History of Flight
On November 8, 2021, at about 1620 central standard time, an experimental, amateur-built Sonex airplane, registration N432SX, was substantially damaged when it crashed near Malone, Florida. The private pilot was fatally injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Earlier that day, the pilot told a friend that the engine had experienced total losses of engine power on two occasions during a previous flight. The friend asked for more details, but the conversation was interrupted, and the pilot did not explain how he restored power.
Another individual who spoke with the pilot before the accident flight reported that the pilot said he thought he had found “the problem” and planned to remain in the airport traffic pattern at Marianna Municipal Airport (MAI), Marianna, Florida, during the accident flight. The witness said the pilot departed from runway 36 and continued straight-out after departure; the witness then diverted his attention and did not see the accident.
A witness located about 0.65 nautical miles south-southwest of the accident site reported being in the cab of a tractor plowing a field when he observed an airplane he thought was a “crop duster” flying in a westerly direction at high speed toward the ground. He did not hear any sound from 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. He did not observe any erratic movements or anything trailing the airplane before the smoke.
Pilot Information
Since purchasing the airplane on March 21, 2021, the pilot logged 9 flights excluding the accident flight. His total flight experience in the accident airplane was not determined.
Aircraft Information
According 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) was 450°F and the maximum allowed oil temperature was 240°F. The document specified spark plug gaps of 0.018 inch for upper plugs and 0.032 inch for lower plugs.
In the Notes section of a document likely a continuation of his pilot logbook, an entry dated October 30, 2021, stated that 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” 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 Information
The airplane impacted federal property that was formerly a United States Coast Guard facility, about 9.4 nautical miles north of the departure end of runway 36 at MAI.
It first struck the top of an oak tree about 25 feet above ground level, located near the east end of an abandoned runway. The airplane then impacted the ground about 154 feet farther on a magnetic heading of 273°. The ground scar was oriented on a magnetic heading of 290°.
The main wreckage, comprising the fuselage, attached but partially fractured left wing, horizontal and vertical stabilizers with attached flight controls, came to rest inverted on a magnetic heading of about 279°, about 275 feet from the impacted tree. Fire damage was noted to the adjacent grass to the west, north, and northeast. The cockpit exhibited extensive heat damage, precluding determination of switch positions.
Pieces of windshield, engine air filter, propeller blade fragments, a pushrod housing, and yellow paint specks were found immediately aft of the heavy ground scar. The right wingtip and a red lens (from the left wing navigation light) were located on the left side of the energy path. A recovered window piece showed heavy scratches consistent with asphalt contact.
Examination of flight controls for roll, pitch, and yaw revealed no evidence of preimpact failure or malfunction. Rudder control cables were continuous from the control surface to clevises in the cockpit. The left wing exhibited tree contact about midspan; a semi-circular indentation about 3-4 inches in diameter was noted on the leading edge of the right wing about 2 feet from the wingtip. Correlation of the indentation with a tree limb suggested an approximate left bank of 40-45° if the airplane was upright at impact. Several tree limbs with live leaves consistent with the impacted tree were found near the right wing; one limb was about 4 inches in diameter. A 2-inch diameter limb with a 45° slash penetrating about 1/2 inch was also near the main wreckage.
The firewall and engine remains were located about 1 foot forward of the flap torque tube. The nose landing gear wheel was deformed, likely by heat. 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. Cylinders No. 1 and 2 were displaced; No. 3 and 4 were in proper orientation. All pushrods for cylinders 3 and 4 were straight; two of four pushrods for cylinders 1 and 2 were bent. Pistons for cylinders 1 and 2 were destroyed by fire; pistons for cylinders 3 and 4 were nearly consumed. The intake for cylinders remained attached, but intake for cylinders 1 and 2 was heat damaged.
The exhaust valve for cylinder No. 2 (left forward) was separated from the cylinder and found on the ground. Rocker arms for cylinders 1 and 2 intake and exhaust valves were fractured. The crankshaft and camshaft were not fractured. All observed piston rings (except cylinder 3) were in place with no evidence of ring breakage. Exhaust was tightly attached to cylinders 3 and 4. The ignition, fuel metering, and oil cooler systems were extensively heat damaged.
Spark plug examination revealed: No. 1 top – light tan, gap at specification; bottom could not be removed. No. 2 top – white, gap at specification; bottom could not be removed. No. 3 top – light tan, ground electrode touching center electrode; bottom – light tan, gap 0.006 inch over specification. No. 4 top – snug, gray, gap 0.001 inch over; bottom – light tan, gap 0.002 inch under.
Cylinder examination: No. 1 – valves satisfactory, rings in place. No. 2 – intake valve in place, exhaust valve separated, rings in cylinder. No. 3 – valves satisfactory, piston in barrel with rings not observed, piston dome had re-solidified aluminum, piston appeared satisfactory. No. 4 – valves satisfactory, rings in place, piston extensively heat damaged with one large piece removed and re-solidified aluminum adhering.
There was no evidence of lubrication issues. Oil pump gears showed no broken or damaged teeth. The oil filter was separated and extensively heat damaged. The propeller was destroyed by the postimpact fire.
Probable Cause
The investigation did not determine a probable cause.