rolfen
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Helios 522 And The B737 Pressure Warning

Mon Dec 20, 2010 4:51 am

Hi, I just watched the helios 522 documentary (again) and something boggles me ... Isn't there a "cabin pressure" warning light somewhere in a visible place in the cockpit?
rolf
 
Fly2HMO
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 20, 2010 4:56 am

Quoting rolfen (Thread starter):
Hi, I just watched the helios 522 documentary (again) and something boggles me ... Isn't there a "cabin pressure" warning light somewhere in a visible place in the cockpit?

IIRC, a master warning annunciation will go off directing attention to the pressurization panel, which will have yet another warning displayed. It will go off when the cabin pressure goes above 14000ft. Been a while since my 737 training though so take that with a grain of salt.

Also, while I haven't seen that documentary, I seem to recall reading that the warning system was defective.
 
KELPkid
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 20, 2010 6:43 am

Quoting Fly2HMO (Reply 1):
Also, while I haven't seen that documentary, I seem to recall reading that the warning system was defective.

As I recall (from reading up on the accident), in the 737 Classic, the cabin altitude warning uses the same warning horn as the takeoff misconfiguration warning. The flight crew (poorly trained, and who could barely communicate with each other due to language issues-the captain was German and the F/O was a Cypriot, and apparently the two did not have enough command of the English language to effectively communicate with each other in English) disregarded the warning as a spurious nuissance, since it did not seem likely that a takeoff misconfiguration warning would be issued while climbing well after takeoff. The warning horn sounded just like it should have, however the crew did not properly recognize the warning as a cabin altitude warning. All communications following this warning showed that the flight crew was suffering the effects of hypoxia.
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tdscanuck
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 20, 2010 6:48 am

Quoting rolfen (Thread starter):
Isn't there a "cabin pressure" warning light somewhere in a visible place in the cockpit?

Yes. There can be a "CABIN ALTITUDE" light right next to the TAKEOFF CONFIG light (center console) but I'm not sure if the Helios flight had that, there's always a warning horn, and (assuming you were in auto mode when the failure happened), you'll get an AUTO FAIL light on the pressurization panel.

Quoting Fly2HMO (Reply 1):
IIRC, a master warning annunciation will go off directing attention to the pressurization panel, which will have yet another warning displayed. It will go off when the cabin pressure goes above 14000ft. Been a while since my 737 training though so take that with a grain of salt.

You should get a master warning and illumination of the AIR COND six-pack light, which directs the flight crew to look up at the air conditioning panel where you would see the actual cabin altitude, the AUTO FAIL light, etc.

Quoting Fly2HMO (Reply 1):
Also, while I haven't seen that documentary, I seem to recall reading that the warning system was defective.

The maintenance crew didn't put the pressurization system back in the mode the flight crew expected. The warning system worked just fine, and correctly annunciated to the crew that the cabin altitude was becoming too high. However, the cabin altitude warning and the takeoff config warning use the same horn...apparently, the crew mistook one for the other. This is somewhat baffling, as you only get takeoff warning on the ground, and only get cabin altitude warning in flight (excepting very high altitude airports, which wasn't the case here).

Basically, the plane correctly told the flight crew exactly what was wrong. They misinterpreted the warning, for reasons unknown, and didn't take the appropriate corrective action.

Tom.
 
rolfen
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 20, 2010 7:10 am

Quoting tdscanuck (Reply 3):
Yes. There can be a "CABIN ALTITUDE" light right next to the TAKEOFF CONFIG light (center console) but I'm not sure if the Helios flight had that,

You are right, here it is:
http://www.b737.org.uk/pressurisation.htm

But followed by the note:

Quote:
Following the Helios accident where the crew did not correctly identify the cabin altitude warning horn, new red "CABIN ALTITUDE" and "TAKEOFF CONFIG" warning lights were fitted to the P1 & P3 panels to supplement the existing aural warning system.

So apparently they did not have it...

The second question I was asking myself is: even if there is no warning light, don't they have a reference at hand for understanding different warning sounds...?

Anyway I'm no pilot I was just under the impression that the 737 cockpit had a clear visible cabin altitude warning, and it does, but unfortunately was only added after the Helios accident.
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HAWK21M
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 20, 2010 10:36 am

Quoting rolfen (Reply 4):
Anyway I'm no pilot I was just under the impression that the 737 cockpit had a clear visible cabin altitude warning, and it does, but unfortunately was only added after the Helios accident.

The Aural warning was always present.The additional lights on the front panel were added.
http://www.b737.org.uk/helios.htm

regds
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tdscanuck
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 20, 2010 2:29 pm

Quoting rolfen (Reply 4):
The second question I was asking myself is: even if there is no warning light, don't they have a reference at hand for understanding different warning sounds...?

Sort of, in this case. The FCOM is very specific that the takeoff config warning and cabin altitude warning use the same horn (same sound). The argument that this was an acceptable thing to do is that the two modes are mutually exclusive (except very high altitude airports, which is a corner case with special planning anyway). If you get the horn in air, it's the cabin altitude. If you get the horn on the ground, it's takeoff config.

The crew had all the information necessary (including the great big cabin pressure readout on the overhead panel) to understand what was happening. However, they got task focussed and misinterpreted the warning. There's obviously a human factors issues there, but it's an open question as to exactly how much misinterpretation can you assume on the behalf of the flight crew.

This isn't a new problem from the Helios accident...pilots have flown aircraft into the ground while fixated on troubleshooting a different problem, or on torubleshooting what they think is the problem instead of what's actually the problem. This was just a particularly egregious example.

Tom.
 
mandala499
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 20, 2010 2:56 pm

Quoting tdscanuck (Reply 6):
This isn't a new problem from the Helios accident

Definitely isn't!

Quoting tdscanuck (Reply 3):
However, the cabin altitude warning and the takeoff config warning use the same horn...apparently, the crew mistook one for the other. This is somewhat baffling, as you only get takeoff warning on the ground, and only get cabin altitude warning in flight (excepting very high altitude airports, which wasn't the case here).

And one would be amazed at how many crew made the mistake (although all but Helios) and only eventually realizing that it was the cabin pressure. A lot of training is on take offs and landings (which is of no surprise) and one tends to immediately realize what the noise is telling you!

Instead of trying to figure out what the noise is (since it can't be take off config if you're already airborne... unless some wiring is screwed up (to which I am told has happened but probably very rarely)), the Captain simply wanted to know "how to switch the damn thing off" by calling Ops...

But am glad that the "CABIN ALTITUDE" and "TAKEOFF CONFIG" lights are now in place.

Mandala499
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 20, 2010 4:43 pm

Quoting KELPkid (Reply 2):
The warning horn sounded just like it should have, however the crew did not properly recognize the warning as a cabin altitude warning.
Quoting tdscanuck (Reply 3):

You should get a master warning and illumination of the AIR COND six-pack light, which directs the flight crew to look up at the air conditioning panel where you would see the actual cabin altitude, the AUTO FAIL light, etc.
Quoting tdscanuck (Reply 3):

Basically, the plane correctly told the flight crew exactly what was wrong. They misinterpreted the warning, for reasons unknown, and didn't take the appropriate corrective action.

