Commander Aircraft Company 114-B — Adrian, MI

What happened

The air traffic controller cleared the flight for a non-precision instrument approach and provided vectors to an intermediate fix located on the inbound course for the airport, which was reporting a ceiling of 700 feet above ground level. Radar track data revealed that, as the airplane proceeded on the inbound approach segment from the intermediate fix toward the final approach fix, there were significant heading changes and large altitude fluctuations, including rapid ascents and descents. As the airplane neared the final approach fix, instead of proceeding straight on the inbound course as called for by the approach procedure, it entered a left descending turn during which the rate of descent increased to 3,600 feet per minute. A witness reported hearing an airplane circle above his residence at a low altitude, but was unable to see the airplane due to a low cloud ceiling and limited ground visibility. He subsequently saw the airplane in a descent, about 200 to 300 feet above the ground, when the left wing separated from the fuselage. Another witness reported seeing the airplane rolling clockwise in a 45-degree nose-low descent before the left wing separated from the airplane. Neither witness reported seeing any smoke or fire until after the airplane collided with terrain.

The postaccident examination did not reveal any preimpact mechanical malfunctions or failures that would have precluded normal operation of the airplane. Additionally, the left wing main spar exhibited upward deformation consistent with an overload separation during flight.

Pilots are vulnerable to spatial disorientation if they do not properly rely on cockpit instrumentation to maintain basic orientation while operating in instrument meteorological conditions. Because the airplane was in an overcast cloud layer throughout the instrument approach, the pilot lacked a discernible horizon; therefore, he would likely have been susceptible to spatial disorientation. The radar flight path and witness observations were consistent with the pilot becoming spatially disorientated and losing control of the airplane.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.