HISTORY OF FLIGHTOn November 8, 2021, about 1620 central standard time, an experimental, amateur-built Sonex airplane, N432SX, was substantially damaged when it was involved in an accident near Malone, Florida. The private pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
The pilot told a friend of his that the engine had experienced total losses of engine power on two occasions during a flight earlier that day. The friend questioned the pilot to get more details, but the conversation was interrupted, and the pilot did not explain what actions he performed to restore engine power.
Another individual who spoke with the pilot before the accident flight reported that the pilot stated that he thought that he had found “the problem” and he was planning to remain in the airport traffic pattern at Marianna Municipal Airport (MAI), Marianna, Florida, during the accident flight. The witness reported that the pilot departed from runway 36 and continued straight-out after departure. He then diverted his attention and did not witness the accident.
A witness, who was located about .65 nautical miles (nm) south-southwest of the accident site reported that he was in the cab of a tractor plowing a field when he observed an airplane that he thought was a “crop duster” flying in a westerly direction at high speed toward the ground. He did not hear any sound associated with the airplane from inside the tractor cab. The airplane disappeared behind trees, and about 1 to 2 seconds later, he saw a big ball of black smoke. Before seeing the black smoke, he did not notice any erratic movements, nor did he see anything trailing the airplane. PERSONNEL INFORMATIONSince purchasing the airplane on March 21, 2021, the pilot logged 9 flights excluding the accident flight; however, his total flight experience in the accident airplane was not determined. AIRCRAFT INFORMATIONAccording to the Aerovee 2.1 Assembly and Installation document, ACV-R02, Revision AE dated April 27, 2021, applicable to the accident engine serial number, the maximum allowed cylinder head temperature (CHT) and oil temperature readings were 450° F and 240° F, respectively. The document indicated that the gap for the upper and lower spark plugs were 0.018 inch and 0.032 inch, respectively.
According to the Notes section of a document which was the likely continuation of his pilot logbook, on October 30, 2021, during takeoff in the accident airplane, the CHT was 452° F, the exhaust gas temperature was “high” and the oil temperature was 206° F with a corresponding “red flashing light” during takeoff requiring an immediate landing on an adjacent runway. The next entry, dated November 3, 2021, read, “[re-adjusted] timing & mixture OK!! Finally.” The maintenance actions were not recorded in the maintenance records. AIRPORT INFORMATIONAccording to the Aerovee 2.1 Assembly and Installation document, ACV-R02, Revision AE dated April 27, 2021, applicable to the accident engine serial number, the maximum allowed cylinder head temperature (CHT) and oil temperature readings were 450° F and 240° F, respectively. The document indicated that the gap for the upper and lower spark plugs were 0.018 inch and 0.032 inch, respectively.
According to the Notes section of a document which was the likely continuation of his pilot logbook, on October 30, 2021, during takeoff in the accident airplane, the CHT was 452° F, the exhaust gas temperature was “high” and the oil temperature was 206° F with a corresponding “red flashing light” during takeoff requiring an immediate landing on an adjacent runway. The next entry, dated November 3, 2021, read, “[re-adjusted] timing & mixture OK!! Finally.” The maintenance actions were not recorded in the maintenance records. WRECKAGE AND IMPACT INFORMATIONThe airplane impacted federal property that was formerly a United States Coast Guard facility. The accident site was located about 9.4 nm north of the departure end of runway 36 at MAI.
The airplane impacted the top of an oak tree about 25 feet above ground level; the tree was located near the east end of an abandoned runway. The airplane then impacted the ground about 154 ft later on a magnetic heading of 273°. The ground scar was oriented on a magnetic heading of 290°.
The main wreckage, which comprised the fuselage, attached but partially fractured left wing, and horizontal and vertical stabilizers with attached primary and secondary flight controls, came to rest inverted on a magnetic heading about 279° and about 275 ft from the impacted tree. Fire damage was noted to the adjacent grass to the west, north, and northeast of the main wreckage. The cockpit exhibited extensive heat damage which precluded determination of switch positions.
