What happened
On October 17, 2014, a Boeing 737-800 was operating a flight from GMAD to EPWA at flight level FL380. After establishing radio contact with the "JR" sector of air traffic services, the flight crew was informed of the expected LOGDA 4U standard terminal arrival route (STAR) for their destination, Warsaw (EPWA).
Shortly after this communication, the air traffic controller observed on radar that the aircraft had deviated from its assigned altitude. When questioned by the controller regarding their intentions, the crew stated they had assumed that the assignment of the arrival procedure implicitly included authorization to descend.
The investigation
The PKBWL investigation focused on the discrepancy between the assigned flight level and the actual altitude maintained by the aircraft. The investigation established that the crew's actions resulted in a deviation from the instructions provided by the air traffic controller.
Findings
- The primary cause of the incident was the crew's failure to adhere to air traffic regulations regarding altitude maintenance.
- The crew operated under the incorrect assumption that receiving a STAR clearance automatically authorized a descent to a lower altitude without explicit vertical clearance.