Fatal ILS Approach Accident Involving Thunderstorm Encounter (N90BP)

Approach and Weather Conditions The flight was cleared for an instrument landing system (ILS) approach to the destination airport. During maneuvering for the final approach course, the aircraft encountered convective activity, specifically thunderstorms. Weather reports recorded level four thunderstorm activity in the immediate vicinity of the destination airport. Air traffic controllers provided the pilot with current weather conditions at the airport during the final minutes of the flight, indicating the pilot was aware of the thunderstorm activity near and at the airport. The ILS approach system was later checked by airways facilities, and no problems were found. ## Deviation and Collision The tower questioned the pilot about his position on the approach course. Tower radar placed the aircraft one-quarter to one-half mile east of the final approach course, while the pilot stated he was on the localizer. The aircraft subsequently collided with trees approximately one and one-half miles northeast of the airport and one-half mile east of the approach course. Wreckage examination did not reveal any mechanical problems with the airplane. All four occupants were killed.