TUI plane with 187 passengers over UK suffered 'serious' mid-air cabin pressure incident, report finds
A TUI plane suffered a serious mid-air cabin pressure incident over the UK - putting crew and passengers at risk.
The event happened with 187 passengers on board as it flew from Manchester Airport to Greece - and occurred three days before the same plane came off a runway at Leeds Bradford Airport during a storm.
The aircraft did not pressurise after taking off from Manchester, and the crew and passengers were exposed to the risk of hypoxia. The life-threatening condition arises when there are low levels of oxygen in body tissues and can cause confusion, restlessness, rapid heart rate and difficulty breathing.
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The Boeing 737-8K5 was en route to Kos Airport after taking off from Manchester at 6.06am on October 17 last year, Hull Live reports. Within minutes, a cabin altitude warning went off.
It alerted crew to a "serious incident", the Air Accidents Investigation Branch said in report published this month. It stated: "A cabin altitude warning was activated as the aircraft passed FL130 [13,000 feet]. Both engine bleed air systems had been inadvertently left off for the departure, so the aircraft failed to pressurise."
The report said the air systems had been turned off by engineers during routine maintenance work but said 'it appears' they had not been turned back on. The crew then turned both systems on and continued the climb before the plane generated a further caution and the plane stopped climbing at 20,000 feet.
The commander decided to return to Manchester Airport after consultation with the operator's maintenance control. However, passengers had to wait because the plane was above the maximum landing weight.
They were therefore forced to wait while the plane went into a holding pattern and burned fuel before it could land. The situation was explained to the passengers over the public address system.
The report said: "The recorded data indicated that the cabin altitude warning remained on for 43 minutes. During that time the associated red warning light should have been illuminated, though neither pilot recalls seeing it.
"As the passenger oxygen masks did not deploy, the cabin altitude did not exceed 14,000 ft but, nevertheless, it was likely that the crew and passengers were exposed to a progressive hypoxia risk. While any loss of consciousness was highly unlikely, a negative impact on the ability of the crew to process information and make decisions was probable."
The report said: "As the aircraft did not pressurise, the crew and passengers were exposed to the risk of hypoxia. At cabin altitudes above 10,000 ft but below 14,000 ft, without the pre-existence of significant medical issues, the likelihood of loss of consciousness is very small.
"However, in this altitude window, the hypoxic exposure can be sufficient to affect cognitive performance and decision-making to the point where the decline would be observable in cognitive tests. In this range of altitudes there are many variables that affect the severity and impact of hypoxia, including duration of exposure, rate of hypoxia onset (eg rate of climb if no pressurisation), physical workload, fatigue, individual responses and type of task being performed.
"In this range of altitudes it is also difficult to separate the relative contribution of hypoxia versus other performance degraders such as fatigue, distraction or other human performance issues." The plane landed safely at Manchester Airport at 8.10am. In an unrelated incident, three days later the plane came off the runway at Leeds Bradford Airport during the rough weather caused by Storm Babet.
Officials at AAIB looked into crew fatigue in the report into the earlier mid-air incident. It found the commander had had just three hours sleep.
It stated: "Analysis found that in terms of acute fatigue, the duty was not in itself particularly fatiguing, but the commander’s pre-duty rest was disturbed with just three hours sleep achieved. There were several indicators from the analysis of the previous eight weeks that suggested chronic fatigue was a possible factor for the commander.
"He had carried out a significant number of overtime duties and, although they were not necessarily individually fatiguing, the cumulative disruption may have been a factor. The SAFE analysis also showed that the commander’s exposure to fatiguing duties was amongst highest across the operator’s B737 fleet and joint highest amongst its commanders at Manchester.
"Though the commander did not believe fatigue was a factor in this event, the analysis of his roster over the eight weeks preceding the event and the rest period immediately before it suggest that fatigue could still have been a contributory factor. It should be noted that fatigue, particularly chronic fatigue, can be insidious such that an individual may not recognise the symptoms in themselves."
The aircraft, registered G-TAWD, slid off the runway on October 20 onto the grass banking while returning from a flight from Greece. Multiple ambulances and specialist resources from West Yorkshire Fire and Rescue Service and Yorkshire Ambulance Services’ Hazardous Area Response Team, were called to the scene.
Nobody was injured. A separate AAIB investigation found the plane's nosewheel bearings had "suffered a catastrophic failure", causing minor damage.
TUI has been approached for comment.