Cypriot airliner crash - the accident and investigation
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this is an important topic
it must be tough being the guy at the beginning of the "trail of errors"
One thing we can all agree on though, I hope:
PPRUNE has a role to play and I think we are all grateful to the guys hard work in the background, even if we do sometimes abuse their goodwill and go over into "rant" mode. An uncensored forum can only assist our industry not hinder it.
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Here's an article by one of the journalists of the Cyprus Mail [from today's Internet edition] concerning a number of unanswered questions about the crash and the subsequent investigation:
Helios: the mysteries remain
By Elias Hazou
To the living we owe respect, but to the dead we owe only the truth
Voltaire
TO MANY in the aviation industry, the fact-finding report into last summer’s air disaster should not be treated as Gospel; it is not the absolute truth on what really happened on that morning of August 14 2005, when 121 souls perished in a ravine at Grammatikos, 50km from Athens.
An alternative theory cites the cause of the accident as an insidious, non-recurrent malfunction – or in plain English, a freak breakdown of the plane’s electronics.
As one airline engineer in Greece put it, “there are a lot of dark areas. I suspect we have a great deal more to uncover, if you look hard enough. There’s more to the tale than meets the eye.”
The source, who did not want to be named, told the Mail that from the outset he has had doubts about the official version of events.
Though he did not as yet wish to commit to a hypothesis, the source did not rule out the “X” factor.
According to the accepted wisdom, as told by the report compiled by the Greek accident investigating team, the primary cause of the crash was human error: the two pilots had failed to notice during checks before and after take-off that the "cabin pressurisation mode selector" was in the manual position. The data suggests that the Helios ground engineer had set the selector on manual the night before the flight, following a pressure leak test. Had the switch been set to automatic, it would have allowed the cabin to pressurise by itself.
After take-off, the plane did not pressurise and the two pilots failed to recognise "the warnings and reasons for the activation of the warnings", including a cabin altitude warning horn and the dropping of oxygen masks.
The steady loss of cabin pressure led to the onset of hypoxia (oxygen deprivation), causing the pilots and passengers to pass out. The jet flew on autopilot for hours before it ran out of fuel and smashed into the ground.
Helios, now known as ajet, has contested the findings. The company says it has conducted “extensive tests” showing it would be virtually impossible for a Boeing 737 to take off with the airflow valve at 14 degrees from the fully closed position, as Tsolakis’ findings contend.
From a purely technical standpoint, actual takeoff is feasible, Helios says, but the excessively high pressure generated inside the cabin once the engines throttled would have caused unbearable pain to passengers, whose eardrums would burst. Thus, it is inconceivable that no one would have noticed this discomfort and taken action to stop the takeoff sequence in its tracks. Speaking to the Mail, engineers and pilots confirmed this much was true.
What the embattled airline is suggesting is that an electrical glitch caused the decompression switch to malfunction. Therefore, the captain and his co-pilots were also later fooled by constant warning signs that developed shortly after takeoff. In short: neither their ground crew nor their pilots committed any errors or omissions.
On the other hand, the Tsolakis report cites incontrovertible evidence – from the Flight Data Recorder (FDR) and the NVM (Non-Volatile Memory, a memory chip that stores components’ settings) – that the airflow valve was at a constant 14 degree angle throughout the flight. Tsolakis concludes that the pilots themselves would have had no reason to set the valve to manual, so the setting was configured on the ground before takeoff. The Helios report even features photos of the celebrated decompression panel corroborating the FDR and NVM data. Case closed.
Or is it?
On September 7, 2005 The International Herald Tribune alleged that the plane's captain heeded the advice of maintenance officials on the ground to pull the fuse on the electrical alarm-signal circuitry.
The paper said this was strictly prohibited by the manufacturers' operating manuals for all airliners and that it was considered criminal negligence.
The FDR showed that at 06:12:38 h and at an aircraft altitude of 12 040 ft and climbing, the cabin altitude warning horn sounded. At 06:14:11 h, at an altitude of 15 966 ft, the Captain contacted the company Operations Centre on the company radio frequency. According to the Operator’s Dispatcher, the Captain reported “Take-off configuration warning on” and “Cooling equipment normal and alternate off line.” The Dispatcher requested an on-duty company Ground Engineer to communicate with the Captain.
According to a written statement by the Ground Engineer written immediately after the accident at the Technical Manager’s instruction, the Captain reported that “the ventilation cooling fan lights were off.” Due to the lack of clarity in the message, the Ground Engineer asked him to repeat. Then, the Captain replied “where are the cooling fan circuit breakers?” The Ground Engineer replied “behind the Captain’s seat.”
It is thought that Captain Hans Juergen-Merten misread the horn for a takeoff configuration warning. As this did not make sense – the sound can only go off while the plane is on the ground – he assumed this was due to a glitch with the horn. Which supposedly explains why he asked the ground engineer for the location of the circuit breakers.
Because of this assumption, the pilots’ troubleshooting was off the mark, and ostensibly they never stopped to think the horns were warning of a decompression problem, wasting crucial time as the plane climbed.
Our source said: “These initial exchanges between the captain and the ground have been overlooked. To my mind, they are critical.”
He explained that circuit breakers are the mechanism controlling aural signals (such as warning horns) on the plane. These are located behind the captain’s seat and to the left.
Once an alarm for a takeoff configuration warning sounds, it will not cease until action is taken. This involves either dealing with the issue (such as correcting the flaps before takeoff) or silencing the alarm by pulling the circuit breakers – which is not recommended.
Frustratingly, the Tsolakis report cannot verify or disprove whether the warning horns were on throughout the flight. The Cockpit Voice Recorder, which was badly damaged, only contained data from the last 30 minutes.
And there’s a good reason why pulling the circuit breakers is forbidden: the mechanism has two ports, one for the takeoff configuration alarm, the other for cabin altitude (read: cabin pressure). So it’s very easy to make a mistake and silence the cabin altitude warning – a very bad idea.
But the Captain had asked the ground engineer about the equipment cooling switch. This, our source says, does not make sense. The equipment cooling switch is located not behind the captain’s seat, but on the overhead panel. The switch has two selectors: Normal and Alternate.
“There are no circuit breakers for equipment cooling. There’s no question of resetting it, such as by pulling a fuse.
“In other words, what may have happened is that – perhaps through some miscommunication with the ground engineer – the captain pulled the fuse on the electrical alarm-signal circuitry, thus inadvertently silencing the cabin altitude warning.”
The source added:
“We can only speculate, of course. But to me, it’s far-fetched to say the pilots ignored all the alarms that were going off, that they did not for a moment consider the possibility of a depressurisation problem. Or that they failed to conduct checks, both before takeoff and after. Their handling of the situation seems childish – too childish. I don’t buy it.
“You have a German pilot who’s been called bossy and arrogant. Perhaps this is a convenient story – an unpopular, headstrong character who did not heed advice from his co-workers.”
Yet the Tsolakis report also seems to come short on another point. Under the section “Analysis”, the report summarily concludes that a combination of stress and carelessness led the pilots to commit a string of errors:
“Exacerbating this tendency (expectation bias) is the rarity with which switches (especially, and directly relevant to this case, the pressurisation mode selector) are in other-than-their-normal position. A pilot automatically performing lengthy verification steps, such as those during preflight, is vulnerable to inadvertently falsely verifying the position of a switch to its expected, usual position (i.e. the pressurisation mode selector to the expected AUTO position) – especially when the mode selector is rarely positioned to settings other than AUTO.”
This is the “meaty” part of the report, where one would expect the most scientific and substantiated examination of events. Instead, it falls back on conjecture and guesswork. Although this is not unheard of in air accident investigations, it does imply there are blanks.
Lastly, looking back to the fateful day, another mystery unfolds. Eyewitness accounts at the wreckage site said that bushfires flared up much later, at least an hour after impact.