Ah yes I remember now. My memory was very fuzzy.   
 
barney captain
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 20, 2010 7:35 pm

Quoting rolfen (Reply 4):
You should get a master warning and illumination of the AIR COND six-pack light, which directs the flight crew to look up at the air conditioning panel where you would see the actual cabin altitude, the AUTO FAIL light, etc.

That is only true if there was a pressurization malfunction - which was not the case with Helios. The crew had inadvertently left the pressurization selector in manual, which left the outflow valve open. The aircraft never pressurized, and the only indication is the intermittent warning horn - no master caution and no AIR COND annunciation. This would also happen if the bleeds were left off for take-off for increased performance and not reset. Since there is not any malfunction of the pressurization controller - no master caution.

New NG's have the additional TAKE OFF CONFIG/ CABIN ALT warning lights on the forward panel in front of both pilots - but only the very newest.
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RE: Helios 522 And The B737 Pressure Warning

Tue Dec 21, 2010 6:24 pm

Quoting Barney Captain (Reply 9):
That is only true if there was a pressurization malfunction - which was not the case with Helios. The crew had inadvertently left the pressurization selector in manual,

IIRC maintenance had left the pressurization selector in manual having carried out a ground pressurization check to rectify a leaking door, however the crew should have corrected this during their pre-flight checks.
 
etherealsky
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RE: Helios 522 And The B737 Pressure Warning

Tue Dec 21, 2010 6:57 pm

Since Helios 522 was a 737 classic, can we assume that if the same thing happened to a newer aircraft, EICAS / ECAM would have saved the day?
"And that's why you always leave a note..."
 
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RE: Helios 522 And The B737 Pressure Warning

Tue Dec 21, 2010 7:37 pm

Quoting Barney Captain (Reply 9):

That is only true if there was a pressurization malfunction - which was not the case with Helios. The crew had inadvertently left the pressurization selector in manual,

Isn't more than one Automatic pressurisation function INOP a NO GO.
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777236ER
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RE: Helios 522 And The B737 Pressure Warning

Tue Dec 21, 2010 7:55 pm

Quoting tdscanuck (Reply 6):
The argument that this was an acceptable thing to do is that the two modes are mutually exclusive (except very high altitude airports, which is a corner case with special planning anyway). If you get the horn in air, it's the cabin altitude. If you get the horn on the ground, it's takeoff config.

The crew had all the information necessary (including the great big cabin pressure readout on the overhead panel) to understand what was happening. However, they got task focussed and misinterpreted the warning. There's obviously a human factors issues there, but it's an open question as to exactly how much misinterpretation can you assume on the behalf of the flight crew.

This isn't a new problem from the Helios accident...pilots have flown aircraft into the ground while fixated on troubleshooting a different problem, or on torubleshooting what they think is the problem instead of what's actually the problem. This was just a particularly egregious example

This is a ridiculous argument. The fact that the two modes are mututally exclusive is nonsense - a t/o config warning is significantly more likely to occur than a cabin altitude warning, hence more likely for the crew to interpret the warning as a t/o config. In a hypoxic state it's clear that flight crew will jump to the cognitively easy solution: it's a t/o warning. The next cognitively easy jump is that it's a spurious warning.

The crew didn't have all the information necessary in the physiological state they were in - a state brought about by a problem with the aircraft.

This isn't the first example of that 737's poor human-machine interface causing deaths (BMA92 and TK1951 spring to mind). It's shocking that this out-moded 60s flight deck design is still being produced and sold as one of the most popular large commercial aircraft. In the days of dark cockpits, EICAS/ECAM, clear warning hierarchy and system synopses it's a travesty that the 737 can still be produced.

This isn't just my conjecture, to quote one of the causes from the final report:

"Ineffectiveness and inadequacy of measures taken by the manufacturer in
response to previous pressurization incidents in the particular type of aircraft,
both with regard to modifications to aircraft systems as well as to guidance to
the crews."
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rolfen
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RE: Helios 522 And The B737 Pressure Warning

Tue Dec 21, 2010 9:19 pm

Quoting 777236ER (Reply 13):
This is a ridiculous argument.

Well, it makes more sense if you call this warning the "misconfiguration warning". It would alert the crew about the aircraft being misconfigured for the current phase of flight. In any case the manufacturer assumes that the pilots are fully trained. Yes it is poor design. A spoken warning would be much better, but I guess the 737 inherited this from the 1st generation. Still I don't think this is an excuse... dont they do cabin depressurization training drills? Simulations?
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RE: Helios 522 And The B737 Pressure Warning

Tue Dec 21, 2010 9:30 pm

Quoting 777236ER (Reply 13):
In a hypoxic state it's clear that flight crew will jump to the cognitively easy solution: it's a t/o warning.

But you wouldn't start suffering until above 12k feet, correct? So they had how many minutes to listen to this horn while doing nothing before the airplane climbed to an altitude where the effects could be seen?
 
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RE: Helios 522 And The B737 Pressure Warning

Tue Dec 21, 2010 9:45 pm

Quoting 413X3 (Reply 16):
But you wouldn't start suffering until above 12k feet, correct? So they had how many minutes to listen to this horn while doing nothing before the airplane climbed to an altitude where the effects could be seen?

IIRC, 14,000' is the magic cabin altitude at which the warning begins to sound...I would imagine a fairly typical climb in a 737 would be around 1500'/minute or so.
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RE: Helios 522 And The B737 Pressure Warning

Wed Dec 22, 2010 12:19 pm

Quoting 777236ER (Reply 13):
This isn't the first example of that 737's poor human-machine interface causing deaths (BMA92 and TK1951 spring to mind). It's shocking that this out-moded 60s flight deck design is still being produced and sold as one of the most popular large commercial aircraft. In the days of dark cockpits, EICAS/ECAM, clear warning hierarchy and system synopses it's a travesty that the 737 can still be produced.

Very well said. Not only is the flight deck poorly designed also the E&E bay is misplaced

Quote:
On 22 October 1995, G-BGJI, a 737-200Adv experienced undemanded yaw & roll oscillations during an air test. This was put down to fluid from the cabin leaking into the E & E bay and onto the yaw damper coupler. The report stated:

"The location of the Electronic and Equipment (E&E) Bay, beneath the cabin floor in the area of the aircraft doors, galleys and toilets made it vulnerable to fluid ingress from a variety of sources
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777236ER
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RE: Helios 522 And The B737 Pressure Warning

Wed Dec 22, 2010 5:45 pm

Quoting 413X3 (Reply 16):
But you wouldn't start suffering until above 12k feet, correct? So they had how many minutes to listen to this horn while doing nothing before the airplane climbed to an altitude where the effects could be seen?

The crew silenced the horn at 14kft, a altitude where they would already feel the effects of hypoxia. The effects of hypoxia were apparent when they ignored the request from maintenance on the ground to check the status of the pressurisation panel.

The fact that the 737 can take off, with no warnings, with the pressurisation system in 'manual' is another simply dangerous feature.
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tdscanuck
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RE: Helios 522 And The B737 Pressure Warning

Thu Dec 23, 2010 7:34 am

Quoting 777236ER (Reply 13):
This is a ridiculous argument. The fact that the two modes are mututally exclusive is nonsense - a t/o config warning is significantly more likely to occur than a cabin altitude warning, hence more likely for the crew to interpret the warning as a t/o config.

