Wellington, FL, USA
N732SX
WILLIAMS CHRISTOPHER T SONEX
The airplane had just departed the airport; one witness reported that during the initial climb the engine "sputtered," and another reported that it "backfired." The pilot then made a steep turn back toward the airport, but the airplane stalled and spiraled to the ground. The airplane was equipped with an electronic flight instrument system that recorded numerous engine and flight parameters. Review of the downloaded data revealed that, initially, the engine was operating normally and within design parameters. However, toward the end of the recorded data, the No. 1 cylinder head and exhaust gas temperatures had begun to decrease while the other cylinder temperature parameters remained fairly constant. The engine data then recorded a decrease in engine rpm followed by a steep 180-degree turn toward the airport. A witness who assisted the pilot with the airplane's oil change 2 days earlier stated that the pilot had cross-threaded a spark plug in the No. 1 cylinder and attempted a helicoil repair. During examination after the accident, the No. 1 sparkplug was easily removed by hand. This was likely the cause of the power loss that preceded the pilot's attempt to return to the airport. The pilot's steep, 180-degree turn exceeded the airplane's critical angle of attack, which resulted in a stall at low altitude and collision with terrain. A review of the pilot's toxicology revealed that even though he tested positive for antidepressants, they were not a factor in the accident.
HISTORY OF FLIGHTOn February 17, 2014, about 1250 eastern standard time, an experimental, amateur-built Sonex, N732SX, collided with terrain shortly after departing the Wellington Aero Club (FD38), West Palm Beach, Florida. The airline transport pilot/owner was fatally injured, and the airplane was destroyed. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under the provisions of 14 Code of Federal Regulations Part 91. The flight was originating at the time of the accident. Witnesses stated that during the initial climb, the engine "back- fired" and made a "sputtering" sound. The pilot entered a steep 180 degree turn back towards the airport. The airplane then stalled and entered a nose-down spiral, descended into a canal. PERSONNEL INFORMATIONThe pilot, age 58, held an airline transport pilot certificate for airplane multiengine land, airplane single-engine land, rotorcraft-helicopter, instrument helicopter, which was issued February 16, 2008, and a first-class airman medical certificate issued February 6, 2012, with no limitations. On the pilot's most recent application for a Federal Aviation Administration (FAA) medical certificate, he reported a total of 13,000 flight hours. The pilot's logbook was not recovered; therefore, his total flight experience could not be determined. AIRCRAFT INFORMATIONThe single engine airplane was manufactured in 2007, and was powered by an AeroVee series engine and equipped with a Sensenich model W54JV544G-AC9751, fixed-pitch propeller. The maintenance logbooks were not located; therefore, the maintenance history of the airplane could not be reconciled. METEOROLOGICAL INFORMATIONAt 1253, the recorded weather at Palm Beach International Airport (PBI), West Palm Beach, Florida, about 10 miles east of the accident site, included variable wind 6 knots, 10 statute miles visibility, few clouds at 4,300 feet above ground level. The temperature was 21 degrees Celsius (C), the dew point was 11 degrees C, and the altimeter setting was 30.19 inches of mercury. AIRPORT INFORMATIONThe single engine airplane was manufactured in 2007, and was powered by an AeroVee series engine and equipped with a Sensenich model W54JV544G-AC9751, fixed-pitch propeller. The maintenance logbooks were not located; therefore, the maintenance history of the airplane could not be reconciled. WRECKAGE AND IMPACT INFORMATIONThe wreckage was located partially submerged in a pond, about 200 yards from the departure end of runway 15. The airplane came to rest on a 109 degree magnetic heading, and was 3 feet from the pond's edge. The airplane was removed from the pond for examination, and all major components of the airplane were accounted for at the accident site. The forward portion of the fuselage, firewall and cockpit were deformed and displaced aft. Both wings remained attached to the fuselage and were crushed along the leading edge aft. The vertical stabilizer, elevators and rudder remained attached to the empennage. Control continuity was traced from the cockpit control stick to the elevators and ailerons and from the rudder pedals to the rudder control horn. The examination of the flight control system components revealed no