N9360SBeech C23

On August 20, 2023, about 1200 eastern daylight time, a Beech C23 airplane, N9360S, was substantially damaged when it was involved in an accident near Greer, South Carolina. The private pilot and the mechanic-certificated passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 postmaintenance test flight after an annual inspection.

A witness who lived at the fly-in community where the airplane was maintained reported that the airplane took off from runway 3 at Chandelle Airport (SC72), Greer, South Carolina. As the airplane passed his house, he heard a slight reduction in engine speed followed by a slight increase. The engine did not sputter or backfire. The airplane then turned toward the northwest and reached an altitude of about 500 ft above the ground. The witness observed that the left wing dipped twice then leveled off, and the airplane descended as it turned to a westerly heading. The airplane descended from his view behind a tree line, then he heard it impact the ground.

The witness’s account of the accident flight was generally consistent with a video of the accident sequence captured by a camera from an unnamed source. The video, which was broadcast by a local news station, showed the airplane on departure. The left wing dipped slightly twice, then the right wing dipped. The airplane then developed a sink rate with the nose slightly up. Shortly before ground impact, the airplane’s nose dropped, and the left wing dipped again. The airplane collided with the ground in a slight left-wing-low attitude.

Two security cameras in the backyard of a residence at SC72 captured video of the airplane during initial climb after takeoff. The video from one camera showed the airplane in a climb over the runway before it exited the camera’s field of view. The video from the other camera captured the airplane in the distance descending to the northwest, trailing faintly visible, light-colored mist, smoke, or vapor before it became obscured from view behind some trees.

The pilot’s flight times were derived from his pilot logbook, in which the most recent entry was July 27, 2023.

The temperature and dew point near the accident site were about 82.4° and 64.4° F, respectively; the calculated relative humidity for these conditions was about 55%. According to carburetor icing charts in FAA Special Airworthiness Information Bulletin (SAIB) CE-09-35, “Carburetor Icing Prevention,” these conditions were “conducive to serious icing at glide [idle] power.”

The wreckage was found upright in an open field about 1 mile north of SC72. The fuselage was buckled in several areas, the forward windscreen was broken, all three landing gear were separated, and there was no evidence of fire. The wreckage was recovered to a salvage facility for a more detailed examination.

Examination revealed the left wing was partially separated from the airframe outboard of the fuel tank and remained attached by control cables. Flight control continuity was established for all primary and secondary flight controls from their surfaces to their respective cockpit controls through separations that were consistent with cuts made during wreckage recovery operations. The stabilator trim actuator measured 1.125 inches, which corresponded to a stabilator trim position of about 2° tab up. The flap actuator jack screw displayed 23 exposed threads, which corresponded to a position of about 10° flaps extended.

The left wing fuel tank was impact-damaged, breached in multiple locations, and devoid of fuel. The left fuel inlet screen was removed and noted to be clear of any debris. Low-pressure air testing of the left fuel tank vent line found it to be unobstructed. The left fuel quantity transducer was removed and the float was observed to stick about mid-travel but would move down with light vibration of the assembly. The left fuel tank line entering the fuselage was deteriorated, but no fuel leaks were observed when air or fuel was pushed into the line.

The right fuel tank was undamaged and contained about 7 gallons of fuel that had color and odor consistent with 100 low lead (100LL) aviation gasoline. The fuel inlet screen was removed and observed to be clear of any debris. Low-pressure air testing of the right fuel tank vent system found it to be unobstructed. The right fuel gauge was removed, and the float was capable of normal movement.

The fuel selector was found in the LEFT tank position. Low-pressure air blown into the engine-driven fuel pump inlet line at the firewall could be felt coming out of the fuel line for the left fuel tank. The fuel selector was moved to the RIGHT tank position, and low pressure air blown into the engine-driven fuel pump inlet line at the firewall could be felt coming out of the fuel line for the right fuel tank. Removal of the fuel selector revealed no visual signs of fuel leaks around valve. The fuel selector valve operated normally when fuel was poured into it in all fuel selector positions.

The fuel strainer remained attached to its installation point and displayed impact damage. The fuel strainer bowl and screen were removed and visually examined. The fuel strainer bowl was devoid of fuel, and the screen contained a small amount of unidentified material but was not obstructed.

