Hypoxia

[TAAMGuy]

The recent event of a TBM700 crew falling to hypoxia (apparently) raises a question. As both a former pilot and controller I am trying to look at this from both sides. The pilot had stated a need to descend from FL280 to 180 because of some erroneous indication but there was nothing alerting the controller that the issue was pressurization. If it was pressurization why not ask for FL100? Since the pilot did not declare an emergency I don't think you can argue that the controller should have moved heaven and earth to approve 180 as requested. He undoubtedly had conflicting traffic and after he cleared the initial descent to 250 then the pilot lost consciousness.

Having said that when dealing with the insidious nature of hypoxia (I remember the chamber all too well) the pilot's judgement is impaired. I think any issue to do with pressurization needs to be dealt with a little differently because the pilots faculties come into question. How should the system be changed to address this? I find it very paradoxical but would like to hear some thoughts.

[Dream Land]

This aircraft was the new TBM 900, one of the changes on this new airframe was an automatic pressurization system that is predicated on the destination city pair.

[malr]

What changes need to be made?

If the pilot feels there might be a pressurization issue, why not don O2 masks and then ask for clearance to descend?

If the pilot felt it was an emergency, why not descend to FL100 and then TELL ATC what's going on?

I'm not sure what happened to the other thread on this topic...but somebody summed it up nicely:

ATCs job is to separate traffic; not read the pilot's mind. The pilot's job is to fly the aircraft, and deal with issues as they arise.

[Dream Land]

Good points, but Taamguy brings out a something (I think) for controllers to possibly be a bit more curious about a situation where the pilot has some technical issue that requires a descent, because by the time the pilot recognizes some problem, he may already be seriously impaired by hypoxia.

[malr]

This seems like a very slippery slope. Can you have ATC question any request that doesn't make sense if it's requested from a pilot currently flying over FL100?

And ultimately, what can ATC do?

Even in this situation, ATC cleared the pilot down to FL200...the pilot acknowledged, yet never descended from 250.

We don't know what the "incorrect indication" was the pilot noticed...but it drove him to request a lower altitude...that tells me it was likely a correct-indication of a pressurization problem. Again...just like they tell the pax..."put on your own mask before helping others..."

[No Fly Zone]

I think Taamguy and Dream Land both make excellent points.

In a potential crunch situation, Fly First. If, as this case suggests, a rapid descent to FL100 is necessary, start down, put the mask(s) on and then call ATC. Time is important. If a PAN or EMERGENCY call is even possibly warranted, skip the "Cool on the Radio" thing, make the declaration for God's sake, Tell ATC what problem is suspected. As once of these writer's notes, ATC's job is to provide separation - and they are darn good at it; they are not mind readers. I'd rather see a few a few more PAN/EMERGENCY calls that perhaps later get cancelled, than I would seeing accidents like this one, where we are still guessing about the cause - and the principals cannot tell us why they needed to descend. ATC's systems can and do identify/alert controllers to major variations in course or altitude and those folks are more than able to start getting others out of the way while they attempt to collect information. Sadly, we do not know what happened. Much of the speculation is probably close to the hard facts, but for some unknown reason, the pilots did not share much detail with ATC before they became unable to communicate. Assuming (admittedly a poor practice) that it was a pressurization issue and recognized by the pilot(s), instantly diving for FL100 and communicating in the way down does NOT violate any regulation that I've ever read. We may eventually know, but this airplane does not carry the same, high-end FDRs and CVRs standard on commercial transports, so even if the wreckage is located, it may not yield a lot of detail. For those lost, RIP; this loss **may** have been preventable. Sad.

[bloom]

Start with a hypoxic pilot, that realizes that there is a problem, and in a semi-conscience state makes some close but no cigar decisions. He realizes he needs lower for oxygen, fixates on the number 10 thousand, and in his stupor does the math and comes up with 28 minus 10 equals 18 thousand, which he asked for, NOT the 10 thousand feet that he needed, with an immediate, emergency decent.

The aircraft was brand new. The ferry from France would indicate that the pressurization system worked.

A pinched seal would be insidious and could be undetected.

And if no one had checked if the crew O2 valve was turned on, well there you go.

[stilton]

Does this Aircraft have a cabin altitude warning horn ?

[glendalegoon]

well meaning posts;


there is a difference between reading someone's mind and anticipation.

Thinking ahead. It is what makes flying and ATC possible.

Why would someone say words like: problem, and lower?

IF the engine quit, you would say: the engine quit, everyone remotely associated with our profession would understand that would mean you were going to descend (assuming everyone knows it is a single engine plane).

We went through this with aerolinas argentina and fuel. I'm sure some of you remember.

