F-22 Grounded

[rondebmar]

Wel-l-l-l...back in the day...(when it was uphill both to and from the schoolhouse!)...our CV suffered a LOX factory failure...IIRC, was down for ~2 weeks ...flying missions up North about every day, seems like. CAG advised no pilot would be chastised for declining to fly...not one sortie ever canceled...and the sortie count remained high...

 

[MIDNJAC]

I always thought you guys had a great ECS. Ever notice that we always taxi with our canopies open? Ever wonder why? Our ECS is worthless on the ground.

The only in-flight ECS issues I've ever had were in the two seaters. One explosive decompression and numerous weak canopy seals in -406 two seaters during the windup turns on FCFs (40k').

Never had a legit O2 problem, either personally or as a witness.

Yeah our ECS sucks on the ground too in many aircraft....some of the later lot -D's got the upgrades that we sold to the Kuwaitis (better on deck cooling), but they still generally suck. Charlies/A+'s aren't as bad, but not a whole ton better. We taxi with our canopies closed because the USMC Hornet SOP says to. Anyway, my complaints are mostly with the in-flight capabilities (or lack thereof) of the system. I flew a particular jet 3 or 4 times in the last few weeks, and each flight it felt like my head was going to explode each time I went from idle back to mid range power.

 

[flaps]

not sure i understand...

...the properties of substandard oxygen.
if it's not 100% oxygen, what else is in it?
thx,
ed

 

[Harrier Dude]

...the properties of substandard oxygen.
if it's not 100% oxygen, what else is in it?
thx,
ed

Primarily nitrogen.

 

[Brett327]

Primarily nitrogen.

Umm... air?

Brett

 

[nittany03]

IIRC, OBOGS works by using an oxygen concentrator which adsorbs (yes, I spelled that right) nitrogen from bleed air after it's run through a heat exchanger. I always thought that the 5 percent was because if you subtract 70 percent nitrogen from air, you get roughly 95 percent O2 and 5 percent other stuff (CO2, etc). That said, I never delved into the topic beyond reading the T-45 NATOPS. Does OBOGS really leave N2 in the final product? Inquiring minds want to know, if anyone has better knowledges.

 

[Jim123]

Rotorhead here... let me make sure I have the general idea straight-

1) High altitude ambient air at nominally 21% oxygen/78% nitrogen but it is thin, low pressure air
2) OBOGS does its magic (scrubs most of the nitrogen by adsorption)
3) Now you have 90% oxygen
4) Figure in cockpit pressurization (which is important but only critical above altitudes of, let me guess, 40-50kft MSL?)

= You breathe fine and your body works normally (physiology, partial pressure, something about Dalton's Law from my high school chemistry, etc.)

Sounds good on paper assuming the details work out.

And the OBOGS malfunction hypoxia incidents are usually caused by... either contamination from something within the OBOGS or by inadequate oxygen concentration (rather inadequate nitrogen removal)?

 

[Harrier Dude]

I'm not a scientist. Just a NITROX diver (and a C student).

Air is primarily N2. If you try to distill it into pure oxygen, and don't get it to 100%, it stands to reason that what's left over is primarily nitrogen (which is basically air anyway).

 

[theblakeness]

the T-6 natops states that max concentration on the OBOGS gives 95% oxygen, 5% inert gas....whatever the hell that means. We are also prone to the fail warning if the mask is off with supply on.

 

[KBayDog]

the T-6 natops states that max concentration on the OBOGS gives 95% oxygen, 5% inert gas....whatever the hell that means.

Radon is an inert gas.

Just throwing that out there.

 

[Marine4life]

I've seen reports of all kinds of OBOGS issues in the Hornet community for years, but almost none in the AV-8B. Why? Are the systems that different?

Just had my ASTC refresh a couple of weeks ago, and was told that there is a significant difference in the design of the Hornet and Harrier's OBOGS systems, and that it is attributable to the number of hypoxia events in the Hornet vs the Harrier. That's ASTCs take on it.

 

[Brett327]

Radon is an inert gas.

Just throwing that out there.

And neither Nitrogen nor any of the other minor atmospheric components are technically chemically or physiologically "inert." Just saying.

Brett

 

[KBayDog]

And neither Nitrogen nor any of the other minor atmospheric components are technically chemically or physiologically "inert." Just saying.

Brett

Yeah, whatever. If I'm ever in an aircraft and breathing from a mask, it's a bad day.

 

[usmarinemike]

The T-45 OBOGS has a solid state oxygen monitor that trips the warning light below 95% O2, but the supply is generally at something like 99%. In addition to N2 the molecular seives also pull out CO2 and H2O which account for the higher partial pressure of remaining O2 that the people are wondering about.

Also in the T45, you'll get an O2 light at ground idle occasionally, and always if you have the flow on and mask off. It's never a problem unless the light doesn't go out when you run the engine up.

I remember reading an Approach article a loooong time ago about a Tomcat with a single hardover rudder. They were able to keep control of the jet with asymetric thrust. The problem was that they didn't have enough LOX to go BINGO profile back home, but they didn't have enough fuel to stay low back home. I always think about this story when I think about LOX.

 

[MIDNJAC]

I remember reading an Approach article a loooong time ago about a Tomcat with a single hardover rudder. They were able to keep control of the jet with asymetric thrust. The problem was that they didn't have enough LOX to go BINGO profile back home, but they didn't have enough fuel to stay low back home. I always think about this story when I think about LOX.

It's certainly something to think about, but barring any cabin pressurization problems, I'd without a doubt execute the bingo and say screw the LOX. Another draw back to LOX is being on the road, and not having LOX servicing at all many of the stopovers. You'll execute the LOX conservation program, and basically pop the mask off once airborne, put it back on for the tactical portion of the flight, then pop it back off only to use it again for landing. It isn't the 3710 answer, but it's how you execute the mission with minimal risk given resources......and it shows you that under normal cabin pressurization (ie nothing being wrong with it), you can fly at altitude with cabin pressure only w/o getting hypoxic. Then again, this practice certainly could have been attributed to some of the hypoxia events of the past