Figure: Sequence of Events Map, from Accident Report, pg. 8.

Eddie Sez:

There is a fascinating television program about this incident. "May Day: Ghost Plane" romanticizes the role of a flight attendant who managed to get into the cockpit and almost saved the day but perhaps lost his will after discovering his girlfriend, another flight attendant on board, had died. It also makes an issue of the captain's belittling of the first officer, shutting him down and possibly rushing him through his preflight duties. None of this is supported in the accident report, but it does make for good T.V.

The report does note CRM issues and does a good job of figuring out what happened. It makes for good reading, but here is the abbreviated version:

  • The airplane had a history of pressurization problems.

  • The mechanic didn't failed to properly apply the maintenance procedure that would have verified the pressurization leakage and failed to return the pressurization switch from its manual position to the automatic position.

  • The first officer, who had a history of SOP problems, failed to detect the improperly set switches.

  • The aircraft was designed with a warning horn that had two meanings: on the ground it meant takeoff configuration and in the air it meant high cabin altitude. The captain misinterpreted it and continued to trouble shoot while continuing the climb and failing to don oxygen.

  • Everyone eventually passed out, the aircraft ran out of gas, all aboard were killed.

Regardless of which version you believe — the romantic Hollywood tale or the cold facts of the accident report — there are several lessons we can take away from this mishap:

  • Fuselage pressure leaks should be addressed immediately and repaired.

  • Oxygen supply and delivery equipment must be pre-flighted.

  • During every climb, part of your 10,000 foot check must be a check of cabin altitude. Most airplanes have a maximum cabin altitude between 6,000 and 8,000 feet. You certainly should not be above that at 10,000 feet aircraft altitude. You should know your normal cabin climb rate, typically around 300 fpm. Even if it takes you ten minutes to get to 10,000 feet aircraft altitude, you should not see more than 3,000 feet cabin altitude at that point. In any case, if it isn't where it should be, level off and investigate.

  • When troubleshooting a pressurization problem, donning oxygen quickly will not only improve your mental capabilities, it can keep you in the game if things go south quickly or insidiously.

  • When in doubt, descend.

What follows are quotes from the sources listed below, as well as my comments in blue.

Accident Report


Figure: Pressurization Panel, from Helenic Republic Accident Report, pg. 51.

Post crash analysis determined the switch was actually in the "MAN" position from before the flight, during the flight, until impact when it was knocked into the position shown. (Actual switch position was recorded by non-volatile memory.)

[Helenic Republic Accident Report, ¶1.1]

  • On 13 August 2005, on the flight prior to the accident, the Helios Airways (the Operator) Boeing 737-300 aircraft, Cyprus registration 5B-DBY, departed London-Heathrow, United Kingdom for Larnaca, Cyprus at 21:00 h. The aircraft landed at Larnaca at 01:25 h on 14 August 2005.

  • During the flight, the cabin crew noted a problem with the right aft service door. The cabin crew made an entry in the Aircraft Cabin Defect Log that “Aft service door (starboard) seal around door freezes & hard bangs are heard during flt [flight]”. The write-up by the cabin crew was transferred to the Aircraft Technical Log by the flight crew as “Aft service door requires full inspection.”

  • Immediately after the arrival of the aircraft in Larnaca, the authorized company Ground Engineer (number one) went to the Boeing 737 aircraft for the required inspections. He performed a visual inspection of the aft service door and he carried out a cabin pressurization leak check. In response to the write-up in the Aircraft Technical Log, the Ground Engineer documented his actions as follows: “Door and local area inspected. NIL defects. Pressure run carried out to max diff. Safety valve operates at 8.25 No leaks or abnormal noises (IAW MM 21 – 32 – 21 – 725 – 001)”.

  • The aircraft took off from Larnaca airport at 06:07:13 h. At 06:11:21 h, the flight crew contacted Nicosia Area Control Centre (ACC) at reporting point LOSOS, climbing through flight level (FL) 100 for FL200. At 06:11:35 h, Nicosia ACC identified the flight and asked for the requested final cruising level. The Captain requested cruising level 340. At 06:11:45 h, flight HCY522 was cleared to climb to FL340 and to proceed direct to the RDS (Rodos) VOR. The Captain acknowledged the clearance. This was the last recorded communication between the flight crew and Nicosia ACC.

  • According to the Flight Data Recorder (FDR), at 06:12:38 h and at an aircraft altitude of 12 040 ft and climbing, the cabin altitude warning horn sounded. At 06:14:11 h, at an aircraft altitude of 15 966 ft, the Captain contacted the company Operations Centre on the company radio frequency, 131.2 MHz. According to the Operator’s Dispatcher, the Captain reported “Take-off configuration warning on” and “Cooling equipment normal and alternate off line.” The Dispatcher requested an on-duty company Ground Engineer to communicate with the Captain.

  • During the communication between the flight crew and the company Operations Centre, the passenger oxygen masks deployed in the cabin as they were designed to do when the cabin altitude exceeded 14 000 ft. It was determined that the passenger oxygen masks deployed at 06:14 h at an aircraft altitude of approximately 18 000 ft (extrapolation of the data from the NVM in the cabin pressure controller).

  • According to the FDR, the microphone keying (communication between the Captain and the Ground Engineer) ended at 06:20:21 h as flight HCY522 was passing through 28 900 ft. Shortly afterwards, the Operator’s Dispatcher called the flight crew again but there was no response.

  • At 06:23:32 h, the aircraft leveled off at FL340.

