What happened
On June 12, 2020, an EXTRA EA 400, registration OK-EKO, was performing a flight from Příbram (LKPM) to Moravská Třebová (LKMK). Approximately ten minutes after takeoff, the pilot noticed a loss of engine performance, characterized by a heavier engine feel and a reduced rate of climb. Shortly thereafter, a noticeable popping sound occurred, followed by a rapid increase in cylinder head temperatures.
As the engine malfunctioned, a coolant leak developed, allowing fluid to spray from the engine compartment into the cockpit. The coolant covered the left windshield, severely obstructing the pilot's forward visibility. While the pilot initially intended to divert to Benešov (LKBE), the loss of visibility made a controlled diversion impossible. The pilot was forced to perform an emergency landing in a field of tall crops north of Vrchotovy Janovice. During the landing, the extended landing gear struck a row of alders, and the aircraft subsequently struck the terrain, causing the nose gear to break, the main gear to collapse, and the wings to separate. The aircraft then overturned onto its back. The pilot sustained a fractured thoracic vertebra but was able to self-extricate from the wreckage.
The investigation
The ÚZPLN investigation focused on the engine's mechanical state and the pilot's ability to monitor the failure. Investigators examined the engine, the EDM 800 engine data recorder, and the aircraft's maintenance history. The engine had recently undergone a major overhaul and had only flown 5 hours and 51 minutes since its release to service. Analysis of the engine data recorder revealed that the temperature at cylinder head number 5 had reached 662°F (350°C), with a simultaneous rise in temperature at cylinder head number 3. The investigation also noted that the EDM 800 data recorder was positioned far to the right on the instrument panel, placing it outside the pilot's primary field of view.
Findings
- The primary cause of the accident was a coolant leak from cylinder number 5, which obscured the pilot's vision.
- The engine failure was caused by the displacement of the cylinder head from its threaded assembly, which is a non-separable component.
- The pilot was unable to detect the rising cylinder temperatures in a timely manner because the engine data recorder was placed outside the pilot's line of sight.
- The aircraft sustained extensive damage, including broken landing gear, wing separation, and propeller destruction.