Amateur/Home Built/Experimental
Flight Crew Private
Flight Crew Type 700
Confusion; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
Flight Crew Landed As Precaution; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Police / Security Involved
Aircraft; Human Factors
I departed for a brief (10-minute) flight to collect a single performance data point above the airport close to sunset. During the flight; a roughness and unexplained power loss was experienced. Since I was above the airport with an assured landing but concerned about the fuel situation and/or engine condition; I chose a power-off landing after clearance was received. After a normal rolling exit from the runway onto the desired taxiway; I requested/advised tower off frequency for a moment. I checked for any leaks or concerns. None were observed; but it was getting dark; so I requested straight ahead to the ramp from Ground and; receiving 'proceed as requested'; pushed the airplane ahead to the ramp. I was greeted unnecessarily by police. I explained the events and he seemed ok with just taking my name. I had about 5 gallons of fuel remaining; since I added 20 and the gauges read afterward 25. It's possible that my original measurements of unusable fuel (almost none) were inaccurate for some combination of the flight conditions. It's possible that the fuel computer had bad data. It's possible that some other issue (debris; etc) was a source of the problem. I had checked the fuel level during preflight and met the night VFR required reserve. The flight was aborted after less than 10 minutes. The engine ran normally for the taxi back to the hangar.
Experimental Aircraft pilot reported engine roughness and unexplained power loss.