On 19 August, the Athens News reported:
"‘As we looked over the cliff where the plane's severed tail stood in a cloud of dust, I saw scores of dead bodies scattered across the slopes of the ravine near countless smouldering pieces of wreckage from the plane,” local villager Costas Michas told reporters gathered at Grammatiko later in the afternoon. “There were small kids still tied to their seats like plastic dolls, body parts and clothing hanging from trees.” He could see that most of the bodies were still recognisable, because the bushfires that burned them only flared up much later, at least an hour after the eyewitnesses were removed from the scene.
“Some of them could have been rescued from complete 'cremation', if only we were allowed to carry them further up on the hillside,” Michas told the Athens News.
“There was the body of a little boy with a gushing wound on its head, lying by a bush halfway down the slope. I took the child in my arms to carry it up to the top of the cliff. But then security people ordered me to leave the body on the ground and clear the area at once. Later the fires broke out and there was nothing left of the child. I will never forgive them for this,” he said, referring to the police and army personnel that cordoned off the area for the rest of the day while the firefighting continued.
The head of the Grammatiko town council, Thanassis Papageorgiou, was also among the first to arrive at the crash site. “When I reached to the bottom of the ravine, I saw dead people everywhere but they weren't burned,” he stressed. “I could smell no jet fuel. There was no raging fire; only smoke from smouldering pieces of the plane wreckage scattered across the hillsides of the ravine. I immediately called the fire department on my mobile.”
The land-based firefighting units arrived at Grammatiko 30 minutes later but were prevented by police from approaching the crash site for another half an hour, Papageorgiou said. “By that time, the ravine was ablaze and required the full force of eight firefighting planes for several hours to put out the fire.”
Other accounts told of a sequence of “crackling” sounds being heard in the area shortly before the hilly terrain flared up – again, much later than the time of the crash.
Given that both the Boeing’s engines had flamed out and – according to witness accounts – there was no smell of fuel – what could have caused a major fire? Did all the people on board die on impact? Will closure – for everyone, but more so for the victims’ relatives – ever be achieved?
With additional reporting by Demetris Yannopoulos from the Athens News
Copyright © Cyprus Mail 2006
Helios: the mysteries remain
By Elias Hazou
To the living we owe respect, but to the dead we owe only the truth
Voltaire
TO MANY in the aviation industry, the fact-finding report into last summer’s air disaster should not be treated as Gospel; it is not the absolute truth on what really happened on that morning of August 14 2005, when 121 souls perished in a ravine at Grammatikos, 50km from Athens.
An alternative theory cites the cause of the accident as an insidious, non-recurrent malfunction – or in plain English, a freak breakdown of the plane’s electronics.
As one airline engineer in Greece put it, “there are a lot of dark areas. I suspect we have a great deal more to uncover, if you look hard enough. There’s more to the tale than meets the eye.”
The source, who did not want to be named, told the Mail that from the outset he has had doubts about the official version of events.
Though he did not as yet wish to commit to a hypothesis, the source did not rule out the “X” factor.
According to the accepted wisdom, as told by the report compiled by the Greek accident investigating team, the primary cause of the crash was human error: the two pilots had failed to notice during checks before and after take-off that the "cabin pressurisation mode selector" was in the manual position. The data suggests that the Helios ground engineer had set the selector on manual the night before the flight, following a pressure leak test. Had the switch been set to automatic, it would have allowed the cabin to pressurise by itself.
After take-off, the plane did not pressurise and the two pilots failed to recognise "the warnings and reasons for the activation of the warnings", including a cabin altitude warning horn and the dropping of oxygen masks.
The steady loss of cabin pressure led to the onset of hypoxia (oxygen deprivation), causing the pilots and passengers to pass out. The jet flew on autopilot for hours before it ran out of fuel and smashed into the ground.
Helios, now known as ajet, has contested the findings. The company says it has conducted “extensive tests” showing it would be virtually impossible for a Boeing 737 to take off with the airflow valve at 14 degrees from the fully closed position, as Tsolakis’ findings contend.
From a purely technical standpoint, actual takeoff is feasible, Helios says, but the excessively high pressure generated inside the cabin once the engines throttled would have caused unbearable pain to passengers, whose eardrums would burst. Thus, it is inconceivable that no one would have noticed this discomfort and taken action to stop the takeoff sequence in its tracks. Speaking to the Mail, engineers and pilots confirmed this much was true.
What the embattled airline is suggesting is that an electrical glitch caused the decompression switch to malfunction. Therefore, the captain and his co-pilots were also later fooled by constant warning signs that developed shortly after takeoff. In short: neither their ground crew nor their pilots committed any errors or omissions.
On the other hand, the Tsolakis report cites incontrovertible evidence – from the Flight Data Recorder (FDR) and the NVM (Non-Volatile Memory, a memory chip that stores components’ settings) – that the airflow valve was at a constant 14 degree angle throughout the flight. Tsolakis concludes that the pilots themselves would have had no reason to set the valve to manual, so the setting was configured on the ground before takeoff. The Helios report even features photos of the celebrated decompression panel corroborating the FDR and NVM data. Case closed.
Or is it?
On September 7, 2005 The International Herald Tribune alleged that the plane's captain heeded the advice of maintenance officials on the ground to pull the fuse on the electrical alarm-signal circuitry.
The paper said this was strictly prohibited by the manufacturers' operating manuals for all airliners and that it was considered criminal negligence.
The FDR showed that at 06:12:38 h and at an aircraft altitude of 12 040 ft and climbing, the cabin altitude warning horn sounded. At 06:14:11 h, at an altitude of 15 966 ft, the Captain contacted the company Operations Centre on the company radio frequency. According to the Operator’s Dispatcher, the Captain reported “Take-off configuration warning on” and “Cooling equipment normal and alternate off line.” The Dispatcher requested an on-duty company Ground Engineer to communicate with the Captain.
According to a written statement by the Ground Engineer written immediately after the accident at the Technical Manager’s instruction, the Captain reported that “the ventilation cooling fan lights were off.” Due to the lack of clarity in the message, the Ground Engineer asked him to repeat. Then, the Captain replied “where are the cooling fan circuit breakers?” The Ground Engineer replied “behind the Captain’s seat.”
It is thought that Captain Hans Juergen-Merten misread the horn for a takeoff configuration warning. As this did not make sense – the sound can only go off while the plane is on the ground – he assumed this was due to a glitch with the horn. Which supposedly explains why he asked the ground engineer for the location of the circuit breakers.
Because of this assumption, the pilots’ troubleshooting was off the mark, and ostensibly they never stopped to think the horns were warning of a decompression problem, wasting crucial time as the plane climbed.
Our source said: “These initial exchanges between the captain and the ground have been overlooked. To my mind, they are critical.”
He explained that circuit breakers are the mechanism controlling aural signals (such as warning horns) on the plane. These are located behind the captain’s seat and to the left.
Once an alarm for a takeoff configuration warning sounds, it will not cease until action is taken. This involves either dealing with the issue (such as correcting the flaps before takeoff) or silencing the alarm by pulling the circuit breakers – which is not recommended.
Frustratingly, the Tsolakis report cannot verify or disprove whether the warning horns were on throughout the flight. The Cockpit Voice Recorder, which was badly damaged, only contained data from the last 30 minutes.
And there’s a good reason why pulling the circuit breakers is forbidden: the mechanism has two ports, one for the takeoff configuration alarm, the other for cabin altitude (read: cabin pressure). So it’s very easy to make a mistake and silence the cabin altitude warning – a very bad idea.
But the Captain had asked the ground engineer about the equipment cooling switch. This, our source says, does not make sense. The equipment cooling switch is located not behind the captain’s seat, but on the overhead panel. The switch has two selectors: Normal and Alternate.
“There are no circuit breakers for equipment cooling. There’s no question of resetting it, such as by pulling a fuse.
“In other words, what may have happened is that – perhaps through some miscommunication with the ground engineer – the captain pulled the fuse on the electrical alarm-signal circuitry, thus inadvertently silencing the cabin altitude warning.”
