Investigation Reveals Cause of Oxygen Drop on Flight: Maintenance Oversight

Investigation Reveals Cause of Oxygen Level Drop on Flight

An investigation has identified the cause of a recent flight incident involving a drop in cabin oxygen levels. Technicians forgot to turn on the switch that controls cabin pressure. The aircraft returned safely to Manchester, and there were no injuries reported. However, the Air Accidents Investigation Branch (AAIB) noted that passengers may have faced a risk of low oxygen levels during the flight.

The investigation indicated that the “bleed air” switch, crucial for maintaining cabin pressure, was turned off during maintenance checks on the air conditioning system before takeoff. This oversight went unnoticed by the crew during pre-flight safety checks.

One technician believed that the switches were returned to their correct positions after inspection. Another technician did not realize that the switches remained off. This mistake was not detected by the pilots before takeoff or during post-takeoff checks.

Upon discovering the issue, the pilots turned the switches back on. However, the crew did not follow other emergency procedures described in the Quick Reference Handbook (QRH), such as using oxygen masks.

The report emphasized that donning oxygen masks could have provided immediate protection against hypoxia and allowed the pilots to clarify the situation with reduced risk.

After the switches were activated, the plane continued to ascend. The warning light remained on for 43 minutes. Eventually, the pilots consulted Tui maintenance teams at Manchester Airport and decided to return to Manchester.

For travelers, cerebral hypoxia can happen if the aircraft reaches a high altitude or experiences cabin pressure loss. It can also result from carbon monoxide poisoning or inhaling smoke from a fire.