Radio work the world over needs improvement, in the meantime, just a reminder...remember apollo 13? I don't think Lovell said MAYDAY, he is quoted (generally) as saying: HOUSTON WE HAVE A PROBLEM. NOT houston we have an emergency.

PLEASE correct me if I am wrong about that.

[ATC Watcher]

I fully support what has been said regarding controllers not being " mind readers"
We also teach our controllers that interpreting pilots voice intonations,or grammar used, and acting upon it , can be very dangerous. Of course after an accident and having a meeting with Captain Hindsight , the point : maybe the controller should have noticed ..etc.., always come back, and worse even on the courts . (for those old enough to remember Avianca B707 or the Yak42 in Tessaloniki to take only 2 cases ).

As it was said here and as I always preach ,please use PAN x3 , and you'll get everyone attention, and we can then all have a beer together at the bar discussing what I should have undertood or not.

[ATC Watcher]

Glendalegoon, you are wrong in nearly all your satements, you obviously do not know how ATC works ,what R/T Pharesology is, and why we have it.

[le Pingouin]

Lovell didn't need to, the telemetry was screaming it at the top of its lungs. We don't have the benefit of telemetry so the pilot is the only means of obtaining information.

[NABLAG]

Lovell also had the full attention of Houston and was not sharing his frequency with multiple others.

[mary meagher]

You will find the first comments on this sad accident on the North America forum, viewed by very few (only 29) under the title AIR FORCE TRACKING.

Perhaps the mods could combine the two threads, as some helpful ideas may evolve, particularly in the training of ATC to suspect possible hypoxia.
The pilot is usually the last person to recognise the problem.

[Noxegon]

I'm wondering whether it might be feasible to develop a system that causes a plane to automatically descend to something like 5000ft and squawk 7700 if there is no pilot input for a reasonable time period.

There are obviously some fairly major issues to be resolved before something like this could work in real life, but might that have prevented this incident?

[fireflybob]

I think we're tackling this from the wrong end as it were.

When I did my commercial pilot training back in 1969 our course was taken to the nearby Royal Navy base where we did the hypoxia training - put in a chamber, taken to circa 40,000 feet pressure and given simple tasks to do having switched the oxygen off etc. This was done one at a time and it was an interesting experience to watch my colleagues' performance when subject to hypoxia.

It's an experience I have never forgotten and we were left in doubt about the dangers of hypoxia in flight.

In my opinion all those who fly pressurised aircraft should do hypoxia training and this would go a long way to avoid these sad incidents which happen from time to time.

Also it is essential to check oxygen systems for quantity, supply, correct fitting of mask prior to flight. At the slightest hint of a pressurisation problem oxygen masks should be donned.

Regarding descent with ATC a pressurisation failure is a MAYDAY as far as I am concerned. Also the whole idea of using the priority calls (MAYDAY or PAN, although the latter is not recognised in some states) is to draw immediate attention to one's plight. A vague request for descent on a busy ATC freq is never going to get the same attention as calling MAYDAY and/or wearing the 7700 badge if necessary.

[fireflybob]

This is one of several Hypoxia videos on youtube - well worth a watch

Hypoxia at high altitude (https://www.youtube.com/watch?v=y-P2NahJ0NY)

[wiggy]

I'm wondering whether it might be feasible to develop a system that causes a plane to automatically descend to something like 5000ft

This was mentioned elsewhere ( probably the other thread) - such a system would have to be tied into a Terrain database since in many parts of the world descending to FL50 will put you under the ground (10000' amsl won't give you clearance in parts of Europe and the States, in some parts of the world even 15000' won't do).

FWIW I've "enjoyed" :ooh: similar training to that fireflybob describes - I agree entirely with his post.

[chuks]

Those guys headed for the Moon did not need any sort of ATC clearance, did they? I don't think you can find a strong parallel to this recent accident in their RT procedures.

ATC is not expected to have to guess at what a pilot needs to do and then sort out his problems for him. This is why we have to say, "Mayday, Mayday, Mayday" or at least in plain speech that magic word, "emergency." Saying that you need a lower altitude, well, yes, okay, but stand by for that; that could take a few minutes to work out on a routine basis.

You do get these tragedies where the crew had said, "We are low on fuel," or "We need priority," or whatever. Well, that's good to know, but if they were Number Six for approach, ATC was not going to jump them to the head of the queue just on the strength of that. You always have that question, asked or unasked by ATC, "What are your intentions?" That's you, the pilot-in-command, not some controller sat in a chair; he's already safely on the ground.

If this aircraft had a pressurization problem then the drill probably should have been something like: masks on; initiate emergency descent to FL100; declare emergency to ATC; squawk 7700; run emergency checklist.

