Helios Airways Flight 522

Helios Airways Flight 522

Occurrence
Date	14 August 2005
Summary	Pilot incapacitation due to gradual decompression, 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 kilometres (25 miles) from Athens. All 121 people on board were killed.

Flight and crash

Hans Jurgen Merten, an 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 copilot. 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 indicates a non-compliance with standard Boeing procedures. Minutes after take-off the cabin altitude horn activated and was identified by the crew as the take-off configuration warning, which means the plane is not ready for take-off. However, the take-off configuration warning can only sound on the ground. The cabin altitude horn is the same horn used for flight control warning and landing gear warning. It will sound when the cabin altitude exceeds 10.000 ft. This 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 will automatically deploy, a Cabin Oxy ON warning light on the overhead panel will illuminate when this happens. The crew then contacted the ground engineers. Minutes later a master caution warning light activated, which means a system annunciator light has illuminated, indicating a non-normal situation in a system. This was being interpreted by the crew that systems were over-heating, creating more confusion.

Later the captain, probably due to hypoxia, told the engineer that the ventilation fan lights were off, though the B737-300 has no such lights. This type of aircraft has Equipment Cooling Off lights which illuminate when the avionics equipment is not sufficiently cooled and they are normally off. When illuminated this will trigger two lights: the OVERHEAD light on the systems annunciator panel and consequently the amber Master Caution Light. The overheating of the equipment can be caused by not pressurising the plane.

The engineer asked the captain to repeat. The captain then said that the equipment cooling lights were off thinking it was a problem but the engineer said, "this is normal, please confirm the problem." Later the engineer asked, "Can you confirm that the pressurization system is set to AUTO," but the captain simply asked, "Where are my equipment cooling circuit breakers?", again possibly because of hypoxia. The engineer asked whether the crew could see the circuit breakers but got 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 accord 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) of the ill-fated aircraft. The fighter pilot saw that the first officer was slumped motionless on the controls, and that the captain was not in the cockpit. Oxygen masks were seen dangling in the passenger cabin.

Later, the F-16 pilots saw a flight attendant enter the cockpit and sit at the controls, seemingly trying to regain control of the aircraft. He eventually noticed the F-16, and signalled him. The F-16 Pilot pointed forward as if to say, "can you carry on flying?" to which the flight attendant shook his head and pointed down as if to say, " no, we're going down". The CVR recorded him calling "mayday" multiple times. Within minutes, first one engine, then the second engine, stopped and the aircraft began to descend. The flight attendant grabbed the yoke and tried to steer the aircraft clear of the mountain. The plane continued to descend, hitting the ground and exploding. The passengers and crew were unconscious but breathing and were killed instantly as the plane hit the ground.

Map of Helios Airways Flight 522

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.

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 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.

The cause of the crash (according to air crash investigations) was that the air pressure valve was set to manual and was not switched back to auto after pressurisation test 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 tanks carried in the passenger cabin.

Investigation

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

Loss of cabin pressure and consequent pilot unconsciousness is the leading theory explaining the accident. This would account for why oxygen masks were released. Weighing against this is the fact that the pilots should have been able to descend the aircraft to a safe altitude after donning oxygen masks if they interpreted the alarm signal properly and acted before their minds were too impaired by hypoxia.

The flight data recorder and cockpit voice recorder were sent to a special centre in 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 under his belt. Autopsies on the crash victims showed that all were alive and maintained cardiac and respiratory function upon impact, but it could not be determined whether they were conscious at the time. Prodromou was not originally scheduled to be on the flight; he joined the crew so he could spend time with his girlfriend, Haris Charalambous, a Helios flight attendant.

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 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.

Decompression hypothesis

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

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 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 outflow valves were one-third in the open position which meant that the cabin would not pressurize after takeoff. The PMS mode was apparently not noted during the pre-departure checks by the crew.

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 a rapid descent to 10,000 feet (3,000 m), where ambient atmospheric pressure is sufficient to sustain life. Cabin crew have access to portable oxygen sets with considerably longer duration. Emergency oxygen for the cockpit comes from a dedicated tank.

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 have also reported problems with air conditioning on Helios flights.

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.

Timeline

Crash area of the flight in red

All times EEST (UTC + 3h because Greece and Cyprus were on daylight saving time)

• 09:00 Scheduled departure time.
• 09:07 Aircraft takes off from Larnaca airport.
• 09:11 Pilots report "air conditioning" problem.
• 09:15 The aircraft's flight data recorder registers an alarm at 14,000 feet (4,300 m).
• 09:16 Flight's last contact with Nicosia air traffic control; the aircraft is flying at 22,000 feet (6,700 m).
• 09:24 Aircraft in cruise at 34,000 feet (10,400 m), probably on autopilot.
• 09:37 Flight enters Athens Flight Information Region, but fails to establish contact.
• 10:07 Flight fails to respond to call from Athens Air traffic control (ATC).
• 10:20 Larnaca ATC indicates to Athens ATC that a "problem with air conditioning" was reported earlier.
• 10:24 Hellenic Armed Forces (HAF) alerted to possible renegade aircraft.
• 10:45 Scheduled arrival time in Athens.
• 10:47 Hellenic Armed Forces (HAF) reassured that the aircraft's technical problem seems to have been solved.
• 10:55 The HAF Joint Chief of Staff, Admiral Panagiotis Chinofotis orders military aircraft to establish visual contact with the airliner.
• 11:05 Two F-16 fighters take off from Nea Anchialos, Greece.
• 11:20 F-16s see the airliner over the Aegean island of Kea.
• 11:25 Fighter pilots see co-pilot slumped unconscious on the aircraft's instrument panel, oxygen masks deployed, but notes no indications of terrorism.
• 11:41 Fighter pilots note an individual in the cockpit presumably trying to regain control of aircraft.
• 11:50 The left engine stops operating, probably due to lack of fuel.
• 12:00 The right engine stops operating.
• 12:05 Aircraft crashes near Grammatiko.

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 06/11/2006.
• 24 July 2007 Helios air crash families sue Boeing

Relatives of victims of the 2005 Helios air crash near Athens have filed a 76 million € lawsuit against aircraft manufacturer Boeing. The lawsuit was filed in an Athens court by relatives of 17 of the victims. They petitioned for damages against the U.S.-based maker of the Boeing 737-300 aircraft. The plaintiffs said that Boeing was responsible for a series of design errors including faulty warning signals that led to fatal mistakes by the pilots of the aircraft. The relatives say the level of compensation being demanded is based on Boeing's profit levels. It is not yet known when the case might go to trial. (In the October 2006 report on the crash, Greek investigators cited human error as the main cause of the crash, saying the pilots had left cabin pressure controls at an incorrect setting. The report also cited Boeing for "ineffectiveness of measures" in response to previously known problems of cabin pressurisation aboard its aircraft.)

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).

38°13.894′N 23°58.214′E