The source added:
“We can only speculate, of course. But to me, it’s far-fetched to say the pilots ignored all the alarms that were going off, that they did not for a moment consider the possibility of a depressurisation problem. Or that they failed to conduct checks, both before takeoff and after. Their handling of the situation seems childish – too childish. I don’t buy it.
“You have a German pilot who’s been called bossy and arrogant. Perhaps this is a convenient story – an unpopular, headstrong character who did not heed advice from his co-workers.”
Yet the Tsolakis report also seems to come short on another point. Under the section “Analysis”, the report summarily concludes that a combination of stress and carelessness led the pilots to commit a string of errors:
“Exacerbating this tendency (expectation bias) is the rarity with which switches (especially, and directly relevant to this case, the pressurisation mode selector) are in other-than-their-normal position. A pilot automatically performing lengthy verification steps, such as those during preflight, is vulnerable to inadvertently falsely verifying the position of a switch to its expected, usual position (i.e. the pressurisation mode selector to the expected AUTO position) – especially when the mode selector is rarely positioned to settings other than AUTO.”
This is the “meaty” part of the report, where one would expect the most scientific and substantiated examination of events. Instead, it falls back on conjecture and guesswork. Although this is not unheard of in air accident investigations, it does imply there are blanks.
Lastly, looking back to the fateful day, another mystery unfolds. Eyewitness accounts at the wreckage site said that bushfires flared up much later, at least an hour after impact.
On 19 August, the Athens News reported:
"‘As we looked over the cliff where the plane's severed tail stood in a cloud of dust, I saw scores of dead bodies scattered across the slopes of the ravine near countless smouldering pieces of wreckage from the plane,” local villager Costas Michas told reporters gathered at Grammatiko later in the afternoon. “There were small kids still tied to their seats like plastic dolls, body parts and clothing hanging from trees.” He could see that most of the bodies were still recognisable, because the bushfires that burned them only flared up much later, at least an hour after the eyewitnesses were removed from the scene.
“Some of them could have been rescued from complete 'cremation', if only we were allowed to carry them further up on the hillside,” Michas told the Athens News.
“There was the body of a little boy with a gushing wound on its head, lying by a bush halfway down the slope. I took the child in my arms to carry it up to the top of the cliff. But then security people ordered me to leave the body on the ground and clear the area at once. Later the fires broke out and there was nothing left of the child. I will never forgive them for this,” he said, referring to the police and army personnel that cordoned off the area for the rest of the day while the firefighting continued.
The head of the Grammatiko town council, Thanassis Papageorgiou, was also among the first to arrive at the crash site. “When I reached to the bottom of the ravine, I saw dead people everywhere but they weren't burned,” he stressed. “I could smell no jet fuel. There was no raging fire; only smoke from smouldering pieces of the plane wreckage scattered across the hillsides of the ravine. I immediately called the fire department on my mobile.”
The land-based firefighting units arrived at Grammatiko 30 minutes later but were prevented by police from approaching the crash site for another half an hour, Papageorgiou said. “By that time, the ravine was ablaze and required the full force of eight firefighting planes for several hours to put out the fire.”
Other accounts told of a sequence of “crackling” sounds being heard in the area shortly before the hilly terrain flared up – again, much later than the time of the crash.
Given that both the Boeing’s engines had flamed out and – according to witness accounts – there was no smell of fuel – what could have caused a major fire? Did all the people on board die on impact? Will closure – for everyone, but more so for the victims’ relatives – ever be achieved?
With additional reporting by Demetris Yannopoulos from the Athens News
Copyright © Cyprus Mail 2006
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The above report raises three crucial technical questions arising from the Helios-ajet dispute with Tsolakis' findings:
1) Is it or isn't it physically (humanly) possible for a commercial airliner with 121 people on board to pressurise normally on the ground prior to takeoff - ie as engine/APU bleeds are turned on - with the Outflow Valve barely open (14 degrees from closed) instead of FULL OPEN as it should have been if the Pressurisation Mode Selector Switch was in AUTO and the ground-air sensors working normally?
2) Is it or isn't it physically (humanly) possible for a commercial airliner with 121 people on board to take off at a cabin rate of climb of 2,500ft/min, when the normal (bearable) rate of cabin altitude change is 500-700ft/min, and the minimum allowable differential with a/c flight altitude is 1,800ft/min (otherwise AUTO-FAIL)?
3) Are there or aren't there separate circuit breaker(s) for E-bay equipment cooling fans on the B737-300 models and, if so, where exactly are they located on either of the CB panels?
1) Is it or isn't it physically (humanly) possible for a commercial airliner with 121 people on board to pressurise normally on the ground prior to takeoff - ie as engine/APU bleeds are turned on - with the Outflow Valve barely open (14 degrees from closed) instead of FULL OPEN as it should have been if the Pressurisation Mode Selector Switch was in AUTO and the ground-air sensors working normally?
2) Is it or isn't it physically (humanly) possible for a commercial airliner with 121 people on board to take off at a cabin rate of climb of 2,500ft/min, when the normal (bearable) rate of cabin altitude change is 500-700ft/min, and the minimum allowable differential with a/c flight altitude is 1,800ft/min (otherwise AUTO-FAIL)?
3) Are there or aren't there separate circuit breaker(s) for E-bay equipment cooling fans on the B737-300 models and, if so, where exactly are they located on either of the CB panels?
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I find the above journo report and it's "reliable sources" totally ludicrous.
Some quotes from it:
"The company says it has conducted “extensive tests” showing it would be virtually impossible for a Boeing 737 to take off with the airflow valve at 14 degrees from the fully closed position, as Tsolakis’ findings contend."
How did Helios conduct these tests? Did they place the outflow to manual and opened it only 14degrees and took off with pax onboard many times ???
"Frustratingly, the Tsolakis report cannot verify or disprove whether the warning horns were on throughout the flight. The Cockpit Voice Recorder, which was badly damaged, only contained data from the last 30 minutes".
Of course it does. Not only on the narrative of the report but also on the FDR printouts that prove that the horn was on and was heard on CVR on the last 30min, until the aircraft altitude dropped below 10'000 (obviously).
“There are no circuit breakers for equipment cooling. There’s no question of resetting it, such as by pulling a fuse."
I don't know what Capt. Merten was trying to achieve with the CBs. But THERE ARE CBs for Equip Cooling, despite the "reliable source's" quotes. They are indeed behind the Captain's seat on the -300 (P18-3, A-B-C-B-E-F)
About the fire that started later.
There is plenty of info on the report about what happened. After the first fire was tackled, the ground force of fire engines did not get there on time because a fire engine overturned on the only narrow road to the site. Then, as it happens hundreds of times in forest fires, it was relighted by the strong winds. There was no need of aircraft fuel. There was plenty of fuel in the form of bushes, dry grass and trees which are ready to catch fire in mid August in Greece.
I am ready to question the Tsolakis report, but PLEASE give me something more solid that the journo's hollow report.
Some quotes from it:
"The company says it has conducted “extensive tests” showing it would be virtually impossible for a Boeing 737 to take off with the airflow valve at 14 degrees from the fully closed position, as Tsolakis’ findings contend."
How did Helios conduct these tests? Did they place the outflow to manual and opened it only 14degrees and took off with pax onboard many times ???
"Frustratingly, the Tsolakis report cannot verify or disprove whether the warning horns were on throughout the flight. The Cockpit Voice Recorder, which was badly damaged, only contained data from the last 30 minutes".
Of course it does. Not only on the narrative of the report but also on the FDR printouts that prove that the horn was on and was heard on CVR on the last 30min, until the aircraft altitude dropped below 10'000 (obviously).
“There are no circuit breakers for equipment cooling. There’s no question of resetting it, such as by pulling a fuse."
I don't know what Capt. Merten was trying to achieve with the CBs. But THERE ARE CBs for Equip Cooling, despite the "reliable source's" quotes. They are indeed behind the Captain's seat on the -300 (P18-3, A-B-C-B-E-F)
About the fire that started later.
