Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 25; Flight Crew Total 4900; Flight Crew Type 100
Situational Awareness; Training / Qualification
Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Flight Crew Inflight Shutdown; Flight Crew Landed in Emergency Condition
Aircraft; Human Factors
After being switched on downwind from XXL to XXR; requiring overflying the field; and then being told to go around and switch again to XXL; the engine sputtered and lost power while on downwind for XXL; approximately abeam the departure end. I immediately began a 90deg turn toward the runway and advised tower I would be landing against traffic (on YYR). I was able to lower the gear and partial flaps; complete the 2nd 90 deg turn onto the runway; landing about 2000 ft down. Tower directed traffic on final to XXL to go around. I turned off the runway at Taxiway X; but had to get out and pull the plane across the line.This experimental aircraft has both fuel gauges and a fuel flow/totalizer instrument. The gauges are not very accurate; and in the past I have depended on the totalizer for actual fuel-on-board.  In this case; the gauges were reading empty (as they often do below ~7 gals/side); but the totalizer reported 13.3 gallons remaining (of 60 gals total capacity) when I entered the pattern. After pulling the plane to a safe area; I sumped both sides and both showed no fuel. I added 3.5 gals from a gas can to the right tank. The engine started fine and I taxied the plane to the hangar without incident.  I was very lucky indeed.I am not the builder; but the 3rd owner of this unusual GP-4 experimental aircraft. In my honest opinion; the discrepancy between the heretofore reliable fuel totalizer and the actual gauges led me to disregard the gauges; the wrong response.  Because of the tank arrangement in the plane; it is not possible to 'stick' the tanks to check fuel. I think that the correct fix for this problem is 3-fold. [1] Replace the unreliable fuel  gauges with a carefully calibrated digital system. [2] Recalibrate the fuel flow/totalizer instrument over a number of flights against actual measured fuel used. [3] Until both #1 and #2 are completed; fully fill the tanks and set a *maximum* flight time of 4.5 hours between fills. (Nominal average fuel burn; chock-to-chock; is 10 gph. Total capacity is 60 gals; so this should leave at least 15 gals as minimum fuel.
GP-4 pilot reported loss of power on downwind due to fuel exhaustion.