Aircraft Accident Due to a Breach of Regulations: Helios Airways Flight 522

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Aircraft Accident Due to a Breach Of Regulations: Helios Airways Flight 522

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Table of Contents

  • Introduction
  • Background
  • Regulatory Knowledge
  • Regulatory Issues
  • Measures Taken
  • Conclusion

This report will be focusing on Helios Airways Flight 522, a fatal flight which crashed into a mountain of Greece on 14 August 2005. The Greek Air Accident Investigation and Aviation Safety Board (AAIASB) was the one who carried out the investigation to find out what were the causing factors that lead to the crash. The main purpose of them doing this is to take down of any factors that were linked to human factors, so as to prevent similar incidents form happening in the future. Hence, this report will be stating the background and the breach of regulations on this incident.

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Air traveling may be frightening to some; however, it is the safest mode of transportation with a rate of 0.07 deaths per one billion passenger miles. Continuous adjustments and amendments are always being made so as to achieve higher standard of safety performance at all time. This is because safety is always the top priority. In addition, IATA will always work with airlines and its industry partners to implement best practices to assure safety. However, with all these safety regulations and practices being put to place, there are still accidents happening. One of the major contributing factor to flight safety is human error with an approximate of 80 percent, the rest of the 20 percent are due to machine failures. Hence, stating all significant cause of flight accidents is vital and necessary.


Back then on 14 August 2005 at 0900hrs, flight Helios Airways 522, was a scheduled Boeing 737-300 carrying 121 passengers and crew from Larnaca, Cyprus, to Athens, Greece. Unfortunately, the flight has crashed at 1204hrs and killed all 121 passengers and crew on board. Initially, all the 121 passengers and crew were incapacitated due to loss of cabin pressurization. Hence, resulting the pilots leaving the aircraft flying on autopilot mode until the fuel was fully consumed causing the aircraft to descend into the ground.

So, the aircraft arrived on Larnaca from London earlier that day, and the previous flight crew had reported a frozen door seal and unusual noises coming from the right aft service door. Hence, the ground engineer conducted a thorough inspection which lead him to execute a pressurization leak check. In order to conduct the check without requiring the aircraft’s engine, the pressurization system was set to “Manual”. After the inspection was done, the engineer did not reset the pressurization system back to “Auto”.

The aircraft was then back to service, however the flight crews were not able to realize the wrong setting with the pressurization system status on three separate occasions: pre-flight, after-start and the after-take-off checks. The aircraft then departs Larnaca International Airport at 0907hrs with the pressurization system on “Manual” and with an open aft outflow valve. During the process of climbing, the pressure in the cabin decreases continuously. When the aircraft passes through an approximate altitude of 12000 feet, the cabin altitude warning horn rang. The warning was an indication for the crew to stop climbing, however they misinterpreted the warning as a take-off configuration warning, that indicate the aircraft not being ready for takeoff, and can only be sound on the ground.

Few moments later, a few of the warning lights located at the cockpit panel lighted up. The lights from an equipment that indicate low airflow through the cooling fans was on when the aircraft was at an approximate altitude of 18200 feet. Therefore, oxygen mask was automatically extended to the passengers in the cabin. The pilot then contact with the operation center and reported the warnings and the air conditioning problem. The ground engineer who had conducted the pressurization leak check asked the pilot “Can you confirm that the pressurization panel is set to AUTO?”. However, the pilot was already under the effects of hypoxia, he ignored the question and asked the ground engineer another question “Where are my equipment cooling circuit breakers?”. That was the last conversation with the pilot as the aircraft carried on to climb up to 28900 feet.

At a later stage, the aircraft entered the holding pattern for 70 minutes when it is nearby to the Athens International Airport. When the Nicosia ATC was unable to get a response from Helios Airways Flight 522, two F-16 fighter aircraft was deployed to intercept the aircraft at its sixth holding pattern at 1124hrs to make a close visual contact. From the two F-16 fighter aircrafts’ point of view, no external damage was found outside the aircraft, oxygen masks were seen dangling in the passenger cabin and the pilot’s seat was unoccupied. They also noticed that a man who was conscious and identified as the flight attendant entered the cockpit and sat down at the pilot’s seat. He was in the cockpit trying very hard to gain back controls, after that he radioed 2 maydays to the control tower but with no avail due to the frequency was not adjusted correctly. His effort was not enough to save the situation, hence 25 minutes later, the left engine loss power due to fuel depletion. 10 minutes after the left engine was out, the right engine also loss power at an approximate altitude of 7100 feet. At 1204hrs, Helios Airways Flight 522 plunged and crashed into hills near Grammatiko, it was just about 33km away from Athens International Airport. The aircraft was then wrecked and all 121 people that were on board died.

Regulatory Knowledge

Regulations are important and were set to provide a standard process for all to follow so as to achieve standardized operations thus keeping the industry efficient and safe. Moreover, there is an organization called International Civil Aviation Organization (ICAO) who manages the international law and provides the procedures for air accident investigations.

Firstly, based on the Flight Crew Operations Manual (FCOM), flight crews are able to read and learn from the manual since it is mandatory for them. From Annex 1.1 and 1.2 in the appendix, we can see that responsibility of checking the air conditioning and pressurization located at the cockpit panel were non-other than the First Officer and the Captain.