The engine remained partially attached to the fuselage through the tubular mount and was canted nose down about 45°. The upper engine cowl was not present, and the lower cowl was impact-damaged. The propeller spinner was crushed and twisted opposite the direction of crankshaft rotation. The induction air filter remained attached to the lower cowl. Dirt was observed on the filter, but it was otherwise unobstructed.

The engine was removed from the airframe, suspended from a lift, and partially disassembled for examination. The exhaust tubing and exhaust tailpipe were partially crushed. The tailpipe was cut to facilitate a lighted borescope examination of the muffler interior, which was found to be unobstructed. The propeller was removed, and the engine crankshaft was rotated using a tool inserted in the vacuum pump drive pad. Continuity of the crankshaft from the crankshaft flange to the accessory drive gears and to the valvetrain was observed. Compression and suction were observed from all four cylinders.

The carburetor remained attached to the engine. The throttle control cable remained attached to the carburetor throttle control arm, which was in a mid-range position. The cockpit throttle control knob was also in a mid-range position. The mixture control cable remained attached to the carburetor mixture control arm, and the cable support structure was impact-damaged. The cockpit mixture control knob was in a forward position. The carburetor heat cable remained attached to the carburetor heat control arm and the induction air box and carburetor heat valve were crushed.

The carburetor was partially disassembled and no damage to the carburetor internal components was observed. The fuel inlet screen was unobstructed. About a teaspoon of liquid resembling 100LL aviation gasoline was observed in the carburetor float bowl.

The engine-driven fuel pump remained attached to the engine. Fuel drained from the pump when it was tilted. The pump produced air at the outlet port when actuated by hand. Partial disassembly revealed no damage on the rubber diaphragms or internal check valves.

Both magnetos remained securely attached to the engine. Both were removed and produced spark from all ignition towers when rotated by hand. The spark plug electrodes exhibited gray coloration and normal condition when compared to a Champion Check-a-Plug chart. No damage on the ignition harness was noted. The bottom Nos. 1 and 2 spark plugs were oil-soaked, consistent with postaccident accumulation.

Oil was observed inside the engine case. No debris was observed on the oil suction screen or the oil filter media.

The two-bladed, fixed-pitch propeller remained attached to the engine crankshaft flange and displayed impact damage. The propeller spinner was crushed and exhibited twisting opposite the direction of crankshaft rotation.

One propeller blade was bent aft about 30° approximately 8 inches outboard of the hub, was twisted toward the blade face, and exhibited leading edge paint abrasion over the length of the blade. The other blade was bent aft about 10° near the tip and exhibited leading edge paint abrasion over the bent section.

FAA Advisory Circular 20-113, “Pilot Precautions and Procedures to be Taken in Preventing Aircraft Reciprocating Engine Induction System and Fuel System Icing Problems," stated that, “to prevent accident due to induction system icing, the pilot should regularly use [carburetor] heat under conditions known to be conducive to atmospheric icing and be alert at all times for indications of icing in the fuel system." The advisory circular recommended that, when operating in conditions where the relative humidity is greater than 50%, "…apply carburetor heat briefly immediately before takeoff, particularly with float type carburetors, to remove any ice which may have been accumulated during taxi and runup." It also stated, "Remain alert for indications of induction system icing during takeoff and climbout, especially when the relative humidity is above 50%, or when visible moisture is present in the atmosphere.".

According to the FAA SAIB CE-09-35, “carburetor ice can be detected by a drop in [engine speed] in fixed-pitch propeller airplanes… [and] usually there will be a roughness in engine operation.”

The Spartanburg County, South Carolina, Coroner’s Office performed the pilot’s autopsy. According to the pilot’s autopsy report, his cause of death the day after the accident was blunt trauma of the head and torso and his manner of death was accident.

Postmortem toxicological testing of the pilot by the FAA Forensic Sciences laboratory identified several substances that can be impairing. These were oxycodone, hydromorphone, oxymorphone, gabapentin, lorazepam, methocarbamol, fentanyl, norfentanyl, etomidate, and levetiracetam. Review of hospital records indicated that these substances were attributable to medications administered to the pilot during his medical care after the accident. FAA toxicology testing did not identify any other substances that are generally considered impairing.