Cessna 172 N724BC accident near Dunnellon, Florida

Probable cause

A total loss of engine power due to fuel exhaustion. Contributing was the pilot’s exceedance of the airplane's critical angle of attack, which resulted in an aerodynamic stall/spin and loss of control.

NTSB analysis

Radar data revealed that, about 20 minutes after departure, the airplane’s groundspeed decreased from 94 knots to 47 knots, and the airplane entered a descending left turn. Data from the airplane’s onboard engine analyzer revealed that this deceleration was preceded by a sudden and simultaneous drop in the airplane’s fuel flow rate and exhaust gas temperature (EGT) values, consistent with a loss of engine power.

Following the accident, less than 1 gallon of fuel was recovered from the intact right wing fuel tank, and about 1 cup was recovered from the left wing (which was breached from impact). About 1 teaspoon of cloudy water was found in the airframe fuel filter bowl and the screen was partially blocked with debris. A review of the airplane’s fueling and flight records, including data from the onboard engine analyzer, revealed there would have been about 1 gallon of usable fuel onboard about the time of the loss of engine power. Examination of the engine revealed no other mechanical deficiencies that would have precluded normal operation at the time of the accident, and the total loss of engine power was likely the result of fuel exhaustion. Following the loss of engine power it is likely that the pilot exceeded the airplane’s critical angle of attack (as evidenced by the low recorded ground speed during the final moments of the flight), which resulted in an aerodynamic stall/spin and loss of control.

Though Diazapam (Valium) and its metabolites were detected in the pilot’s system in post-accident toxicology testing, it could not be determined if the pilot’s use of diazepam contributed to the accident.

Text from the NTSB. Open the NTSB docket for ERA21FA029 for the full record.