump obscene amounts of fuel into ridiculously large aircraft. The Navy doesn't need something silly like that, because everything that flies off a carrier only needs a small amount of fuel, relatively speaking. Anything they fly that needs large amounts of fuel, which requires a boom, is too big to fit on a ship, so it will be safely back away from where it will get shot at, with the tankers.

a reply to: Zaphod58

I hear that.

I think, however, that when you consider that the airframe, not to mention the pilots themselves, are put at risk by relying on through flow from the engines, especially in the event of a re-fueling error, or a less than snappy cut off after the tank is full, then you have to come around to the idea that no matter how much more complicated it might be, an independent and guaranteed clean air source is necessary!

It really does not matter how much more costly it is. The pilot is the only non-replaceable and utterly unique asset that a flying force can bring to bear. Keeping them alive and in as near to perfect condition as physically, not financially possible, ought to be the first priority of any aircraft design.

a reply to: Zaphod58

But nowadays, the fuel load of most navy aircraft isn't that far behind boom-fed designs from when that decision was made, and their newer, heavier airwing seems pretty thirsty to the point that the legs of aircraft like the Rhino are seriously in question. A KC-2 or KS-3 could fix that overnight.

a reply to: TrueBrit

At the very least, they need to have an emergency LOX bottle. Even if it's only like 15-20 minutes worth. Even that would be enough to clear the pilot's head, and in many cases, declare an emergency and land somewhere.

hrmm... dam that's scary.

And a serious problem.

originally posted by: Zaphod58
a reply to: introvert

It could be just about anything. Under certain conditions when they refuel in flight jet fuel can get into the system, a hydraulic or oil leak could get into the system, bleed air, etc. That's why it's so hard to track down.

Thanks for the clarification.

Two things:

1. In flight refueling. The drogue system also means the Navy can organically tank. I don't think anybody wants to jump into the back end of a Hornet and man the boom, so the ability to buddy tank and recover on the ship drives a drogue system.

2. There is an emergency LOX bottle in the ejection seat. Commonly referred to as the Green Apple. I think in the NACES/ACES seat, it's still a green ring under your left thigh. You can see it on this website. www.ejectionsite.com...

So there is an Oxygen bottle that can be used (I used mine in a T-45A once, not good times)

Sure hope they figure this one out. Single seat, no O2 = not good.

a reply to: cosmania

They need more than just that bottle IMO. The F-22 ended up putting a backup system to resolve their problems. They might have to look at doing something similar here. I haven't heard any reports about hypoxia events since they did.

Have they done a full set of tests on all parts of the system?It might be an Oring thats made of some bad stuff..Or is it something entering the system which is weird as most O2 systems are sealed.

a reply to: Blackfinger

The cockpit is pressurized, and pilots will fly with their masks off, especially on long flights, so they can eat and be comfortable. That means they're being affected by both pressurization, or environmental system problems depending on if it's a Bug or a Rhino/Growler.