Engine failure causing Hypoxia?

[Chief Instructor]

When at high altitude, a complete engine failure is causing the rapid onset of what looks like Hypoxia. I can understand that an engine failure would lead to a gradual loss of cabin pressure, but with the pilot breathing through a mask, it should't matter...

 

Is the supply of pilot oxygen from the reservoir somehow linked to the engine operation? That would seem strange!

[TOViper]

Hello ChiefInstructor!

 

The manual says:

"The cabin is sealed automatically if the canopy is closed and the engine is on."

 

So ... lets consider the following:

You fly high, and pressurized, everything is fine.

Suddenly the air pressure support is lost due to a failed engine.

What happens?

The still existing air pressure will immediately press the cockpit glass (and its frame) away from the aircraft, maybe back to the engine where it came from (I dont know this exactly, but I guess).

The air will then find its way through gaps out of the aircraft very quickly - pfffffffft ... and its gone.

In this case the total air pressure - and thus the partial pressure of oxygen also - will decrease very quickly in the cockpit -> not good, but up to 12km survivable if you have oxygen as your friend.

 

Above 12 km (this is not well investigated by me) the body slowly gets more and more difficulties to absorb oxygen, even if it is undiluted.

Here the missing environmental pressure is already a problem.

 

Above ~15 (up to 18 km) altitude, the human body has generally big difficulties to survive, due to missing environmental pressure.

The water in the human body comes within range of the boiling point for the surrounding pressure, and this is really the difficult point ...

If this happens to you, use the remaining time to say :bye_3:, "and tell my wife dinner is cancelled").

 

Please consider information from this interesting article:

https://en.wikipedia.org/wiki/Armstrong_limit (called "Armstrong limit")

 

I actually dont know how high you have been ...

I had these problems at altitudes of 10km up to 16km...

 

See pictures here, where I was at 12,6 km altitude:

https://forums.eagle.ru/showthread.php?p=3066089#post3066089

 

Greetings,

TOViper

Edited March 16, 2017 by TOViper

[Buzzles]

To build on TOViper's answer:

Why do you think U2 and SR-71 pilots have to wear pressure suits?

 

OP is missing some info though, how high were you?

 

It might be a bug if you were only at 40k feet though, but the Viggen's ceiling is just shy of 60k.

Edited March 16, 2017 by Buzzles

[Chief Instructor]

To build on TOViper's answer:

Why do you think U2 and SR-71 pilots have to wear pressure suits?

 

OP is missing some info though, how high were you?

 

It might be a bug if you were only at 40k feet though, but the Viggen's ceiling is just shy of 60k.

 

Good answers thanks. I get the feeling there is a bug in play here as my altitude was not too excessive, though I can't remember exactly where. I'll do some more testing when I have time.

 

I guess this isn't quite the full story though, otherwise the effects that can be seen in a decompression chamber wouldn't make any sense. For example, candidates are given simple tasks to carry out, such as writing and counting. When the chamber is decompressed they rapidly start to feel the effects of the hypoxia setting in. However, when they are given their supplementary oxygen masks back, they rapidly regain their marbles, despite not wearing additional pressure suits.

 

So, at altitudes where partial pressures are sufficiently low to prevent the required level of oxygen absorption without an increased mixture via a mask, it is perfectly possible to maintain useful consciousness with supplementary oxygen. However, at far lower atmospheric pressures, the entire body needs to be pressurised for the respiratory system to remain effective, even with supplementary oxygen.

 

More research required to fully answer the question I think.... :thumbup:

[outlawal2]

I believe that the oxygen supply IS related to the engine as the oxygen is pulled from the engine itself.. (I don't know how that works, but I remember that when the F-22 had issues with the "Raptor Cough" it was surmised that fumes were being pumped in from the engine since the oxygen is fed from the engine..) Turns out in the case of the F-22 that the cough and issues they were having was actually due to the oxygen lines being made of the wrong material and was breaking down causing toxic fumes for the pilots. They replaced the lines with the correct material and all is well now..

 

But my takeaway from that situation was I found out that the oxygen is pulled in from the engines so if the engines are nut running this will directly affect the pilot oxygen supply.. I believe this is rather typical of fighter planes today..

