What happened
On January 18, 2016, an A320-232, registration PR-MAA, operated by TAM Airlines, was performing a scheduled flight from Brasilia to Aracaju. During the initial climb, while passing Flight Level 100, the crew noticed oscillations in the airflow at the cabin nozzle exits.
As the aircraft continued its climb to Flight Level 275, the chief flight attendant notified the cockpit of a significant lack of oxygen in the cabin. Although flight data from the CVDR indicated that cabin altitude and pressure differential parameters remained within normal limits, the crew manually commanded the release of the oxygen masks. Some passengers and crew members utilized the masks. The commander subsequently interrupted the climb and requested an immediate return to Brasilia, where the aircraft landed safely without damage or injuries to the 179 passengers and 6 crewmembers.
The investigation
CENIPA's investigation focused on the discrepancy between the reported physiological symptoms and the aircraft's technical performance. Technical analysis of the Cabin Pressure Controllers (CPCs) in Germany showed no bench test failures, and ground pressurization tests were normal.
Investigators examined the crew's training and the physiological state of the cabin crew. It was noted that the flight attendants' training regarding hypoxia was primarily theoretical, focusing on aircraft warning lights and sounds rather than the identification of clinical symptoms. The investigation also looked into the potential impact of medication, noting that some crew members had recently used or were under treatment for medications such as antidepressants and analgesics, which might have influenced their sensitivity to physiological changes.
Findings
- The crew's focus during the ECAM verification was diverted toward less relevant stimuli, such as the outflow valve, rather than monitoring cabin altitude indications.
- Insufficient training regarding the physiological clinical manifestations of hypoxia prevented the crew from accurately identifying the situation.
- The sudden increase in airflow during the early climb phase created an atmosphere of uncertainty that may have contributed to the crew's perceived malaise.
- There was a lack of physiological training for crewmembers to recognize the physical symptoms of oxygen deprivation beyond automated aircraft alerts.