Pressurisation: An after takeoff check that may save your life
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Pressurisation: An after takeoff check that may save your life
https://www.skybrary.aero/index.php/...066f-276530305
This latest article in the SKYbrary website about the Helios Airline 737 that crashed in 2005 when the crew lost consciousness due lack of oxygen, is worth revisiting. Except for a stroke of sheer good luck, a similar fate could have happened to the crew of a RAAF HS 748. Read on:
The HS 748 crewed by two pilots and a navigator, was en route Rockhampton to Canberra having dropped a VIP at Rockhampton. The Commanding Officer of the squadron was PF under the supervision of the unit QFI (Centaurus) who acted as co-pilot. Soon after takeoff, the QFI adjourned to the cabin leaving the PF and navigator up front. The weather was fine. The aircraft planned cruise altitude was 15,000 feet.
Soon after the aircraft reached cruise altitude, the QFI experienced symptoms of hypoxia. As he explained later, these were green spots in front of his eyes and dizziness. He remembered these symptoms from his aviation medicine course 15 years earlier. That course involved training at the RAAF School of Aviation Medicine at Point Cook in a Hyperbaric Chamber to simulate the effects of high altitude on the human body, especially hypoxia (low oxygen).
He immediately returned to the cockpit and found the navigator slumped over his desk and the Commanding Officer singing loudly like a drunk. A glance at the pressurisation instruments revealed the aircraft was unpressurised and had been since takeoff.
The QFI then saw why. The pressurisation out-flow valve in the HS 748 was controlled by a manually operated lever on the co-pilot's side of the cockpit. It was normal procedure to have the out-flow valve open on the ground and for take off and for the co-pilot to close the outflow valve as part of the after take off checklist. Thereafter pressurisation was maintained automatically.
For some reason the QFI had forgotten to close the out-flow valve after take off and missed the item during the after take off checklist. The CO being new to type missed the item as well.
It was indeed fortunate the QFI recognised the symptoms of hypoxia before it was too late. Clearly the flight safety value of the RAAF hypoxia aviation medicine course proved inestimable. In 2017 it a pity that such a course is not available to civilian crews
This latest article in the SKYbrary website about the Helios Airline 737 that crashed in 2005 when the crew lost consciousness due lack of oxygen, is worth revisiting. Except for a stroke of sheer good luck, a similar fate could have happened to the crew of a RAAF HS 748. Read on:
The HS 748 crewed by two pilots and a navigator, was en route Rockhampton to Canberra having dropped a VIP at Rockhampton. The Commanding Officer of the squadron was PF under the supervision of the unit QFI (Centaurus) who acted as co-pilot. Soon after takeoff, the QFI adjourned to the cabin leaving the PF and navigator up front. The weather was fine. The aircraft planned cruise altitude was 15,000 feet.
Soon after the aircraft reached cruise altitude, the QFI experienced symptoms of hypoxia. As he explained later, these were green spots in front of his eyes and dizziness. He remembered these symptoms from his aviation medicine course 15 years earlier. That course involved training at the RAAF School of Aviation Medicine at Point Cook in a Hyperbaric Chamber to simulate the effects of high altitude on the human body, especially hypoxia (low oxygen).
He immediately returned to the cockpit and found the navigator slumped over his desk and the Commanding Officer singing loudly like a drunk. A glance at the pressurisation instruments revealed the aircraft was unpressurised and had been since takeoff.
The QFI then saw why. The pressurisation out-flow valve in the HS 748 was controlled by a manually operated lever on the co-pilot's side of the cockpit. It was normal procedure to have the out-flow valve open on the ground and for take off and for the co-pilot to close the outflow valve as part of the after take off checklist. Thereafter pressurisation was maintained automatically.
For some reason the QFI had forgotten to close the out-flow valve after take off and missed the item during the after take off checklist. The CO being new to type missed the item as well.
It was indeed fortunate the QFI recognised the symptoms of hypoxia before it was too late. Clearly the flight safety value of the RAAF hypoxia aviation medicine course proved inestimable. In 2017 it a pity that such a course is not available to civilian crews
Great reminder, Centaurus, of a potential killer.
