LAX98FA154 · Mooney M20K

While descending for an instrument approach in instrument meteorological conditions, the airplane's airspeed exceeded its never exceed velocity (Vne) of 196 knots. The elevators fluttered and separated from the airplane. Thereafter, the stabilizers departed, the nose pitched downward, and both wings failed in a negative direction. A ground witness heard a 'pop' sound, and observed airplane parts falling from the low clouds; the surface winds were reported by the witness as gusty. Earlier during the flight, the pilot had been cruising about 19,000 feet, and tracking in a southerly direction at 191 knots (ground speed). The winds aloft were westerly. While communicating with flight watch and radar controllers, he indicated that his airplane was not equipped with deicing equipment. The pilot was advised that icing conditions existed between 13,000 and 15,000 feet, and the freezing level was 7,000 feet. Due to traffic, at 0923 the controller cleared the pilot to descend to 15,000 feet. The pilot accepted the clearance, and requested a clearance to divert to a nearby airport. The controller approved the request. During the last 24 seconds of radar-recorded flight, the airplane's rate of descent increased to 3,500 feet per minute, and over its southerly course its ground speed increased to 240 knots. Shortly after this at 0930:21, the sound of an emergency locator beacon was recorded in the radar control facility. Pilot reports covering the area of the accident around the time of the event reported light to moderate turbulence and light to moderate rime/clear icing conditions. Engineering analysis and testing by the airframe manufacturer predicted the onset of flutter to occur at 241 knots. The airplane was modified by the installation of a larger engine with 95 additional horsepower available.

Verbatim NTSB analysis and probable cause from the NTSB dataset