ERA15FA141

An in-flight loss of control for reasons that could not be determined based on the available evidence.

The airline transport pilot departed in his light sport aircraft with a friend, who held a student pilot certificate, on a cross-country flight to another airport for lunch. GPS data showed the airplane maneuvered near the accident site for about 30 minutes, performing multiple climbs, descents, and turns. Several witnesses reported hearing the engine "sputter," which was immediately followed by an advance in engine power. Although the airplane's final movements were not captured by witness reports or radar/GPS data, examination of the accident site showed that the airplane was in a steep descent when it impacted a swamp. The impact geometry was consistent with an in-flight loss of control and subsequent uncontrolled descent to ground impact. A postcrash fire ensued, which consumed most of the airplane. Postaccident examination of the airplane and the engine did not reveal any mechanical anomalies that would have precluded normal operation. Although the environmental conditions were favorable for light icing at glide or cruise power, witnesses reported that the engine regained power after "sputtering"; such a gain in power is not consistent with a carburetor ice condition. The cause of the "sputtering" reported by the witnesses could not be determined because the extensive fire damage precluded testing of the engine-driven fuel pump, carburetors, and ignition system components. The pilot reported a vibration in the control stick to the airplane manufacturer in the days leading up to the accident. The manufacturer responded to the pilot on the morning of the accident and stated that the vibration could be the result of an inadequately balanced engine or propeller. However, the propeller's effect on the airplane's performance could not be determined because two of the blades were not recovered from the accident site and the acetal pitch change slide block within the propeller hub was consumed by postcrash fire. Although sedating medications were found in toxicological specimens from both occupants, and the pilot's autopsy found evidence of severe coronary artery disease, the investigation could not determine if these physiological conditions contributed to the accident.

