Helios Airways Flight 522 - Investigation

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.

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.

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 12 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.

The Hellenic Air Accident Investigation and Aviation Safety Board (AAIASB) determined that the direct causal chain of events that led to the accident was

• non-recognition by the pilots that the pressurisation system was set to "manual",
• non-identification by the crew of the true nature of the problem,
• incapacitation of the crew due to hypoxia,
• eventual fuel starvation,
• impact with the ground.