Helios Crash
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The FAA have released a new AD 2008-23-07 calling for a revision of the AFM.
SUMMARY: We are adopting a new airworthiness directive (AD) for all Boeing Model 737 airplanes. This AD requires revising the airplane flight manual to include a new flightcrew briefing that must be done before the first flight of the day and following any change in flightcrew members, and to advise the flightcrew of this additional briefing.
This AD results from continuing reports that flightcrews have failed to recognize and react properly to the cabin altitude warning horn. We are issuing this AD to prevent failure of the flightcrew to recognize and react properly to a valid cabin altitude warning horn, which could result in incapacitation of the flightcrew due to hypoxia (lack of oxygen in body) and consequent loss of airplane control.
SUMMARY: We are adopting a new airworthiness directive (AD) for all Boeing Model 737 airplanes. This AD requires revising the airplane flight manual to include a new flightcrew briefing that must be done before the first flight of the day and following any change in flightcrew members, and to advise the flightcrew of this additional briefing.
This AD results from continuing reports that flightcrews have failed to recognize and react properly to the cabin altitude warning horn. We are issuing this AD to prevent failure of the flightcrew to recognize and react properly to a valid cabin altitude warning horn, which could result in incapacitation of the flightcrew due to hypoxia (lack of oxygen in body) and consequent loss of airplane control.
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Originally Posted by Litebulbs
Does such a thing as an Operations Manual Engineering exist?
IIRC the maintenance did a leak check on one of the aft doors.
Every switching is mentioned in the AMM.
Here you see a quote out of the actual "Cabin Pressure Leak Test" Task:
05-51-91-702-001
...
D. Prepare for the Cabin Pressure Leakage Test
...
(9) (a) Move the pressurization mode selector on the forward overhead panel to MAN.
...
...
F. Put the Airplane Back to its Usual Condition
(1) Do a check of the Pitot Static system for leaks and correct operation if it is necessary
(2) Open the equipment cooling flow control valve.
(3) If the equipment cooling fans were selected from NORMAL to ALTERNATE, the switches must be returned to the NORMAL position.
(4) Move the pressurization mode selector on the forward overhead panel to AUTO.
But the point F(4) did not exist in the AMM revision valid at august 2005.
This sentence appears in the revision januar 2006.
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If the AMM did not state that the control should be returned to the Auto then the engineers have nothing to fear and the responsibility surely lies at Boeings door.
Maybe if the cockpit check had been more thorough the situation may have been averted but hind sight is a wonderful pill that cures all ailments
Maybe if the cockpit check had been more thorough the situation may have been averted but hind sight is a wonderful pill that cures all ailments
One aspect of the Helos accident which interests me is whether either of the flight crew had had hypoxia training. During my commercial pilot training (back in 1969) we were all taken to the nearby Navy base and put in the chamber and taken up to 35,000 ft or so and then asked to do simple tasks after the oxygen was turned off. (We had previously covered all the various physiological aspects in the classroom). It was really impressed on us how vital it was to get onto oxygen should there be a pressurisation failure and the dangers of not doing so. But the actual experience of hypoxia in that chamber is something I have never forgotten.
As a professional pilot I have asked some of the new entrant pilots whether they have had hypoxia training and have been very surprised that this was not included in the syllabus for their commercial training. I would have thought that all commercial pilots who may be involved in operating pressurised a/c ought to have had practical training concerning hypoxia.
As a professional pilot I have asked some of the new entrant pilots whether they have had hypoxia training and have been very surprised that this was not included in the syllabus for their commercial training. I would have thought that all commercial pilots who may be involved in operating pressurised a/c ought to have had practical training concerning hypoxia.
More bang for your buck
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If the AMM did not state that the control should be returned to the Auto then the engineers have nothing to fear
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totally agree . . . . . . !
I would have thought that all commercial pilots who may be involved in operating pressurised a/c ought to have had practical training concerning hypoxia
The really frightening thing is that you get ZERO warning or prior awareness when you are drifting into potentially fatal hypoxia. I'd agree that a much increased awareness even of the possibility should be an essential part of the initial and recurrent training of all crews operating pressurised aircraft.
