Bleed-air switch lapse preceded TUI 737 cabin-altitude incident

Pilots of a Boeing 737-800 did not notice that the aircraft’s bleed-air system was not active before the jet took off from Manchester, triggering a cabin-altitude warning that remained active for over 40min.

UK investigators found that the bleed-air switches had incorrectly been left off during air-conditioning pack maintenance, and not turned on during pre-flight procedures. Nor was the omission picked up by the crew during the ‘after take-off’ checklist.

The cabin-altitude warning sounded as the TUI Airways aircraft – bound for Kos on 17 October last year – climbed through 13,000ft.

Flight-data recorder information shows the crew reduced the target altitude from 28,000ft to 15,000ft.

Just after the aircraft’s autopilot had captured 15,000ft both bleed-air switches were turned on.

According to the Air Accidents Investigation Branch, the captain recalled that memory items for the ‘cabin altitude warning’ checklist – including the use of oxygen masks – should…