There is plenty of info on the report about what happened. After the first fire was tackled, the ground force of fire engines did not get there on time because a fire engine overturned on the only narrow road to the site. Then, as it happens hundreds of times in forest fires, it was relighted by the strong winds. There was no need of aircraft fuel. There was plenty of fuel in the form of bushes, dry grass and trees which are ready to catch fire in mid August in Greece.
I am ready to question the Tsolakis report, but PLEASE give me something more solid that the journo's hollow report.
I've only made a few posts so I don't feel the need to order a Personal Title and help support PPRuNe
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As an ex-B737 pilot I am still amazed at the lack of debate about the simple fact that as soon as the warning horn went off, no one looked at the gauges next to the pressurisation panel, namely the cabin rate of climb indicator and more importantly, the cabin altitude indicator. Whist this crew may have confused the warning horn for the configuration warning, they and every other B737 pilot n the world will have learnt AND been examined at some stage on the fact that the cabin altitude warning also uses the same horn.
Besides the fact that they didn't spot the misset pressurisation controller several times is crucial. It matters not one iota that the engineer may not have set it back to Auto after the maintenance. I defy one PROFESSIONAL pilot on here to write on here that they have ever received an aircraft back from maintenance without something not back in the right position. It is a known fact that if we have been informed that maintenance have been fixing the aircraft then we do our pre-flight checks extra carefully in order to spot anything that may not have been returned to its pre-flight position.
That aside, a warning whilst in the initial climb phase should warrant a stop in the climb if safety altitude is not a factor in order that everything can be assessed without the added worry of hypoxia or other high altitude complexities to interfere with fault finding. This crew simply did not do what they were supposedly trained to do. As the report concludes, they were the primary reason that this accident ever took place. There have been other incidences of crew mistakenly misidentifying the cabin altitude warning horn but at least one of the crew members on those flights had the fortunate ability to remember to look at the cabin altitude gauge and realise that the real reason for the warning horn was not a configuration warning.
In short, the crew were ultimately responsible and all this new hype about an electrical problem or some sort of conspiracy theory to hide other problems does not answer why the pilots of the accident flight didn't check their cabin altitude even if they had forgotten that the same warning horn was used for both config and cab alt. I'm sorry to have to say that these fellow pilots made fundamental mistakes and paid the ultimate price. All we can do is learn from their mistakes and hope we can apply the memory if and when it should ever happen to us.
Besides the fact that they didn't spot the misset pressurisation controller several times is crucial. It matters not one iota that the engineer may not have set it back to Auto after the maintenance. I defy one PROFESSIONAL pilot on here to write on here that they have ever received an aircraft back from maintenance without something not back in the right position. It is a known fact that if we have been informed that maintenance have been fixing the aircraft then we do our pre-flight checks extra carefully in order to spot anything that may not have been returned to its pre-flight position.
That aside, a warning whilst in the initial climb phase should warrant a stop in the climb if safety altitude is not a factor in order that everything can be assessed without the added worry of hypoxia or other high altitude complexities to interfere with fault finding. This crew simply did not do what they were supposedly trained to do. As the report concludes, they were the primary reason that this accident ever took place. There have been other incidences of crew mistakenly misidentifying the cabin altitude warning horn but at least one of the crew members on those flights had the fortunate ability to remember to look at the cabin altitude gauge and realise that the real reason for the warning horn was not a configuration warning.
In short, the crew were ultimately responsible and all this new hype about an electrical problem or some sort of conspiracy theory to hide other problems does not answer why the pilots of the accident flight didn't check their cabin altitude even if they had forgotten that the same warning horn was used for both config and cab alt. I'm sorry to have to say that these fellow pilots made fundamental mistakes and paid the ultimate price. All we can do is learn from their mistakes and hope we can apply the memory if and when it should ever happen to us.
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The Laws of Physics and Logic are not a 'new hype' merely because the dead are not here to respond to the gullible.
I therefore repeat two of my questions that have not yet received an answer (with thanks to Gonzo for answering the third one most accurately).
I therefore repeat two of my questions that have not yet received an answer (with thanks to Gonzo for answering the third one most accurately).
1) Is it or isn't it physically (humanly) possible for a commercial airliner with 121 people on board to pressurise normally on the ground prior to takeoff - ie as engine/APU bleeds are turned on - with the Outflow Valve barely open (14 degrees from closed) instead of FULL OPEN as it should have been if the Pressurisation Mode Selector Switch was in AUTO and the ground-air sensors working normally?
2) Is it or isn't it physically (humanly) possible for a commercial airliner with 121 people on board to take off at a cabin rate of climb of 2,500ft/min, when the normal (bearable) rate of cabin altitude change is 500-700ft/min, and the minimum allowable differential with a/c flight altitude is 1,800ft/min (otherwise AUTO-FAIL)?
2) Is it or isn't it physically (humanly) possible for a commercial airliner with 121 people on board to take off at a cabin rate of climb of 2,500ft/min, when the normal (bearable) rate of cabin altitude change is 500-700ft/min, and the minimum allowable differential with a/c flight altitude is 1,800ft/min (otherwise AUTO-FAIL)?
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EyeWideShut
Answer for 2)
As was said in previous thread and I am sure was said to one of your alter egos - an ascending cabin altitude even of 2500 ft/min won't cause pain and is unlikely to cause much discomfort. It is a descending cabin altitude that causes the discomfort or pain at high rates of descent.
If you have flown on a hot summers day it is possible, even likely you have been a pax for a bleeds closed takeoff and never known it was occuring.
TH
Answer for 2)
As was said in previous thread and I am sure was said to one of your alter egos - an ascending cabin altitude even of 2500 ft/min won't cause pain and is unlikely to cause much discomfort. It is a descending cabin altitude that causes the discomfort or pain at high rates of descent.
If you have flown on a hot summers day it is possible, even likely you have been a pax for a bleeds closed takeoff and never known it was occuring.
TH
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Merely an interested pax also but have read the report. There didn't seem to be any explanation for how the male cabin crew survived?
My understanding was that there wouldn't have been sufficient oxygen available in the portable bottles for the duration of the flight?
JBS
My understanding was that there wouldn't have been sufficient oxygen available in the portable bottles for the duration of the flight?
JBS
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Eyes wide shut,
I would not know the answer to your 2 questions. BUT, the report explains the configuration of the test flight, (14degrees outflow, "frozen" by the selector in manual, up to 10.000ft). There is no mention in the report about "unbearable ear pain" or "significant ear pain" in the identical conditions demonstrated. I am sure that if symptoms like these were present, they would have been included in the report.
The company claims (according to the journalist) that they have conducted extensive testing and they claim it is "impossible". I would like them to give us the exact parameters and nature of the testing, so we can have an opinion.
jbsharpe,
The report mentions the 4 portable oxy bottles in the cabin, each with endurance of 1:15h to 2:45. Only one bottle would have been enough. 2 or 3 were found used in the wreckage.
If you are asking the exact actions and survival techniques of the steward the first 2hrs of the flight, we will never know. That would be pure speculation. The reports (usually) don't speculate (much).
I would not know the answer to your 2 questions. BUT, the report explains the configuration of the test flight, (14degrees outflow, "frozen" by the selector in manual, up to 10.000ft). There is no mention in the report about "unbearable ear pain" or "significant ear pain" in the identical conditions demonstrated. I am sure that if symptoms like these were present, they would have been included in the report.
The company claims (according to the journalist) that they have conducted extensive testing and they claim it is "impossible". I would like them to give us the exact parameters and nature of the testing, so we can have an opinion.
jbsharpe,
The report mentions the 4 portable oxy bottles in the cabin, each with endurance of 1:15h to 2:45. Only one bottle would have been enough. 2 or 3 were found used in the wreckage.
If you are asking the exact actions and survival techniques of the steward the first 2hrs of the flight, we will never know. That would be pure speculation. The reports (usually) don't speculate (much).
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Merely an interested pax also but have read the report. There didn't seem to be any explanation for how the male cabin crew survived?
My understanding was that there wouldn't have been sufficient oxygen available in the portable bottles for the duration of the flight?
