One of four ACH-47A attack helicopters assigned to "Guns-A-Go-Go". Tail number 64-13145, it was lost on May 5, 1967 at Bong Son when a fitting on the forward 20mm cannon came loose and the cannon swung upward and fired into the forward engine, causing the aircraft to crash.
Source: Frank White's "Guns-A-Go-Go" reunion site at http://www.atomic.net/~whitef/