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Helios Airways Flight 522
Crashed on August 14, 2005

On August 14, 2005, at approximately 12:04 PM, Helios Airways Flight 522, crashed into hilly terrain in the vicinity of Grammatiko village, approximately 33 kilometers northwest of Athens International Airport. The plane was traveling from Larnaca, Cyprus to Prague, Czech Republic with a stop over in Athens, Greece. The scheduled arrival time in Athens, Greece was to be at 10:45 AM local time.

At approximately 9:07 AM, Helios Airways Flight 522, takes off from Larnaca International Airport.  Approximately, 5 minutes later, once the plane reaches an altitude of 12,040 feet, there is a "Cabin Altitude Warning" alarm. At approximately 9:12 AM, the pilot reported Take Off Configuration Warning and air conditioning problems to the company Operations Centre. These conversations continued for approximately 8 minutes. As the aircraft climbed to an altitude of 18,200 feet, the cabin oxygen masks were deployed. At  approximately 9:20 AM, the aircraft climbed to an altitude of 28,900 feet. At this time, there were no further communications from the aircraft. The aircraft leveled off at FL340 (Flight level 34,000 feet), and continued on it's previous programmed route via autopilot.

At approximately 9:37 AM, Helios Airways Flight 522 enters the Athens Flight Information Region. At 10:20 AM, Athens Air Traffic Control communicates with Larnaca Air Traffic Control receiving information about the aircraft air conditioning problems. At 10:21 AM, the aircraft flies over the Athens International Airport region and enters a holding pattern.

At approximately 10:24 AM, Hellenic Air Force is notified of a possible unresponsive and hostile aircraft.  At 10:55 AM, after continued attempts to make contact with Helios Airways Flight 522, Hellenic Air Force Chief of General Staff member Admiral Panagiotis Chinofotis orders two F-16s to intercept the aircraft. The two F-16s take off at 11:05 AM.

At approximately 11:24 AM, Helios Airway Flight 522 is intercepted by the two F-16s over the island of Kea while it is in it's sixth holding pattern. At approximately 11:32 AM, one of the F-16 pilots observes the Helios Captain's seat being vacant; and a body slumped over the controls in the First Officer's seat. He observes the oxygen masks are deployed and dangling in the main cabin. The F-16 pilot also sees motionless bodies in the main cabin. There were no visual signs of terrorism. There were no visual signs of damage or fire to the exterior of the aircraft.

At approximately 11:49 AM, one of the F-16 pilots sees a person enter the cockpit of Helios Airway Flight 522. The unidentified person is not wearing an oxygen mask. The F-16 pilot tries unsuccessfully to attract the attention of the individual inside the cockpit.

At approximately 8:50 AM, the left engine flames out due to fuel starvation. Helios Airways Flight 522 starts to descend. At 8:54 AM, there are two MAYDAY messages heard on the Cockpit Voice Recorder (CVR). At approximately 9:00 AM, at an altitude of 7,100 feet, the right engine of Helios Airways Flight 522 flames out due to fuel starvation. At this point, the aircraft continued descending rapidly and crashed.

It was thought the unidentified individual entering the cockpit was flight attendant Andreas Prodromou who tried unsuccessfully to gain control of the aircraft. Prodromou most likely used supplemental oxygen in the cabin to combat hypoxia caused by the depressurization of the aircraft. Unfortunately, he was unable to take control of the aircraft due to his hypoxic state and/or time constraints due to the aircraft running out of fuel.

The airplane was carrying 115 passengers and 6 crew members aboard on the flight. All individuals perished in the crash.

The Air Accident Investigation and Aviation Safety Board (AAIASB) of the Hellenic Ministry of Transport & Communications investigated the accident following ICAO concluded the direct causes of the accident was due to the non-recognition that the cabin pressurization mode selector was in the MAN (manual) position during the performance of the Preflight procedure, the Before Start checklist and the After Takeoff checklist.; non-identification of the warnings and the reasons for the activation of the warnings (Cabin Altitude Warning Horn, Passenger Oxygen Masks Deployment indication, Master Caution); and incapacitation of the flight crew due to hypoxia, resulting in the continuation of the flight via the flight management computer and the autopilot, depletion of the fuel and engine flameout, and the impact of the aircraft with the ground.

Also, it was determined on a previous flight, the previous flight crew had reported a frozen door seal and abnormal noises coming from the right aft service door, and requested a full inspection of the door. The inspection was carried out by a ground engineer who then performed a pressurization leak check. In order to carry out this check without requiring the aircraft's engines, the pressurization system was set to "manual", and was not set back to "auto" on completion of the test. When the aircraft was returned to service, the crew of Helios Airway Flight 522 overlooked the setting on the control panel and as the plane gain altitude the cabin started to slowly depressurize thus setting off all the warning alarms which still went unrecognized.


Download the AAIASB Aircraft Accident Investigation Report for Helios Airways Flight 522
(File Size is 3.94 MB)