  • At 07:20:59 h, the flight passed the KEA VOR, and began what appeared to be a standard instrument approach procedure for landing at Athens International Airport, runway 03L, but remained at FL340. At 07:29 h, flight HCY522 flew over the Athens International Airport still at FL340 and following the missed approach procedure for runway 03L turned right towards the KEA VOR. At 07:37:39 h, flight HCY522 reached the KEA VOR and entered the published holding pattern.

  • At 08:23:51 h, during the sixth holding pattern, flight HCY522 was intercepted by two F- 16 fighter aircraft of the Hellenic Air Force. The F-16s made close visual contact with the flight in the holding pattern, at FL340. During the interception, the F16s communicated on the military radar frequency and with Athinai ACC. One of the F-16 pilots attempted to attract the attention of the flight crew using prescribed interception signals and radio calls on the emergency and Athinai ACC frequencies, without success. He maneuvered around the aircraft to acquire various views from the right and left sides of the cockpit and the fuselage in an effort to identify the reasons for the lack of radio communication. No external structural damage or fire/smoke was observed.

  • At 08:32 h, the F-16 pilot reported by radio that the Captain’s seat was vacant. The First Officer’s seat was occupied by someone who was slumped over the controls. Two passengers on the left side of the aircraft, one wearing white clothing and the other red clothing, sat motionless in their seats and were wearing oxygen masks on their faces. Additional oxygen masks could be seen dangling from their overhead units. The passenger cabin was dark, but the shadow of the oxygen hoses and masks could be seen against the daylight shining through the windows on the other side of the passenger cabin. Another passenger was seen from the right side of the aircraft wearing white clothing, sat motionless and wore an oxygen mask.

  • At 08:48:31 h, two chimes were heard on the CVR and, at 08:48:51 h, another two chimes were heard followed after 20 seconds by a continuous chime which lasted 20 seconds. Some seconds later, a click sound similar to the cockpit door opening was recorded. Also, sounds similar to movement in the cockpit, seat adjustment, and oxygen mask removal from its stowage box and oxygen flow during donning of the mask were recorded.

  • Approximately 08:49 h, during the tenth holding pattern, the F-16 pilot observed a person wearing a light blue shirt and dark vest, but not wearing an oxygen mask, enter the cockpit and sit down in the Captain’s seat. He put on a set of headphones and appeared to place his hands on the panel directly in front of him.

  • According to the FDR, at 08:49:50 h, the left engine flamed out. At this time, the F-16 pilot observed what he assumed was fuel coming out of the left engine. The aircraft turned steeply to the left and headed in a northerly direction. The person in the Captain’s seat did not respond to any of the attempts of the F-16 pilot to attract his attention. He appeared to be bending forward every now and then. Flight HCY522 began a descent on a northwesterly heading. The two F-16s followed at a distance due to the maneuvering by the Boeing 737.

  • When the F-16 pilot next came close to the Boeing 737, he saw the upper body of the person in the First Officer’s seat lean backwards as if he was sitting up. It became evident that this person was not wearing an oxygen mask and remained motionless.

  • At 08:54:18 h, the following distress was recorded by the CVR “MAYDAY, MAYDAY, MAYDAY, Helios Airways Flight 522 Athens ... (unintelligible word)”. A few seconds later, another “MAYDAY, MAYDAY” with a very weak voice was recorded.

  • When the Boeing 737 was at about 7 000 ft, the person in the Captain’s seat for the first time appeared to acknowledge the presence of the F-16s and he made a hand motion. The F-16 pilot responded with a hand signal for the person to follow him on down towards the airport. The person in the Captain’s seat only pointed downwards but did not follow the F-16.

  • At 08:59:20 h, the heading of the Boeing 737 changed to a southwesterly direction. The aircraft continued to descend. At 08:59:47 h, according to the FDR, the right engine flamed out at an altitude of 7 084 ft.

  • The aircraft continued to descend rapidly and collided with rolling hilly terrain in the vicinity of Grammatiko village, approximately 33 km northwest of the Athens International Airport at 09:03:32 h.


[Helenic Republic Accident Report, ¶1.5]

[Helenic Republic Accident Report, ¶1.6]

Figure: Air Conditioning Panel, from Helenic Republic Accident Report, pg. 50.

[Helenic Republic Accident Report, ¶1.12.2]

  • The left engine bleed toggle switch (BLEED 1) was found in the OFF position. The right engine bleed toggle switch (BLEED 2) was visually found in the OFF position. The APU toggle switch was found in the OFF Position. The isolation valve toggle switch was found in the AUTO Position. The left air conditioning pack switch appeared to be in the AUTO position. The position of the right pack switch could not be determined because of impact damage.

[Helenic Republic Accident Report, ¶1.16]

[Helenic Republic Accident Report, ¶1.18.2]

[Helenic Republic Accident Report, ¶2.2]

Probable Cause

[Helenic Republic Accident Report, ¶3.1]

See Also:

Abnormal Procedures & Techniques / Hypoxia

Abnormal Procedures & Techniques / Maintenance Malpractice

Abnormal Procedures & Techniques / Slow Onset Hypoxia

Normal Procedures & Techniques / Crew Resource Management

Technical / Oxygen


Hellenic Republic, Air Accident Investigation & Aviation Safety Board Aircraft Accident Report, Helios Airways Flight HCY522, Boeing 737-31S, at Grammatiko, Hellas, on 14 August 2005

May Day: Ghost Plane, Cineflix, Episode 33, Season 4, 17 June 2007 (Helios 522)