How would you handle this Crew Oxygen Low situation

[Una Due Tfc]

Depends on what part of the world you are in. You declare a pan with us you WILL get priority. Calling a Pan with us IS declaring an emergency. The way it was explained to me in simple terms in training was

Pan Pan Pan = we may be in danger
Mayday Mayday Mayday = we are in serious danger

[mustafagander]

On our B744 we simply get the emergency oxy bottles fitted with an Eros adapter and position them in the locker beside the pilots. Then we connect the masks and we're ready for a deco or smoke. We do, however, need to action the step to turn the bottle on. Not really a big deal, all in our EP manual.

[Ovation]

Ever since I have tried to determine the minimum blood oxygen percentage which will just keep an average human conscious. It seems to be about 65 to 70 %. Does anyone out there have a more accurate figure? Climbers of Everest should know.

Mountain climbers are conditioned to tolerate low oxygen environment, however a normal earthling will experience difficulties if the O2 level gets down around 85%. The brain and eyes need an enormous amount of oxygen so the initial effects will be impaired vision and cognitive function. The effects are insidious with primarily a feeling of warmth and euphoria, and an affected person will have difficulty recognising they are in a hypoxic state.

[FullWings]

It's an interesting scenario which has probably been used many times as a training "discussion item".

IMHO there isn't really a wrong answer to this as it's down to the discretion of the crew and how they feel about it at the time. You have to balance the probability of an explosive decompression occurring during the rest of the cruise segment (extremely low) with the risk to the airframe and occupants should this happen (high). If you have a source of supplemental oxygen, like a bottle and mask, it reduces the risk somewhat but it's not going to provide anywhere near the 100% O2 concentration, pressure breathing and protection from smoke/fumes that the aircraft system can. You can use smoke hoods with their own oxygen supply but it makes the aircraft operation more problematic than it could be. A half-way house could be to descend to an level where a portable O2 set will sustain you while you complete the descent to a breathable altitude.

It's somewhat akin to the old MEL/QRH divide: the MEL expects a further failure but the QRH doesn't. On the 777, a "CREW OXYGEN LOW" advisory indication has the explanation: "Crew oxygen pressure is low" but doesn't go on to say: "land at nearest suitable" or "descend immediately". The MEL does not allow dispatch below a certain pressure.

[beardy]

The cabin portable oxy bottles are not of the same standard as the flight crew fixed masks and may not provide enough Oxygen under the ambient conditions or keep smoke out of your lungs.

I suppose it depends on your fit. Ours are of the same quality and will last long enough to keep smoke out of one's lungs for an emergency descent until the DV window can be opened.

Still it is a good discussion point, I see Airbus has no FCOM procedure that I could find and nor do our SOPs.

[HDRW]

I once had a problem after giving blood, where I blacked-out. I didn't become unconscious, I felt "out of it", as if I was watching what was happening without being there. Then my vision went grey, and a nurse noticed I wasn't looking well, and asked "Are you OK?" - I didn't have the brainpower to answer. Then my vision went black, closing in from the outside, and she took over and she and a colleague physically led me to a bed to lie down with my feet raised, at which point I recovered my vision, and I stayed in that position for a quarter of an hour until I felt OK again. Looking back, the surprising aspects were that I remained consious but couldn't see - previously I'd thought that blacking out meant losing consciousness - and that I didn't realise there was a problem until it was too late for me to take any action of my own. Obviously the root cause of this was low blood pressure, but I'm pretty sure hypoxia from other causes would present similarly. Seeing the data on how rapidly the crew would have become incapaciated by a sudden decompression at their initial altitude, I think they acted exactly right. They had lost the safety feature that would have saved them if a fire or decompression happened, and they wouldn't have had time to get out a MAYDAY, let alone get the aircraft down to a breathable level, if it had suddenly gone from a possibility to an actual emergency. Gambling that it wouldn't happen is just not on!

[cosmo kramer]

Una:
Depends on what part of the world you are in. You declare a pan with us you WILL get priority. Calling a Pan with us IS declaring an emergency. The way it was explained to me in simple terms in training was

Pan Pan Pan = we may be in danger
Mayday Mayday Mayday = we are in serious danger

Show me the document!

You can't declare a PAN. It doesn't exist, there is no such thing.

A PAN call is an urgent message concerning safety, nothing more, nothing less.

That ATC may give you priority anyway, will simply be because they are aware of the poor training level of many pilots and that the will treat their so-called "PAN declaration" as a mayday call - in which case the pilot could have done it properly to begin with and use correct phraseology with a mayday call.

[beardy]

The following comes from a Eurocontrol document which can be found at
http://www.skybrary.aero/bookshelf/books/115.pdf
And quotes ICAO standard phraseology :

A distress call (situation where the aircraft requires immediate assistance) is prefixed: MAYDAY, MAYDAY, MAYDAY.

An urgency message (situation not requiring immediate assistance) is prefixed: PAN-PAN, PAN-PAN, PAN-PAN.

Make the initial call on the frequency in use, but if that is not possible squawk 7700 and call on 121.5.

Pan exists, has a meaning that most of us understand, it is not an urgent message, it is an urgency message meaning that the caller requires urgent attention (but not immediate assistance), pedantry I know but important. Neither Mayday nor Pan is "declared" they prefix a message of the relevant category. Luckily most Air Traffic Controllers, worldwide, are trained to be aware of ICAO standards and of the differences in their countries.

I am so sorry for the thread drift, I was enervated by the previous poster's assertions.

