CHI94DTK01

The commercial pilot said he was flying aerial application swath runs and shortly after he changed the fuel selector from the right to the left tank the engine lost power. He turned on the fuel boost pump but the engine did not recover. He made a forced landing into a wooded area. Inspection of the fuel system disclosed no evidence of preimpact anomalies.

On May 24, 1994, at 0900 mountain daylight time, a Weatherly 620 airplane, N5296W, operated by West River Aerial of Timber Lake, South Dakota, sustained substantial damage when it collided with trees in the bottom of a ravine during a forced landing seven miles south of Ridgeview, SD. The commercial pilot sustained no injuries. Visual meteorological conditions prevailed for the aerial application flight conducted under CFR 14 Part 137. The flight originated at Timber Lake, SD at 0800 to provide aerial application of herbicides to fields in the area where the accident occurred. No flight plan was filed.

The pilot/owner reported that prior to departing he topped off all fuel tanks with 80 octane Avgas and auto fuel 50/50 mix and loaded the hopper with 120 gallons of herbicides.

After the pilot departed Timber Lake Airport he flew 16 miles southeast to where he said he sprayed three fields, 20, 40, and 56 acre fields, then switched from the right tank to left tank. The pilot said the right fuel tank indicator on the right wing was in the (low) red zone when he switched from the right to left tank. After switching tanks the pilot said he made one last pass then pulled up in a left turn (30-45 degree bank) when the engine coughed and lost power. He said he then turned on the fuel boost pump but never regained power. The pilot reported he immediately leveled the wings and lowered the nose of the airplane and felt the buffeting as he did it. He then continued descending down into a ravine to the southeast of the fields where the aircraft wheels touched the ground and then struck trees before coming to a stop. The pilot reported the accident occurred about 0900. He reported before leaving the aircraft he turned off the fuel selector valve, electric boost pump switch and master switch.

Examination revealed the right wing was torn off. The left wing tip was crushed and the left gear and spray booms were torn partially off. The hopper tank, right fuel tank, and center fuel tanks were ruptured and empty. The center fuel tank is interconnected with the left fuel tank. The left tank had approximately five gallons remaining.

The ground showed evidence of spillage from the ruptured fuel tank and hopper tank. The pilot reported having only about five gallons of herbicides mix remaining when the accident occurred. The fuselage was in a near level position. The propeller blades were bent aft from about the middle of the blades and outward. Post accident examination of the fuel system and engine revealed no contamination of the fuel system or preaccident defects to the fuel system or engine.

The right fuel tank capacity is 27.5 gallons with 25 gallons usable fuel. The left fuel tank combined with center tank capacity is 45 gallons with 40 gallons usable fuel. The Weatherly model 620 flight manual does not have a chart for fuel consumption or any information about the use of the fuel boost pump. The Weatherly model 620 maintenance manual description of the fuel boost pump specifies this pump is to be used in emergency situations for supplying fuel to the carburetor anytime the engine driven fuel pump is not operating. The Weatherly Aviation Company, Inc. states fuel consumption in cruise is 22-23 gallons per hour.

The fuel gauges on this airplane are about two inches in diameter and are located on the wings above the fuel tanks. This airplane also has low fuel warning lights on the instrument panel. The pilot stated he didn't notice the low warning light come on but said they are hard to see in bright daylight. However, he said they operated when he pushed to test.