JBS
My understanding was that there wouldn't have been sufficient oxygen available in the portable bottles for the duration of the flight?
JBS
----------------------------------------
Page 55 (1.12.2.10)
A total of four portable oxygen bottles were located at the accident site [...]. The following describes the condition of each of the four bottles:
• Bottle number 1: [...] The shut-off valve was rotated one revolution clockwise (360 degrees) until it was in the fully closed position.• Bottle number 2: [...] The shut-off valve was rotated one revolution clockwise (360 degrees) until it was in the fully closed position.
• Bottle number 3: [...] The shut-off valve was found in the fully closed position.
• Bottle number 4: [...] The shut-off valve was rotated 1½ revolutions clockwise to the fully closed position.
-----------------------------------------------------page 126
The amount of oxygen supplied by the passenger
oxygen system was designed to last 12 minutes. In order to retain consciousness after the depletion of the oxygen from the passenger oxygen system, a person on board would have had to make use of one of the additional means of oxygen supply available on board
the aircraft, i.e. the portable oxygen bottles. All four oxygen bottles were retrieved from the wreckage; three bottles were found with their valves in the open position. The Board concluded that these bottles were most likely used by someone on board the aircraft.
The amount of oxygen supplied by the passenger
oxygen system was designed to last 12 minutes. In order to retain consciousness after the depletion of the oxygen from the passenger oxygen system, a person on board would have had to make use of one of the additional means of oxygen supply available on board
the aircraft, i.e. the portable oxygen bottles. All four oxygen bottles were retrieved from the wreckage; three bottles were found with their valves in the open position. The Board concluded that these bottles were most likely used by someone on board the aircraft.
--------------------------------------------------
page 33
1.6.3.5.2.2 Passenger Portable Oxygen
The cylinders have a maximum capacity of 311 liters (11 cubic feet) of free oxygen when pressurized to 1 800 psi. The oxygen could be used either through a four liter per minute outlet, or through a two liter per minute outlet, resulting in an oxygen availability duration of 1h 17 minutes or 2h 35 minutes, respectively.
-------------------------------------------------1.6.3.5.2.2 Passenger Portable Oxygen
The cylinders have a maximum capacity of 311 liters (11 cubic feet) of free oxygen when pressurized to 1 800 psi. The oxygen could be used either through a four liter per minute outlet, or through a two liter per minute outlet, resulting in an oxygen availability duration of 1h 17 minutes or 2h 35 minutes, respectively.
Always according to the report
, during the FL340 cruise, the cabin was estimated to reach and maintain approximately an altitude of 24,000ft (ie a lot lower that the one attained by the aircraft).The cabin crew would have initially donned the oxygen masks which activate with the rest of the passenger oxygen supply "rubber jungle" (and cannot be stopped once activated), while strapped in their seats .
Passenger oxygen masks were deployed at 061453Z when the aircraft was passing 18200 ft (cabin altitude 14000ft). The last 30 minutes of the CVR reveal that a chime similar to someone entering the code necessary to unlock the flight deck door was recorded at 084851Z ie 2h and 34min into the "partial compression" phase and noises were recorded consistent with someone donning of the oxygen mask and adjusting the captain's seat.
QED
TR
-------------------------------
ThinkRate! ThinkRate! Don't Think!
-------------------------------
ThinkRate! ThinkRate! Don't Think!
Holes in the cheese
Originally I and others were working with the assumption that the crew realised the pressurisation problem and that their O2 system had been compromised in some way, but the report makes it plain that that was not so.
A common thread of the non-fatal pressurisation incidents discussed in the report is that the cabin crews did not let much time elapse before raising a fuss when there was no descent after the rubber jungle came down.
And it does raise issues of training and SOPs on both sides of the cockpit door.
Perhaps we need something a bit more obvious to let the flight crew know the rubber jungle's about to come down or has.
Maybe the crew oxygen masks could pop out? Provided of course that they stay within reach.
In the interim, how about hanging a balloon off the overhead panel
More likely this scenario will be included in the recurrent training syllabus if it's not already there.
A common thread of the non-fatal pressurisation incidents discussed in the report is that the cabin crews did not let much time elapse before raising a fuss when there was no descent after the rubber jungle came down.
And it does raise issues of training and SOPs on both sides of the cockpit door.
Perhaps we need something a bit more obvious to let the flight crew know the rubber jungle's about to come down or has.
Maybe the crew oxygen masks could pop out? Provided of course that they stay within reach.
In the interim, how about hanging a balloon off the overhead panel
More likely this scenario will be included in the recurrent training syllabus if it's not already there.
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Have often wondered about the rubber jungle. Are there not different types? It's usually chemical reaction produced O2 in this type for the pax right? Are all the masks in the jungle spilling oxygen from the moment they drop? What's the briefed "pull sharply down" action for? Doesn't that start the flow in some systems?
Just found this in the other thread:
So is there a chance the spares in the rubber jungle may have been exploited by a number of people who knew how they were triggered (or not triggered yet)? I remember early (still unsubstantiated?) reports that there seemed to be evidence of a number of conscious passengers at the end. How many spares this flight? Was this 733 configured up to 149 max seats plus JAA mandatory min 10% extra masks or was it the earlier 128 max seats plus min 10% extra masks? So in a 149 config you have perhaps 50 separate pax oxygen triggers and if Pointer is correct you could have as many as nearly 200 total masks in the jungle for the 121 on board?
Just found this in the other thread:
RatherBeFlying and others;
For my 737's;on every seat row(3 seats) there are L and R, 4 masks availlable, wich are activated when pulled, if one is pulled all are activated, used or not,(in that row)
Think there is a mask in toilet as well. no masks for so called cue.
Pointer
For my 737's;on every seat row(3 seats) there are L and R, 4 masks availlable, wich are activated when pulled, if one is pulled all are activated, used or not,(in that row)
Think there is a mask in toilet as well. no masks for so called cue.
Pointer
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From today's Cyprus Mail Internet edition:
Helios criminal case opened in Greece
AN ATHENS public prosecutor yesterday launched criminal proceedings into the Helios air crash of August 14, 2005.
The proceedings concern “voluntary manslaughter with probable malice against all involved parties,” or gross negligence leading to death.
It paves the way for Greek police investigators to begin questioning people both here and in Greece.
The crash victims’ relatives welcomed the news. Speaking on CyBC television last night, the relatives’ spokesman Nicolas Yiasoumis said: “This finally gives the green light… so that the guilty - who murdered 121 people in the air - may be brought to justice.”
Lawyer Efstathios Efstathiou was also optimistic that convictions would be possible in Greece.
He said the Greek justice system was more “flexible” in cases of gross negligence.
He was alluding to recent comments by Attorney-general Petros Klerides that prosecuting anyone in Cyprus would be “very difficult.”
Klerides’ remarks had infuriated the relatives and their lawyers, who have been waiting for 14 months for the cogs of justice to turn.
According to Efstathiou, in Greece it is even possible for civil suit lawyers to attend criminal trial hearings.
The victims’ relatives are suing plane manufacturers Boeing in the United States for a string of build and design omissions, which they say contributed to the crash.
The fact-finding report into the accident named pilot error as the primary cause, merely citing the airline’s operating deficiencies under the “latent causes.”
A police investigation is also underway on the island. Despite conflicting reports, the latest interpretation is that the Attorney-general will use this together with the findings of an independent commission of inquiry to decide whether to prosecute.
The broad mandate of the commission, headed by ex Supreme Court judge Panayiotis Kallis, is to “recommend” who is responsible for the accident. However, it was only after the publication of the Tsolakis accident report earlier this month that it emerged the commission’s findings were not binding on authorities.
Even more confusingly, this week Kallis said his commission would base its conclusions exclusively on the Tsolakis report - which raises the question of why the commission should function at all.
Moreover, Kallis’ assertion does not appear to be consistent with the train of events: if the commission was to be based solely on the report, then why did it start convening before the report was out?
