Date: 201207
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: RV-6
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Descent
Airspace: Class E ZZZ
Reporter organization: Personal
Reporter function: Pilot Not Flying; Instructor
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer
Human factors: Communication Breakdown; Situational Awareness; Training / Qualification
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition
Contributing factors: Aircraft; Human Factors
Primary problem: Human Factors

Narrative: I was providing transition training in an RV-6A to a 95 hour private pilot who had just purchased the aircraft. Today's flight was to be about 2.2 hours long. The prior evening I was with the owner and witnessed him refuel the aircraft with 20 gallons of 100LL. I told the owner that there were already six gallons of fuel aboard - based on our previous flying; our observed fuel burn of 8.2 GPH; and the fact that we started with full tanks and kept very careful track of fuel burned; added; or removed.The next morning I arrived at the airport; watched the owner perform the pre-flight and asked him about our fuel state. He told me the 'gas is fine.'We made an uneventful takeoff; climbed to altitude for a short cross country trip so he could practice descents and perform traffic pattern work. We departed that airport for a second airport using the same training profile and they headed back home. Approximately 16 miles from the airport at 2.1 hours into the planned mission; the engine coughed so the owner correctly reacted and switched fuel tanks using the proper procedures. I remarked to him that the event was strange because according to my watch we should have a little over 8 gallons of fuel remaining. At this point the owner goes 'Oh.' I asked Oh what? He tells me 'I probably should have told you before; but early this morning before you got to the airport I drained 8 gallons of gas out of the airplane into my gas cans.' The owner told me he was concerned we may be too heavy as he was worried we had too much gas on the airplane. He had no rational basis for this belief and no explanation as to why he did not tell me his concern or the fact that he removed fuel from the airplane and did not tell me. Concerned that we could experience fuel exhaustion; I opted to make a precautionary landing in a field about 12 miles northwest of the airport. The landing was uneventful. The owner refueled the airplane with the 8 gallons he had removed and with the permission of the land owner; I flew the aircraft out of the clover field back to the airport.




Synopsis: After it was necessary to switch tanks earlier than anticipated; an instructor pilot providing transition training to the new owner of an RV-6A initiated an emergency off airport landing when he was advised by the owner that he had drained eight of the twenty gallons of fuel added the previous evening due to concerns over weight.