Ryanair B738 near Madrid on Sep 7th 2012, loss of cabin pressure
Last Update: August 26, 2015 / 14:06:38 GMT/Zulu time
Incident Facts
Date of incident
Sep 7, 2012
Classification
Incident
Cause
Loss of cabin pressure
Airline
Ryanair
Flight number
FR-2011
Departure
Madrid, Spain
Destination
Las Palmas, Spain
Aircraft Registration
EI-EKV
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
A replacement Boeing 737-800 registration EI-DCN reached Las Palmas with a delay of 3 hours.
On Sep 21st 2012 Spain's CIAIAC announced to open an investigation into the occurrence reporting, that following an uneventful takeoff cabin and flight crew began to feel unwell during the climb. Upon checking the instruments while climbing through FL220 the crew recognized an unusual cabin altitude indication, donned their oxygen masks and declared Mayday reporting pressurization problems. Following uneventful return to Madrid four passengers received treatment by medical staff on board of the aircraft, their medical problems related to throat and ear issues as well as anxiety.
On Sep 26th 2013 (one year after the occurrence) Spain's CIAIAC released an interim statement reporting that the aircraft was climbing following an uneventful takeoff and initial climb, when both flight and cabin crew, without communication between them, started to notice strange sensations and felt physically unwell. The purser, after consultation with other cabin crew members, informed the flight deck which prompted the captain to stop the climb and return to Madrid, the aircraft reached a maximum altitude of 21,868 feet MSL. The cabin altitude at that point was 3,930 feet. The aircraft landed back in Madrid about 25 minutes, but remained in a pressurized state. The main left hand door were opened 9 minutes after landing as result.
Four passengers were treated in hospital showing symptoms involving ears and throats, that were caused by the rapid depressurization on the ground, as well as anxiety.
The examination of aircraft pressurization systems, search for contamination in food, air conditioning system, cleaning products used internally of the aircraft, a possible halon leak from fire extinguishers as well as medical examination and analysis of symptoms, analysis of symptoms with respect to hypoxia and motion sickness, which are similiar, and motion of aircraft did not provide "any objective information that can unequivocally account for the symptoms reported by the crew".
The CIAIAC reported in their interim statement one year after the event that the investigation has concluded, the final report is currently being drafted.
On Aug 26th 2015 the CIAIAC released their final report concluding the probable causes were:
The cause of the symptoms reported by several members of the crew (the two pilots, and particularly by two of the four flight attendants) onboard aircraft EI-EKV could not be determined. The hypotheses considered to possibly explain said symptoms were hypoxia by poisoning, motion sickness, suggestion among members of the crew or a combination of the last two.
The following factors contributed to the incident and to the handling of the emergency:
- the crew’s suspicion that the aircraft was malfunctioning, as evidenced by the constant problems since taking off, specifically the operation of the aural warning of the CABIN ALTITUDE WARNING, which had not worked prior to the flight, and
- the possible confusion in executing the CABIN ALTITUDE WARNING or Rapid Depressurization checklist due to:
+ including an option between two choices as part of memory item 5,
+ having a second option (item 6) on a different page, and
+ completing the checklist and redirecting to another as part of the memory items.
The CIAIAC reported that the aircraft had undergone unannounced maintenance the night prior to the occurrence flight, a circuit breaker and a switch were left in the wrong positions. The circuit breaker prevented the takeoff configuration horn (the same signal used for cabin altitude warning) to operate, the incorrect STAB Trim Switch prevented the engagement of autopilots. The wrong position of the circuit breaker was detected and corrected prior to takeoff. The wrong stab trim switch position was not detected and caused about 20 master caution activations during the flight as well as prevented the engagement of autopilots.
About 10 minutes into the flight cabin crew reported feeling unwell with symptoms consistent with hypoxia, the flight crew also felt unwell. The cabin altitude however was equivalent to 3,774 feet MSL and the air conditioning systems were all operating normally. The outflow valve was subsequently kept closed until after landing causing the aircraft to remain pressurized while taxiing on the ground, in fact the aircraft had overpressurized reaching a cabin altitude of -10,000 feet (10,000 feet below sea level). The aircraft subsequently depressurized from that pressure in 87 seconds on the ground causing the barotraumas to passengers and the discomfort to the captain.
The CIAIAC analysed:
Regardless of the reason for the physical ailments suffered by the crew (hypoxia, nausea, suggestion or some combination of the three), within ten minutes of taking off the cabin crew thought that something was wrong and that what they were feeling was not normal. Before calling and alerting the cockpit crew, the purser checked with FAs 2 and 4, both of whom, especially FA 2, confirmed his suspicions. Following this confirmation the purser called the captain. This action by the cabin crew is regarded as highly appropriate, especially considering the consequences that a depressurization can have on flight safety. The captain, too, used the call from the purser to confirm that something was wrong. The immediate order to stop the climb after the call suggests that he was already unwell and that his own condition must have been similar to that described by the purser.