That's all very well to sit here now writing about, but think of being sat there just enjoying the ride, your shiny-new turboprop humming along, when "BONG!" you have to start thinking, "Uh. What was that?" You could eat up a good minute or so just trying to figure out what your problem is, and then waste further time with this sort of "I need [this or that]," asking, when the controller is not going to drop everything to help you unless you declare an emergency and tell him what you are doing.

The TUC at FL280 is about three minutes or less. If this accident pilot were sat there, mask off at a pressure altitude of 28 thousand feet, then by the time the controller had sorted out the requested lower altitudes for him he might well have already been unable to respond effectively. It certainly looks as if that were the case.

[Jwscud]

There already is an automatic descend system fitted to the Cirrus (unpressurised turbocharged piston single). Details here:

http://cirrusengineering.b l o g s p o t.co.uk/2011/01/hypoxia-prevention-and-automatic.html

My understanding is that some bizjets are developing or implementing a similar system.

PS You need to manually fix the URL as PPRuNe doesn't like blog spot for some reason

[Dream Land]

ATC is not expected to have to guess at what a pilot needs to do and then sort out his problems for him. This is why we have to say, "Mayday, Mayday, Mayday" or at least in plain speech that magic word, "emergency." Saying that you need a lower altitude, well, yes, okay, but stand by for that; that could take a few minutes to work out on a routine basis. Wow, brilliant idea old chap, why didn't all of us pilots think of that!

Hopefully there will be some more positive input on this thread, since alarms and training seem to be falling short in several unfortunate instances.

[TAAMGuy]

The recent incident, apparently, involving hypoxia has raised a point about the ATC involvement. As both a former pilot and controller I am trying to look at this from both sides. Prior to being rendered unresponsive, the pilot requested descent from FL280 to FL180. He accepted an interim descent to FL250 but reiterated he needed lower. The controller responded "I'm working on that'; meaning (I assume) he had conflicting traffic. The pilot stated he had some sort of indication in the cockpit but never said it was related to pressurization, and never declared an emergency.

What I am wondering about is in a situation where a controller is informed that pressurization is potentially compromised, should the controller not 'force' the aircraft down, because the pilots judgement is now called into question?

We as controllers certainly do not want to be in the business of flying the aircraft on your behalf, but since hypoxia is often insidious, at what point do we save you from yourself? Is this an additional layer of safety that the pilot community would want to be added?

Obviously this is a very sensitive issue, but i would love to generate some constructive discussion.

[roninmission]

Technically it would be relatively simple for pilots to wear a blood oxygen level meter which could give a wireless warning either to the pilot or some other device which would alert ATC

[Dream Land]

Pilots wouldn't need to wear something like that, but a transducer could easily give ATC the cabin altitude if it becomes dangerous. I'm not asking for controllers to be mind readers, but there has to be a way to make things safer.

I was also trained in the high altitude chamber, but it doesn't make me anymore resistant to the effects of hypoxia, it was only a demonstration.

[stilton]

In a depressurization situation, especially a rapid one you don't wait for permission from a controller.


You put your mask on and start down. When you have time, after completing your immediate action items you TELL them you are descending and declaring an emergency.


Obviously you have to be aware of traffic beneath you and monitor your TCAS but I wouldn't be waiting on ATC, there's just no time as this pilot found out the hard way.

[Dream Land]

Yes Stilton, I think most people sitting in a class room can figure that out, what I think some are discussing here is how the effects of hypoxia has interfered with that plan.

Take a look at just some of the accidents, LJ, 737, Cirrus, TBM, there's probably more.

It's very easy in the simulator because they tell you by making a big bang sound, not always that simple in real life. :hmm:

[fireflybob]

Yes Stilton, I think most people sitting in a class room can figure that out, what I think some are discussing here is how the effects of hypoxia has interfered with that plan.

Take a look at just some of the accidents, LJ, 737, Cirrus, TBM, there's probably more.

It's very easy in the simulator because they tell you by making a big bang sound, not always that simple in real life.

Not always! As an instructor on the simulator I often used the slow loss of pressure as this was a much more likely scenario and brought out some salient points.

No disrespect to private owners but how often do they practice the loss of press/emergency descent drill?

Within the airline world there is a requirement to do this on a regular basis and also the drills are often covered during line checks too.

This is mainly a matter of discipline and training.

What stilton says is correct and this is what should be taught and practised.

[Dream Land]

Practicing the "High Dive" is one of the items practiced in training for most TBM owners, some in the simulator, some train in their own aircraft. Again, pointing out the obvious is not doing a lot to help the problem here, all pilots are taught this maneuver.

Somehow getting an earlier notice needs to happen.

[BOAC]

Does the a/c have any cabin altitude warning?