Copyright © Cyprus Mail 2006
Helios criminal case opened in Greece
AN ATHENS public prosecutor yesterday launched criminal proceedings into the Helios air crash of August 14, 2005.
The proceedings concern “voluntary manslaughter with probable malice against all involved parties,” or gross negligence leading to death.
It paves the way for Greek police investigators to begin questioning people both here and in Greece.
The crash victims’ relatives welcomed the news. Speaking on CyBC television last night, the relatives’ spokesman Nicolas Yiasoumis said: “This finally gives the green light… so that the guilty - who murdered 121 people in the air - may be brought to justice.”
Lawyer Efstathios Efstathiou was also optimistic that convictions would be possible in Greece.
He said the Greek justice system was more “flexible” in cases of gross negligence.
He was alluding to recent comments by Attorney-general Petros Klerides that prosecuting anyone in Cyprus would be “very difficult.”
Klerides’ remarks had infuriated the relatives and their lawyers, who have been waiting for 14 months for the cogs of justice to turn.
According to Efstathiou, in Greece it is even possible for civil suit lawyers to attend criminal trial hearings.
The victims’ relatives are suing plane manufacturers Boeing in the United States for a string of build and design omissions, which they say contributed to the crash.
The fact-finding report into the accident named pilot error as the primary cause, merely citing the airline’s operating deficiencies under the “latent causes.”
A police investigation is also underway on the island. Despite conflicting reports, the latest interpretation is that the Attorney-general will use this together with the findings of an independent commission of inquiry to decide whether to prosecute.
The broad mandate of the commission, headed by ex Supreme Court judge Panayiotis Kallis, is to “recommend” who is responsible for the accident. However, it was only after the publication of the Tsolakis accident report earlier this month that it emerged the commission’s findings were not binding on authorities.
Even more confusingly, this week Kallis said his commission would base its conclusions exclusively on the Tsolakis report - which raises the question of why the commission should function at all.
Moreover, Kallis’ assertion does not appear to be consistent with the train of events: if the commission was to be based solely on the report, then why did it start convening before the report was out?
Copyright © Cyprus Mail 2006
Late developer,
Just some background info on the pax oxy masks in the 737.
The flow of oxygen in the pax oxy masks will not start until you pull sharply down on one of your individual group of 3 or 4 masks. This little snippet of info is one of the reasons why the cabin crew do a safety demo before every flight.
There are a couple of good reasons why the oxy does not flow until pulled:
1. In case the oxy masks were deployed accidentally (wrong switch or heavy landing) you would then have no oxy left if you needed it.
2. If the flight were not full it would introduce large amounts of oxy into the cabin which would be a fire risk.
It should be noted that any unpulled masks give the cabin crew to option to “monkey swing” around the cabin without portable oxy if reqd. This may be what the cabin crew member in the flight deck did to extend his time of useful consciousness.
The spare 10% is usually achieved by having 3 masks on one side and 4 on the other, this allows for infants carried on parents knees. It is also to allow for either a unit not dropping out or a unit not producing oxygen when demanded. In my experience at least one group of oxy masks do not drop when demanded, sometimes more. Even if there were only one pax in each seat block who had activated their oxy then there would be no more spares (other than those in the galley & toilets) because pulling one mask activates all the masks in the group.
S&L
Just some background info on the pax oxy masks in the 737.
The flow of oxygen in the pax oxy masks will not start until you pull sharply down on one of your individual group of 3 or 4 masks. This little snippet of info is one of the reasons why the cabin crew do a safety demo before every flight.
There are a couple of good reasons why the oxy does not flow until pulled:
1. In case the oxy masks were deployed accidentally (wrong switch or heavy landing) you would then have no oxy left if you needed it.
2. If the flight were not full it would introduce large amounts of oxy into the cabin which would be a fire risk.
It should be noted that any unpulled masks give the cabin crew to option to “monkey swing” around the cabin without portable oxy if reqd. This may be what the cabin crew member in the flight deck did to extend his time of useful consciousness.
The spare 10% is usually achieved by having 3 masks on one side and 4 on the other, this allows for infants carried on parents knees. It is also to allow for either a unit not dropping out or a unit not producing oxygen when demanded. In my experience at least one group of oxy masks do not drop when demanded, sometimes more. Even if there were only one pax in each seat block who had activated their oxy then there would be no more spares (other than those in the galley & toilets) because pulling one mask activates all the masks in the group.
S&L
Last edited by CaptainSandL; 25th Oct 2006 at 08:44. Reason: monkey walk changed to monkey swing
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Trash Hauler,
My 'aliases' do not include the person named as Ground Engineer Number One in the Tsolakis Report, and whose “extensive tests” reported by Helios/Ajet will be detailed below.
As for your comment regarding cabin altitude rate of climb reaching 2,000-2,500 ft/min without noticeable discomfort, human physiology (say, of the eardrums) is not known to differentiate between ascent and descent – only between rates of change of atmospheric pressure. Therefore your comment about descent effectively supports the logical assumption that the discomfort (especially with 25 children on board) would indeed be very noticeable at a much earlier stage of the takeoff than FL120 when the Horn started beeping.
Gonzo,
Thank you for your constructive posts on this thread. Your query about the actual tests conducted by Helios is answered below. The text reflects the OFFICIAL position of the Cypriot company, as well as that of several Greek and British pilots, engineers and accident investigators whose names are withheld by request:
There is deep concern in Cyprus and Greece about the Report scenario being founded on the single assumption that the engineer left the pressurisation mode selector in MANual with the outflow valve at about 14.6° from the closed position. Total travel from fully open to fully closed is 110°.
The evidence presented by Chief Investigator Akrivos Tsolakis suggests that the bleeds were on throughout the flight and that the aircraft only partially pressurised to a 1 psi differential because the outflow valve was at about 14.6° from the closed position.
The argument is about not whether but at what stage this became the situation.
The assumption in the AAIASB Report is that it was at the end of the maintenance procedure, due to the alleged omission of the ground engineers to switch the Pressurisation Mode Selector back to AUTO.
However there are convincing arguments and empirical evidence that this is unlikely and that for reason or reasons yet unknown it occurred after takeoff but likely before the cabin altitude reached 10,000 ft.
The first point is that the captain and the first officer must each have made serious errors of omission during their independent preflight check of different components of the pressurisation system; the captain by not checking that the main outflow valve was fully open and the first officer by not checking that the mode selector was in AUTO.
They must then both have missed the abnormalities on the pressurisation panel during the various challenge and response checklist actioned before and after take off.
The engineer who did the maintenance, Mr Alan Irwin, (named Ground Engineer Number One in the Report), contested this scenario when interviewed in the UK by British aviation experts and his comments on the Report were considered and formally submitted to the AAIASB by the UK Air Accidents Investigation Branch (AAIB) itself.
One comment related to the significant pressure fluctuations that would occur during the aircraft start sequence if the mode selector was in Manual and the OFV about 14.6° from closed. The validity of the submission was verified by a competent UK AAIB engineer before it was sent to AAIASB for consideration.
To reinforce the engineer’s submission a practical test was devised by Mr Irwin in Britain. The UK AAIB declined to attend as they were satisfied that the written report he had submitted through their office accurately reflected the situation, consequently they did not require empirical proof.
Reassurance was given by the Greek AAIASB in July that the engineer’s comments on the Preliminary Report would be appended to the Final Report if no agreement could be reached. Although this is required by ICAO Annex 13 and - more importantly - by Greek Law, it was not done. Helios/Ajet’s comments were also not appended.
The tests conducted and incorporated in Mr Irwin’s submission to the AAIASB confirmed the following:
Under normal circumstances, there are no significant fluctuations of cabin pressure while the aircraft is on the ground because the selector is at AUTOmatic and the OFV is driven fully open. Even when all the doors are closed this is sufficient to keep the cabin at the same pressure as the outside world.
The AAIASB Report assumes that the selector was in MANual and the OFV about 14.6° from closed when the flight crew started their various preflight preparations.