It is not known whether he looked at the cabin altitude value, which at the moment read 3,774 ft. In their statements the captain and first officer reported having seen an abnormal reading, but they did not recall the exact value. Hypoxia diminishes one’s cognitive abilities, and could have made it difficult for them to process the value or to remember it. In any case, the situation facing the captain at that moment was one in which the cabin and cockpit crews, with no previous communications between them, both reported feeling symptoms related to hypoxia. Furthermore, as the aural warning for cabin altitude warning had not worked on the ground, even had the cabin altitude readings been normal, the decision not to take any risks under those conditions was correct. Thus, the captain’s decision to stop the climb, declare a MAYDAY, deploy the oxygen masks and immediately start the CABIN ALTITUDE WARNING or Rapid Depressurization procedure was the best response to the situation they thought themselves in, due to the risk of incapacitation and loss of control posed by this emergency.
The captain’s immediate order to stop the climb after the call from the passenger cabin initially surprised the first officer who was relatively inexperienced. They had spoken among themselves about how they felt before the purser’s call, meaning that apart from his own physical condition, he had no additional information. The captain’s actions were clear and immediate: to stop the climb and declare an emergency to ATC. Seconds later the pilots’ and passengers’ masks were deployed and the rest of the actions in the CABIN ALTITUDE WARNING, including closing the outflow valve, quickly followed.
The communications that followed show that the first officer read item 5 of the CABIN ALTITUDE WARNING checklist. The rest was spoken literally word by word from the checklist, meaning that the five memory items had been executed and they were reading the checklist, as specified in the operator’s procedure for carrying out non-normal checklists.
The entry into this checklist was one of the critical moments in this incident, as it was then that the crew closed the outflow valve and kept it closed until the end of the flight, causing the subsequent overpressurization and depressurization of the cabin.
The checklist, as described in Section 1.10.2, included five memory items. Number 3 was to place the pressurization system in manual mode and 4 was to fully close the outflow valve, which the crew did. Item 5, despite being a memory item, gives the crew a choice between two options. The other option, item 6, which was the condition in effect in this incident, is not a memory item and is on a different page. Furthermore, there is a “checklist complete” and a redirection to another checklist after item 5. This means that crews memorize the cabin depressurization only in the event that the cabin altitude cannot be controlled.
In this case it is not known whether or not the crew attempted to verify if the cabin altitude was controllable or not, and thus determine if the correct option was item 5 or 6. But subsequent communications suggest they were sure that the first 5 steps (the memory items) were the ones that were applicable. The crew thought they had applied the procedure correctly and focused on the remaining tasks involved in the emergency: flying the aircraft, procedures, coordinating with ATC, informing the cabin crew and configuring the aircraft for a safe landing. That is why the captain was so surprised on touching down when he saw that the cabin was pressurized.
This mistake in applying the checklist is more significant in a crew that throughout the flight, not only before the incident but also afterwards, exhibited excellent discipline and adherence to every procedure and to flight management, identifying the start and end of each checklist, perfectly dealing with interruptions to checklists, prioritizing the aircraft’s configuration rather than landing immediately and hastily, restarting checklists when interrupted and using the PIOSEE methodology after addressing the immediate emergency.
Throughout the flight, and especially after the emergency declaration, the captain clearly exercised his leadership role by taking the initiative, organizing and communicating all of his actions and intentions to the first officer, who was sure at all times of what he had to do and of what the captain’s intentions were (“I’m back to you”, “you have controls”, “you keep the controls and I make the aircraft ready for the 33”). The crew was focused on rigorously adhering to the checklists at all times and balanced the constant communications with ATC with the handling of the emergency.
The full management of the emergency comprised the use of the CABIN ALTITUDE WARNING checklist and, as directed by this checklist, of the EMERGENCY DESCENT checklist. It took the crew 6 minutes 3 seconds to complete the first one, and 3 minutes 40 seconds for the second one. The reason was the frequent communications with ATC that took place during the emergency, forcing the crew to interrupt the checklists. The captain handled communications with ATC (figure 4). From an ATC standpoint, the aircraft was in a busy traffic area, the approach to the Madrid-Barajas Airport, in a transitional phase of flight where handling emergency traffic required considerable coordination. In addition the crew, which were focused on the emergency they were attempting to manage, did not make their intentions clear, having to specify them with each call from ATC.
ATC’s intention from the start was to give them landing priority by clearing them to descend and directing them to the airport. Within two minutes of the emergency declaration, ATC offered them the choice of heading directly to the airport. It was the captain, who was still carrying out the CABIN ALTITUDE WARNING checklist, who reported needing to maintain altitude. From then on, the captain’s demands to ATC were frequent, as they needed more time to complete the approach. ATC did not wait until the captain called them when he was ready; rather, it was the controller who, on several occasions, asked about how much time they needed.
The crew followed ATC’s instructions at all times. The only initiative they took was to stop the climb at the start of the emergency, an action they reported to ATC along with the emergency declaration. They did not start the descent until cleared to do so by ATC. ATC also facilitated the hold maneuvers for as long as required by the aircraft.
Aircraft Registration Data
Incident Facts
Date of incident
Sep 7, 2012
Classification
Incident
Cause
Loss of cabin pressure
Airline
Ryanair
Flight number
FR-2011
Departure
Madrid, Spain
Destination
Las Palmas, Spain
Aircraft Registration
EI-EKV
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
This article is published under license from Avherald.com. © of text by Avherald.com.
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