The system could be better (and now is better on new aircraft), but to say that something that's fully accepted by the FAA, EASA, and the vast majority of airlines is "ridiculous" and "nonsense" is stretching it a little far. If the flight crew is so unfamiliar with the aircraft as to think they've got a takeoff config warning *after* takeoff, there is more at work than just bad flight deck design.

Quoting 777236ER (Reply 13):
The crew didn't have all the information necessary in the physiological state they were in

The warning horn goes off at 10,000' cabin altitude. The whole point of having it there is that you *haven't* started changing physiological state at that point and you're supposed to respond properly.

Quoting 777236ER (Reply 13):
In the days of dark cockpits, EICAS/ECAM, clear warning hierarchy and system synopses it's a travesty that the 737 can still be produced.

The 737 is essentially a dark cockpit, it does have a clear warning hierarchy, and it does have system synoptics. It just uses master caution/warning, rather than CAS/CAM (the EI/E function is already there).

Quoting KELPkid (Reply 16):
IIRC, 14,000' is the magic cabin altitude at which the warning begins to sound...I would imagine a fairly typical climb in a 737 would be around 1500'/minute or so.

Horn goes off at 10,000'. The 14,000' (actually 13,875') trigger is the AUTO FAIL annunciation for auto pressurization.

Quoting autothrust (Reply 17):
Very well said. Not only is the flight deck poorly designed also the E&E bay is misplaced

Then it's misplaced on every modern jet. It's always under the flight deck and aft of the nose gear well, which is always where you have a pair of doors, at least one galley, and at least one lav.

Quoting 777236ER (Reply 18):
The fact that the 737 can take off, with no warnings, with the pressurisation system in 'manual' is another simply dangerous feature.

Why? You're supposed to set it during preflight, and if you forget to set it you get a warning before it becomes dangerous. It's only dangerous if you forget to set it *and* ignore the warning horn. Takeoff warnings are supposed to warn you of things that threaten *the takeoff*. Even EICAS/ECAM airplanes inhibit non-takeoff-critical warnings during the takeoff period.

Tom.
 
LTC8K6
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RE: Helios 522 And The B737 Pressure Warning

Thu Dec 23, 2010 12:50 pm

Clearly, the 737 should set itself up preflight, and then fly itself, auto correcting any errors those pesky humans make...how dare Boeing produce a plane that doesn't...
 
tdscanuck
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RE: Helios 522 And The B737 Pressure Warning

Thu Dec 23, 2010 2:37 pm

Quoting LTC8K6 (Reply 20):
Clearly, the 737 should set itself up preflight, and then fly itself, auto correcting any errors those pesky humans make...how dare Boeing produce a plane that doesn't...

Actually, this is almost what the Helios aircraft did...with the crew incapacitated, the aircraft flew its flight plan properly and, absent further instructions, continued to fly safety until it exhausted its fuel.

Tom.
 
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RE: Helios 522 And The B737 Pressure Warning

Thu Dec 23, 2010 6:39 pm

Quoting tdscanuck (Reply 21):
Actually, this is almost what the Helios aircraft did...with the crew incapacitated, the aircraft flew its flight plan properly and, absent further instructions, continued to fly safety until it exhausted its fuel.

Tom.

Didn't a PPL-rated flight attendant, wearing a portable oxygen mask, attempt to gain access to the cockpit, as I recall? (too late to do any good...)
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777236ER
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RE: Helios 522 And The B737 Pressure Warning

Thu Dec 23, 2010 6:51 pm

Quoting tdscanuck (Reply 19):
The system could be better (and now is better on new aircraft), but to say that something that's fully accepted by the FAA, EASA, and the vast majority of airlines is "ridiculous" and "nonsense" is stretching it a little far. If the flight crew is so unfamiliar with the aircraft as to think they've got a takeoff config warning *after* takeoff, there is more at work than just bad flight deck design.

It's not stretching anything. The 737 has the most archaic systems of any large commercial aircraft being produced in the West. It doesn't get anywhere near the certification standards of today. The classics didn't even get near the certification standarsd of the 80s.

Quoting tdscanuck (Reply 19):
The whole point of having it there is that you *haven't* started changing physiological state at that point and you're supposed to respond properly

The reality proves you wrong.

Quoting tdscanuck (Reply 19):
The 737 is essentially a dark cockpit, i

Demonstrably incorrect! The dark cockpit means that when everything is normal, it's dark. A simple glance upwards at a A320, A330/A340, A380, 777 or 787 flight deck will tell you if everything is normal. With the 737? No. The mistake the pilots made resulted in no abnormal lights, and regardless of that normal operation lights glare away on every 737 cockpit (window heat lights being a good example). It's archaic design, completely superceded by even Boeing. Yet these aircraft still roll out of the factory every day.

Quoting tdscanuck (Reply 19):
and it does have system synoptics

No, it doesn't. It has a bunch of warning lights that correspond to problems, like the 707 did. There are no system synoptics.

Quoting tdscanuck (Reply 19):
Why? You're supposed to set it during preflight, and if you forget to set it you get a warning before it becomes dangerous. It's only dangerous if you forget to set it *and* ignore the warning horn. Takeoff warnings are supposed to warn you of things that threaten *the takeoff*

And yet Boeing, Airbus and modern regulators disagree with you. It's crazy to allow an aircraft to depart, with no warnings of an unsafe condition, then expect the flight crew to understand the details of a system they hardly ever touch in flight, whilst hypoxic, with a warning they assosicate exclusively with another flight phase.

Quoting LTC8K6 (Reply 20):
Clearly, the 737 should set itself up preflight, and then fly itself, auto correcting any errors those pesky humans make...how dare Boeing produce a plane that doesn't...

This is meant pejoratively, but an aircraft that did that would have saved the lives of the innocent people on the 737. A modern aircraft will provide a warning for the unsafe state of any system before take off. The 737 still doesn't.

Quoting tdscanuck (Reply 21):
Actually, this is almost what the Helios aircraft did...with the crew incapacitated, the aircraft flew its flight plan properly and, absent further instructions, continued to fly safety until it exhausted its fuel

This is a slightly sleazy attempt at suggesting that the Helios 737 actually displayed good system design in what it did. The 737 did NOT auto-correct any of the flight crew errors. The actions of the 737 did nothing to save the passengers - are you suggesting this 'marvel' of actually following the flight plan is a somehow remarkable design? It's a bit like saying that despite the pressurisation failures, the oxygen masks in the cabin deployed...how clever of the 737! Nonsense - the 737's poor design caused this crash, as you have admitted yourself.
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tdscanuck
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RE: Helios 522 And The B737 Pressure Warning

Thu Dec 23, 2010 9:19 pm

Quoting KELPkid (Reply 22):
Didn't a PPL-rated flight attendant, wearing a portable oxygen mask, attempt to gain access to the cockpit, as I recall? (too late to do any good...)

I'm not sure if they were PPL-rated, but the F-16's sent to intercept saw a cabin crew member enter the flight deck, attempted to communicated with them via handsignals, and heard them make repeated Mayday calls on the radio.