It's worth noting that this is one of the few areas which cannot be realistically practised in simulators, which, however sophisticated they may be, never leave the ground !
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It would be good to have at least one experience of hypoxia at some stage during training - cost and logistics no doubt being the determining factor in this case.
Although a good number of pilots have no doubt seen the videos of aircrew in a chamber, it cannot bring home the reality as AMEandPPL states - and he should know!
I know that when I did my initial type rating on the B737 it was impressed on us that we should check the position of the oxygen selector on the first flight of a duty as a part of the 'rainbow' check - and over the years I always did this check thoroughly - and found on at least one occasion that the selector was OFF.
It's so sad when such a simple check results in a tragedy - but what about the other indications along the way during the course of the flight?! It's hard to believe that ALL the warnings and indications were missed during standard operations - but they obviously were.
FOK
Although a good number of pilots have no doubt seen the videos of aircrew in a chamber, it cannot bring home the reality as AMEandPPL states - and he should know!
I know that when I did my initial type rating on the B737 it was impressed on us that we should check the position of the oxygen selector on the first flight of a duty as a part of the 'rainbow' check - and over the years I always did this check thoroughly - and found on at least one occasion that the selector was OFF.
It's so sad when such a simple check results in a tragedy - but what about the other indications along the way during the course of the flight?! It's hard to believe that ALL the warnings and indications were missed during standard operations - but they obviously were.
FOK
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My humble opinion is that this is a combination of boeings' incomplete AMM and the crews inability to realise what the problem was when the cabin altitude warning sounded. Nevertheless responsibility lies with the management of Helios who although received 5 reports from F/O's about the certain Captain, continued to employ him. Apparently the reports dissapeared by magic although the F/O's involved gave the info to the police during their testimony.
Finally as a proffessional pilot myself and as some of you have commented, i take it as my responsibility to prepare my a/c prior a flight and make sure all is ok. We must learn as pilots to learn from ours and other peoples mistakes and take responsibility for them.
As for the inquiry i hope justice is awarded.
Fly safe.
Finally as a proffessional pilot myself and as some of you have commented, i take it as my responsibility to prepare my a/c prior a flight and make sure all is ok. We must learn as pilots to learn from ours and other peoples mistakes and take responsibility for them.
As for the inquiry i hope justice is awarded.
Fly safe.
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I've been called out to departing aircraft a fair few times with 'faults' only to discover a bus-tie switch or fire loop detector switch in the wrong position, enough so that when I'm called to a snag I do a switch check first. These are invariably switches that are always left in their default positions. I suppose if you're checking the same switches every day you become blind to ones that 'never move'. I've been caught out myself on ground runs.
If I'm working a u/s aircraft my thoughts are directed at fixing the fault, not leaving the flight deck switching in a ready to fly state. If I'm working a snag when the crew 'own' the plane, I'll always ask them to move a switch rather than do it myself.
Pre-flight checks just aren't part of an engineer's remit. Harsh as it may be, I'm afraid the buck stops with the flight crew on this one.
Perhaps the problem IS that switches are always left in a flight ready position?!
If I'm working a u/s aircraft my thoughts are directed at fixing the fault, not leaving the flight deck switching in a ready to fly state. If I'm working a snag when the crew 'own' the plane, I'll always ask them to move a switch rather than do it myself.
Pre-flight checks just aren't part of an engineer's remit. Harsh as it may be, I'm afraid the buck stops with the flight crew on this one.
Perhaps the problem IS that switches are always left in a flight ready position?!
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Ever seen this before.
During cruise, defect xxx, QRH actioned. (pilot report)
Defect xxx tested as per MM, test ok, xxx now servicable. (eng entry)
Next pilots may find switches out of normal positions ?
Whos job is it to reverse QRH actions ?
During cruise, defect xxx, QRH actioned. (pilot report)
Defect xxx tested as per MM, test ok, xxx now servicable. (eng entry)
Next pilots may find switches out of normal positions ?
