The pilot was on final approach when the engine started to run out of fuel. She said her boss had a similar problem on a previous flight, and had to correct for it by pitching the nose up and down to force fuel into the fuel lines. The pilot recalled pitching the nose up and down but nothing after that. A witness, who saw the airplane pitching up and down several times before it impacted the ground, responded to the crash. He noted that the fuel selector was set to the "both" position and no fuel was leaking from either fuel tank's gas cap. When the airplane was righted, the witness said he saw several gallons of fuel drain from the left tank but not the right tank. When he visually checked the right fuel tank, it was empty. The left tank had about 9 gallons (about 6.5 gallons usable) still in the tank. A postaccident examination of the airplane by a Federal Aviation Administration inspector revealed the airplane sustained substantial damage to the firewall, forward engine mounts, right wing and vertical stabilizer and rudder. About 6 gallons of fuel was drained from the left wing tank and the right tank was empty. A review of the terrain where the airplane impacted the ground revealed the vegetation around the left tank was discolored from fuel, but the area around the right tank was not. No pre mishap mechanical discrepancies were noted with the engine or airplane that would have precluded normal operation.