Jet2 B752 near Tenerife on Aug 7th 2012, loss of cabin pressure
Last Update: February 2, 2015 / 17:50:25 GMT/Zulu time
Spain's CIAIAC reported that the passengers oxygen masks were released during the emergency descent, both crew and passengers used their oxygen masks. An investigation has been opened.
On Feb 2nd 2015 the CIAIAC released their final report concluding the probable cause was:
As a result, it may be concluded that the aircraft experienced an in-flight depressurization due to an air leak through the area where the deteriorated drain valve for the aft bathrooms was located. This was caused due to an improper action of maintenance, without taking into account the relevant documentation on aircraft maintenance or the process for deferring items. The acceptance by the flight crew of the maintenance measures taken on the ground was a determining factor in the incident.
The shortage of telephone and computer resources and the absence of technical instructions, added to the self-induced pressure not to cause any delays, contributed to the eventual outcome of the incident.
The CIAIAC reported that the operator responsible to service the bathrooms on the ground in Tenerife reported that the drain valve had detached from the aircraft and was hanging by its rubber seal inside the service panel. A mechanics was dispatched to repair the damage.
The CIAIC wrote: "The technician investigated the malfunction and concluded that the valve, which was stuck to the fuselage, had detached due to use and time in service. The clamp that holds the rubber to the drain valve was also loose. He thought the valve was in an unpressurized area because the captain had not reported any pressurization problems in the previous flight. Since reattaching the valve and clamp would have required unloading all the baggage from the aft cargo hold to access the front panel, he decided to remove the valve from the airplane to minimize the delay."
The CIAIAC continued: "He notified the captain of his intention and removed the valve, giving it to the crew so that it could be installed and sealed at the destination airport. Maintenance control was advised of this and a deferred entry, ADD 66979/1A, was made. He checked the levels in the aft bathrooms and found them to be half full. He reported this to the crew and they decided it would be sufficient for the flight to LBA since the forward bathrooms had been properly serviced and were fully operational."
The aircraft subsequently departed and was climbing through FL230 when a cabin pressure alert was issued. The crew selected the packs into manual mode, however to no avail. When the cabin altitude climbed through 13,500 feet the crew released the passenger oxygen masks manually.
The CIAIAC summarized: "The engineer did a test of both cabin pressure controllers using the built-in test equipment (BITE), which resulted in a “LOW INFLOW” fault light. The seals on the cargo and cabin doors, as well as the outflow and the positive and negative pressure relief valves, were inspected and found to be in good condition. A final inspection of the area around the bathroom drain valve exhibited evidence of an air leak."
The CIAIAC analysed: "The maintenance action taken that was carried out was not included in any documented instruction (AMM, SRM, etc.). In keeping with the MEL, the aircraft would actually have been airworthy had the rest of the wastewater system been properly isolated after removing the valve so as to eliminate any leaks. The results of the post-incident inspection indicate that the epressurization took place in the area of the detached valve and that the valve had deteriorated as a result of corrosion. In addition, the company´s own personnel stated that the telephone and computer systems in place at TFS for communicating with the maintenance center were deficient, as was the availability of technical information."
This article is published under license from Avherald.com. © of text by Avherald.com.
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