Overview
The aircraft was conducting a routine fire reconnaissance patrol when it crashed. No eyewitnesses were present. Air Route Traffic Control Center radar data showed no primary or secondary targets at or above 3,000 feet AGL. No record was found of either crew member initiating an emergency transmission. No weather phenomena were observed by any source in the area.
Accident Scenario
The aircraft came to rest on a sandbar at the apex of a river bed in a narrow canyon, at an elevation of 5,620 feet MSL. The site featured a measured 400-foot radius bend in the river. The terrain on the west side of the river rises steeply to approximately 6,100 feet MSL, while the east side rises to similar heights over a longer horizontal distance. A review of past reconnaissance flights over this same route indicated that the flight's position reports and computed ground speed were consistent with all previous flights.
Aircraft Performance Data
Beech Aircraft computed the aircraft's trim speed at 120 knots, based on the elevator trim tab position relative to gross weight and center of gravity. At this speed, a 73-degree bank angle is required for the aircraft to execute a 400-foot-radius turn. The stall speed at that bank angle is 111 knots.
Wreckage and Impact
An extensive postcrash fire consumed the aircraft. No ground scars were observed outside the immediate area of the main wreckage.
Engine and Systems Examination
According to a Hartzell Propeller report, both propellers were operating symmetrically at blade angles within the governed range during the impact sequence. No preimpact failures or system/component malfunctions were found.