The pilot of the float-equipped Rans S-7 Courier reported that, following takeoff from a lake in Cordova, Alaska, he turned to left downwind about 750′ above the water.
He added that, once the turn was completed, the plane encountered a strong downdraft that “pushed the tail of the airplane down and away to the left,” and the airplane began to descend.
He corrected with left rudder and was able to “straighten the airplane just prior to the right float tip contacting water.”
The airplane hit the water, nosed over, and sank, sustaining substantial damage to both wings.
The pilot reported there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.
He reported on NTSB Form 6120.1 that the wind was from the east/southeast at 15 to 20 knots, gusting to 25 knots. The pilot reported a takeoff to the east.
A review of recorded data from an automated weather observation station about seven nautical miles east of the accident, about the time of the accident, revealed winds calm, 10 statues miles visibility, few clouds at 600′, scattered clouds at 1,200′, an overcast ceiling at 3,200′, temperature 54°F, dew point 54°F, and an altimeter setting at 30.19 inches of mercury.
The computed density altitude at 750′ was 322′.
The FAA’s Airport Facility Directory for an airport two nautical miles west of the accident site stated, in part: “strong East winds, runway subject to strong downdrafts.”
Probable cause: The pilot’s improper decision to take off from a lake in gusting wind conditions, which resulted in a loss of airplane control.
NTSB Identification: GAA17CA440
This July 2017 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.