Grumman American AA-5B N321GD accident near Reserve, Louisiana

Probable cause

The partial loss of engine power due to carburetor icing and the flight instructor’s failure to use carburetor heat in weather conditions conducive to serious carburetor icing.

NTSB analysis

The pilot receiving instruction and his flight instructor were conducting an instructional flight in night instrument meteorological conditions when the airplane had a partial loss of engine power shortly after takeoff. The pilot-receiving-instruction reported that about 500 ft above the ground the engine began “coughing/sputtering” and there was a decrease in engine rpm. The flight instructor stated that the engine speed decreased to about 1,400 rpm, but when he leaned the fuel mixture the engine speed increased about 200 rpm. The flight instructor made a left 180° turn back toward the airport. The airplane’s left-wing tip impacted the ground, the nose gear collapsed, and the engine partially separated from the firewall when the airplane impacted the terrain during the forced landing.

The postaccident engine examination did not reveal any evidence of mechanical malfunction that would have precluded normal operation. Additionally, the airplane had ample fuel available that did not contain any water or debris.

The weather conditions at the time of the accident were conducive to a serious accumulation of carburetor icing with the engine operating at cruise power. According to a Federal Aviation Administration Special Airworthiness Information Bulletin, pilots should use carburetor heat while in weather conditions where carburetor icing is probable. The flight instructor stated that he did not use carburetor heat after the loss of engine power.

Based on the available information, the partial loss of engine power was likely due to carburetor ice accumulation. Additionally, the low altitude at which the loss of engine power occurred significantly reduced the amount of time available to the flight instructor to troubleshoot and restore engine power before the forced landing.

Text from the NTSB. Open the NTSB docket for CEN23LA068 for the full record.