Reserve, LA, USA
N321GD
Grumman American AA-5B
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.
On December 21, 2022, about 1954 central standard time, a Grumman American AA-5B airplane, N321GD, was substantially damaged when it was involved in an accident at the Port of South Louisiana Executive Regional Airport (APS), Reserve, Louisiana. The pilot and his flight instructor were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor reported that the purpose of the night flight was to fly multiple instrument approaches at several airports before returning to APS. He observed no issues with the airplane or its engine during his preflight inspection and engine runup. The airplane had about 50 gallons of fuel available before the flight. The flight instructor obtained an instrument clearance from New Orleans Approach Control before taxiing onto runway 35 for takeoff. He reported the engine rpm, fuel flow, and engine temperatures were normal during the takeoff and initial climb; however, shortly after the airplane climbed into instrument meteorological conditions there was a sudden loss of engine power. The flight instructor reported that he felt and heard the engine lose power at least twice, and he immediately entered a left 180° turn back to the airport. The airplane was about 380 ft above the ground when it descended below the overcast cloud ceiling on a south heading. The flight instructor reported that based on the airplane’s altitude, ground speed, and the canal off the end of runway 17, he believed the safest option was to land on the taxiway versus trying to land on the remaining runway. The airplane was about 2 ft above the ground when the left wingtip impacted the ground, and the nose gear subsequently collapsed when it impacted soft terrain. After the accident, the flight instructor repositioned the fuel valve to off, leaned the fuel mixture, and turned-off the magneto and electrical master switches. The pilot receiving instruction reported that before the flight he observed his flight instructor strain the fuel system and that there was no evidence of contamination. He reported that the before-takeoff engine runup, takeoff, and the initial climb were uneventful. However, about 500 ft above the ground, the engine began “coughing/sputtering” and there was a decrease in engine rpm. The flight instructor immediately took control of the airplane and entered a left turn back to the airport. The pilot receiving instruction stated that after the airplane descended below the clouds there was not enough runway remaining to safely land on runway 17, and that the flight instructor made a left turn toward the taxiway. He reported that the airplane entered an aerodynamic stall a couple of feet above the ground and the left wing struck the ground. When interviewed by a Federal Aviation Administration operations inspector, the flight instructor stated that the engine speed decreased to about 1,400 rpm when the loss of engine power occurred during the climb. The flight instructor stated that he leaned the fuel mixture after the loss of engine power, which resulted in a 200 rpm increase in engine speed. The electric fuel pump was already turned-on for the takeoff. The flight instructor stated that he did not use carburetor heat after the loss of engine power. A postaccident examination of the engine was conducted following the accident. The engine separated from the firewall during impact. The carburetor heat valve position at the time of the accident could not be conclusively determined due to impact damage. Internal engine and valve train continuity were confirmed as the engine crankshaft was rotated, and compression and suction were noted on all cylinders. The mechanical fuel pump and oil pump discharged fuel and oil, respectively, as the crankshaft was rotated. The left magneto, equipped with an impulse coupling, produced spark as the engine crankshaft was rotated. The right magneto was not equipped with an impulse coupling, but it produced spark when removed from the engine and rotated by hand. The spark plugs exhibited features consistent with normal engine operation. Movement of the throttle arm discharged fuel from the accelerator pump into the carburetor venturi. The carburetor bowl remained intact and contained uncontaminated fuel. There were no anomalies noted with the carburetor. The propeller remained attached to the engine crankshaft flange. Both propeller blades were relatively straight and partially covered in dried mud. Neither propeller blade exhibited any chordwise burnishing or leading-edge damage. The postaccident engine examination did not reveal any evidence of mechanical malfunction that would have precluded normal operation. According to a carburetor icing probability chart contained in Federal Aviation Administration Special Airworthiness Information Bulletin CE-09-35, Carburetor Icing Prevention, the recorded temperature and dew point at the time of the accident were in the range of susceptibility for the formation of serious carburetor icing at cruise engine power. According to the bulletin, a pilot should use carburetor heat when operating the engine at low power settings or while in weather conditions in which carburetor icing is probable.
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.
Source: NTSB Aviation Accident Database
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