Helios Airways Flight 522

Helios Airways Flight 522

CG render: 5B-DBY being met by two F-16s of the Hellenic Air Force at flight level 340
Occurrence
Date	14 August 2005
Summary	Pilot incapacitation due to hypoxia brought about by depressurization, leading to fuel starvation
Site	Marathon, Greece
Aircraft type	Boeing 737-31S
Operator	Helios Airways
Registration	5B-DBY
Passengers	115
Crew	6
Fatalities	121
Injuries	0
Survivors	0

Helios Airways Flight 522 (HCY 522 or ZU522) was a Helios Airways Boeing 737-31S flight that crashed on 14 August 2005 at 12:04 EEST into a mountain north of Marathon and Varnavas, Greece. Rescue teams located wreckage near the community of Grammatiko 40 km (25 miles) from Athens. All 121 on board were killed.

Background

The aircraft involved in this incident was first flown on 29 December 1997 and had been operated by dba until it was leased by Helios Airways on 16 April 2004 and nicknamed Olympia, with registration 5B-DBY. Aside from the downed aircraft, the Helios fleet consisted of two leased Boeing 737-800s and an Airbus A319-111 delivered May 14, 2005.

With 121 dead, this was 2005's deadliest aircraft crash to that date (it was exceeded two days later by the West Caribbean Airways Flight 708 crash, which killed 160) and was the second accident of the year that caused more than 100 fatalities, the first being Kam Air Flight 904 with 104 deaths. It is the 69th crash of a Boeing 737 (the most numerous passenger jet aircraft in the world) since it was brought into service in 1968.

Flight and crash

Path of Helios Airways Flight 522
Date: 14 August 2005 All times EEST (UTC + 3h), PM in bold
Time	Event
0900	Scheduled departure
0907	Departs Larnaca International Airport
0911	Pilots report air conditioning problem
0915	Alarm sounds at 14,000 feet (4,300 m)
0916	Last contact with Nicosia ATC; Altitude is 22,000 feet (6,700 m)
0924	Now at 34,000 feet (10,400 m); Probably on autopilot
0937	Enters Athens Flight Information Region
1007	No response to radio calls from Athens ATC
1020	Athens ATC calls Larnaca ATC; Gets report of air conditioning problem
1024	Hellenic Air Force (HAF) alerted to possible renegade aircraft
1045	Scheduled arrival in Athens
1047	HAF reassured that the problem seemed to have been solved
1055	HAF ordered to intercept by Chief of General Staff, Admiral Panagiotis Chinofotis
1105	Two F-16 fighters depart Nea Anchialos
1120	Located by F-16s over Aegean island of Kea
1125	Fighters see co-pilot slumped over, cabin oxygen deployed, no signs of terrorism
1141	Fighters see an individual in the cockpit, apparently trying to regain control of aircraft
1150	Left (#1) engine stops operating, presumably due to fuel starvation
1200	Right (#2) engine stops operating
1205	Aircraft crashes in mountains near Grammatikos, Greece

Hans-Jürgen Merten, a former East German who was a contract pilot hired by Helios for the holiday flights, served as the captain. Pampos Charalambous, a Cypriot who flew for Helios, served as the first officer. 32-year old Louisa Vouteri, a Greek national living in Cyprus who served as a chief purser, replaced a sick colleague.

The flight, which left Larnaca, Cyprus at 09:07 local time, was en route to Athens, and was scheduled to continue to Prague. Before take-off the crew failed to set the pressurisation system to "Auto," which is contrary to standard Boeing procedures. Minutes after take-off the cabin altitude horn activated as a result of pressurization. It was, however, misidentified by the crew as a take-off configuration warning, which signals the plane is not ready for take-off, and can only sound on the ground. The horn can be silenced by the crew with a switch on the overhead panel.

Above 14,000 ft cabin altitude, the oxygen masks in the cabin automatically deployed. An Oxy ON warning light on the overhead panel in the cabin illuminates when this happens. At this point, the crew contacted the ground engineers. Minutes later a master caution warning light activated, indicating an abnormal situation in a system. This was misinterpreted by the crew that systems were overheating.

At some point later the captain told radioed the engineer on the ground to say that the ventilation fan lights were off. This is evidence that the captain was suffering from hypoxia, as the B737-300 has no such lights. The engineer asked the captain to repeat. The captain then said that the equipment cooling lights were off, which again was evidence of confusion. The engineer said, "this is normal, please confirm the problem." The engineer then asked, "Can you confirm that the pressurization system is set to AUTO?" The captain, however, disregarded the question and instead asked in reply, "Where are my equipment cooling circuit breakers?" The engineer then asked whether the crew could see the circuit breakers, but received no response.

After the flight failed to contact air traffic control upon entering Greek air space, two F-16 fighter aircraft from the Hellenic Air Force 111th Combat Wing were scrambled from Nea Anchialos Air Base to establish visual contact. They noted that the aircraft appeared to be on autopilot. In accordance with the rules for handling "renegade" aircraft incidents (where the aircraft is not under pilot control), one fighter approached to within 300 feet (100 m), and saw the first officer was slumped motionless at the controls. The pilot could also see that the captain was not upright in the cockpit and that xxygen masks were seen dangling in the passenger cabin.

