Accident Description
The airplane collided with the ground during a low altitude, steep banked, base-to-final left turn toward the landing runway while executing a circling instrument approach. The impact occurred 1/3 mile from the approach end of runway 28, north of its extended centerline.
A witness located in the airport's administration building reported observing the aircraft in and out of clouds on a close base for runway 28. The witness saw the aircraft emerge from a cloud in a base-to-final turn at an estimated altitude of 300–400 feet above ground level. The left wing was observed nearly 90 degrees down, and the aircraft appeared north of the runway 28 centerline. The aircraft then pitched nose down approximately 30–40 degrees and appeared to perform a half cartwheel on the ground before exploding.
Weather and Approach
Air traffic control had cleared the airplane to perform a GPS-A (circling) approach. The published weather minimums for category C and D airplanes at the 5,900-foot mean sea level airport required 3 miles visibility, with a minimum descent altitude of 8,200 feet mean sea level.
Airport weather observers recorded that at the time of the accident, visibility ranged from 1 1/2 to 5 miles. Scattered clouds existed at 1,200 feet above ground level (7,100 feet msl), a broken ceiling at 1,500 feet agl (7,400 feet msl), and an overcast condition at 2,400 feet agl (8,300 feet msl).
During the approach, the first officer acknowledged to the controller that he had received the airport's weather. The airplane overflew the airport in a southerly direction, turned east, and entered a left downwind pattern toward runway 28. Surface winds were from 220 degrees at 20 to 30 knots, gusty. The pilot inadequately compensated for the wind during the base leg-to-final approach turning maneuver.
Flight Data and Findings
The airplane was equipped with Digital Electronic Engine Controls (DEEC) that recorded specific data bits including engine speed, power lever position, and time. The last 4 seconds of recorded data showed that both power levers were moved from a mid-range point to takeoff power, and the engines responded accordingly. No evidence of any preimpact mechanical malfunction was found.
The operator's flight training program emphasized that during approaches, consideration of wind drift is essential, and a circling approach should not be attempted in marginal conditions.