An Alternative Helios Flt ZU522 Explanation - see below

based upon the info released 22 Aug 05 (below)

Last Minutes of Cypriot Flight Are Described in a Greek Report


By IAN FISHER
Published: August 23, 2005
ROME, Aug. 22 - An exhausted-sounding man apparently worked to take control of a Cypriot jetliner in the last 10 minutes of its flight, trying to radio in a final distress call just two seconds before the plane crashed last week in the mountains north of Athens, a preliminary report said Monday.

The report, by a chief Greek investigator, said there were indications that the Helios Airways plane had suffered a problem in its pressurization system that possibly incapacitated the two pilots. But the final cause of the crash, on Aug. 14, was that the Boeing 737-300 ran out of fuel after flying nearly three hours, double the planned duration from Larnaka, Cyprus, to Athens.

"There is proof that the engines of the plane stopped working because the fuel supply was exhausted, and that this was the final cause of the crash," the report said.

There were no survivors among the 115 passengers and 6 crew members on the flight, bound for Prague after a stop in Athens.

After a string of major air crashes in the last month, 136 French tourists refused Monday to board a charter flight from Crete to Paris because of safety concerns. Agence France-Presse quoted a passenger as saying that passengers were worried because the jet had made a recent emergency landing in Milan and had been delayed twice for technical reasons, and that one pilot was 21.

In the Greek crash, the man believed to have tried to take control of the plane was a flight attendant, Andreas Prodromou, who was learning how to fly small airplanes.

The report, which was read on Greek television on Monday, said there were indications that someone had tried to take control of the plane toward the end of the flight. The plane's voice recorder, recovered after the crash, picked up the sound of a man, sounding "distressed or suffering from exhaustion," yelling, "Mayday! Mayday! Mayday!" 10 minutes before the crash, then again two seconds before impact.

The radio was set to the wrong frequency, the report said, and the call was not heard on the ground.

About 30 minutes into the flight, the pilot reported problems with the air-conditioning. Autopsies on bodies from the flight did not show any intoxication from fumes, adding to the theory that decompression and a resulting loss of oxygen incapacitated those on the plane.

A former chief mechanic of Helios recently acknowledged that the same plane lost cabin pressure on a flight in December because a door was not properly closed. Helios, a low-cost airline, maintains that its operations are safe.

From The Cyprus Mail:

"Tsolakis confirmed that they had asked for a recording of the captain’s dialogue with the company just after takeoff

 

 from Larnaca when he contacted them to report a problem.

But they were told there was no such recording, the Greek investigator said.
The existence of a problem is further reinforced by reports that the black box had shown that the alarm in Boeing’s cockpit sounded at 9.15am, just before the German captain spoke to the company’s British chief engineer.

The alarm went off when the aircraft was flying at 14,500 feet.

It also transpired that the passenger oxygen masks had been deployed, indicating that the aircraft lost pressure shortly after departure.

According to the reports, the German captain told the chief engineer that he was having problems with the computer cooling system.

The engineer told him to shut it down and switch to the backup system, followed by instructions regarding the location of the switches.

Reports insisted that the two men could not communicate: the engineer’s last words were “word confuse”.

After that the communication was terminated with the engineer asking the captain to put the co-pilot on so that he could speak to a Greek engineer.

But apparently those words never reached the plane, the reports said."

ANALYSIS

If this report in The Cyprus Mail is correct then it becomes quite likely that the aircraft was never pressurized to begin with. Consider that the aircraft took off at 0907 and at 0915, only 8 minutes later, it was at 14,500' with the cabin altitude warning (triggered passing 10,000' in the B737) annunciated. 14,500' in 8 minutes is just under 2000 fpm rate of climb, which is probably about right, and the only way the cabin gets there that fast (as well) is if there was no source of pressurization at all.

Additionally, without the packs there would have been no cooling air being provided to the avionics, which would likely precipitate problems with flight displays, FMC, and etc. Those problems occurring at the same time as the pressurization warning might cause a crew to mis-attribute the source of the warning to the avionics problem, and not the cabin pressurization. If the computer cooling reset instructions received from the ground engineer seemed to be having some effect, then it's possible that they decided that continuing the climb was acceptable, still not recognizing that the real source of the problem lay with the lack of an air-supply from the packs, and not a failure of the avionics cooling system or ground/air sensing.

