What happened
The pilot was operating an airplane with the intention of landing on a frozen lake. The specific objective of this maneuver was to exchange the main landing gear wheels for ski equipment, a common procedure for winter operations in remote areas. The pilot's original destination was a designated seaplane base; however, that facility had been closed due to hazardous conditions characterized by slush and soft ice.
Prior to the flight, a Notice to Airmen (NOTAM) had been issued regarding these conditions. The pilot received advice concerning this NOTAM before attempting the landing on the frozen lake. During the landing roll on the ice surface, the airplane encountered areas of soft ice mixed with snow. This loss of traction and stability caused the aircraft to nose over.
The investigation
The investigation focused on the physical condition of the landing site and the mechanical state of the aircraft following the incident. Investigators examined the frozen lake surface where the landing occurred, confirming the presence of soft ice and snow that contributed to the loss of control during the rollout. The mechanical inspection determined that the nose gear sustained damage as a result of the nose-over event.
Findings
Several factors contributed to this accident. The primary cause was the pilot's decision to land on a surface with inadequate structural integrity for the aircraft's weight. Although the pilot was aware of the NOTAM warning about the closed seaplane base, the frozen lake presented similar or worse conditions. The encounter with soft ice and snow during the landing roll prevented the pilot from maintaining directional control and stopping safely.
Safety message
Pilots must carefully evaluate alternative landing sites when primary airports are closed. A NOTAM provides critical information about surface conditions; ignoring or underestimating these warnings can lead to accidents even on seemingly suitable surfaces like frozen lakes, which may have hidden layers of soft ice or snow.