Crash area of the flight in red

Later, the F-16 pilots saw the flight attendant Andreas Prodromou enter the cockpit and sit at the controls, seemingly trying to regain control of the aircraft. He eventually noticed the F-16, and signaled him. The pilot pointed forward as if to ask, "Can you carry on flying?" Prodromou responded by shaking his head and pointing downward. The Cockpit voice recorder recorded him calling "mayday" multiple times. Within minutes, the engines failed in quick succession and the aircraft began to descend. Prodromou grabbed the yoke and attempted to steer, but the plane continued hit the ground and exploded. At the time of impact, the passengers and crew were likely unconscious but breathing. None survived.

The aircraft was carrying 115 passengers and a crew of 6. The passengers included 67 due to disembark at Athens, with the remainder continuing to Prague. The bodies of 118 individuals have been recovered. The passenger list included 93 adults and 22 people under the age of 18. Cypriot nationals comprised 103 of the passengers and Greek nationals comprised the remaining 12.

The cause of the crash (according to air crash investigations) was that the cabin pressurization control valve was set to manual and was not switched back to auto after post-maintenance pressurisation testing was completed. As a result, the cabin never pressurised during the ascent to 35,000 feet. The flight attendant seen in the cockpit managed to stay conscious by using the spare oxygen bottles provided in the passenger cabin for crew use.

Investigation

Suspicions that the aircraft had been hijacked were ruled out by Greece's foreign ministry. Initial claims that the aircraft was shot down by the fighter jets have been refuted by eyewitnesses and the government.

Loss of cabin pressure -- which, without prompt alleviation, would cause pilot unconsciousness -- is the leading theory explaining the accident. This would account for the release of oxygen masks in the passenger cabin. Weighing against this is the fact that the pilots should have been able to don their own fast-acting masks and make an emergency descent to a safe altitude provided that they recognized the pressurization system as the source of the alarm and acted before their minds were too impaired by hypoxia.

The flight data recorder and cockpit voice recorder were sent to Paris for analysis. Authorities served a search warrant on Helios Airways headquarters in Larnaca, Cyprus and seized "documents or any other evidence which might be useful in the investigation of the possibility of criminal offences."

Most of the bodies recovered were burned beyond visual identification by the fierce fires that raged for hours in the dry brush and grass covering the crash site. However, it was determined that a body found in the cockpit area was that of a male flight attendant and DNA testing revealed that the blood on the aircraft controls was that of flight attendant Andreas Prodromou, a pilot-in-training with approximately 260-270 hours of training completed. Autopsies on the crash victims showed that all were alive at the time of impact, but it could not be determined whether they were conscious as well. Prodromou was not originally scheduled to be on the flight; he joined the crew so he could spend time with his girlfriend, a fellow Helios flight attendant.

Decompression hypothesis

Helios Airways aircraft 5B-DBY at London Luton Airport in 2004.

The preliminary investigation reports state that the maintenance performed on the aircraft had left the pressurization control on a 'manual' setting, in which the aircraft would not pressurise automatically on ascending; the pre-takeoff check had not disclosed nor corrected this. As the aircraft passed 10,000 feet (3,000 metres), the cabin altitude alert horn sounded. The horn also sounds if the aircraft is not properly set for take off, e.g. flaps not set, and thus it was assumed to be a false warning. The aircrew found a lack of a common language and inadequate English a hindrance in solving the problem. The aircrew called maintenance to ask how to disable the horn, and were told where to find the circuit-breaker. The pilot left his seat to see to the circuit breaker and both aircrew lost consciousness shortly afterwards.

The leading explanation for the accident is that the cabin pressurisation did not operate and this condition was not recognised by the crew before they became disabled. This model of Boeing 737 has a warning horn which is used both to signal loss of pressurization and incorrect take-off configuration such as incorrect flap or trim setting. The crew may have failed to realise that the warning horn indicated pressurisation failure and became incapacitated while attempting to suppress a warning occurring in what seemed to them an inappropriate phase of flight. Decompression would have been fairly gradual as the aircraft climbed under the control of the flight management system. The pressurisation failure warning on this model should operate when the effective altitude of the cabin air reaches 10,000 ft at which altitude a fit person will have full mental capacity.

The emergency oxygen supply in the passenger cabin of this model of Boeing 737 is provided by chemical generators that provide enough oxygen, through breathing masks, to sustain consciousness for about 15 minutes, normally sufficient for an emergency descent to 10,000 feet (3,000 m), where atmospheric pressure is sufficient to sustain life without supplemental oxygen. Cabin crew have access to portable oxygen sets with considerably longer duration. Emergency oxygen for the flight crew comes from a dedicated tank.