Autopsies were performed on both occupants by District 15 - State of Florida, Office of the District Medical Examiner, West Palm Beach, Florida. The autopsy reports listed the cause of death for the pilot and the passenger as blunt impact injuries of head, neck, torso, and thermal injuries. The pilot's autopsy found significant diffuse, calcific, severe coronary artery disease with focal narrowing by 75-80% in both the left anterior descending and right coronary arteries and a scar along the septum. Forensic toxicology testing was performed on specimens of the pilot and passenger by the FAA Bioaeronautical Science Research Laboratory, Oklahoma City, Oklahoma. Testing on specimens of the pilot detected the presence of cetirizine and losartan in the blood and urine and salicylate in the urine. Toxicology testing performed on specimens of the passenger detected cetirizine, chlorpheniramine, diphenhydramine, hydroxyzine, losartan, naproxen, quinine, and salicylate in the urine. Cetirizine, chlorpheniramine (0.022 ug/ml), diphenhydramine (0.0031 ug/ml), and losartan were also identified in the passenger's cavity blood. Cetirizine is an antihistamine available over the counter, commonly marketed with the name Zyrtec. It carries a warning, "When using this product, drowsiness may occur; avoid alcoholic drinks; alcohol, sedatives, and tranquilizers may increase drowsiness; be careful when driving a motor vehicle or operating machinery." Chlorpheniramine, diphenhydramine, and hydroxyzine are all sedating antihistamines, and each carries a warning about operating machinery due to drowsiness or "marked drowsiness." Chlorpheniramine is commonly sold under the names Chlortrimeton and Chlor-tab; therapeutic blood levels are between 0.0100 and 0.0400 ug/ml. Diphenhydramine is available in a large number of products marketed as treatments for cold symptoms and allergies. Additionally, diphenhydramine is used as the active ingredient in a number of over the counter sleep aids. Therapeutic blood levels are between 0.0250 and 0.1120 ug/ml. Finally, hydroxyzine is a prescription sedating antihistamine commonly sold under the names Atarax and Vistaril. Due to their warnings of drowsiness, all four of the antihistamines found in the passenger's blood meet the FAA's criteria for waiting 5 maximum dosing intervals before flight. The airplane came to rest upright in swamp water on a southeasterly heading about 40 ft from a dirt road and 1 nm from the airplane's final GPS target. All major components of the airplane were accounted for at the accident site. Most of the fuselage and empennage were consumed by fire. The right wing displayed fire damage, the wingtip was separated, and the inboard wood spar was broken at the fuselage. The elevator separated from the tail section and was located several feet behind the main wreckage. All three composite propeller blades had fractured and separated from the propeller hub. Airframe Postaccident examination of the airframe was completed at a secure facility by a Federal Aviation Administration inspector (FAA), the NTSB Investigator-in-Charge, and a representative from the engine manufacturer. The aileron flexball cable was traced from the cockpit flight controls to the right aileron through the center bellcrank. The left aileron was destroyed by fire; however, although thermally damaged, the left aileron flexball cable extended from the center bellcrank to an allen bolt that is normally coupled to the left aileron. The wing flap control system was not recovered. Continuity of the elevator flexball control cable was confirmed from the elevator to the cockpit flight controls. The right and left occupants' rudder pedals moved synchronously, which actuated the center bellcrank assembly. About 6 inches of push rod, which extended from the rudder into the vertical stabilizer, was present; however, the rudder control tubes that connected to the push rod at the vertical stabilizer were not recovered. The wing fuel tanks were destroyed by fire, but the fuselage tank remained intact and contained trace amounts of blue colored fuel that resembled 100 low lead aviation grade gasoline. The gascolator filter was free of debris, and the gascolator bowl was void of fuel. The throttle and choke controls were confirmed from the throttle/choke quadrant to the carburetors. All three composite propeller blades were separated and about 6 inches of each blade remained connected to the propeller hub. Each of the remaining blade sections displayed composite fibers that were thermally damaged. The propeller blade ferrules were covered in soot, and the propeller spinner exhibited blistering, consistent with fire damage. A section of propeller blade that measured about 15 inches in length was co-located with the main wreckage and did not exhibit any fire damage. The other two propeller blades were not recovered. A visual inspection of the propeller extension shaft found that it was about 10 inches in length, which was 4.72 inches beyond the engine manufacturer's maximum limitation. The propeller hub and blade remnants were sent to the NTSB material's laboratory in Washington, D.C., for further examination. The control wires and metallic components of the pitch change mechanism within the hub were intact; however, the pitch change slide, which was composed of acetal, was melted and not attached to the drive screw. Engine The engine was intact and remained attached to the engine mounts. An attempt to rotate the crankshaft at the propeller flange was unsuccessful as a result of the thermal damage to the engine crankcase. A nut on the ignition housing was fused to the crankshaft, which precluded disassembly of the crankcase. A visual examination of the connecting rods and crankshaft through the cylinder portholes did not reveal any anomalies. The electronic modules and external triggers to the engine's dual capacitor discharge ignition system were consumed by postcrash fire and could not be examined. The functionality of the ignition coils and cables could not be confirmed due to extensive damage. Both the stator and flywheel were damaged by fire, which precluded functional testing. The engine driven fuel pump was destroyed by fire and could not tested. Both constant depression diaphragm carburetors were displaced from the intake manifolds and destroyed by fire, which precluded an inspection of the floats, fuel bowls, and diaphragms. Both the top and bottom spark plugs were removed from each cylinder for inspection; each plug appeared grey in color, consistent with normal operating signatures. All 8 spark plug electrode gaps were within the gap range prescribed by the manufacturer. Rust deposits were observed along the rim of several of the spark plug cases. The cylinder heads exhibited evidence of exposure to postcrash fire; however, each piston displayed signatures consistent with normal combustion, and all of the cylinder valve faces and seats were in place. Each cylinder bore exhibited cross-hatching with no indications of scoring or oil starvation. An inspection of the valves, valve springs, rocker arms, and push rods did not reveal any anomalies. An inspection of the oil pump did not reveal any anomalies; however, the unit was thermally damaged and could not be functionally tested. The oil tank was partially damaged by fire, but remained intact and displayed some oil residue within the sump case. The oil cooler, oil filter, and oil lines were consumed by postcrash fire and could not be examined. The engine reduction gearbox displayed some soot residue on the case; however, the internal gearset did not display any anomalies. Remnants of oil were observed within the gearbox. The 1253 recorded weather observation at Boca Raton Airport, Boca Raton, Florida, included wind from 090° at 7 knots gusting 14 knots, 10 statute miles visibility, clouds scattered at 2,200 ft and 2,700 ft, and broken at 3,700 ft, temp