Pieces of windshield, engine air filter, propeller blade pieces/fragments, other engine parts consisting of a pushrod housing, and yellow paint specks were noted immediately aft of the heavy ground scar location. The right wingtip, and red colored lens (associated with the left wing navigation light) were located on the left side of the energy path. Further examination of a window piece recovered near the initial impact point revealed heavy/coarse scratches consistent with contact with the asphalt surface.
Examination of the flight controls for roll, pitch, and yaw revealed no evidence of preimpact failure or malfunction. The rudder control cables were continuous from the control surface to each clevis in the cockpit. The left wing exhibited tree contact about midspan, while a semi-circular indentation about 3 to 4 inches in diameter was noted on the leading edge of the right wing about 2 ft from the wingtip. Correlation of the indentation with the tree limb revealed an approximate left bank of 40 to 45° if the airplane was upright when the contact was made. Located on the ground near the right wing were several tree limbs with live leaves consistent with the species of the impacted tree; one tree limb was about 4 inches in diameter. A 2-inch diameter tree limb with 45° slash that penetrated about 1/2 inch into the limb was also located on the ground in close proximity to the main wreckage.
The firewall and remains of the engine were located about 1 ft forward of the flap torque tube. The nose landing gear wheel was deformed, likely by heat damage.
The fuel tank was destroyed; the outlet finger screen was clean and the fuel shutoff valve was in the open position.
The engine crankcase was nearly consumed by the postcrash fire, exposing the crankshaft, camshaft, lifters, pushrods, oil pump gears, cast iron oil pump cover, steel band clamps, and other small steel parts. Cylinder Nos. 1 and 2 were displaced from their normal orientation while the Nos. 3 and 4 cylinders were still in their proper orientation. All pushrods for cylinder Nos. 3 and 4 were straight, while two of the four pushrods for the Nos. 1 and 2 cylinders were bent. The Nos. 1 and 2 pistons were destroyed by the fire, while the Nos. 3 and 4 pistons were nearly consumed. The intake for the cylinders remained attached but the intake for the Nos. 1 and 2 cylinders was heat damaged.
The exhaust valve for the No. 2 cylinder (left forward) was separated from the cylinder and found on the ground. The rocker arms for the Nos. 1 and 2 cylinders intake and exhaust valves were fractured. The crankshaft and camshaft were not fractured. All piston rings except from the No. 3 cylinder were observed; all observed piston rings were in place which no evidence of ring breakage in any cylinder. The exhaust was tightly attached to cylinder Nos. 3 and 4. The ignition, fuel metering, and oil cooler systems were extensively heat damaged.
An examination of the spark plugs revealed the following:
No. 1 Top - Plug snug, light tan color. Plug Gap at Specification No. 1 Bottom – Could not remove No. 2 Top – White Color. Plug Gap at Specification No. 2 Bottom - Could not remove No. 3 Top - Light Tan. Ground electrode touching center electrode No. 3 Bottom - Light Tan. Plug gap 0.006 inch greater than Specification No. 4 Top - Plug snug, Gray Color. Plug Gap 0.001 inch greater than Specification No. 4 Bottom - Light Tan. Plug gap 0.002 inch less than Specification
Examination of the cylinders revealed the following:
No. 1 - Valves appeared satisfactory. Rings in place No. 2 - Intake valve in place exhaust valve separated. Rings in cylinder No. 3 - Valves appeared satisfactory. The piston was in the cylinder barrel and the rings were not observed. Piston dome had re-solidified aluminum. Piston appeared satisfactory. No. 4 - Valves satisfactory. Rings in place. Piston extensively heat damaged. One large piece of piston removed. Resolidified aluminum adhering to remaining portion of piston.
There was no evidence of any lubrication issue. The oil pump gears which were recovered and examined revealing no broken or damaged teeth. The oil filter was separated from the engine and was extensively heat damaged. The oil filter element and oil cooler were extensively heat damaged.
The propeller was destroyed by the postimpact fire.