In this condition, air is fed into the cabin and escapes through the various open doors and apertures, a relatively small amount also escaping through the almost closed OFV. The differential between the cabin and the outside world would remain at zero.
When the passengers are on board and the last door is closed, the air can only escape through the partially closed OFV and natural leakage points. The aircraft starts to pressurise immediately. All the aircraft occupants would immediately feel the effect on their ears and the attention of the flight crew would be drawn naturally to the pressurisation panel by this abnormal situation.
Immediately before engine start, the air supply to the cabin is switched off and it would start to depressurise immediately. All the aircraft occupants would again feel the effect on their ears and the attention of the flight crew would be drawn naturally to the pressurisation panel by this abnormal situation.
After the engines are started, the air supply to the cabin is reinstated. The cabin would start to pressurise immediately. All the aircraft occupants would feel the effect on their ears and the attention of the flight crew would be drawn naturally to the pressurisation panel by this abnormal situation.
These three significant fluctuations of pressure during this period would be abnormal and evident to all occupants of the aircraft and there significance would be obvious to the flight crew.
Pilots are very aware that it is very important that the aircraft is not pressurised for take off, or landing. If the aircraft is pressurised and an emergency occurs on the ground that required an aircraft evacuation, it would not be possible to open the doors and hatches to allow the occupants to escape.
The long string of ostensibly co-incidental omissions by the flight crew and the abnormal pressure fluctuations during the engine start sequence are compelling evidence that the selector would not have been in MANual with the OFV 14.54° from closed when the flight crew arrived at the aircraft.
The point made about a cabin rate of climb of 2,500 feet per minute being noticeable is valid in its own right, regardless of the preceding implausible situation on the ground. While the aircraft climbs at up to 3,000 fpm to its cruise altitude, the cabin being pressurised only has to climb to about 8,000 feet so climbs at a much lower rate, 500 to 700 fpm. This is comfortable to the occupants and is not normally noticeable with unbearable discomfort. The rapid pressure changes experienced in a climb at 2,000-2,500 fpm would be very noticeable even for the experienced flight crew.
Conclusion
The accident scenario in Final Report depends entirely on the assumption that the pressurisation mode selector was left at MANual, with the outflow valve at about 14.6° from closed, after the unscheduled maintenance procedure earlier that morning. Although there is circumstantial evidence that the system was in manual from shortly after take off , there is no firm evidence to support the theory that it was left in MANual by the engineer.
The Report does not consider any alternative scenario.
Therefore if the Board accepted the statement by the engineer that he left the selector in AUTOmatic and considered the comments on the Draft Report by both the engineer and Helios/Ajet that supported this, the Board would have been obliged to reopen the investigation and start again, as the whole accident scenario was based on this single assumption.
My 'aliases' do not include the person named as Ground Engineer Number One in the Tsolakis Report, and whose “extensive tests” reported by Helios/Ajet will be detailed below.
As for your comment regarding cabin altitude rate of climb reaching 2,000-2,500 ft/min without noticeable discomfort, human physiology (say, of the eardrums) is not known to differentiate between ascent and descent – only between rates of change of atmospheric pressure. Therefore your comment about descent effectively supports the logical assumption that the discomfort (especially with 25 children on board) would indeed be very noticeable at a much earlier stage of the takeoff than FL120 when the Horn started beeping.
Gonzo,
Thank you for your constructive posts on this thread. Your query about the actual tests conducted by Helios is answered below. The text reflects the OFFICIAL position of the Cypriot company, as well as that of several Greek and British pilots, engineers and accident investigators whose names are withheld by request:
There is deep concern in Cyprus and Greece about the Report scenario being founded on the single assumption that the engineer left the pressurisation mode selector in MANual with the outflow valve at about 14.6° from the closed position. Total travel from fully open to fully closed is 110°.
The evidence presented by Chief Investigator Akrivos Tsolakis suggests that the bleeds were on throughout the flight and that the aircraft only partially pressurised to a 1 psi differential because the outflow valve was at about 14.6° from the closed position.
The argument is about not whether but at what stage this became the situation.
The assumption in the AAIASB Report is that it was at the end of the maintenance procedure, due to the alleged omission of the ground engineers to switch the Pressurisation Mode Selector back to AUTO.
However there are convincing arguments and empirical evidence that this is unlikely and that for reason or reasons yet unknown it occurred after takeoff but likely before the cabin altitude reached 10,000 ft.
The first point is that the captain and the first officer must each have made serious errors of omission during their independent preflight check of different components of the pressurisation system; the captain by not checking that the main outflow valve was fully open and the first officer by not checking that the mode selector was in AUTO.
They must then both have missed the abnormalities on the pressurisation panel during the various challenge and response checklist actioned before and after take off.
The engineer who did the maintenance, Mr Alan Irwin, (named Ground Engineer Number One in the Report), contested this scenario when interviewed in the UK by British aviation experts and his comments on the Report were considered and formally submitted to the AAIASB by the UK Air Accidents Investigation Branch (AAIB) itself.
One comment related to the significant pressure fluctuations that would occur during the aircraft start sequence if the mode selector was in Manual and the OFV about 14.6° from closed. The validity of the submission was verified by a competent UK AAIB engineer before it was sent to AAIASB for consideration.
To reinforce the engineer’s submission a practical test was devised by Mr Irwin in Britain. The UK AAIB declined to attend as they were satisfied that the written report he had submitted through their office accurately reflected the situation, consequently they did not require empirical proof.
Reassurance was given by the Greek AAIASB in July that the engineer’s comments on the Preliminary Report would be appended to the Final Report if no agreement could be reached. Although this is required by ICAO Annex 13 and - more importantly - by Greek Law, it was not done. Helios/Ajet’s comments were also not appended.
The tests conducted and incorporated in Mr Irwin’s submission to the AAIASB confirmed the following:
Under normal circumstances, there are no significant fluctuations of cabin pressure while the aircraft is on the ground because the selector is at AUTOmatic and the OFV is driven fully open. Even when all the doors are closed this is sufficient to keep the cabin at the same pressure as the outside world.
The AAIASB Report assumes that the selector was in MANual and the OFV about 14.6° from closed when the flight crew started their various preflight preparations.
In this condition, air is fed into the cabin and escapes through the various open doors and apertures, a relatively small amount also escaping through the almost closed OFV. The differential between the cabin and the outside world would remain at zero.
When the passengers are on board and the last door is closed, the air can only escape through the partially closed OFV and natural leakage points. The aircraft starts to pressurise immediately. All the aircraft occupants would immediately feel the effect on their ears and the attention of the flight crew would be drawn naturally to the pressurisation panel by this abnormal situation.
Immediately before engine start, the air supply to the cabin is switched off and it would start to depressurise immediately. All the aircraft occupants would again feel the effect on their ears and the attention of the flight crew would be drawn naturally to the pressurisation panel by this abnormal situation.
After the engines are started, the air supply to the cabin is reinstated. The cabin would start to pressurise immediately. All the aircraft occupants would feel the effect on their ears and the attention of the flight crew would be drawn naturally to the pressurisation panel by this abnormal situation.
These three significant fluctuations of pressure during this period would be abnormal and evident to all occupants of the aircraft and there significance would be obvious to the flight crew.
Pilots are very aware that it is very important that the aircraft is not pressurised for take off, or landing. If the aircraft is pressurised and an emergency occurs on the ground that required an aircraft evacuation, it would not be possible to open the doors and hatches to allow the occupants to escape.
The long string of ostensibly co-incidental omissions by the flight crew and the abnormal pressure fluctuations during the engine start sequence are compelling evidence that the selector would not have been in MANual with the OFV 14.54° from closed when the flight crew arrived at the aircraft.
The point made about a cabin rate of climb of 2,500 feet per minute being noticeable is valid in its own right, regardless of the preceding implausible situation on the ground. While the aircraft climbs at up to 3,000 fpm to its cruise altitude, the cabin being pressurised only has to climb to about 8,000 feet so climbs at a much lower rate, 500 to 700 fpm. This is comfortable to the occupants and is not normally noticeable with unbearable discomfort. The rapid pressure changes experienced in a climb at 2,000-2,500 fpm would be very noticeable even for the experienced flight crew.
