Background
On 6 May 1981, an EC-135N aircraft, serial number 61-0328, call sign AGAR 23, departed Wright Patterson Air Force Base, Ohio, at 1005 Eastern Daylight Savings Time on a routine training mission. The aircraft carried 17 crew members and four authorized passengers.
Flight Events
The flight proceeded uneventfully for approximately 45 minutes. At 1049:48 EDT, the Federal Aviation Administration lost radar contact with the aircraft. At the time, the aircraft was cruising at Flight Level 290 at Mach 0.78 while performing a navigational training leg. The aircraft commander, Captain Emilio, occupied the right pilot seat, and a passenger, Mrs. Emilio, occupied the left pilot seat. Also in the crew compartment were two navigators, Lieutenant Colonel Frederick and Captain Fonke, and two passengers, Mrs. Fonke and Staff Sergeant Brundige.
Accident Sequence
For undetermined reasons, the aircraft pitch trim moved to the full nose-down position. The aircraft then rapidly pitched over, most likely upon release of the autopilot, inducing sufficient negative G forces to trip the generators off line, resulting in loss of all AC electrical power. The pitch trim could not be moved electrically. This condition, while unusual, can be controlled if prompt corrective action is taken; however, if corrective action is delayed approximately eight seconds, the aircraft pitch angle exceeds 30 degrees nose-down at an airspeed in excess of 350 knots indicated. Under these conditions, control cannot be regained until the pitch trim is moved toward neutral. While recovery was clearly delayed, the reason for the delay is unknown. The aircraft became uncontrollable and entered a steep descent.
During the rapid descent, an explosion occurred at approximately 1,300 feet above ground level, followed immediately by catastrophic failure and complete break-up of the aircraft. The wreckage was found north of Walkersville. All 21 occupants were killed.
Probable Cause
The official investigation concluded that for undetermined reasons, the aircraft pitch trim moved to the full nose-down position, leading to loss of control. The subsequent explosion, though of undetermined origin, occurred when the aircraft was already unrecoverable.