Background
The pilot reported an alternator failure while operating in the vicinity of Cajon Pass. He requested and received radar vectors toward Rialto Municipal Airport.
Sequence of Events
During the diversion, the pilot sighted Cable Airport, approximately 14 miles west of Rialto, and mistakenly identified it as his intended destination. To conserve battery power, he reduced the electrical load and had a front-seat passenger illuminate the instruments with a flashlight.
While approaching Cable Airport under the belief it was Rialto Municipal, the pilot heard a Cessna broadcasting that it was on final approach to Rialto. Unable to locate the other aircraft, he activated the anti-collision light. The pilot reported that the flashlight beam was removed from his airspeed indicator at a critical point during the final approach, causing confusion in the cockpit.
Landing and Overrun
The aircraft was landed with excessive airspeed, overran the runway, and subsequently experienced an on-ground collision with terrain.