Incident Summary
On 5 April 2019, a Boeing B-737-524 aircraft, registration LY-KLJ, operated by UAB KLASEJET, took off from Adolfo Suárez Madrid-Barajas Airport (LEMD) en route to Kaunas Airport (EYKA) in Lithuania. The flight was conducted under instrument flight rules as a commercial air transport landing.
Sequence of Events
During the pre-flight inspection, a fault was identified in the captain’s automatic flight system. Both pilots, with assistance from a company engineer, reviewed the Minimum Equipment List (MEL), which allowed dispatching the aircraft with this equipment inoperative. The crew decided to proceed. The aircraft took off from runway 14L at 14:15:26 h local time.
During the climb, several faults occurred with the first officer’s automatic flight system, which became fully inoperative at 14:17:32 h. The crew decided to return to the departure airport, flying without automatic flight systems. Shortly after takeoff, the crew declared an emergency but did not specify the exact nature of the problem. At 14:20 h, the operations supervisor informed the approach controller that an aircraft that had just taken off from Madrid-Barajas was declaring an emergency and wanted to return. The controller cleared the runway 18R localizer by diverting two other aircraft on approach.
The crew performed two go-arounds on runway 18L in adverse weather conditions. After declaring an emergency, air traffic control diverted the aircraft to Getafe Air Base (LEGT) in Madrid, where it landed on runway 23. There were no injuries and the aircraft was not damaged.
Investigation
The Civil Aviation Accident and Incident Investigation Commission (CIAIAC) opened an investigation. The flight recorders were retrieved, but the cockpit voice recorder recordings were unavailable because the operator had sequestered them on the day of the incident but did not protect the information they contained. The investigation focused on the loss of both automatic flight control systems and the crew's handling of the situation in instrument meteorological conditions.
Probable Cause
The investigation determined that the incident was caused by the problems the crew had operating the aircraft in instrument conditions following the loss of the aircraft’s two automatic flight control systems.