As the climb continued without pressurization, the hypoxic effects would quickly become more severe and the warning would continue to be ignored, having already been attributed to the avionics cooling. With mental capacities decreasing and pilot fixation still centered on solving the cooling problem, it's quite possible the crew lost consciousness without ever realizing what the source of their problems was. It's likely that the cabin crew were informed about the reason for the interim level-off, and that would have allayed initial F/A alarm about the rubber jungle having come down. They'd have noted the aircraft continuing its climb and assumed all was well. Only when the pax started dropping off into unconsciousness would they have realized it wasn't...

It would seem to me that a +/- 2000 fpm cabin vertical speed should have been noticeable to the crew, but then again at Alaskan Airlines there was a very similar incident [Alaska Flt 506 on 20 Mar 2000 - link) where a 737NG departed with both packs off and the crew failed to recognize the condition until the alarm bells went off at 10,000' and the rubber jungle made its appearance at 14,000ft. The pilots were later sacked for pressing on to destination. ALPA took up their case.

If this latest report is credible, then departing with the engine bleeds off ( a common practice in runway/weight limited situations) or aircon packs off, has to be considered another simple and plausible explanation for what happened to Helios Flight ZU522 on 14 Aug 2005.
 
A later deeper analysis
MindSets, Mis-idents and Misinterpretations - the Case of the dual function warning horn

As one pilot related:

Warning Horns

"As others have pointed out, warning horns can really mentally incapacitate a flight crew into a thinking paralysis if not cancelled in time.

Take the Birgen Air 757 Accident as an example. They had a constant overspeed warning, which could not be cancelled, right into the stall. We train the same scenario once in a while during simulator checks and I am still amazed how many mistakes are made until the horn is silenced (by pulling C/Bs).

Another example: A few years back I had a fire bell during T/O. Just the bell - no EICAS messages and no fire lights. And worse, the fire bell could not be cancelled. Again we made some mistakes until the bell was silenced by pulling the aural warning C/Bs. (It did require a full power down to actually reset the glitch in the warning system)."

So I would consider it possible, that while the Helios crew was working on some technical problems during departure they misinterpreted the Cabin Alt Warning Horn as being the take-off configuration warning horn that they were totally familiar with - and were immediately stressed out by the noise so that they never realised where the warning was coming from and how to react correctly. It never occurred to them to press the horn cancel button - so that is why that alarm sounded throughout the flight.....above 10,000ft cabin altitude. Their attempt to discuss their problem with a Helios engineer didn't work out due to the Greek/German language barrier..... and the enervating uncancellable horn in the background wouldn't have helped either.

A voice message clearly annunciating (twice) the problem as  "pressurization / Check cabin altitude" would have avoided this accident - as would an FMS automatic 90 degree turn off airways and descent mode (after 3 minutes) if crew had not retarded thrust levers for an emergency descent.

Leaving engine bleeds off intentionally for improved performance on take-off and initial climb is a common tactic for crews. Accidentally leaving aircon packs off can also happen per the incident related below. From a cabin crew point of view, once told by the flight-crew that they were working a problem, they'd not be surprised if the rubber jungle of masks came down. They'd tend not to query the crew about that, at least not straightaway. They'd just tend to the pax and assist them with their masks. The F/A's would be unaware that the aircraft was continuing its climb. Unfortunately it would only take about 4 to 5 minutes (in that cont'd climb) for the pilots to succumb to the hypoxia. By FL340 they'd be brain-dead.

So whether the lack of pressurization was due to a leaky door seal or engine bleeds or packs left off or an outflow valve left at OFF (and not AUTO), the problem is the same - and the same across all airplane types also. If crews aren't schooled in aviation medicine and have not had a hypobaric chamber run and thus don't know their personal hypoxia onset symptoms, then they are very vulnerable.

According to the reports, the German captain told the chief engineer that he was having problems with the computer cooling system.

The engineer told him to shut it down and switch to the backup cooling system, followed by instructions regarding the location of the switches.

Reports insisted that the two men could not communicate: the engineer’s last words were “word confuse”.

After that the communication was terminated with the engineer asking the captain to put the co-pilot on so that he could speak to a Greek engineer.

But apparently those words never reached the plane, the reports said."

That warning horn issue

http://www.aaiu.ie/upload/general/3893-0.pdf   (A Ryanair Incident)

(FO turned packs off when reconfiguring the Pressurization panel after a "bleeds off" take off.)

