Accident Sequence
On the day of the accident, at 1400 central standard time, a modified Douglas DC-3C/BT-67R (registration TZ-389) and a Beech A36 (registration N3657A) began a formation flight. The purpose was for the DC-3 to accrue flying time and for the second occupant of the A36 to take aerial photographs of the DC-3.
Witness Observations
A witness observed the two aircraft at an altitude of 500 to 700 feet above ground level, flying close together in a northerly direction. The witness reported that the larger aircraft, the DC-3, was flying straight and level, while the smaller A36 was positioned just to its west. The A36 then struck the DC-3 near its midsection. Following the impact, pieces of both aircraft were observed falling.
Another witness saw the DC-3 heading north with the A36 circling around it, both above and below. On its final pass, the A36 circled behind the DC-3, crossed over the top, and struck the top of the DC-3. Approximately five seconds after impact, the DC-3 began a gentle roll and turn to the west, apparently descending and gaining airspeed. The left wing separated from the DC-3, followed by the right wing about two seconds later. Parts of the A36's empennage were found between 3,590 and 4,910 feet from the main wreckage.
Aircraft and Control System Evidence
Examination revealed that during the impact, the elevator and rudder control cables of the DC-3 were severed. No preimpact mechanical anomalies were identified in either aircraft.
Meteorological Conditions
At 1445 central standard time, an AIRMET was issued forecasting light to moderate turbulence below 8,000 feet above mean sea level.
Toxicology
Toxicology tests on the DC-3 copilot's blood detected 0.127 micrograms per milliliter of amitriptyline, a prescription antidepressant with sedative side effects; 0.039 micrograms per milliliter of nortriptyline, a metabolite of amitriptyline; and an undetermined amount of ephedrine and phenylpropanolamine, over-the-counter medications used in cold preparations, diet aids, and stimulants.
Probable Cause
The official probable cause was the failure of the Beech A36 pilot to maintain clearance from the modified Douglas DC-3 while positioning the A36 for photography of the DC-3.