Incident Overview
On 31 December 2004, at approximately 11:30 UTC, a Zenair CH 701 STOL amphibious ultralight aircraft, bearing French registration 55-LX, departed from Azambuja Aerodrome with two occupants aboard. The intended destination was Montargil Dam, where the pilot planned to perform a water landing. The flight was conducted under Visual Flight Rules (VFR) at an average altitude between 900 and 1000 feet and lasted about 30 minutes.
Sequence of Events
After overflying the dam wall, the pilot turned right over the river arm serving the village of Foros do Mocho and performed the standard pre-water landing checks for an amphibious aircraft, including a visual confirmation of the nose gear retracted using a mirror. With the aircraft aligned with the axis of the dam arm, the pilot reduced power slightly and initiated a long final approach, as recommended for this aircraft type.
As the pilot prepared to flare, the aircraft contacted the water surface at a speed of 130 km/h—approximately 40 km/h above the reference speed of 90 km/h. The impact damaged the right float, causing the aircraft to bounce and become airborne again. Upon returning to the water, the aircraft yawed uncontrollably due to the lack of effective support on the right side, struck the propeller against the water, and came to rest semi-submerged, nose-down.
Occupant and Aircraft Status
Both occupants, who were wearing life vests, exited the aircraft unaided and swam to shore. They sustained no injuries. The aircraft initially remained afloat long enough for the occupants to evacuate before sinking. The right float was destroyed, and all three propeller blades were fractured during the hard landing. The left float was damaged during recovery when the aircraft was dragged along the riverbed.
Meteorological Conditions
The pilot reported clear skies, good visibility, and no wind (CAVOK conditions). The water surface was described as smooth and glassy, reflecting sunlight.
Pilot Information
The male pilot, aged 67, held a valid ultralight license (ULM) and a private pilot license (PPA). His total flight experience was 616 hours, of which 415 hours were on ultralight aircraft, and 11 hours were on the accident aircraft.
Aircraft Information
The aircraft's documents were lost in the water. At the time of the incident, the hour meter on the instrument panel recorded 11.0 hours of engine operation.
Investigation and Cause
The investigation by the Portuguese Aircraft Accident Prevention and Investigation Bureau (GPIAA) determined that the incident resulted from the pilot's deficient planning, including an incorrect assessment of the aircraft's height above the water, leading to premature contact, and excessive speed during the water landing.