An R22 B11 departed with the electronic fuel quantity indicators showing half full tanks. Approximately three minutes into the flight both tank gauges indicated low fuel. A precautionary off airport landing was completed. Inaccurate fuel guages are suspected.

Narrative

I picked up a helicopter from ZZZ and was taking it to ZZZ1. I performed all preflight checks; including turning the master switch on; and checking the low fuel light warning system; which worked. I observed that the gauges indicated I had sufficient fuel in both tanks for the 10 minute flight. The AUX fuel gauge registered at half; and the main fuel gauge registered just under half. Based on the R22 B11 consumption rate; there was more than enough indicated fuel to complete the flight with the required 20 minutes extra fuel. I picked the helicopter up into a hover; checked the pad for residual fluids; checked my gauges; got the clearance and departed ZZZ to the East. Roughly 3 minutes into the flight I saw the main gauge drop to empty and the low fuel light flickered; at the same time the AUX gauge showed a little over half. After approximately another minute the AUX gauge then dropped to empty and the fuel light remained on full alert. At this point I was already in contact with ZZZ1. Due to the erratic fuel gauge; fuel light; and clutch light flicker: I decided to make a precautionary landing on a golf driving range just off the charted VFR helicopter approach route. I contacted the tower again; informed them of my decision and executed a safe off field landing under full power. After meeting with fire; police; and FAA officials; a mechanic inspected the fuel system and after adding fuel and signing the log book; I flew the helicopter back to ZZZ1. During this flight the AUX fuel gauge again registered just under half; which was impossible as not enough fuel was added to the fuel system for the AUX gauge to register that amount. I have contacted the A&P mechanics for further inspection.Callback conversation with reporter revealed the following information: The reporter states that this aircraft had sat idle for two to three days prior to this event. Because the gauges indicated more than sufficient fuel for a ten minute flight the reporter did not feel the necessity to visually check the tank quantity. A visual inspection of the fuel tanks is suggested but is not required. After this event he learned that similar events have occurred with this aircraft type after a period of non flight. After the aircraft was returned to the airport and the tanks filled the quantity was again accurate. Maintenance could find nothing wrong with the fuel system.