Cessna 152 — Fort Rice, ND

What happened

The pilot was conducting his second low-level aerial photography flight that day; the pilot would take the photographs through the left window of the airplane. A review of surveillance data showed the airplane depart from the airport and fly to the target areas for aerial photographs. After the pilot completed the photography work over the target areas, the airplane traveled over a river. The airplane then made several low-level turns over the river, most of which were to the left. The last recorded data point showed that the airplane at 1,700 ft. msl and a groundspeed of 49 knots. The airplane wreckage was found partially submerged in the river. The photographs from the pilot's camera were extracted, and the last several images showed a fish in the river. It was undetermined why the pilot was taking photos of the fish.

Postaccident examination of the airplane and engine revealed no anomalies that would have precluded normal operation of the airplane.

Given the temperature and dew point at the time of the accident, the airplane was susceptible to serious carburetor icing at glide power settings. The airplane was equipped with a carburetor temperature system that was installed on the right side of the cockpit. The system had an "ice zone" warning light that illuminated before carburetor ice could form. It is likely that, during the low-level turns to the left over the river, the pilot was focusing on taking photographs through the airplane's left window and did not see that the ice zone light had illuminated. After illumination of this light, a pilot was expected to apply carburetor heat. However, the airplane's carburetor heat was found in the off position. Thus, given the ambient conditions at the time of the accident, it is likely that carburetor ice formed and resulted in a loss of engine power. Because the pilot's attention was diverted while taking photos of a fish in the river, he likely did not notice the loss of airspeed, which resulted in the airplane exceeding its critical angle of attack, and a subsequent low-level aerodynamic stall.

Before the accident flight, a mechanic who assisted the pilot with refueling the airplane observed that the pilot kept rubbing his eyes. The mechanic surmised the pilot was fatigued. The mechanic suggested that the pilot that take a nap before continuing flight operations and the pilot replied that he can't make any money if he isn't flying, and subsequently departed for the accident flight. Evidence does not suggest that the pilot had a reduced sleep opportunity or circadian disruption during the days preceding the accident. However, at the time of the accident the pilot had completed one photo flight in the morning and was about 57 minutes into a second photo flight when the accident occurred. Although the pilot's total flight time that day was not extreme, the single-pilot aerial photography flight required low level maneuvering and divided attention which could have been fatigue inducing from a workload and time-on-task perspective. However, there was insufficient information from which to determine whether fatigue played a role in the sequence of events.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.