Drayton Associates

IAI 1124 Westwind

Airplane crashed during a uncontrolled descent, following a turbulence upset at FL370. The upset occurred as a result of clear air turbulences associated with a vip level 6 thunderstorm located within 7 miles of the last position of the airplane. After the upset, the airplane penetrated and descended thru the cell which contained lightning, extreme turbulences and severe icing. During the upset/descent both engines flamed out and the crew's attempts to recover the airplane were unsuccessful due to conditions in the cell. Crew received an improper briefing from FSS and reported their radar was malfunctioning to the deputy controller. Sigmet and AWW info was not given during the briefing. As the airplane came out of the bottom of the cell at 4,000 feet, the crew overstressed the airplane causing the left main landing door to separate and hit the left horizontal stab which subsequently separated in overload. Impact was 82° nose down. Nature of the airplane radar malfunction could not be determined. All seven occupants were killed.