[Buzzles]

But my takeaway from that situation was I found out that the oxygen is pulled in from the engines so if the engines are nut running this will directly affect the pilot oxygen supply.. I believe this is rather typical of fighter planes today..

 

I don't think that's true at all. I'd be very very surprised if pilot oxygen is not supplied via pre-filled bottles in pretty much all aircraft.

 

Environmental systems are definitely fed from the engine feeds (or APU), but actual breathing oxygen? Nah.

[Chief Instructor]

The cabin is pressurised using bleed air from either the intermediate or high pressure turbine section of the engine in most cases. Pilot's breathing oxygen is from a separate bottled reservoir. So, an engine problem may potentially cause fumes to enter the cabin but the pilot's breathing air would not be affected. Crew oxygen supplies are always provided by a separate and sterile source for obvious reasons...

[outlawal2]

The cabin is pressurised using bleed air from either the intermediate or high pressure turbine section of the engine in most cases. Pilot's breathing oxygen is from a separate bottled reservoir. So, an engine problem may potentially cause fumes to enter the cabin but the pilot's breathing air would not be affected. Crew oxygen supplies are always provided by a separate and sterile source for obvious reasons...

 

Thank you very much for that clarification as I thought it odd and a bit alarming to use oxygen from the engines..

 

Your explanation makes perfect sense now.

Thanks!

[Rangi]

Could it be something to do with the cold weather simulation? If you are on the ground with canopy open in cold weather you get an effect. Maybe with no engine the environmental controls can't give heat and you get cold. Without knowing exactly what effect the OP was experiencing it's just a guess.

[RagnarDa]

It's a bug and I have fixed it right now. The cabin pressure will still drop though when the engine is shut off so depending on your altitude your blood might boil under your skin.

[Bad Idea Hat]

Related question, do I need to enable oxygen if I never make it above 2000 meters?

Because I feel like I'm wasting virtual Os by doing that.

[Vampyre]

Thank you very much for that clarification as I thought it odd and a bit alarming to use oxygen from the engines..

 

Your explanation makes perfect sense now.

Thanks!

 

The problem was with the comparison between the Viggen and F-22. The Viggen is not an F-22. The F-22 uses OBOGS (On Board Oxygen Generating System) which does indeed use engine bleed air to supply breathing oxygen to the pilot. The Viggen uses a LOX (Liquid Oxygen) bottle which has to be replaced when depleted. The advantage of OBOGS over LOX is that with OBOGS you do not have to worry about generating and handling volatile LOX. OBOGS is a system of the aircraft that actually requires a lot less attention than LOX from a maintenance standpoint.

[Chief Instructor]

It's a bug and I have fixed it right now. The cabin pressure will still drop though when the engine is shut off so depending on your altitude your blood might boil under your skin.

 

That's great news! Hopefully you can make the cabin pressure gauge work too, so that we can monitor the pressure loss :thumbup:

 

Cheers!

[TOViper]

It's a bug and I have fixed it right now. The cabin pressure will still drop though when the engine is shut off so depending on your altitude your blood might boil under your skin.

 

Following your post, ... hmm ... may I kindly ask you to present the relevant data you are using for the simulation of your "human body model"?

I mean altitudes, time of useful conciousness, pressure drop, time ...

I would be good to know, for flight planning purposes, emergency planning, what to do in case of .... you know the pilot's stuff that has to be done before each flight :megalol:

 

In fact we are talking about human behaviour in physical terms.

I would love to have the data/information - in any case - included in the new "really sophisticated viggen flight manual for the really well prepared pilots", which I am waiting for ... .

 

What do you mean?

Anyway, RagnarDa, thanks for your fast reaction and the information given, and also to all other posters for collecting infos on this "human issue" :thumbup:

 

Kind regards,

TOViper

[outlawal2]

The problem was with the comparison between the Viggen and F-22. The Viggen is not an F-22. The F-22 uses OBOGS (On Board Oxygen Generating System) which does indeed use engine bleed air to supply breathing oxygen to the pilot. The Viggen uses a LOX (Liquid Oxygen) bottle which has to be replaced when depleted. The advantage of OBOGS over LOX is that with OBOGS you do not have to worry about generating and handling volatile LOX. OBOGS is a system of the aircraft that actually requires a lot less attention than LOX from a maintenance standpoint.

