Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 10; Flight Crew Total 3300; Flight Crew Type 8
Situational Awareness; Human-Machine Interface
Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Flight Crew Diverted; Flight Crew Landed in Emergency Condition
Human Factors; Aircraft
Aircraft was being flown under Part 91 on a special airworthiness certificate for Experimental (amateur-built) aircraft.  The purpose of the flight was to conduct flight testing Phase I flight limitations issued for this aircraft.  Two miles short of the intended landing field (the airfield specified as home base in the aircraft's Phase I operating limitations) the engine stopped due to fuel starvation.  I landed uneventfully in a field.  There was no damage to the aircraft or to property on the ground.  I refueled and; with the permission of the farmer who owns the field; took off to return to base.  At the time of the flight; the aircraft had flown fewer than five of the Phase I flight hours.  As the aircraft had experienced cylinder-head cooling issues; most flight time to date had focused on getting the CHT's within limits.  This flight was meant to test a new; enlarged cooling baffle that had been installed for that purpose.  Because of the need to address the cooling issues; I had not yet had time to perform the planned test flights to verify expected fuel flow; nor to cross-check expected fuel-quantity indications (as shown on the ground with the aircraft in flight attitude) with the actual indications airborne.  As a result; actual fuel quantity was less than expected.  When I realized that; about twenty miles from base; I immediately began my return to home field; the fuel supply ran out just outside of glide range.  Per my test plan; developed with the assistance of AC 90-89A; test flights to determine actual fuel flow and to crosscheck airborne fuel-quantity indications are planned.  The data derived  will provide planning data that will prevent a recurrence of this incident.
Experimental aircraft pilot experiences fuel exhaustion while attempting to return to base during a Phase 1 test flight.  An emergency landing in a farmers field ensues without damage to the aircraft.