[Una Due Tfc]

Well I've never had somebody call a Mayday on me (and hopefully never will), but I've had a few Pans, 1 for an engine failure on a 744 and a few for medicals and hydraulic failures etc, In essence you are right it's not an declaring an emergency in itself but I've never had a Pan called by an aircraft that wasn't looking for a diversion or looking to deviate due to an emergency. I hear Pan or Mayday then I'm treating you as an emergency aircraft unless you tell me otherwise

[NigelOnDraft]

Another way of looking at this is using the Prefix appropriate to the service you are (or not) getting from ATC.

Slow Oxy problem, decide descent in next 5 mins is a good scheme.
"Request Descend FL150 for minor tech problem"
"Maintain FL350, will check with next sector"
"Pan (x3) request descent" gets the message across

i.e. use the prefix to get the service you need, not according to the problem (which ATC can do diddly squat about anyway).

NoD

[Basil]

HDRW, What you describe is similar to blacking out due mishandling one's physiological response to high G. --- Don't ask

[Iron Duke]

As Basil said ... 1. Situation 2. Crew response 3. A/C landed safely .. Perfect.

Statistics may play a part in this ... It is statistically unlikely to have a further issue with pressurisation or smoke/ fire in cockpit. In this case maybe portable oxygen/ Drager hoods could have sufficed as back up until a diversion could be effected at cruise levels, thereby minimising any proximity conflicts. For me Land As Soon As Possible is correct.

If a decision is made to operate outside (or, you have no choice) of your NAT procedural clearance then it is a MAYDAY call. Another scenario where this can happen is on the high latitude Canadian routes with a LOW FUEL TEMP warning, and either an acceleration or a descent is decided upon ... MAYDAY.

I. Duke

[cosmo kramer]

Neither Mayday nor Pan is "declared" they prefix a message of the relevant category.

You can declare an emergency using "mayday". You can't declare anything using pan. Which is exactly what the document says that you posted.

Also, mayday has to do with YOU. You can't declare an emergency on behalf of others. However, you can use Pan to send an "urgent message regarding safety", that being other aircrafts or people on ground. Hence, the example in my previous post with the forest fire. Or you can use Pan to tell ATC that you saw another plane crash, as another example.

[beardy]

Cosmo,
Please read these links regarding the use of Mayday and Pan, one is from the FAA the other from the CAA (UK.) Your view of the limitations of each phrase don't seem to be represented here. Also please note there is no reference to any form of 'declaration.'

http://www.faa.gov/air_traffic/publi...m/aim0603.html

http://www.atac.ca/web/images/Docume...al%20Pilot.pdf

[framer]

Tell that to the ATC who told me I would have to 'declare a Pan' if I wanted priority tracking to the field.

[cosmo kramer]

Please read these links regarding the use of Mayday and Pan, one is from the FAA the other from the CAA (UK.) Your view of the limitations of each phrase don't seem to be represented here.

From the CAA document:
"An urgency message (situation not requiring immediate assistance) is prefixed: PAN-PAN, PAN-PAN, PAN-PAN."

That is exactly what I said. A Pan call is nothing more than an urgent message. You can not expect immediate assistance, since you do not require it (that some ATC may give you the same assistance as if you declared an emergency, is because they are nice, cautious, bored, whatever... But you are not entitled to any priority or special treatment.

Why the reluctance to use a proper mayday like the crew of the US Airways did?
They wanted to descent and required immediate assistance in doing so. Why do you people have a problem with a mayday call. You don't have to pay for it.

Also please note there is no reference to any form of 'declaration.'

From your document:
"Fuel Emergency or fuel priority are not recognised terms. Flight crews short of fuel must declare a PAN(????) or MAYDAY to be sure of being given the appropriate priority."

...thought I wonder how the English CAA would want you to declare an "urgent message".

Mayday = distress = emergency = something your can declare
Pan = urgent message = something you can't declare

[cosmo kramer]

... and just for good order, the section about minimum fuel quoted above has been changed. Though not relevant for this thread:
http://aviation.osu.edu/wp-content/u...gency-fuel.pdf

[VinRouge]

It's all about risk mitigation. Descent without clearance is less risky than a measured approach, a discussion amongst the crew and a plan of action?

Really?

What is the probability that there will be a fumes or depress event whilst the oxy was low, vs the risk induced by busting your level in busy procedural airspace?

[VinRouge]

Ever since I have tried to determine the minimum blood oxygen percentage which will just keep an average human conscious. It seems to be about 65 to 70 %. Does anyone out there have a more accurate figure? Climbers of Everest should know.

Having done hyperbaric training with a O2 sensor on in the last 3 months for my requal, I can tell you that by 70% you are symptomatic, (for me, tingling fingers and loss of colour perception) 60% your judgement is affected and by 50% you are on the verge of losing the chance to detect an issue.

The worst feeling was going onto 100% at the end of the run, the oxygen flushes the co2 out of the blood and your blood 02 initially takes a huge dive. The sense is pretty nasty and paradoxically if hypoxia you may be tempted to remove oxygen fearing that the supply is contaminated.

[dkz]

Great job, we can argue on a forum about the "need" to declare an emergency but probably 99% faced with the same issue would.

The point about the portable oxygen is not exactly valid because of comms, oxy pressure at high altitude and lack of smoke goggles. On the portable mask there is no mic, on the next sim try to handle an emergency descent without one ... also try a smoke drill without goggles.