BEECH A36

Full Narrative

On November 18, 2024, at about 1223 eastern standard time, a Beechcraft A36, N8152R, was substantially damaged when it was involved in an accident near Doylestown, Pennsylvania. The pilot received minor injuries, the pilot-rated passenger and the back seat passenger were seriously injured. The airplane was operated as a Title 14 Code of Federal Regulation Part 91 personal flight.
According to the pilot rated passenger, he was interested in purchasing a share of the airplane and the purpose of the flight was to demonstrate the airplane’s characteristics. During the preflight inspection, takeoff, and flight, the airplane performed normally with no anomalies noted by the pilot or the pilot-rated passenger. After performing some maneuvers in the local area, the they elected to return to the Doylestown Airport (DYL), Doylestown, Pennsylvania.
The pilot reported that they entered the traffic pattern at 1,400 ft mean sea level (msl), before the pilot then put the landing gear down and extended one “notch” of flaps. After turning from the base leg of the traffic pattern to final approach, the pilot ensured that the landing gear was down, he set the flaps to fully extended, and ensured that the mixture and propeller controls were full forward. During the landing flare, about 3 ft above the runway, the pilot reported the airplane ballooned to about 20 ft in the air. The pilot decided to perform a go-around and he pushed in for full throttle and began to retract the flaps and the landing gear. Shortly after beginning the go-around, the pilot felt the airplane “drop out from under me.” The airplane descended and impacted the ground to the left of the runway and continued to slide onto the ramp where an unoccupied airplane was parked. The accident airplane impacted the parked airplane’s right wing and the right side of the fuselage. The accident resulted in substantial damage to the fuselage and left wing of the accident airplane.
An airport surveillance video showed the accident sequence. As the airplane came into view, it was in a shallow climb and the landing gear was retracting. The airplane started to descend, and the wings rocked back and forth while the airplane started to deviate to the left of the runway. As the airplane neared the ground, the airplane’s nose pitched up and then the airplane impacted the median between the runway and the taxiway.
The airplane was equipped with an engine data monitor capable of storing the flight data. The engine monitor was set to record at a very low rate, and only captured a snapshot of engine data once every 5 seconds. When compared with the surveillance video of the accident, the data also did not record the last 8 seconds of the flight prior to the airplane impacting the ground. The data revealed that between 25 to 30 seconds prior to the accident, the engine rpm, fuel flow, manifold pressure (MAP), and the exhaust gas temperatures (EGT) were all decreased to a level consistent with the engine being at idle. About 20 seconds before the accident, the rpm, fuel flow, MAP, and EGTs all started to increase. The last data datapoint (about 8 seconds prior to impact) indicated the engine was at 2,606 rpm, the MAP was 22.9 inches of mercury, and the fuel flow was reading 20.3 gallons per hour. The engine data also recorded the fuel levels of both main fuel tanks. According to the last datapoint, the left fuel tank still contained 27.1 gallons, and the right fuel tank contained 34.2 gallons.
A postaccident examination of the airplane established flight control continuity for all primary and secondary flight controls from their flight control surfaces to their respective cockpit controls through disconnects from recovery. The flap position was determined to be set to 15°, and the landing gear motor was in the retracted position. All of the fuel caps remained secure, intact, and had pliable seals. The fuel tank outlet screens were examined and were clear of any contamination or blockages. Continuity of the fuel lines was verified by blowing low pressure air through the fuel lines to the firewall outlet fitting; there were no obstructions in any of the fuel lines. Both wing fuel tank vents were inspected and were found to be clear of obstructions. The fuel selector was found in the “OFF” position at the time of the examination., Photographs taken of the airplane immediately after the accident by FAA inspectors showed that the “LEFT” fuel tank was selected. The fuel selector was moved to each position and had noticeable detents for each selected position and the fuel selector operated normally in each position. The fuel strainer contained a small amount of residual fuel that had the color and odor consistent with 100LL Avgas. There were no contaminants or signs of water within the fuel sample. The fuel strainer screen was removed and was clear of any contaminants. Control continuity for the engine controls was verified by moving the cockpit control and observing its respective control on the engine. The throttle, propeller, and mixture controls worked from stop to stop with no anomalies.
The propeller remained attached to the engine and displayed impact damage. One blade displayed aft bending and twisting deformation, polishing of the cambered end, and the face side. Another blade displayed aft bending and twisting deformation, polishing of the cambered end, and the face side. A portion of the blade’s tip was missing. The remaining propeller blade displayed aft bending with tip curling.
The engine’s top spark plugs were removed. The electrodes displayed normal operating and wear signatures. The cylinders were inspected using a lighted borescope; the cylinder walls, piston faces, and valve heads displayed normal operating and combustion signatures. Continuity was established between the crankshaft, camshaft, connecting rods, and associated components by rotating the crankshaft 720°. All six cylinders displayed thumb pressure and suction during crankshaft rotation. The engine throttle and fuel metering inlet screen contained light debris; however, it was not obstructed. There were no signs of leaks in the fuel system between the firewall and the engine injector nozzles.
Due to impact damage, the engine was sent to the manufacture for a test run. Prior to the engine run, the impact damaged components were repaired or replaced. The magneto to engine timing was checked, and the left magneto was found to be 25° before top dead center (BTDC), and the right magneto was found to be 26° BTDC. The magneto timing specifications for the engine was 22° BTDC.
The engine was placed on a test stand, and a test club propeller was installed on the crankshaft. The engine started on its first attempt without any stumbling or hesitation. The engine rpm was advanced in steps for warm-up and preparation for full power operation. While at 2,100 rpm, a magneto check was performed, when running on the left magneto, the rpm drop was 50 rpm. When the magneto was switched to the right magneto, the rpm dropped by 220 rpm, and the No. 5 cylinder EGT level dropped to levels consistent with combustion no longer occurring in the cylinder. The magneto switch was put back into the both position and the No. 5 cylinder EGT levels indicated normal combustion within the cylinder. The engine run continued, the throttle was then advanced to full throttle, and the engine rpm increased to approximately 2,620 rpm, and the engine continued to run smoothly without any stumbling or hesitation.
After the engine was shut down, the engine was troubleshot to determine the cause of the high rpm drop during the right magneto check. The No. 5 top spark plug was found to have the outer and center electrodes contacting each other, resulting in a short that would have prevented a spark from forming between the gap. The spark plug electrode gap was compared with the photographs taken of the spark plug prior to the engine run. The photographs showed a clear gap between the electrodes during the examination. This is consistent with the spark plug being damaged during engine preparation for the engine run. A new spark plug was installed into the No. 5 cylinder top position, and another engine run was performed. At 2,100 rpm, another magneto check was performed; the engine rpm only dropped approximately 50 rpm, and the No. 5 cylinder EGTs were normal. Another full power check was performed, and the engine rpm increased to 2,700 rpm without any stumbling or hesitation. While at full power, it was observed that the unmetered fuel pressure was higher than specifications; however, it did not prevent the engine from operating normally at full throttle. The engine was then brought back to idle rpm, and multiple throttle bursts from idle to full power were performed. The engine accelerated normally during each throttle burst and would reach 2,700 rpm during each throttle burst.