This is why I always check the 'air con and press' system in the climb, passing FL100 and FL200, no matter how automated the system is.
In the Helios accident, I always felt that Boeing should accept some responsibility for having an identical warning horn for 'take-off config' and 'cabin altitude' warnings. I wonder if the Helios crew thought that the audible horn was a false 'take-off config' warning?
This is why I always check the 'air con and press' system in the climb, passing FL100 and FL200, no matter how automated the system is.
In the Helios accident, I always felt that Boeing should accept some responsibility for having an identical warning horn for 'take-off config' and 'cabin altitude' warnings. I wonder if the Helios crew thought that the audible horn was a false 'take-off config' warning?
Of all the training I received in the RAAF, I believe the decompression chamber is/has been one of the most useful. Each and every person has their own symptoms and until you experience it you will never know what yours are.
Yes, you can read about the potential symptoms in a book but after every chamber run the variety of symptoms amongst the victims was all varied and very few exactly like the book.
I know it's all about dollars these days but it would be handy if every ATPL (or CPL) had to go through it once.
Yes, you can read about the potential symptoms in a book but after every chamber run the variety of symptoms amongst the victims was all varied and very few exactly like the book.
I know it's all about dollars these days but it would be handy if every ATPL (or CPL) had to go through it once.
Civilians can no longer use the hyperbaric chamber. The Victorian one was moved to SA.
But, the simulated high altitude by go2altitude near Moorabbin is very good and a really valuable thing for anyone who flies in the flight levels - or even those regularly flying at 9,000 / 10,000 ft
Contact GO2Altitude
But, the simulated high altitude by go2altitude near Moorabbin is very good and a really valuable thing for anyone who flies in the flight levels - or even those regularly flying at 9,000 / 10,000 ft
Contact GO2Altitude
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I wonder if the Helios crew thought that the audible horn was a false 'take-off config' warning?
I remember the Australian flight safety journal, quite a few years ago, having a special issue devoted to hypoxia incidents. It contained story after story of incidents of non-pressurisation that were detected by the crew, just in the nick of time.
Young readers of that edition of the journal could have taken away the impression that, one way or another, you would detect when hypoxia was setting in, and then take action to save the day.
To me, a glaring omission from that edition was some sort of great big emphasis that luck played a part in the detection of the hypoxia, and that luck cannot be relied on!
I think they should have featured a number of cases where luck didn't present itself, with the incident then going on to become fatal for all concerned.
When discussing pressurisation with young pilots I always endeavour to describe the risk as something that can quietly sneak up on you from behind. Let it get close enough and it will snatch your life. You won't know a thing.
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and the Commanding Officer singing loudly like a drunk.
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Cabin Pressurisation
I am unable to understand why in cases such as the Helios B737 loss that (1), neither pilot understood the Cabin Altitude Aural warning as indicated by FGD135 and (2), that having failed to recognize such warning that no action was taken when the emergency masks deployed, if they did as they should have, when the cabin altitude reached approximately 14000 feet. Neither pilot should have been hypoxic at that stage. That, again as cited by FGD135, the engineering department could not guide the pilots is hard to comprehend.
Centaurus, as Old Akro has already mentioned there are some Civilian Hypoxia courses available, my company has one that we use for all new staff as we operate at high altitude on Oxygen and it's extremely valuable. Would be great I'd think if some of the schools out there employed these companies to come in a couple of times a year and show people the effects.
I don't think the masks they use are as accurate as a Decompression Chamber but well worth the time and money me thinks!
I don't think the masks they use are as accurate as a Decompression Chamber but well worth the time and money me thinks!
Out here in the Wild West of Perth, we are fortunate to be having the first normobaric hypoxia training enclosure in the country. All the benefits of the hypobaric chamber without the side effects of decompression sickness/bends. This much-neglected safety training will be open to all civilian pilots.
It will be up and running in the next month or so. PM for more details...
