What happened
On 5 April 2019, a BOEING B-737-524, registration LY-KLJ, departed from Adolfo Suárez Madrid-Barajas Airport (LEMD) bound for Kaunas, Lithuania. During the pre-flight phase, the crew identified a fault in the captain's automatic flight system. After consulting the Minimum Equipment List (MEL) with a company engineer, they determined the aircraft was legal for dispatch and proceeded with the flight.
Shortly after takeoff from runway 14L, the aircraft entered its climb phase. While the captain's autopilot was already inoperative, a subsequent failure occurred in the first officer's automatic flight system. With both automatic flight control systems now inoperative, the crew decided to return to the departure airport.
During the return to Madrid-Barajas, the crew attempted to land on runway 18L under instrument flight rules (IFR). The approach was complicated by adverse weather and high traffic density. The crew performed two go-arounds on runway 18L after failing to maintain required altitudes and separation from other arriving aircraft. Due to the continued difficulty operating the aircraft without automated assistance, air traffic control diverted the flight to Getafe Air Base (LEGT), where the aircraft landed safely on runway 23. There were no injuries and no damage to the aircraft.
The investigation
The CIAIAC investigation focused on the sequence of failures within the automatic flight control systems and the crew's ability to manage the aircraft during the emergency. The investigation examined the aircraft's flight recorders, the technical logs, and the maintenance history. Investigators also reviewed the air traffic control communications and the operational challenges faced by the crew while flying manually in instrument conditions.