Quoting 777236ER (Reply 23):
It doesn't get anywhere near the certification standards of today. The classics didn't even get near the certification standarsd of the 80s.

I love it when this red herring comes up. The classics were certified to Amendment 25-15 (1967), the original basis, *but* included specific supercessions up to and including 25-51 (1980). The FAA never lets you grandfather superceded safety regulations, so you'll always be within 5 years of whenever you applied for the amended TC.

Quoting 777236ER (Reply 23):
Quoting tdscanuck (Reply 19):
The whole point of having it there is that you *haven't* started changing physiological state at that point and you're supposed to respond properly

The reality proves you wrong.

You know something to suggest they were going hypoxic at 10,000'? That suggests a medical issue with the crew that wasn't mentioned, *at all*, in the accident report.

Quoting 777236ER (Reply 23):
The dark cockpit means that when everything is normal, it's dark.

No exactly. All the panel lights still run just fine, all the way up through the A380/787. It does mean the *indication* lights are dark in normal configuration...the 737classics follow this on some, but not all, systems.

Quoting 777236ER (Reply 23):
A simple glance upwards at a A320, A330/A340, A380, 777 or 787 flight deck will tell you if everything is normal.

Yes, but not because it's literally dark. Specially, you're looking for absence of color, not absence of light.

Quoting 777236ER (Reply 23):
With the 737? No. The mistake the pilots made resulted in no abnormal lights, and regardless of that normal operation lights glare away on every 737 cockpit (window heat lights being a good example).

It did not result in an abnormal light. It did result in an abnormal dial. The information was all there. Could it have been presented in a clearer way? Certainly, and improvements have been made to the 737 specifically, and more modern flight decks in general, to mitigate that. But that does not excuse the flight crew from 1) incorrectly doing their preflight, 2) incorrectly responding to a clear warning, 3) allowing the warning to continue to the point that hypoxia did start to take hold.

Quoting 777236ER (Reply 23):
No, it doesn't. It has a bunch of warning lights that correspond to problems, like the 707 did. There are no system synoptics.

Absolutely right, I was thinking 737NG. Sorry for the confusion.

Quoting 777236ER (Reply 23):
And yet Boeing, Airbus and modern regulators disagree with you.

Which regulators disagree? If it were a safety issue, by definition, there would be an AD. The fact that there isn't means that the regulators don't think it's a safety issue. Boeing certainly doesn't consider it a safety issue or they'd have said so as well (determination of safety/non-safety is part of every modification disposition).

Quoting 777236ER (Reply 23):
It's crazy to allow an aircraft to depart, with no warnings of an unsafe condition, then expect the flight crew to understand the details of a system they hardly ever touch in flight, whilst hypoxic, with a warning they assosicate exclusively with another flight phase.

"This horn means your cabin altitude is too high" is hardly "understand the details", it's a fundamental part of the aircraft's warning system. One that is explicitely trained to the flight crews. You experience high cabin altitude *way* more often than some other failures, like inflight fire, but you can bet that crews have no problem responding appropriately to that.

And, unless you've got evidence that never showed up in the investigation report, they weren't hypoxic when the warning started.

Quoting 777236ER (Reply 23):
A modern aircraft will provide a warning for the unsafe state of any system before take off. The 737 still doesn't.

No modern aircraft will provide a warning for *all* unsafe systems prior to takeoff. It will provide a warning for *some* unsafe systems.

Quoting 777236ER (Reply 23):
This is a slightly sleazy attempt at suggesting that the Helios 737 actually displayed good system design in what it did. The 737 did NOT auto-correct any of the flight crew errors. The actions of the 737 did nothing to save the passengers - are you suggesting this 'marvel' of actually following the flight plan is a somehow remarkable design? It's a bit like saying that despite the pressurisation failures, the oxygen masks in the cabin deployed...how clever of the 737! Nonsense - the 737's poor design caused this crash, as you have admitted yourself.

1) I stated the facts. If you want to call that sleazy, that's certainly your call.
2) The 737 did not auto-correct any of the flight crew errors. The 737, of any generation, has never had that capability and every flight crew knows it. The fundamental design of the airplane is to tell the flight crew there is a problem and allow the flight crew to respond. If you think this is truly a safety issue, then you've got no alternative than to argue for grounding of the entire 737 fleet.
3) I did not, nor would I, state that "the 737's poor design caused this crash." I will state, flat out, that the 737's design (poor or not) did *not* cause this crash. This crash was caused by improper flight crew actions during the preflight and after takeoff. Contributing factors were, certainly, prior maintenance actions and the warning system, but it's ludicrous to suggest that the design *caused* the crash when the flight crew took off in the wrong configuration and then did not restore the configuration when the problem was brought to their attention by the airplane.

Tom.
 
mandala499
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RE: Helios 522 And The B737 Pressure Warning

Fri Dec 24, 2010 2:40 am

Quoting 777236ER (Reply 23):
A modern aircraft will provide a warning for the unsafe state of any system before take off. The 737 still doesn't.

Really? How does one ferry flight a defective aircraft from an outbase with "limited/conditional" release? Again... checklists are there for a reason! Use it!

Quoting 777236ER (Reply 23):
The 737 did NOT auto-correct any of the flight crew errors.

And neither did the TAM A320 when the flight crew did not put both throttle levers to idle upon landing...

Quoting tdscanuck (Reply 24):
But that does not excuse the flight crew from 1) incorrectly doing their preflight, 2) incorrectly responding to a clear warning, 3) allowing the warning to continue to the point that hypoxia did start to take hold.

Exactly. I for one think the warning horn is "silly" and is prone to misinterpretation BUT I agree, it does not provide an excuse to not correctly do the preflight nor does it give an excuse for the pilot to not diagnose the problem and prefers to shut the damn warning off!
Archaic? Yes. Can do with a lot of improvements? Yes!
Dangerous to fully/adequately trained crew? NO!
Dangerous to poorly trained crew? Heck! Any aircraft is!

Quoting 777236ER (Reply 23):
t doesn't get anywhere near the certification standards of today. The classics didn't even get near the certification standarsd of the 80s.

Then why is it certified then?

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
777236ER
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RE: Helios 522 And The B737 Pressure Warning

Fri Dec 24, 2010 11:59 am

Quoting tdscanuck (Reply 24):
I love it when this red herring comes up. The classics were certified to Amendment 25-15 (1967), the original basis, *but* included specific supercessions up to and including 25-51 (1980). The FAA never lets you grandfather superceded safety regulations, so you'll always be within 5 years of whenever you applied for the amended TC

And yet newly created 737-800s (certified to 25-77 from 1992) are certified to hold 189 passengers with only 4x Type C doors and 4x Type IIIs, despite the 737's record of poor evacuation standards (see the Manchester Airport Fire). A320s on the other hand, are certified to 179 pax under FAA, in accordance with the actual regulations, and putting them at a competitive disadvantage compared to the 737-800 when operated by LCCs. Yet another example of the 737 not complying with the regulations, yet still being certified. How about 737CLs and NGs with centre tank pumps that don't turn off when they go low pressure, or CLs with rudder PCUs that didn't fail safe, or CLs and NGs with spoilers that don't automatically retract when power is added.

