The pilot reported that while in a descent from 16,000 feet, at 1,500 feet per minute, slowing from 190 knots indicated airspeed to 160 knots, the Raytheon Aircraft Co. B300 encountered extreme turbulence.
He reported one hard jolt up/down, followed by about 15 seconds of light turbulence, then one final hard jolt similar to the first.
The weather in the area of Mammoth Lakes, California, was visual conditions and no turbulence was encountered prior to or after the event.
A postflight examination revealed that the extreme turbulence resulted in substantial structural damage to both wing spars.
Probable cause: The airplane encountered extreme turbulence during descent.
NTSB Identification: WPR15CA110
This February 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.