Incident
A FAR 135 flight was diverted to a remote airstrip to pick up additional passengers. The dispatcher was not aware that the runway was covered by 4 ft of snow until the aircraft was beyond radio range. The pilot assumed that the runway had been plowed, as it had been in previous winters. The box canyon configuration of the surrounding terrain prevented the pilot from overflying the runway to check its condition. On approach, the runway appeared to be a normal snow-packed surface. The pilot landed the amphibious float aircraft with the landing gear down, and the airplane nosed over during the landing.
Background
The flight was operating under FAR 135 regulations. The remote strip was not routinely serviced for snow removal in the same manner as other airports. The dispatcher had no means to verify runway conditions once the aircraft lost radio contact.
Sequence of Events
The aircraft diverted to the remote strip without prior knowledge of the runway's condition. The pilot relied on past experience, expecting the runway to be cleared. The inability to visually inspect the runway from above due to terrain limits left the pilot with no alternative assessment. Upon touchdown, the deep snow caused the aircraft to nose over.