On September 23, 2019, about 1754 Pacific daylight time, a Beech B35 airplane, N5277C, was substantially damaged when it was involved in an accident near Portland, Oregon. The flight instructor and the student pilot were seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 instructional flight. The flight instructor stated that the airplane was serviced to capacity with 24 gallons of fuel before the flight. The individual who refueled the airplane confirmed that he added fuel “to the bottom of the fuel caps.” A mechanic who had assisted starting the accident airplane before the flight stated that the airplane held short of the runway running its engine for about 30 minutes before taking off. The instructor stated that, while practicing maneuvers, the engine speed increased as though the propeller control had been moved full forward; shortly thereafter, the engine “audibly slowed down drastically.” The instructor stated that they cycled the propeller control and adjusted the throttle, but neither had any effect. The instructor subsequently performed a forced landing to a small field. Examination of the wreckage by a Federal Aviation Administration (FAA) inspector revealed that the left-wing tank was full, and the right-wing tank was empty. The fuel selector was positioned to the right fuel tank. After the airplane was recovered, the FAA inspector examined the airplane again and stated that the right fuel tank appeared intact. The fuel selector operated normally when each detent was selected. Flight tracking data from a commercially available website indicated that the accident flight was about 1 hour and 19 minutes in duration. According to the Beech B35 Pilot's Operating Handbook (POH), each main fuel tank held about 17 gallons of usable fuel.