CEN22LA093

The pilot stated that, about 30 minutes after departure and while in cruise flight at an altitude of about 10,500 ft mean sea level, he observed the fuel pressure decrease from 44 to 39 pounds per square inch (psi), increase to 40 psi, and decreased to 0 psi as the engine speed decreased to 0 rpm. For about the next 3 to 5 minutes, the fuel pressure and RPMs fluctuated between normal and zero. He activated the backup fuel pump with no effect noted. The airplane sustained substantial damage to both wings during the forced landing. A postaccident examination revealed no mechanical malfunctions or anomalies that would have precluded normal operation. Engine runs were performed with no anomalies noted that were consistent with the pilot’s statements and onboard recorded data. The onboard recorded data showed fluctuations in fuel pressure and intermittent operation of the engine consistent with the pilot’s statement. As a result, the reason for the partial loss of engine power could not be determined based on the available evidence for this investigation.

On January 2, 2022, about 1040 mountain standard time, a Zenith CH750, N750DP, was substantially damaged when it was involved in an accident near Montrose, Colorado. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that, before taking off, he added 23 gallons of 92 octane, ethanol free automotive gas to the fuel tanks. After the fuel settled, he checked the sump in the fuel tanks and observed no contamination or water in the fuel. About 30 minutes after departure and while in cruise flight at an altitude of about 10,500 ft mean sea level, the pilot observed the fuel pressure decrease from 44 to 39 pounds per square inch (psi). The fuel pressure then increased to 40 psi before decreasing to 0 psi as the engine speed decreased to 0 rpm. For about the next 3 to 5 minutes, the fuel pressure and engine speed fluctuated between a normal psi and rpm, respectively, and zero. The pilot activated the backup fuel pump with no effect noted. The pilot decided to execute a forced landing on top of a snow-covered plateau about 20 miles south of Montrose. During the landing, the nosewheel dug into the snow, causing the airplane to flip over, which resulted in substantial damage to both wings. During a postaccident examination, fuel was supplied to the airplane’s engine, which started without hesitation. After the engine warmed up, the throttle was increased, and the engine continued to run at almost full power. When the backup engine control unit was activated, the engine coughed and then quit. After the unit was turned off, the engine restarted, but the engine quit when the unit was turned back on again. The airplane was installed with a Dynon Skyview electronic device. The data retrieved from the device showed that, between about 1035 and 1037, the fuel flow rate decreased from 5.9 to about 5.0 gallons per hour with no other changes noted. About 1037, the engine rpm and fuel pressure both decreased to zero, returned to their original value, and then decreased back to zero. These fluctuations continued until the data ended about 1040:30. During this same timeframe, the fuel flow rate steadily decreased, the oil pressure fluctuated between about 60 and 75 psi, and the amperage fluctuated between about 5.7 and 9.5 amperes.