It will be up and running in the next month or so. PM for more details...
The 737 pressurization system in manual is very easy to cock-up if you are not careful. What happened to Helios nearly happened to Ryanair and Westjet but for slightly different reasons.
It was a design flaw in the 737 that the Take-off warning Config horn sounded the same as the Cabin Alt warning horn. Pilots were more used to associating it with take-off as that is the warning they would most often hear (usually the speedbrakes not set properly). In the report it was stated that the engineers asked the crew to check whether the pressurisation was set to AUTO but the crew did not respond to the instruction. The crew also failed to properly set the panel pre-departure and after take-off. The Captain and F/O were in their 50's so the early onset of hypoxia would not have been unusual and by that stage they were fixated on the warning horn and an avionics cooling warning.
One of the issues often forgotten about is the hardened cockpit door installed as a result of 9/11. The CM could not just enter the cockpit and query the masks having deployed as he probably would have done pre 9/11. In the Ryanair case it was only the CMs persistence on the interphone that alerted the crew to the lack of pressurisation.
It was a design flaw in the 737 that the Take-off warning Config horn sounded the same as the Cabin Alt warning horn. Pilots were more used to associating it with take-off as that is the warning they would most often hear (usually the speedbrakes not set properly). In the report it was stated that the engineers asked the crew to check whether the pressurisation was set to AUTO but the crew did not respond to the instruction. The crew also failed to properly set the panel pre-departure and after take-off. The Captain and F/O were in their 50's so the early onset of hypoxia would not have been unusual and by that stage they were fixated on the warning horn and an avionics cooling warning.
One of the issues often forgotten about is the hardened cockpit door installed as a result of 9/11. The CM could not just enter the cockpit and query the masks having deployed as he probably would have done pre 9/11. In the Ryanair case it was only the CMs persistence on the interphone that alerted the crew to the lack of pressurisation.
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This is why I always check the 'air con and press' system in the climb, passing FL100 and FL200, no matter how automated the system is.
I think it was after the Helios accident, Boeing changed it to: 'Packs....Auto.
Bleeds....On. The former Air Con and Pressurisation was removed.
I have always believed that was a retrograde step. On the former check list , the amplified section referred the crew to confirm the cabin altitude was normal and the pressurisation needle indicated the aircraft was pressurising.
Now that has vanished, in the simulator we see in the after take off scan and checklist,the PM challenging himself and replying to himself the items Bleeds on and Pack Auto and neither pilot looks at the pressurisation instruments because it is not mentioned in the check list anymore.
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The solution is simple-This system (pressurisation) IS one that requires serious monitoring because any problem with it, at altitude can result in death, for all on board. Aircraft capable of ceilings above 14,000 ft used to carry a flight engineer, a systems man and pressurisation was one of the prime systems. Now, this system is supposed to be "Automatic" but then -other systems that have that same degree of reliance, are monitored in a better way, than that of pressurisation. If cockpit management was updated to include regular monitoring of that system and there was a little mor instrumentation put in to show flow and outflow valve condition, this would go a long way in to making a safer operation.
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I check the pressurization system periodically during both climb & descent. I also check during cruise, but less often. Just the way I was taught I guess, but I trust nothing, particularly stuff that can kill me.
Passing FL300 on descent one day in a B737-800, I checked the system & saw that the cabin was climbing at around 900fpm. There was no indication of the fault, even with recall. No auto changeover, nothing. If I hadn't checked it, the first thing we would have known about it was when the cabin altitude warning went off.
There is far too much reliance on the system to tell us when things misbehave. I prefer to know about a developing problem rather than wait until it becomes a major issue.
Passing FL300 on descent one day in a B737-800, I checked the system & saw that the cabin was climbing at around 900fpm. There was no indication of the fault, even with recall. No auto changeover, nothing. If I hadn't checked it, the first thing we would have known about it was when the cabin altitude warning went off.
There is far too much reliance on the system to tell us when things misbehave. I prefer to know about a developing problem rather than wait until it becomes a major issue.