"At approximately FL240 the crew heard what they understood to be the configuration warning horn sounding. Checks on the aircraft take-off configuration and reference to the Quick Reference Handbook (QRH) failed to detect the cause of the warning. At 08.18Z, 612 asked ATC could he hold at FL 260? FL 270 was given, with a slight heading change. Cabin service continued normally during this time, with the No 1 CCM attending the cockpit on call from the Captain. However, the crew were engrossed in the problem and the Captain told her he would call her again shortly when the situation was sorted. Trouble shooting continued, the FO was concerned that the QRH held no rectification measures, the Captain initially thought that there might be a micro-switch problem on the thrust lever quadrant, closing the thrust levers had no effect on the warning horn, which continued to sound. Further re-assessment led the crew to check the overhead panel where the Captain noticed that the Packs were OFF. He immediately switched both Packs ON and controlled the rate of repressurization in Standby Mode. A check on the cabin altitude showed approx 14,000 ft. The Captain instructed oxygen masks on and as the FO read out the Rapid Decompression checklist from the QRH, ........"

 

Further similar incident

http://www.aaiu.ie/upload/general/3496-0.pdf   makes instructive reading. Both a/c packs off and pilot doesn't put on o2 mask - but does descend.

SYNOPSIS
During climb-out from Stansted Airport (EGSS), the flight crew experienced an illumination of the “Master Caution” indicating “Overhead” on the main instrument panel. A short time later, the “Master Caution” (Overhead) illuminated again, followed by an additional warning light on the rear overhead panel, indicating that the passenger oxygen masks had automatically deployed in the cabin. Having reached FL 143, the aircraft was descended to and levelled at FL 100, where further analysis by the flight crew determined that the pressurisation system had not been properly configured for flight. The aircraft returned to the airport of departure, where it landed without further incident.
Narrative: on passing FL 100 and as the normal Standard Operating Procedures (SOP’s) were being carried out, the “Master Caution” illuminated advising “Overhead.” Further analysis identified that the passenger oxygen system had deployed in the cabin. The cabin altitude aural warning horn, (which alerts the flight crew that the cabin altitude is 10,000 ft above mean sea level) did not sound on the flight deck. Having reached FL 113, the aircraft was descended with clearance from ATC down to FL 100. The SCCM was called to the flight deck to report on the status of the cabin and she confirmed that the passenger oxygen masks had in fact deployed. The SCCM was then informed by the Captain that the pressurisation system had failed and that the aircraft would be returning un-pressurised to EGSS. The Captain then made a public address (PA) announcement to the passengers informing then of the situation.
Prior to the commencement of the descent from FL 100 to EGSS, the flight crew observed that the No 1 and No 2 Engine Bleed Air Switches were not selected to “On”. When both Engine Bleed Switches were configured correctly, the pressurisation system returned to a normal condition. It was also noted by the flight crew that the circuit breaker for the cabin altitude aural warning horn was found to be in the “Open” position. The pressurised aircraft then continued its descent to EGSS, where it landed without further incident at 1338 hours.
 
See also the identical Alaska 506 incident at this URL
 
Nightmare cruise at FL340:  The fact that the airplane climbed itself to and cruised at FL340, the pax all nodded off and became brain-dead (as did the flt crew) - all that is classified as merely the outcome - as is the fact that some cabin crew members managed to stay conscious on portable oxygen and finally access the cockpit. The F/A's would've been frantically trying to assist pax in the cruise by running around with their portable oxygen but once hypoxia sets in and consciousness is lost, giving an unconscious pax a whiff of oxygen would become clearly futile to the F/A's.

Once into the cockpit, the F/A's would've tried desperately to revive the pilots with their own oxygen but probably would not have been knowledgeable enough to select 100% or ensure a good facial seal. Eventually they'd have removed the captain to the rear to free up his seat for the attempt to fly a recovery. The inability to transmit probably relates to the mikes being diverted to the oxy-masks as much as still being on Nicosia frequencies. The weak mayday calls heard on the CVR were possibly made on intercom and/or just picked up by the cockpit area mike (CAM). The F/A's may not even have been able to identify the transmitter selector switch or the PTT (press-to-talk).

Hearkening back to the original problem, it could easily have been the repeat of that Dec 04 door-seal (as it's alleged to have been causing a hissing noise on the prior flight). Equally it may have been a switch out of position. Use of a WARNING HORN that they couldn't cancel was a sufficiently mind-numbing distraction for the flight-crew that their minds were oriented towards avionics cooling - as sometimes happens on the ground - as evidenced by what they said to their maint plus the fact that the horn was never cancelled - simply because they'd completely forgotten about the deadly DUAL FUNCTION of that warning horn.

 

 It is after all, quite a simple scenario. Just more holes in Swiss Cheese lining up and a below average crew getting totally distracted by a misinterpreted blaring and uncancellable warning horn (that's often heard on the ground but very rarely airborne).