Quoting tdscanuck (Reply 24):
You know something to suggest they were going hypoxic at 10,000'? That suggests a medical issue with the crew that wasn't mentioned, *at all*, in the accident report.

I suggest they continued to climb whilst troubleshooting, which is understandable and trained for. The fact that the horn was ambiguous just increased the trouble shooting time. An EICAS/ECAM 'Cabin Pressure' is much simpler and much more likely to result in the correct action. Yet Boeing produced 737s without these simple warnings, at a time when they were also producing 777s, 757/757s and 747-400s with exactly these warnings.

Quoting tdscanuck (Reply 24):
It does mean the *indication* lights are dark in normal configuration...the 737classics follow this on some, but not all, systems.

Even worse! It's ambiguous.

Quoting tdscanuck (Reply 24):
It did not result in an abnormal light. It did result in an abnormal dial. The information was all there. Could it have been presented in a clearer way? Certainly, and improvements have been made to the 737 specifically, and more modern flight decks in general, to mitigate that

Even today, on the latest 737NG that rolls out of the assembly line, if a flight crew makes the same mistake as the Helios crew they will not know when glancing up at the overhead panel. They will only know when the cabin pressure is approaching a dangerous state. This is different to all other large commercial aircraft built in the west, including those designed and certified before the 737NG.

Quoting tdscanuck (Reply 24):
2) The 737 did not auto-correct any of the flight crew errors. The 737, of any generation, has never had that capability and every flight crew knows it. The fundamental design of the airplane is to tell the flight crew there is a problem and allow the flight crew to respond

It failed. The aircraft did not tell them there was a problem.

Quoting tdscanuck (Reply 24):
but it's ludicrous to suggest that the design *caused* the crash

From the accident report under 'causes':

Ineffectiveness and inadequacy of measures taken by the manufacturer in
response to previous pressurization incidents in the particular type of aircraft,
both with regard to modifications to aircraft systems as well as to guidance to
the crews.


Quoting tdscanuck (Reply 24):
Then why is it certified then?

Good question.
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mandala499
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RE: Helios 522 And The B737 Pressure Warning

Fri Dec 24, 2010 1:43 pm

Quoting 777236ER (Reply 26):
are certified to hold 189 passengers with only 4x Type C doors and 4x Type IIIs, despite the 737's record of poor evacuation standards (see the Manchester Airport Fire).

The 737NG exits are upward hinging swing type and not the "manually remove and manually dispose/stow prior to use" type. This reduces the time required to start using the emergency exit which enables total cabin evac using 1/2 the available exits within 90 seconds.

Well... you may be interested in the following:
http://www.flightglobal.com/pdfarchive/view/1996/1996%20-%203332.html
The NG type of exits is a solution of the shortcomings of the current (non-NG) type III exits.

And then:
"EASA is working on a final rule that, among other things, would require Type III exits [to] have a fixed stowage point, similar to other types of exits" and "This means that the Type III exits could not be removable hatches that require a person to find somewhere to place them (for example, on seats or on the wing)." and "At present, a removable hatch is the typical Type III exit, except on Boeing 737NGs, which have a top-hinged hatch."
The FAA is considering adopting the proposed EASA ruling, to which the 737NG is currently the only aircraft that complies with the "have a fixed stowage point".
From:
http://www.flightglobal.com/articles...-easa-with-aircraft-exit-rule.html

And then:
Airbus is/was studying ways to raise the A320's max capacity to meet the max capacity deficit against the 738.
http://www.flightglobal.com/articles...ncrease-a320-seating-capacity.html
And that in my discussions with Airbus concludes that the NG type exits could increase the max capacity based on the types exits used.

The use of "Type III exits with a fixed stowage point" can/does increase your maximum capacity based on exit limits!

Quoting 777236ER (Reply 26):
or CLs and NGs with spoilers that don't automatically retract when power is added.

I do not see that as a problem.
In the air or on the ground?
There was a previous discussion on this at: Landing With Speed Brakes Deployed (by Bio15 Mar 3 2005 in Tech Ops)

On the ground whenever the ground spoilers are extended and the thrust levers are advanced the spoilers will retract. That has been standard feature for a loooong time!
In the air... well the 757 does not auto-stow the spoilers when power is added. In reply 12 it was written: "757 Speedbrakes/flight spoilers can be deployed in flight without automatic stow if full power is selected. There is a message in the EICAS, though" and on the 737 there is a "SPEEDBRAKE EXTENDED" light that goes on whenever it's not in the stowed position... in the ground or in the air!
On the 777 there's an EICAS message "SPEEDBRAKES EXTENDED" with a beeper whenever you extend them when either thrust levers are not in idle position. And yes... you can extend them with power above idle except when on the ground (just like a 737 with it's lights)

On the Airbus fly-by-wire you it is the same (except it autostows when you put the thrust levers above MCT position (ie: TOGA)

So are you suggesting that all those aircraft shouldn't be certified because you can have the speedbrake extended with power being added (below TOGA for the Bus fly by wire) whilst inflight?

Quoting 777236ER (Reply 26):
Yet Boeing produced 737s without these simple warnings, at a time when they were also producing 777s, 757/757s and 747-400s with exactly these warnings.

Simple warning of a horn is legally adequate.

Quoting 777236ER (Reply 26):
I suggest they continued to climb whilst troubleshooting, which is understandable and trained for.

Well if one is properly trained and has the right mindset to troubleshooting, then one should realize that hearing that horn whilst airborne means your cabin pressure is having problems.
The NG does not have the CAS/CAM part of EICAS/ECAM... it's an EIS not an EICAS. Are you suggesting that non EICAS aircraft be refused certification?

Quoting 777236ER (Reply 26):
They will only know when the cabin pressure is approaching a dangerous state. This is different to all other large commercial aircraft built in the west, including those designed and certified before the 737NG.

The horn will sound when cabin altitude exceeds 10k ft.
That's not much difference from other aircraft... albeit EICAS/ECAM equipped aircraft will display the alert.

Quoting 777236ER (Reply 26):
It failed. The aircraft did not tell them there was a problem.

It did not fail. It told them that the cabin altitude had gone beyond 10k ft. The problem was on the crew. You can have all the wonderful bells and whistles to alert the crew but it will all be useless if the crew ignores it! Just like the A310 crew that decided to ignore the "fuel insufficient" on the CAM and ended up landing with no fuel... or that A330 that ended up as a glider because they saw thought the computer had gone bonkers.

Mandala499
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tdscanuck
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RE: Helios 522 And The B737 Pressure Warning

Fri Dec 24, 2010 9:52 pm

Mandala499 already covered most of my comments more eloquently than I would have. Just a couple of add ons:

Quoting 777236ER (Reply 26):
How about 737CLs and NGs with centre tank pumps that don't turn off when they go low pressure

The service bulletin for that has been out for years. In addition, dry-running a center pump is a violation of procedure and, even if you do do it, it's only dangerous if you have another concurrent failure (faulty fuel pump).

Quoting 777236ER (Reply 26):
CLs with rudder PCUs that didn't fail safe

An issue that has *long* since been fixed. If your argument is that 737's have been produced with safety issues, that's obviously true. But it's true of *every single aircraft in existance*...an AD is, by definition, a safety issue that got through type certification.