Conclusion
The accident scenario in Final Report depends entirely on the assumption that the pressurisation mode selector was left at MANual, with the outflow valve at about 14.6° from closed, after the unscheduled maintenance procedure earlier that morning. Although there is circumstantial evidence that the system was in manual from shortly after take off , there is no firm evidence to support the theory that it was left in MANual by the engineer.
The Report does not consider any alternative scenario.
Therefore if the Board accepted the statement by the engineer that he left the selector in AUTOmatic and considered the comments on the Draft Report by both the engineer and Helios/Ajet that supported this, the Board would have been obliged to reopen the investigation and start again, as the whole accident scenario was based on this single assumption.
Per Ardua ad Astraeus
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I would add a couple of clarification points here, without commenting on either the accident or the investigation except to say that I am, sadly, probably as uncertain now as to the cause as I was last year.
- this is in fact not so, as Trash hauler said. The physiology of the ear/eustachion tube system is such that increasing altitude is normally coped with without discomfort as the 'flow' of air through the tubes from the middle ear is outwards, thus opening the end of the tube without difficulty. Decreasing altitude requires an 'inflow' of air via the tube, and this is when the mouth of the tube tends to be forced closed by the pressure differential, making 'descent' more noticeable as stated. Whilst the quoted '2500-3000' rate of climb would probably be noticed by the passengers/crew, it would probably not cause any discomfort.
- this and subsequent references are not always born out in reality. My ears have always been more 'sensitive' to pressure change throughout my flying career than 'the average', and many is the time I have 'noticed' a change in cabin pressure and commented on it to find that the other pilot had not. Although one might expect the crew to pick up such pressure changes as you describe, it is by no means assured.
human physiology (say, of the eardrums) is not known to differentiate between ascent and descent
All the aircraft occupants would immediately feel the effect on their ears and the attention of the flight crew would be drawn naturally to the pressurisation panel by this abnormal situation.
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.... regarding cabin altitude rate of climb reaching 2,000-2,500 ft/min without noticeable discomfort, human physiology (say, of the eardrums) is not known to differentiate between ascent and descent – only between rates of change of atmospheric pressure. Therefore your comment about descent effectively supports the logical assumption that the discomfort (especially with 25 children on board) would indeed be very noticeable at a much earlier stage of the takeoff than FL120 when the Horn started beeping.
You would not expect a difference, but there is one. JAA maximum permitted rate of cabin pressure descent during normal operation is only -300 feet/min i.e. a whopping minimum nearly 27 mins for a normal descent if the cabin altitude reaches 8000 feet in the cruise.
The JAA maximum permitted rate of ascent is I believe +500 feet per min. I don't know the theory behind these JAA differences, although my old physics with biophysics degree head is actually quite capable of accepting that there probably IS a physiological difference between pumping out your inner ear through the Eustachians on the way up and pumping it up the same way on the way down. A bit like a football bladder in reverse perhaps?
My daughter is something of a mineshaft canary for monitoring what happens. She suffers from inflammed Eustachian Tubes more than the average person as she has childhood asthma and is allergic to housedust/seatdust etc. She NEVER has a problem going up although she notices it. She almost ALWAYS has a problem coming down which reduces her to tears if she is unprepared with earplugs and maybe Calpol if we know she starts the flight under par. This is especially the case when the JAA limit is 'somewhat tested' on the way down.
Edit: Got there before me BOAC!
Last edited by late developer; 25th Oct 2006 at 09:03.
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English Final Report available
For those who have not obtained the Final Report yet. It is available now on:
http://www.moi.gov.cy/moi/pio/pio.ns...ghlight=5B-DBY
If there are problems try : http://rapidshare.com/files/599544/F...ORT_5B-DBY.pdf
Regards
CS
http://www.moi.gov.cy/moi/pio/pio.ns...ghlight=5B-DBY
If there are problems try : http://rapidshare.com/files/599544/F...ORT_5B-DBY.pdf
Regards
CS
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Eyewideshut wrote
"As for your comment regarding cabin altitude rate of climb reaching 2,000-2,500 ft/min without noticeable discomfort, human physiology (say, of the eardrums) is not known to differentiate between ascent and descent – only between rates of change of atmospheric pressure. Therefore your comment about descent effectively supports the logical assumption that the discomfort (especially with 25 children on board) would indeed be very noticeable at a much earlier stage of the takeoff than FL120 when the Horn started beeping."
You are incorrect in that portion of your statement bolded above. If you do some research on the "physiology" of the ear and the function of the Eustachian tube you will discover that it is descending altitude (increase in air pressure) that is the most difficult for the ear pressure to equalise and this causes the discomfort and pain. I first flew in an aircraft at 2 months old and all through my growing up years as well. As a child it was always the descent that caused discomfort not the ascent. I have had 18 years flying aircraft professionally and my experience is the same.
Aliases eh.........your writing style is still the same as it was 12 months ago although I suspect you change computers a little more often than you did then.
"As for your comment regarding cabin altitude rate of climb reaching 2,000-2,500 ft/min without noticeable discomfort, human physiology (say, of the eardrums) is not known to differentiate between ascent and descent – only between rates of change of atmospheric pressure. Therefore your comment about descent effectively supports the logical assumption that the discomfort (especially with 25 children on board) would indeed be very noticeable at a much earlier stage of the takeoff than FL120 when the Horn started beeping."
You are incorrect in that portion of your statement bolded above. If you do some research on the "physiology" of the ear and the function of the Eustachian tube you will discover that it is descending altitude (increase in air pressure) that is the most difficult for the ear pressure to equalise and this causes the discomfort and pain. I first flew in an aircraft at 2 months old and all through my growing up years as well. As a child it was always the descent that caused discomfort not the ascent. I have had 18 years flying aircraft professionally and my experience is the same.
Aliases eh.........your writing style is still the same as it was 12 months ago although I suspect you change computers a little more often than you did then.
Last edited by Trash Hauler; 25th Oct 2006 at 11:37. Reason: to correct grammar
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Perhaps aerobatic pilots and divers can offer more observations and any PP who has deliberately gone up at that rate unpressurised.
I don't know why JAA limit going up is set at +500ft/min cabin altitude. It could be for reasons other than discomfort.
I also know from more than one experience that cabin crews do not immediately alert the flight deck if only a few children are experiencing problems. They are more likely to put some hot water on a tissue in the bottom of a plastic cup and suggest the injured child then cups it over their ear! (Truly!)
Even if there was fuss in the cabin it might soon calm down as the effects of hypoxia took hold.
Before we leave this, some readers might be interested in a 2004 UK Department of Transport study of various types of cabin observation in two types, one of which was 733. http://www.dft.gov.uk/stellent/group...ion_027562.pdf. Forgive me if this report has been highlighted before. It shows that +500/-300 limits are routinely broken albeit max breaches were measured at +554/-449 in the 6x733 study flights (greater routine breaches were measured on a sample of 7xBAe146 flights in the same study). Interestingly, they also measured max 733 cabin altitude at about 6800 with average 6500 in their sample which tallies better with what I was taught was the general case ('usually between 6000 and 8000, and certainly not above 8000'). We were also taught that the worst affected regular smokers experienced effects 5000 feet worse than healthy passengers and crew. 8000+5000=13000 hence the 8000 absolute maximum cabin altitude so that smokers (pilots or pax) do not get rendered unconscious on any regular basis.
By all means let's now get back to the other question you raised I will bump back down here for you:
Now, can we get back to the dispute over the single Switch Assumption scenario... please?
Let's start with the obvious question: Could the Ground Engineers Numbers One and Two of the Tsolakis Report open the door to exit the plane after their pressurisation test, if they had left the OFV almost closed at a 14.6-degree angle (which means the plane had barely 'depressurised' from its maximum 8psi differential reached during the test)?