Whos job is it to reverse QRH actions ?
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If Engineering has worked the defect then certified the aircraft as serviceable, responsibility to move switches to the ready for flight position lies with the next crew taking the aircraft. We will make switch selections required for our tests and should leave them in the normal position or where the Aircraft Maintenance Manual states. This may or may not be where the Ops manual requires them to be for flight which is why pre-flight checks are so important.
The only people that know where pilots want switches placed are pilots. We work to the AMM not a Flt Ops Manual.
The only people that know where pilots want switches placed are pilots. We work to the AMM not a Flt Ops Manual.
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Originally Posted by itsresidualmate
....meant to add that Boeings cabin alt warning looks a bit shabby, doesn't do much to help the crew when one warning has multiple meanings.
On gound = T/O config warning
In air = cabin altitude warning
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Ifixplanes - I think it would be fair to say that under conditions of potential hypoxia, it is probably not a good idea to have a warning horn that has 2 meanings. As far as I can see it can only lead to a strong potential for confusion in a period where judgement is possibly impaired. So much so that Boeing have modified the warning horn to also trigger a light which indicates whether it is sounding for takeoff config or cabin pressurisation. An admission, surely, that there is a problem with the design of this system? Not only that, but the config warning can sound in flight, for example retarding the thrust levers to less than 68% N1 with flaps out and gear not down will trigger it. So its not quite as clear cut as you seem to think (Edit: this sentence is garbage - I was thinking of the steady warning horn, but the rest of this paragraph is accurate!).
Furthermore, regardless of the position of the pack switches/pressurisation mode selectors, I find it quite amazing that they were not reset as part of the normal procedures or caught in the normal checklist sequence. I don't know the Helios SOPs but at my outfit the auto mode selector should have been checked at least 3 times by the time 10,000' is reached, the pack switches having been reset as part of the after start sequence and checked in the A/S checks. So perhaps someone could explain where the maintenance personnel fit into the story here? I can't see how they could be blamed?
Furthermore, regardless of the position of the pack switches/pressurisation mode selectors, I find it quite amazing that they were not reset as part of the normal procedures or caught in the normal checklist sequence. I don't know the Helios SOPs but at my outfit the auto mode selector should have been checked at least 3 times by the time 10,000' is reached, the pack switches having been reset as part of the after start sequence and checked in the A/S checks. So perhaps someone could explain where the maintenance personnel fit into the story here? I can't see how they could be blamed?
Last edited by D O Guerrero; 21st Nov 2008 at 20:49.
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Originally Posted by D O Guerrero
I think it would be fair to say that under conditions of potential hypoxia, it is probably not a good idea to have a warning horn that has 2 meanings. ...
Again: in air it must be "cabin altitude warning". There is no other meaning.
If there is a fault in the AIR/GRD you can easyly find out a incorrectly T/O Config Warning by retarding the throttle (the Helios Crew did this...)
Originally Posted by D O Guerrero
...but the config warning can sound in flight, for example retarding the thrust levers to less than 68% N1 with flaps out and gear not down will trigger it. ...
The second part I agree too ...
I can understand missing it pre-flight and taking off, but for the life of me I can't imagine not noticing the climbing cabin. I have taken off in a 737 with the packs off and I had felt it, looked up and identified the problem, and made a decision not to say anything about it until 500ft, all before the gear was up. It was that obvious. I didn't have a cold or restricted sinuses either.
Hopefully that doesn't come across as 'look how great I am', ( I was the idiot who got distracted and left packs off), the point I'm trying to make is that it is incredible that they didn't notice the cabin climbing. Any thoughts on that? Was it some sort of low climb rate with a hold down or something?
Hopefully that doesn't come across as 'look how great I am', ( I was the idiot who got distracted and left packs off), the point I'm trying to make is that it is incredible that they didn't notice the cabin climbing. Any thoughts on that? Was it some sort of low climb rate with a hold down or something?
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Please read the accident report.