Quoting 777236ER (Reply 26):
The fact that the horn was ambiguous just increased the trouble shooting time.

How is "horn in air = low cabin pressure" ambiguous? Or, as was eloquently put earlier in another post, "Horn = out of configuration for current operation"? There is no reasonable interpretation of a warning horn in flight as a takeoff configuration warning; the only other alternative is high cabin altitude.

Quoting 777236ER (Reply 26):
An EICAS/ECAM 'Cabin Pressure' is much simpler and much more likely to result in the correct action.

Absolutely true, but the 737 (and many other jets still in commercial service) aren't EICAS/ECAM airplanes.

Quoting 777236ER (Reply 26):
Yet Boeing produced 737s without these simple warnings, at a time when they were also producing 777s, 757/757s and 747-400s with exactly these warnings.

So what? There is no way they could have maintained a common type rating while switching to EICAS/ECAM, and the common type rating is something the airlines and pilots very much wanted. Your argument can't be that all non-EICAS/ECAM aircraft should be removed from commercial service, can it?

Quoting 777236ER (Reply 26):
It failed. The aircraft did not tell them there was a problem.

What do you think the warning horn was?

Quoting 777236ER (Reply 26):
Quoting tdscanuck (Reply 24):
Then why is it certified then?

Good question.

If your argument is just that all 737's, or all non-EICAS/ECAM aircraft, should have their certification pulled, we might as well let the thread die because I don't think there's any common ground to work with.

Quoting 777236ER (Reply 26):

From the accident report under 'causes':

Note the "s" on the end. Cause*s*, not "cause". Saying "the design was the cause" implies that it was the only factor...it very obviously wasn't, as the accident report agrees.

There is no question that the flight crew screwed up. The aircraft didn't help. Had the flight crew not screwed up, the flight would have been fine without any aircraft design change. Had the aircraft been designed differently the flight *may* have been OK but, given a flight crew screwup, that's far from assured.

Tom.
 
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RE: Helios 522 And The B737 Pressure Warning

Sat Dec 25, 2010 4:07 am

Quoting 777236ER (Reply 23):
A modern aircraft will provide a warning for the unsafe state of any system before take off.

And a modern pilot will ignore or misinterpret that modern warning...

Maybe the plane should slap them?
 
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RE: Helios 522 And The B737 Pressure Warning

Sat Dec 25, 2010 11:56 am

Quoting 777236ER (Reply 13):
The crew didn't have all the information necessary in the physiological state they were in - a state brought about by a problem with the aircraft.

I've always wondered why most flight decks designs rely on a non-vocal alert for the cabin altitude alarm. Instead of an actual voice prompt stating, "CABIN ALTITUDE", most pilots will have to hear the horn or buzzing sound, interpret it, and then react to it. Valuable seconds lost of you already are behind the oxygen saturation curve! If you see some of the hypoxia chamber tests the FAA runs, it is clear that pilots in their hypoxic state need to be FIRMLY told to do certain things, like put on oxygen. (Even a warning light that states Cabin Alt might not be assertive enough because hypoxia causes remarkable vision changes like blurriness or loss of color vision)

The CAWS system on MD aircraft has the bitching betty voice ("Cabin Altitude!"), along with some Russian aircraft I believe, but I'd be intrested if regulators in the future look to see if a voice prompt could improve hypoxic response times.

If TCAS prompts provide instructions ("Descend, DESCEND NOW!"), I don't see why the cabin altitude alert could be "CABIN ALTITUDE - DON OXYGEN!"

Quoting LTC8K6 (Reply 29):
Maybe the plane should slap them?

In the future, flight decks will have one pilot and one dog...the pilot to feed the dog, and the dog to bite the pilot if he try to touch anything.  
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RE: Helios 522 And The B737 Pressure Warning

Sun Dec 26, 2010 6:04 am

Quoting MarkHKG (Reply 30):
In the future, flight decks will have one pilot and one dog...the pilot to feed the dog, and the dog to bite the pilot if he try to touch anything.

Would this Dog have special qualification requirements  .

Isn't Multiple snags on the Pressurisation system with Two systems INOP a nogo.
regds
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777236ER
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RE: Helios 522 And The B737 Pressure Warning

Sun Dec 26, 2010 11:13 pm

Quoting mandala499 (Reply 27):
The 737NG exits are upward hinging swing type and not the "manually remove and manually dispose/stow prior to use" type. This reduces the time required to start using the emergency exit which enables total cabin evac using 1/2 the available exits within 90 seconds.

Yes, but they're still Type IIIs. The regulations are clear.

Quoting mandala499 (Reply 27):
The use of "Type III exits with a fixed stowage point" can/does increase your maximum capacity based on exit limits!

Not yet it doesn't. There is a proposed EASA rule, but if Boeing or Airbus applied for certification for their new short range aircraft today, they would have to comply with the existing regulations which are clear about Type IIIs. In the late 80s and mid-90s when the A320 and 737NGs were certified, the exit ratings were clear and there was no NPRM.

Quoting mandala499 (Reply 27):
Simple warning of a horn is legally adequate

It seems not, as the FAA created an AD to fix the 737's safety flaws following Helios. I would also argue that 'legally adequate' is not the level of safety that manufacturers should strive for.

Quoting mandala499 (Reply 27):
Well if one is properly trained and has the right mindset to troubleshooting, then one should realize that hearing that horn whilst airborne means your cabin pressure is having problems.

'Proper training' and 'should realise' are the type of weasel words that gloss over systems that can be improved. 'Proper training' and 'should realise' would have prevented nearly every CFIT, yet GPWS and its further enhancements has improved safety.

Quoting mandala499 (Reply 27):
The NG does not have the CAS/CAM part of EICAS/ECAM... it's an EIS not an EICAS. Are you suggesting that non EICAS aircraft be refused certification?

Why not? Every modern large commercial aircraft has these systems, except the 737.

Quoting mandala499 (Reply 27):
The horn will sound when cabin altitude exceeds 10k ft.
That's not much difference from other aircraft... albeit EICAS/ECAM equipped aircraft will display the alert

This is the key point though: there was ambiguity in the 737's warnings. This ambiguity existed (and was certified) in an era when Boeing (and Airbus) were certifying aircraft with much clearer warnings. Why wasn't the 737 held to the same standards?

Quoting mandala499 (Reply 27):
The problem was on the crew. You can have all the wonderful bells and whistles to alert the crew but it will all be useless if the crew ignores it!

This concerns me, because you seem to be implying that the AD was frivolous and not required for continuing airworthiness. The fact is that the investigating authority found deficites in the 737's warning architecture, and the FAA mandated remedial action.

Quoting tdscanuck (Reply 28):
The service bulletin for that has been out for years. In addition, dry-running a center pump is a violation of procedure and, even if you do do it, it's only dangerous if you have another concurrent failure (faulty fuel pump).

But again, that isn't my point. My point is simple: aircraft certified at around the same time that the 737NG was certified had automatic cutoff of the centre tank pumps.

Quoting tdscanuck (Reply 28):
How is "horn in air = low cabin pressure" ambiguous?

