Helios Airways Flight 522

From Wikipedia, the free encyclopedia

Helios Airways Flight 522

Summary
Date	August 14, 2005
Type	Lack of cabin pressure
Site	Marathon, Greece
Fatalities	121
Injuries	0
Aircraft
Aircraft type	Boeing 737
Operator	Helios Airways
Tail number	5B-DBY
Passengers	115
Crew	6
Survivors	0

Helios Airways Flight 522 (HCY 522 or ZU522) was a Helios Airways Boeing 737-31S flight that crashed on August 14, 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—the highest death toll for an aviation accident in 2005 until the West Caribbean Airways Flight 708 in Venezuela just two days later.

Contents 1 Flight and crash 2 Background 3 Investigation 3.1 Decompression hypothesis 4 Private Investigation 5 Hoaxes 6 Timeline 7 Further developments 8 References 9 External links 10 See also

[edit] Flight and crash

The flight, which left Larnaca, Cyprus at 09:07 local time, was en route to Athens, and was scheduled to continue to Prague. 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 the pilots' 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 cabin.

Somewhat later, the F-16 pilots saw someone enter the cockpit and sit at the controls, soon to be joined by another person where the first officer had been sitting, both seemingly trying to regain control of the aircraft. Within minutes one engine, then the other ran out of fuel and the aircraft crashed into a hill, scattering wreckage and bodies and bursting into flame.^[1]

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^[2]. The passenger list included 93 adults and 22 people under the age of 18. Cypriot nationals comprised 103 of the passengers (mostly Greek Cypriots as well as a family of Armenian Cypriots) and Greek nationals comprised the remaining 12.^[3]

[edit] Background

The aircraft involved in this incident was first flown on December 29, 1997 and had been operated by a dba until it was leased by Helios Airways on April 16, 2004 and nicknamed Olympia, with registration 5B-DBY.^[4] Aside from the downed aircraft, the Helios fleet consists of two leased Boeing 737-800s and an Airbus A319-111 delivered May 14, 2005.

With 121 dead, this was 2005's worst aircraft crash to date (although it was exceeded only 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 aircraft in the world) since it was brought into service in 1968.

[edit] 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 center 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 penal 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 female flight attendant^[5], suggesting that she was indeed trying to prevent a crash. DNA testing revealed that the blood on the aircraft controls was that of flight attendant Andreas Prodromou, a novice private pilot, suggesting he was the other person the F-16 pilots saw in the pilot's seat. 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.

The investigation showed that the cockpit door was locked during the flight. However, in the last few minutes of the flight, as the engines consumed the last drops of fuel, power was cut to several parts of the plane, including the cockpit door. This resulted in the door unlocking, giving access to the two.^[6]

The two flight attendants most likely didn't know the code as the purser had probably already lost consciousness. It is speculated that they had retained their awareness using oxygen bottles.

During the two months before the crash the aircraft's Environmental Control System required repair five times.^[7] 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.^[1] 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 recognizing 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 pressurize automatically on ascending; the pre-takeoff check had not disclosed nor corrected this. As the aircraft passed 10,000 feet (3,000 m), 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.

[edit] Decompression hypothesis

The leading explanation for the accident is that the cabin pressurization 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 takeoff configuration such as incorrect flap or trim setting. The crew may have failed to realise that the warning horn indicated pressurization failure and become 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 pressurization failure warning on this model should operate when the effective altitude of the cabin air reaches 10,000' 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 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 flight deck comes from a dedicated tank.

On December 16, 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.^{[citation needed]}

[edit] 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.^[8] 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 the Helios 522 final report, in a previous pressurization 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.

[edit] 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 August 17, 2005 and received a suspended 6-month imprisonment sentence under a 42-month probation term.^{[citation needed]}

The hoax was significant because it seemed to contradict accepted knowledge of cabin-pressure emergencies, especially when combined with other early and erroneous reports.

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.^[9]

[edit] Timeline

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 individuals in 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.
• 13:10 Scheduled arrival time in Prague.

[edit] Further 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 August 26, 2005.
• The company announced successful safety checks of their Boeing fleet August 29, 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.

[edit] References

[edit] 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
• PPrune thread
• ikypros.com (Greek)
• in.gr (Greek)
• 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

[edit] See also

• 1999 South Dakota Learjet crash