Synopsis
On 17 May 2020, at 15:10 UTC, a Jabiru SK ultralight aircraft, registration CS-UIN, departed from Alqueidão UL – Azambuja aerodrome for a recreational flight with one pilot and one passenger. The flight plan coordinated with air traffic control (CTA) included overflying the northern Alentejo coastline and returning to the departure aerodrome.
Factual Occurrence
About 10 minutes into the flight, after receiving CTA authorization, the pilot initiated a steady climb from 1,500 to 3,500 feet, adjusting engine power accordingly. While climbing through approximately 3,000 feet, about two miles west of Fajarda, the pilot felt an intense engine vibration with partial power loss, followed by a sudden propeller stop. The pilot declared a MAYDAY to CTA and began searching for an emergency landing site. Multiple attempts to restart the engine were unsuccessful. After three left turns, the aircraft was aligned with the wind and configured for landing on an agricultural field. The aircraft touched down and rolled for approximately 40 meters, during which the nose gear buried in the soft ground, causing the aircraft to nose over and come to rest inverted.
Injuries and Damage
Both pilot and passenger left the aircraft unharmed. The aircraft sustained substantial damage, including internal engine failure, damage to the nose gear, vertical stabilizer and rudder, left wing, and propeller. No other damage was reported.
Aircraft and Engine Details
The Jabiru SK is an Australian-manufactured high-wing two-seat ultralight with composite construction. It was equipped with a first-generation Jabiru 2200A four-cylinder, four-stroke horizontally opposed engine, normally aspirated and air-cooled, producing 85 hp at 3,300 rpm. The engine uses solid lifters requiring regular adjustments. The aircraft had cylinder head temperature (CHT) and exhaust gas temperature (EGT) probes connected to MGL digital gauges. The pilot reported no anomalies in the temperature indications. Post-accident examination revealed that the engine ran on three cylinders for a few seconds after a failure of cylinder #1.
The aircraft was registered in Portugal in July 1998 and held flight certificate No. 2033/6 issued in May 2019. Total flight time was just over 650 hours, with at least five owner changes.
Meteorological Conditions
At the time of the event, the reported weather included wind from 300° at 9 knots, variable between 270° and 340°, visibility 10 km or more, atmospheric pressure 1021 hPa, air temperature 25°C, and dew point 13°C.
Investigation
The GPIAAF (Portuguese Aviation Accident Investigation Authority) was notified at 15:28 and initiated a safety investigation. The investigation team concluded that the event had low complexity and limited safety learning, and the results were presented in a summary report.