Read the report. The only time the crew hear this warning, in training and almost always in operation, is for takeoff config. It's clear that many crew's first thought would be 'take off config', leading them down a dangerous chain of spurious warnings and confusing indications. The fact that Helios happens shows that this warning IS ambiguous.

Quoting tdscanuck (Reply 28):
There is no reasonable interpretation of a warning horn in flight as a takeoff configuration warning; the only other alternative is high cabin altitude

So you disagree with the FAA and the investigating authority? It's also rather callous of you to accuse a properly licensed and professional flight crew of being not reasonable (irrational?) - especially when they cannot defend themselves.

Quoting tdscanuck (Reply 28):
Absolutely true, but the 737 (and many other jets still in commercial service) aren't EICAS/ECAM airplanes.

What large Western commercial aircraft certified since 1990 doesn't have EICAS/ECAM?

Quoting tdscanuck (Reply 28):
If your argument is just that all 737's, or all non-EICAS/ECAM aircraft, should have their certification pulled, we might as well let the thread die because I don't think there's any common ground to work with.

My argument is that there are serious flaws in the 737's sytems and certification basis, as shown by the Helios crash. What happens next is for a different thread, but I would suggest a partial re-certification exercise and a thorough review of the continuing airworthiness of the 737.

Quoting mandala499 (Reply 27):
On the ground whenever the ground spoilers are extended and the thrust levers are advanced the spoilers will retract. That has been standard feature for a loooong time!
In the air... well the 757 does not auto-stow the spoilers when power is added. In reply 12 it was written: "757 Speedbrakes/flight spoilers can be deployed in flight without automatic stow if full power is selected. There is a message in the EICAS, though" and on the 737 there is a "SPEEDBRAKE EXTENDED" light that goes on whenever it's not in the stowed position... in the ground or in the air!
On the 777 there's an EICAS message "SPEEDBRAKES EXTENDED" with a beeper whenever you extend them when either thrust levers are not in idle position. And yes... you can extend them with power above idle except when on the ground (just like a 737 with it's lights)

Let's compare types for a typical go-around or escape manoeuvre. On the 777, 747-400 and (likely) 787, you got a master caution if the spoilers are UP and the TLA is higher than idle.

On the 757/767, the failure of the spoilers to auto-retract has already resulted in a hull-loss and the loss of 159 lives (AA965). Indeed, one of the causes is listed as the flight crew executing an GPWS escape with the spoilers up.

On 737CL, there's no auto-stow, and there's no light. On 737NG there's a single light, no warning.

On A320/A330/A340/A380, the spoilers will auto-stow, (see below).

Yet again it's an example of the 737 having the least robust systems, even among aircraft certified before it, and following an accident where the lack of robustness in this particular system was a contributory factor.

Quoting mandala499 (Reply 27):
On the Airbus fly-by-wire you it is the same (except it autostows when you put the thrust levers above MCT position (ie: TOGA

True, but not the whole story. Crucially, speedbrake extension is also inhibited if alpha floor is activated, AoA protection is active or flaps are FULL (plus a number of failure conditions). The covers all reasonable situations where the flight crew is executing an escape manoeuvre where speedbrake extension would compromise climb rate.
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 27, 2010 12:26 pm

A type III exit is a type III exit...
But... just because a type can only have 180 seats with 2 type I and 2 type III a side does not mean that others are restricted by the same limit.
As long as no pax is more than 60ft away from 2 exits a side (along the aircraft's longitudinal axis)... the above config's exit limit is 220 pax.
But... they also have to be able to evac the cabin with 1/2 the exits avail in 90 secs.

The reason why the 738 can seat 189 instead of 180 is because of the modified type III allows a faster egress while qualifying with the above.
FAR/CFR 25.803 and 25.807 enables the above. (CFR 25.807(g)(5) is interesting)

Quoting 777236ER (Reply 32):
It seems not, as the FAA created an AD to fix the 737's safety flaws following Helios. I would also argue that 'legally adequate' is not the level of safety that manufacturers should strive for.

Well... it was legally adequate when it was certified. I for one think that the changes after Helios was late.

Quoting 777236ER (Reply 32):
'Proper training' and 'should realise' would have prevented nearly every CFIT, yet GPWS and its further enhancements has improved safety.

And yet when GPWS was first available, there was nothing making that mandatory... a few CFITs changed that in the same way Helios made the changes. Now why only point the finger at the 737?

Quoting 777236ER (Reply 32):
The fact that Helios happens shows that this warning IS ambiguous.

Saying it IS ambiguous is stretching it too far. No one here disagrees that the warning CAN be ambiguous.
I come from a country that is accused of poor training standards and poor safety oversight (EU Ban and FAA Cat II category country)... yet, we don't have any instances of misinterpretation of that CAB ALT HORN... the nearest we got was a near total crew hypoxia when the cabin altitude alert warning failed (screwed up maintenance). There are always 2 ways to look at it... We're lucky that no one misinterpret it... or those guys on Helios were just out of luck and wanted to just shut the damn thing off. But yes... a light to indicate the warning to prevent (or further reduce the chance of) misinterpretation/ambiguity is a good thing.

Quoting 777236ER (Reply 32):
What large Western commercial aircraft certified since 1990 doesn't have EICAS/ECAM?

You should be looking at Southwest (and Continental) instead of Boeing who decided old tech on warnings were adequate and told Boeing "No... we won't buy it if you change these things." It's like saying "why are people still making airplanes with no FBW and/or envelope protection?"

Quoting 777236ER (Reply 32):
This concerns me, because you seem to be implying that the AD was frivolous and not required for continuing airworthiness. The fact is that the investigating authority found deficites in the 737's warning architecture, and the FAA mandated remedial action.

And that previledge/misfortune extends to almost every single type there is out there! (if there's an aircraft with no AD between it's initial type certification until its retirement from service, then I'd like to know... it's always a pleasure to learn something new everyday)

Quoting 777236ER (Reply 32):
On 737CL, there's no auto-stow, and there's no light. On 737NG there's a single light, no warning.

Of course. Having the light / warning is better. Here's a question... does the 764 have the warning? Because if it does, it is a mere "update" of the 763... and the 737NG is also a mere "update". This is however, different from your original point of:

Quoting 777236ER (Reply 26):
or CLs and NGs with spoilers that don't automatically retract when power is added.

To which citing that as a weakness would be rather strange.

I for one think the 320 is a better aircraft than the NG... but some of the point of criticism that has been thrown seems rather strange.
Back to this Helios issue... I myself still wonder to this day... "Why didn't Boeing change that warning before people got killed from it?"

Mandala499
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tdscanuck
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RE: Helios 522 And The B737 Pressure Warning

Mon Dec 27, 2010 6:16 pm

Quoting 777236ER (Reply 32):

Quoting mandala499 (Reply 27):
The NG does not have the CAS/CAM part of EICAS/ECAM... it's an EIS not an EICAS. Are you suggesting that non EICAS aircraft be refused certification?

Why not? Every modern large commercial aircraft has these systems, except the 737.

It appears you're using "modern" = "EICAS/ECAM"...so yes, by your definition, all "modern" aircraft have EICAS/ECAM. But that's not the definition the regulators, OEM's, or airlines use.

