Accident Overview
On March 4, 2020, at 1240 mountain standard time, a Flight Design CTLS airplane, registration N505MA, was substantially damaged when it impacted terrain near Encino, New Mexico. The pilot sustained minor injuries. The airplane was being operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
Pilot Actions
During the preflight inspection, the pilot visually checked fuel levels through the sight gauges in each wing, noting 7 gallons in the right wing and 6 gallons in the left. He considered this sufficient for a one-hour local flight. Approximately 35 minutes after takeoff, the engine began to surge. The pilot manipulated the throttle lever multiple times but observed no corresponding engine response. He decided to land on a nearby road. While turning from base to final approach, the engine surged back to life. The landing gear contacted the grass, and the airplane came to rest inverted, resulting in substantial damage to the wings and fuselage.
Postaccident Examination
Following recovery, a postaccident examination was performed. The engine remained attached to the airframe, and all accessories were secured. The top spark plugs exhibited normal wear. Manual rotation of the crankshaft via the propeller confirmed continuity throughout the engine and valve train; thumb compression and suction were confirmed on all four cylinders.
Examination of the engine-driven fuel pump showed the diaphragm appeared normal. However, the fuel pump vent/overflow hose nipple was missing the drain hose, which is designed to route to a neutral air pressure area. The area around the fuel pump had evidence of a previous leak.
The gascolator drain valve was opened, and no liquid drained. The gascolator housing was removed, revealing that the filter was missing.
Both wings were removed during recovery. The right wing contained an unmeasured amount of fuel, while the left wing appeared empty. Low air pressure applied to the right wing fuel line fitting resulted in fuel expelled through the vent tube. Similar application to the left wing produced no fuel or air expulsion through the vent tube. Both wing fuel tank caps remained secure; no fuel samples were obtained from the right wing.
Examination of the fuselage lower belly skin aft of the engine compartment revealed an accumulation of dirt near the fuel drain tube exiting the engine compartment. A sample of the dirt was secured for laboratory analysis.
Laboratory Analysis
The dirt sample was examined at the NTSB Materials Laboratory using Fourier Transform Infrared spectrometry. A spectral library comparison indicated the residue consisted mainly of soil. The presence of hydrocarbons such as fuel or oil may have been masked by the strong soil spectrum.