What happened
On December 31, 2004, an amphibious ZENAIR CH 701 STOL, registration 55-LX, departed from Aeródromo da Azambuja for a recreational flight to the Montargil Dam. The flight was conducted under Visual Flight Rules (VFR) at altitudes between 900 and 1000 feet.
As the pilot approached the water for landing, they aligned the aircraft with the river arm near the village of Foros do Mocho. The pilot performed standard amphibious procedures, including a visual check to confirm the nose gear was retracted. While preparing to flare, the aircraft struck the water surface at 130 km/h, which was 40 km/h above the recommended reference speed of 90 km/h.
The impact caused the aircraft to bounce and then strike the water again in a nose-low attitude. The force of the initial impact destroyed the right float, causing the aircraft to spin uncontrollably. During this rotation, the propeller struck the water, and the aircraft eventually came to rest semi-submerged. Both occupants, wearing life jackets, were able to exit the aircraft and swim to the shore without injury.
The investigation
The GPIAAF investigation established that the meteorological conditions were excellent, with CAVOK conditions and no wind. The investigation focused on the pilot's approach and the physical state of the water surface. The investigation found that the water was smooth and reflective due to the lack of wind, which likely created an optical illusion regarding the aircraft's height above the surface.
Technical examination of the aircraft revealed that the impact caused significant damage, including the destruction of the right float and the fracturing of all three propeller blades. The aircraft subsequently sank after the incident.
Findings
- The landing was performed at a speed 40 km/h above the recommended reference speed.
- The smooth, mirror-like surface of the water likely caused the pilot to misjudge the aircraft's altitude during the approach.
- The pilot's planning was deficient due to the incorrect assessment of the aircraft's height above the water.