Quoting 777236ER (Reply 32):
This ambiguity existed (and was certified) in an era when Boeing (and Airbus) were certifying aircraft with much clearer warnings. Why wasn't the 737 held to the same standards?

Because the customers (airlines), those with the legal responsibility for safe operation of the aircraft, wanted it that way.

Quoting 777236ER (Reply 32):
My point is simple: aircraft certified at around the same time that the 737NG was certified had automatic cutoff of the centre tank pumps.

Auto shutoff didn't come in to any of the Boeing production fleet until the early 2000's.

Quoting 777236ER (Reply 32):
The only time the crew hear this warning, in training and almost always in operation, is for takeoff config. It's clear that many crew's first thought would be 'take off config', leading them down a dangerous chain of spurious warnings and confusing indications.

If the crew were never trained on the cabin altitude warning, I agree that's a major issue. But poor training is certainly not an aircraft design flaw.

Quoting 777236ER (Reply 32):
The fact that Helios happens shows that this warning IS ambiguous.

By that logic, the Tenerife crash shows that the entire ATC communication system is ambiguous, or the Egyptair crash shows that Airbus envelope protection is inadequate.

Quoting 777236ER (Reply 32):
So you disagree with the FAA and the investigating authority?

No, I agree with them that the warning system was *a* contributing cause and that it can be improved. I (and the FAA and the investigating authority) disagree with you that 1) the warning system was *the* cause for the crash, 2) the 737 should be grounded due to being non-EICAS/ECAM.

Quoting 777236ER (Reply 32):
It's also rather callous of you to accuse a properly licensed and professional flight crew of being not reasonable (irrational?) - especially when they cannot defend themselves.

They didn't do their preflight properly, they responded incorrectly to a clear warning (either through improper training or negligence) and, as a result, their passengers died. Which definition of "professional" are we filing this under?

Quoting 777236ER (Reply 32):

Quoting tdscanuck (Reply 28):
Absolutely true, but the 737 (and many other jets still in commercial service) aren't EICAS/ECAM airplanes.

What large Western commercial aircraft certified since 1990 doesn't have EICAS/ECAM?

I very clearly said "still in commercial service." By your logic, the DC-8, MD-80/90, DC-10, 707, 727, 737, 747-100/200/300, A300/A310, and about half the RJ fleet should be grounded as being unsafe.

Tom.
 
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RE: Helios 522 And The B737 Pressure Warning

Tue Dec 28, 2010 5:21 pm

Quoting 777236ER (Reply 13):

This isn't just my conjecture, to quote one of the causes from the final report:

"Ineffectiveness and inadequacy of measures taken by the manufacturer in
response to previous pressurization incidents in the particular type of aircraft,
both with regard to modifications to aircraft systems as well as to guidance to
the crews."

The report breaks down the causes into two categories, direct and latent, and the one you cite is one of the latent causes.

The direct causes are given as:

Quote:

   Non-recognition that the cabin pressurization mode selector was in the MAN (manual) position during the performance of the Preflight procedure, the Before Start checklist and the After Takeoff checklist.
   Non-identification of the warnings and the reasons for the activation of the warnings (Cabin Altitude Warning Horn, Passenger Oxygen Masks Deployment indication, Master Caution).
   Incapacitation of the flight crew due to hypoxia, resulting in the continuation of the flight via the flight management computer and the autopilot, depletion of the fuel and engine flameout, and the impact of the aircraft with the ground.

The latent causes are given as:

Quote:

   Operator�s deficiencies in the organization, quality management, and safety culture.
   Regulatory Authority�s diachronic inadequate execution of its safety oversight responsibilities.
   Inadequate application of Crew Resource Management principles.
   Ineffectiveness of measures taken by the manufacturer in response to previous pressurization incidents in the particular type of aircraft.

It's interesting that you are so concerned about the last given direct cause.

I'm a lot more concerned about the first direct cause (airmen who blow through their procedures and have an unacceptably poor understanding of their aircraft's systems) and the first two latent causes (an operator and a regulator who did not weed out such airmen).

BTW, shouldn't the Passenger Oxygen Masks Deployment indication also have clued in the pilots as to what was going on? I guess if they didn't know the horn had multiple purposes they would not have known to interpret that correctly either.
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Hold away despair, more than this I will not ask.
Faced with mysteries dark and vast, statements just seem vain at last.
Some rise, some fall, some climb, to get to Terrapin!
 
nycbjr
Posts: 118
Joined: Wed Aug 22, 2007 6:45 am

RE: Helios 522 And The B737 Pressure Warning

Tue Dec 28, 2010 7:08 pm

Quoting tdscanuck (Reply 34):
Egyptair crash shows that Airbus envelope protection is inadequate

  

Tom I would never try and correct you, so I'm going to ask a question instead, are you referring to 990? If so then it was a 767. my bad if it was another incident you were bringing up..

Your point is still valid, 777236ER has it out for the 737, I wonder if he would feel safe to fly on one? Or would he avoid them.

Cheers
     
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Helios 522 And The B737 Pressure Warning

Tue Dec 28, 2010 9:40 pm

Quoting nycbjr (Reply 36):
Tom I would never try and correct you, so I'm going to ask a question instead, are you referring to 990? If so then it was a 767.

Arrgghhh!! Too much eggnog, my sincere appologies. I was trying to think up good examples, was thinking about both Egyptair (pilot intentionally crashed the plane) and some Airbus cases where envelope protection surprised the flight crew, and I ended up sticking them together completely incorrectly.

You're absolutely right, I was talking 990, which was a 767.

In which case, we should call for grounding all 767's too since, even though they're EICAS/ECAM, their envelope protection and unusual attitude warnings and auto-correction is clearly inadequate.

Tom.
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Helios 522 And The B737 Pressure Warning

Wed Dec 29, 2010 6:25 am

Quoting tdscanuck (Reply 37):
Too much eggnog,

Just eggnog, or eggnog and rum?   

'Tis the season...  
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
rheinwaldner
Posts: 1261
Joined: Wed Jan 02, 2008 4:58 pm

RE: Helios 522 And The B737 Pressure Warning

Wed Dec 29, 2010 7:58 am

Quoting tdscanuck (Reply 34):
the Egyptair crash shows that Airbus envelope protection is inadequate.

Beside the otehr mishap there is another problem with this:
IIRC the envelope protection does not prevent a flight into terrain. As long as the aircraft is doing that within the flight envelope!

It only prevents leaving the safe flight envelope (mostly speed limits) in all circumstances.

It does not prevent you willingly to crash.

And it gives no guarantee that the aircraft can climb over obstacles in front of it (Habsheim crash).
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Helios 522 And The B737 Pressure Warning

Wed Dec 29, 2010 8:50 pm

Quoting rheinwaldner (Reply 39):
IIRC the envelope protection does not prevent a flight into terrain. As long as the aircraft is doing that within the flight envelope!

Exactly. That was my point. 777236ER appears to be taking the stance that any unsafe situation that resulted in a crash demonstrates inadequate design on behalf of the airframe. I was trying to take that idea to its logical extreme.

The flight crew will *always* be able to defeat all annunciations, warnings, and protections of the aircraft if they're sufficiently motivated or confused.

Tom.

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