Secondly, based on the Boeing Aircraft Maintenance Manual (AMM), from Annex 2 we can see that there is an instruction inside the manual indicated that the engineer should put the aircraft back to its initial condition after the pressurization check.

Therefore, the First Officer and the Captain are responsible to go through the checklist for all three pre-flight phases; pre-flight, after-start and after-take off. The cabin pressurization was one of the necessary checks and it should be set to “Auto”. The checklist also consists of flight safety which are linked to an alerting system which includes the pressurization and air-conditioning kit.

According to the Operator’s Standard Operating Procedures Manual from Annex 3, we can see that flight crew should put on their oxygen masks when the cabin altitude warning alarm is on. This action is important as it will keep the flight crew conscious, in order not to lose control of the aircraft.

Regulatory Issues

Air Accident Investigation and Safety Board (AAIASB) did a detailed investigation and declared that this flight incident was caused by a chain of events. They followed ICAO practices and realized that it was breaches at different events that lead to the crashed.

Firstly, the 1st breach occurred was when the ground engineer did not switch the setting of the pressurization control back to “Auto” from “Manual” after he performed the pressurization leak check earlier that day. From this mistake, it would highly likely cause the aircraft to face dire consequences as the cabin will not be automatically pressurized. There might be a chance that the flight crew notice the setting of the pressurization control was wrong, however it was not for this flight case. Thus, there are more breaches in this case.

Secondly, for the 2nd breach that has occurred, the first officer was not able to realize that the settings for the pressurization panel was not correct for takeoff when the aircraft was still on the ground. The Flight Crew Operation Manual stated that when the aircraft is on the ground, the First Officer is required to check that the switches in the aircraft are in the correct position. However, the pressurization setting was still not noticed by both of the pilots for the remaining two checks; after-start and after-take off. Even when the warning lights came on and oxygen mask being extended to the passengers; which was an indication that there is a problem with the air in the cabin, both pilots were still unable to identify the reasons behind it. This evidently shows that both of the pilots were not proficient at all.

Lastly, for the 3rd breach that has occurred, it is after the cabin altitude warning alarm came on. Based on the Operator’s Standard Operating Procedures Manual, when the oxygen masks were being extended, the flight crews are required to put them on immediately. However, the flight crew did not do so. The flight crew did notify the ground that oxygen masks were being extended, but they did not know that the reason behind this was due to problem with the pressurization of the cabin. Hence, this was the reason why the flight crew did not stop climbing the aircraft, which the situation eventually got dire. Both of the pilots were then believed to be under incapacitation due to hypoxia, this causing them not being able to make the correct decision and eventually both of them lost conscious. The aircraft then continued to cruise in autopilot mode and crashed into hills after the engine consumed all the fuel. Therefore, this shows that if flight crew were not equipped with sufficient knowledge, they can jeopardize air passengers’ life.

Measures Taken

Safety is always important and it is the top priority in aviation. Safety measures must always be taken at all times, also updating whenever an aircraft accident happens. This is to prevent history from repeating itself. Hence, all the mistakes from this incident was listed out. There were many suggestions being made, one of it was to change the instruction in the manual to make it clearer. Thus, the process for the cabin pressurization leak test in the AMM was altered to “put the pressure mode to the position of Auto” instead of the previous “back to its initial condition”. This will definitely be much clearer than the previous one, hence lowering the chance of mistake.

On the other hand, AAIASB did some suggestions for the update of the checklist used by the First Officer and Captain to Boeing. They want to change the design of the air conditioning and air pressurization in the checklist; this is to allow the pilots to differentiate between the two easily. They also suggested to Boeing that the warning indication light have to change, so as to catch the attention of the pilots easier.

There was also adjustment being made to the Federal Aviation Administration (FAA) manual and warning alarm. They included that for normal operations, the pressurization mode setting should be in Auto mode, prior to take off. In addition, the reason behind the warning alarm will different in air and on ground. If the alarm goes off on air, it would mean that the aircraft is at 10000 feet, otherwise it would mean that the aircraft is having a configuration issue when on the ground. FAA introduced all these changes and implementations are to show us that they are putting in all of their effort to keep the aviation industry safe.

Changes and amendments are always important as it will enhance safety. Hence, there should be constant adding of new regulations or measures so as to ensure safety and improvement.


In conclusion, I feel that having a set of regulations are vital. This is because it will be able to set standards across all the aviation bodies. Hence, allowing operations to be more standardized rather than different organization doing different stuff. The most important factor of following regulations is to ensure safety. Humans are prone to making mistake, thus we must keep improving our regulations for safety purposes and also ensuring that everyone have to follow regulations as it can minimize the error we make. From the incident of Helios Airways Flight 522, we learnt that everyone’s role and responsibility is important. One person’s minor mistake can cause a drastic domino effect. This is the reason why everyone should put in all their effort and follow regulations to minimize human error, breaching of regulations should not be tolerated. Hence, we can see that organizations are making effort to make regulations an easier guide to read. If all the organizations can keep safety as their top priority, this will allow aviation industry to be more efficient and safe.

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