Helicopter Blades Breaking The Sound Barrier

I was not expecting to photograph a U.S. Military helicopter today at Top Sail Beach in North Carolina. I still had my 90mm macro lens mounted when all of a sudden I hear a military helicopter coming on quickly above. I deviated from imaging ocean beach stuff to capturing some images of the helicopter which had started to hover directly overhead. I did switch to shutter priority to image at 1/1250 sec. Since the outer tips of a helicopter are actually traveling faster than the speed of sound, a known phenomenon of the vapor trail that is created right at the front edge of the structure when that item is traveling faster than the speed of sound. Often visible on the nose of low flying jets when video filmed at a high frame per second speed setting.
This small vapor trail can be seen on this image right at the area of the tip of the main rotor blades.
Rather an interesting image capture today.