What happened
On February 28, 2018, an Airbus A320-214, registration ES-SAN, was conducting training flights at Tallinn Lennart Meri Airport, Estonia. The flight crew, consisting of a captain, a safety pilot, four students, and an inspector, was performing a series of touch-and-go training cycles. During one of the maneuvers, the aircraft failed to respond as expected to sidestick inputs upon reaching rotation speed. After a brief period of lift-off, the aircraft lost altitude and struck the ground near the end of the runway, causing damage to the engines and landing gear doors.
Following the initial impact, the aircraft briefly climbed to 1,590 feet before pitching down again. Although the crew managed to stabilize the flight path using manual pitch trim and engine thrust to perform a U-turn, the aircraft suffered a loss of power in both engines during the emergency approach. The aircraft landed approximately 150 meters before the runway threshold, where the tires burst, causing the aircraft to veer off the runway. The accident resulted in minor injuries to the safety pilot and one student, but the aircraft sustained severe damage to the fuselage, engines, and landing gear, leading to a total hull loss.
The investigation
The Estonian Safety Investigation Bureau (ESIB) examined the flight data, cockpit voice recordings, and maintenance history. The investigation focused on the flight control systems, specifically the interaction between the Elevator Aileron Computers (ELAC) and the Spoiler Elevator Computers (SEC), as well as the maintenance practices regarding the Trimmable Horizontal Stabilizer Actuator (THSA) override mechanism.
Findings
- The primary cause was a malfunction in the THSA override mechanism, which allowed for a loss of pitch control by both ELACs. This was triggered by the use of inappropriate lubricating oil in the mechanism.
- A design flaw in the SEC allowed a temporary decompression in the left landing gear to cause a simultaneous loss of pitch control by both SECs.
- The instructor's decision to continue the flight despite receiving repetitive ELAC pitch fault messages contributed to the sequence of events.
- Maintenance documentation lacked specific requirements to test the override mechanism, allowing the incorrect oil to remain undetected.