Previous pressurization problems

On 16 December 2004, during a flight from Warsaw, the ill-fated aircraft had suffered a loss of cabin pressure and three passengers were rushed to hospital upon arrival in Larnaca. The mother of the first officer killed in the crash of Flight 522 claimed that her son had repeatedly complained to Helios about the aircraft getting cold. Passengers also reported problems with air conditioning on Helios flights.

During the two months before the crash, the aircraft's Environmental Control System required repair five times. On the morning of the crash, after the aircraft arrived at Larnaca on a flight from the United Kingdom, the cabin crew complained about an abnormal noise coming from its rear door. Inspection by Helios engineers disclosed no problem and the aircraft was allowed to take off without any repairs. In retrospect, the noise is consistent with faulty sealing of the door that would allow gradual decompression of cabin air as the aircraft gained altitude, resulting in initially subtle but increasing cognitive dysfunction among the flight crew and delay in recognising the danger until it was too late.

The aircraft underwent maintenance on the night prior to the accident. The pressurisation system was checked, but after completion of the tests the Pressurisation Mode Selector (PMS) was reportedly left in the "Manual" position instead of the "Auto" mode. In manual mode the crew had to manually open or close the outflow valves in order to control the cabin pressure. The post-crash position of the outflow valves was one-third in the open position, so that the cabin would not pressurize after takeoff. The PMS mode selection was apparently not changed to automatic during the pre-departure checks by the crew.

Private Investigation

One year after the accident, the Discovery Channel aired a documentary detailing a private investigation made in cooperation with Advanced Aviation Technology Ltd. It presented evidence that a design failure of the Boeing 737 may have contributed to the accident. Contrary to the concept of redundancy, all wiring related to the pressure system were in one wiring loom to the outflow valve in the aft of the aircraft. A failure in this loom caused a pressurization incident with a Boeing 737-436 G-DOCE in May 2003. During this incident the pressurisation control system presented wrong indications to the pilots and was finally switched to manual position like found in the Helios 522 wreckage.

According to the Helios 522 final report, in a previous pressurisation incident with the Helios accident aircraft: "The Captain stated that there might have been a problem with the outflow valve." The Air Accident and Incident Investigation Board (AAIB) of Cyprus was not able to reach a conclusive decision as to the causes of this previous incident, but indicated as one of two possibilities: "An electrical malfunction caused the opening of the outflow valve."

The official accident investigation board was informed by Discovery Channel of the similarities with the G-DOCE incident. But in the final report neither the G-DOCE incident nor any wiring loom issues were mentioned.

Hoaxes

News media widely reported that shortly before the crash a passenger sent a SMS transmission indicating that one of the flight crew had become blue in the face, or roughly translated as "The pilot is dead. Farewell, my cousin, here we're frozen." Police later arrested Nektarios-Sotirios Voutas, a 32 year-old private employee from Thessaloniki, who admitted that he had made up the story and given several interviews in order to get attention. Voutas was tried by a court of first instance on 17 August 2005 and received a suspended 6-month imprisonment sentence under a 42-month probation term. The hoax was treated so seriously because it contradicts accepted knowledge of cabin-pressure emergencies and such false information could lead to fatalities and serious harm if people "accepted" the falsities of the hoax.

Another hoax involved photographs allegedly showing the aircraft being chased by Greek fighter jets. The photos were actually of a Helios 737-800 (rather than the crashed 737-300) with the registration altered and the fighter jets added.

Media

The Discovery Channel documentary mentioned above, Flight 522, originally aired as an episode of the Canadian television series Mayday, which examines aerial incidents, their causes and results.

Subsequent developments

• The flight Larnaca-Athens-Prague has been renumbered to ZU604/5.
• The service between Larnaca and Prague has been announced by the company to be discontinued since 26 August 2005.
• The company announced successful safety checks of their Boeing fleet 29 August 2005, and put them back to service.
• The company renamed itself from "Helios Airways (www.flyhelios.com)" to "αjet (www.ajet.com)".
• The Government of the Republic of Cyprus detained Ajet’s aircraft and froze the company’s bank accounts. Ajet no longer operates flights as of June 11, 2006.
• 24 July 2007 Helios air crash families sue Boeing

See also

• 1999 South Dakota Learjet crash

External links

• Aircraft Incident Report of Helios Airways Flight HCY522 at Grammatiko, Greece on 14 August 2005 (published in English, released in November 2006)
• Complete report of the official investigation by the Greek air safety investigations committee (published in Greek, released in October 2006).
• 360° Virtual tours & panoramic photos taken shortly after the crash
• Complete passenger list
• BBC article
• CNN article
• ERT article
• Sky News article
• Helios Airways
• Cyprus News Agency
• in.gr Template:El icon
• Aviation Safety Network
• CBS News on Voice recorder
• The Age timeline
• ERT article in English: First official estimations
• Debate in comp.risks regarding possible design problems that contributed to the crash
• Aviation Safety Network Accident Description
• Greek News Online article
• "Helios 737 crashed with no fuel", Flight International, 2005-08-24
• http://www.carsurvey.org/air/review_11283.html (Complaint about AC written one week before the crash by a passenger).

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