 

And some more excellent clarification. I feel a little better that I wasn't totally losing my mind regarding what I thought I had read..

Now I am back to being a bit disturbed at the thought of breathing engine bleed air! :cry:

 

Thanks!

[RagnarDa]

Following your post, ... hmm ... may I kindly ask you to present the relevant data you are using for the simulation of your "human body model"?

I mean altitudes, time of useful conciousness, pressure drop, time ...

I would be good to know, for flight planning purposes, emergency planning, what to do in case of .... you know the pilot's stuff that has to be done before each flight :megalol:

 

In fact we are talking about human behaviour in physical terms.

I would love to have the data/information - in any case - included in the new "really sophisticated viggen flight manual for the really well prepared pilots", which I am waiting for ... .

 

What do you mean?

Anyway, RagnarDa, thanks for your fast reaction and the information given, and also to all other posters for collecting infos on this "human issue" :thumbup:

 

Kind regards,

TOViper

 

I am not entirely sure I understand what you mean, but at the pressure thats at 16km altitude the boiling point of water is 35 degrees celsius - just under the normal temperature of your body. So the water in your blood will theoretically boil because of the heat from your body. This is not simulated in the game though.

[TOViper]

I am not entirely sure I understand what you mean, but at the pressure thats at 16km altitude the boiling point of water is 35 degrees celsius - just under the normal temperature of your body. So the water in your blood will theoretically boil because of the heat from your body. This is not simulated in the game though.

 

Sorry for being not clear enough, so please let me clear my this up a bit.

I really hope that you don't understand this as grumbling around.

I'm interested in the altitude values you will use for your "body model".

 

There will be a certain altitude where it is 100% unlikely that the player will die due to the pressure loss (maybe its 14 km?), and there will be an altitude where the player dies definitely (which you already stated would be 16 km).

 

So the following two questions arise, assuming an engine out and its related pressure drop in the cockpit:

a.) At which altitude will the player definitely die in all cases within seconds.

b.) At which altitude will the player never die.

 

Working with these two altitudes now, we may define a transition area where the probability increases/decreases linearly (or maybe progressively, this must be investigated with doctors, specialists, ... or just fixed by you assuming something), where the probability increases or decreases. In all cases, TIME will also be a factor, which I think must not be forgotten.

 

Let me underline this with two examples, which I can imagine:

Example no 1: in 15 km the player will have slow blacking out, and will die after ... dont know ... lets say 2 minutes. The emergency procedure would then be to descent below 14 km within 2 minutes .... which can be performed easily.

Example no 2: in 15.6 km the player will have rapid blackout, and will die after ... dont know ... 1 minute. Emergency procedure would then be to quickly descent below 14km within 1 minute, ... which can be performed not so easy (he blacks out quicker, and has more altitude to go which takes longer, "doubling the trouble in half the time").

Maybe there will be a certain point where you don't have enough time to start a descent, and only have a slight chance to trim the aircraft nose down ... and pray.

 

Hope that I cleared my request up ... and you now understand what I am hunting for ... :smartass:

 

Background:

Knowing that human behaviour doesn't always follow rules strictly, but swings/sweeps out also, ... you know ... not everything is black & white, but sometimes a little grey, having a factor X in the system (statement is "sometimes it works different than in most cases ...").

A former girl friend of mine was a doctor, and she told me "human medicine works as intended in 66% of all cases, but in 33% it works completely different".

That is what she said. :noexpression:

 

Kind regards,

TOViper

:smilewink:

 

P.S.: Every day I fly the Viggen I more and more understand what you must have gone through ... IT IS AN AMAZING MODEL that you created here.

Let me say "thank you" 1000 times!

[grunf]

Altitude at which the water boiling point equals human body temperature is 18,000m, and it's called Armstrong's line. The blood in the blood vessels wouldn't boil because it's still under pressure, but exposed liquids (eyes, mouth, nose, lungs) would. A person would lose conciseness 10s after decompression, and would die a minute or two after. A standard oxygen mask would not prevent this, only a pressure suit would.

 

I don't think this is modeled in DCS.

[Ice_Cougar]

Managing the Mig-15's oxygen system was a blast! (Literally...the canopy will pop if one bullet punctures it.) :P

 

Thanks for the updates RagnarDa ;)