[TAAMGuy]

As a controller, if I was informed that there was a pressurization issue, and a descent request, i would consider that as good as a declaration of emergency. However, just the fact that the pilot has told me he has a pressurization issue, I'm going to really be paying attention to his voice in an effort to assess how he is being affected. If i hear the voice wavering, i would inclined to force the aircraft down. I would also be more wary of a GA pilot than airline.

Should there be an SOP introduced for both parties that mandates a descent in the event an issue with pressurization has been identified? Whether or not the pilot requests it? Morally, at what point do I believe the pilots judgement has been compromised and take action?

[4Greens]

Agree entirely with the respondents who say immediate 'Mayday'. Apart from ATC it warns all other aircraft on the frequency.

Nuff said.

[glendalegoon]

dear atcwatcher

I actually do know quite a bit about ATC, Radio phraseology and more. I've been making my living as a pilot for 35 years or more. By the way, we don't say R/T here in the USA. Its just radio. Ask a fellow named Lee DeForest.

BUT I do know that many pilots are imprecise in their use of radio. And ATC has adjusted to non standard phraseology. Indeed, I've heard ATC use some non standard phraseology now and again. I realize that in europe, everything is perfect.

Those who wonder why the pilot didn't request 10,000'? Well, he may have been impaired. He may have seen the cabin differential would hold a cabin altitude of 8000' at FL180. He may have been trying to salvage things instead of declaring an emergency. Pilots are like that. Declare an emergency and most likely things are going to heck in a handbasket quickly and may (subconsciously) signal defeat.

While many can read the controller/pilot glossary, it takes someone who has been around awhile to read a situation.

Does anyone know how long the controller had been checked out at Center? Was he a journeyman of many years or a newly checked out controller?

Taamguy makes a good point.

[Tarq57]

As a controller, if I was informed that there was a pressurization issue, and a descent request, i would consider that as good as a declaration of emergency. However, just the fact that the pilot has told me he has a pressurization issue, I'm going to really be paying attention to his voice in an effort to assess how he is being affected. If i hear the voice wavering, i would inclined to force the aircraft down. I would also be more wary of a GA pilot than airline. That's how I'd treat it, too. I think that's how most controllers - particularly experienced controllers - would treat it.

Should there be an SOP introduced for both parties that mandates a descent in the event an issue with pressurization has been identified? Whether or not the pilot requests it? Morally, at what point do I believe the pilots judgement has been compromised and take action?Tricky. Unless such info (cabin pressure) is datalinked to ATC, or is displayed as part of a mode "s" readout on the datablock, or the pilot actually informs ATC there's a pressure issue (say, prior to to becoming incapacitated) you're just groping around in the dark. And with probably little or no reason to suspect anything is wrong.
If the pilot mentions it but sounds vague the effect is probably already happening, and strongly encouraging a descent/reminding them to put the mast on might work, or it might already be too late.
I don't think a telepathy rating can be mandated via a SOP, but it's a nice idea.

[TAAMGuy]

I think that Mode S could definitely be exploited for this purpose. A message could easily be sent as part of regularly broadcast telemetry that would present on the controller's display that the pressurization system has been compromised. If after being queried, the crew does not confirm they are using supplementary O2, then the controller forces the flight down to FL130, or at least an altitude low enough to bring the pilots back some of their brain function. Obviously factors such as MEA, MAA, and MRA need to be considered. (Terrain)

I know that there is a culture prevalent among pilots that does not embrace the idea of transmitting data about the aircraft beyond what is currently available, but honestly it is about CDM. System Wide Information Management (SWIM) or Cloud, is being embraced by ANSP's, airlines, and others as the way of the future. The more data a controller has access to about a flight, the better the SA. My two cents worth.

[Una Due Tfc]

If the cabin altitude warning goes off, the aircraft should be descending without clearance, and when the crew has time, squawking 7700. The squawk is much more important than the Mayday transmission as all effected sectors will see it.

If there needs to be a Mode S feed from the cabin altitude sensor to my display so that I can tell a crew to do something that realistically they should already be doing, then I despair for this industry

[Tarq57]

Just for anyone not in the industry reading this thread, there is no way a controller can force an aircraft to descend.

We can instruct or clear, even urge. Only the flight crew (or fuel exhaustion) can "force" the flight to descend.

[BOAC]

Does the a/c have any cabin altitude warning? (Again!)

[glendalegoon]

dear boac

I read on another thread that a warning happens at 10,500' cabin altitude and it is displayed on one of the electronic displays.

I've not flown this type but am guessing its not a big horn like on a 737 or something.

I think the other thread is on pprune under the title: air force tracking...

good luck.

[BOAC]

Ta, Glen - found it in North America.