evidence of preimpact mechanical malfunction. Examination of the engine revealed that it was separated from the firewall with sections of engine mount still attached and bent. The engine revealed impact damage on multiple areas on the external surface. Further examination revealed that the ignition lead wires were all attached to the respective sparkplugs and separated from the coil packs on the firewall. Examination of the wires revealed no breaks or chaffed sparkplug wires. Examination of the sparkplugs revealed that the top spark plug on cylinder No. 1 was not seated in the cylinder head and finger tight within the cylinder head threads. The lower sparkplug was found seated to the cylinder and secure. The engine cylinders revealed that the top sparkplug, associated with cylinder No. 4, top sparkplug was seated and finger tight. All other sparkplugs were found seated within the cylinders and secure. All of the spark plugs were removed and the cylinders were checked for blockage. No blockage was noted and the crankshaft was rotated freely by hand. Engine valve train continuity and thumb compression was observed on all cylinders. The throttle body revealed that it was still attached to the throttle cables, but broken away from the manifold. The throttle body lever actuated when the throttle control was manipulated. The air filter was found crushed and impact damaged. The fuel line was connected to the throttle body and was impact damaged and separated from the electric fuel pump attached to the firewall. Examination of the accessory plate revealed that it was impact damaged. The oil cooler was crushed and the oil flow input and output lines remained attached. The oil lines were broken away from the oil pump and oil was within the lines and the oil sump can. The propeller remained attached to the propeller hub and the hub remained attached to the crankshaft. The wooden propeller revealed that one propeller blade was splintered, and the other propeller blade displayed span-wise cracks across the forward face. ADDITIONAL INFORMATIONAccording to a friend of the pilot, he assisted the pilot during an oil change two days prior to the accident. He stated that while conducting the oil change the pilot attempted to change the sparkplugs and cross-threaded the upper sparkplug on the No. 1 cylinder; and made an attempt to helicoil the cylinder thread. The friend further stated that he inspected the sparkplug and noted that the sparkplug along with the helicoil were able to be pulled out of the cylinder head. The pilot continued to work on the engine but the friend did not know if the pilot eventually repaired the cylinder head or if the pilot had flown the airplane after the repair, prior to the accident flight. During the examination of the engine a helicoil was not observed within the cylinder head threads of the No. 1 sparkplug. The airplane was equipped with a Stratomaster Enigma electronic flight instrument system (EFIS) that is capable of recording primary flight data, GPS positions and engine monitor data. The device supports data recording to a secured digital (SD) card. The SD card was recovered and sent to the NTSB Vehicle Recorder Division for data recovery. Review of the data revealed that all engine parameters were normal during the initial climb. Further review revealed that the No. 1 cylinder head and exhaust gas temperature dropped approximately 100 degrees, followed by a loss in rpm and a loss in airspeed. GPS data then showed the airplane making a banking left turn as described by witnesses. MEDICAL AND PATHOLOGICAL INFORMATIONAn autopsy was performed on the pilot on February 18, 2014, by Office of the District Medical Examiner, District 15 State of Florida, West Palm Beach, Florida. Toxicological testing was performed on the pilot by the FAA Bioaeronautical Science Research Laboratory, Oklahoma City, Oklahoma. Review of the toxicology report revealed, no carbon monoxide was detected in the cavity blood. No ethanol was detected in the vitreous. The following drugs were detected in the blood cavity; 0.091 (ug/ml, ug/g) Citalopram and 0.04 (ug/mL, ug/g) N-Desmethylcitalopram detected in blood cavity. Citalopram and Desmethylcitalopram is an antidepressant drug used to treat depression.
The pilot's failure to maintain adequate airspeed following a partial loss of engine power during initial climb, which led to the airplane exceeding its critical angle of attack and experiencing an aerodynamic stall. Contributing to the accident was the pilot's improper repair of a stripped spark plug hole, which led to a partial loss of engine power during initial climb.
Source: NTSB Aviation Accident Database
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