ANC93FA152

The on-demand fishing/hunting charter air carrier pilot experienced a total loss of power and landed in a small lake. During the ground run following the emergency landing a oil-fed fire destroyed the acft. Investigators found inadequate flight following documentation, and fuel records or maintenance records for accident acft or operation. Passenger witnesses reported low fuel gauges prior to takeoff. Fuel pump examination indicated fuel starvation.

History of flight

On August 19, 1993, at approximately 1522 Alaska daylight time, a float equipped de Havilland DHC3 Otter, N321KA, operated by Ketchum Air Service of Anchorage, Alaska, experienced a non- mechanical loss of engine power during climb from Nikabuna Lake, near Iliamna, Alaska. The commercial pilot executed a forced landing on a small pond, and the airplane overran the water area into woodland and caught fire. The airplane was destroyed. The pilot and two passengers were uninjured, while three passengers received minor injuries. The flight had originated in Anchorage at approximately 0800 on a company VFR flight plan with multiple stops on a 14 CFR Part 135 on-demand flight to transport passengers and cargo between lakes and to Anchorage. Visual meteorological conditions existed.

The pilot told investigators that he had 100 gallons of fuel on board, 85 gallons in the centre tank and 15 gallons in the forward tank. Recalling that the engine lost power as he leveled into cruise flight below 1000 feet, above ground level (agl), he said that he "switched tanks to the forward tank and hit the boost pump when it quit, but (the engine) didn't start." The pilot then glided the airplane to a small tundra pond and attempted an emergency landing. The available water landing area was approximately 750 feet in length and the airplane overran the water and entered a wooded area, coming to rest approximately 350 feet from the water's edge.

A passenger, a U.S.A.F. mechanic in the right seat of the airplane, provided a statement that said the "fuel gauges read E" at the time of takeoff from Nickabuna Lake, approximately three minutes before power was lost. That passenger confirmed that the pilot attempted to restart the airplane by use of the electrical boost pump and the starter, but stated that he did not observe the pilot switch fuel tanks.

Witnesses told investigators that a "fire with red flames and black smoke, about 10 feet high lasted about a minute and then turned to white smoke and burned the plane. (See photographs taken by witness.)

Injuries to persons

Three of the five passengers reported minor injuries sustained in the impact with the terrain following the forced landing on the small lake.

Damage to aircraft

The aircraft fuselage was destroyed from the rear of the engine at the accessory section through the cockpit and cabin to the tail cone by being reduced to ashes by fire. While the accessories mounted on the rear of the engine, as well as the rear of the engine case itself, sustained substantial thermal damage, the front of the cylinders and the propeller was unremarkable. The tail cone and wings, while burned off at their respective junctions with the fuselage, were themselves undamaged. There was no evidence of hydrocarbon soot underneath the horizontal tail surfaces or wing surfaces.

Molten metal and thermal damage to aircraft frame structure was centered at the location of the 40 quart oil tank behind the pilot's seat. (Refer to Wreckage and Impact Information for details of damage to the aircraft.)

Aircraft information

The operator advised the investigators that the airplane had undergone a 100 hour inspection on August 9, 1993. An investigation of company records failed to locate certain inspection records for the 100 hour inspection, including the oil sample analysis sheet, or the engine cylinder compression sheet.

The company maintenance director told investigators that an oil sample was drawn and sent for analysis and an engine cylinder compression check was completed at that time. Mr. Craig Ketchum, a company owner, told investigators that an oil sample had been sent to Skywatch Oil Analysis Company following the 100 hour inspection of the engine. The president of Skywatch Oil Analysis Company was contacted and he told investigators that his company had not received an oil sample from the Ketchum company on or after August 9, 1993, nor did the Skywatch company have record of any other recent oil sample drawn from the accident airplane.

Investigators, in reviewing maintenance records for the accident airplane, found that six Airworthiness Directives (AD's) had not been completed on the accident airplane. These AD's required that inspections be performed since 1992 on airplane flight controls, propeller blades, engine cylinders and flight surface integrity.

Meteorological information

Witnesses indicated that visual meteorological conditions prevailed at the time of the accident. Photographs of the accident scene, taken by a pilot from the same operator, showed low stratus clouds of an undetermined height, and visibility of three to six miles.

Wreckage and impact information

Investigators measured parallel ground scars from west to east, beginning at the edge of a shallow lake, approximately 400 yards in diameter. The scars ended at the wreckage approximately 170 yards from the lake edge. Sixty feet from the wreckage, a rock outcropping found in the left continuous ground scar, was marked and scarred with paint and particles matching those on the left float.

The engine's carburetor had been exposed to thermal energy and was removed for examination.

The propeller was found without visible indication of rotation at impact. One blade of the three-bladed propeller had been thrust vertically into the tundra and the engine, which had been burned away at the firewall mountings, rested on that propeller blade. There was no evidence that the blade had been rotating when it penetrated the tundra. When that blade was withdrawn from the soil and vegetation, there were no scratches of a rotational origin.

The airplane's wings were intact except for a leading edge strike of approximately 6 inches in diameter, on the left wing near the tip. Both wings were drooped as they were burned off at the roots, however they remained aligned at right angles to the fuselage. Neither wing showed evidence of soot on the underside, nor was any scorching found. No soot was found under the horizontal stabilizers of the burned-off tail cone.

The right float showed no impact damage, however showed thermal damage to the inboard face. The right float showed impact damage to the front, misalignment to the diagonal and nearly total thermal destruction under the fuselage.

Witness interview information

The pilot stated, that prior to takeoff from Nikabuna Lake and total power loss shortly thereafter, he observed approximately 100 gallons of fuel indicated on the aircraft's fuel gauge indicator. He said that it was distributed roughly 85 gallons in the centre tank and 15 gallons in the forward tank.

See statements of witnesses attached.

Fire

No evidence of fuel or oil residue was found along the ground scar track, before or after the impact mark on the rock outcropping. No fire pattern, burned material or charring was found along the track. No fuel residue was found near or around, in any direction, of the aircraft hull. Scorching of bushes was found adjacent the left fuselage from the firewall location aft to the trailing edge of the left wing, out to approximately two feet.

Scorching of bushes and small trees was similar of the right side of the aircraft to a distance limited by the right float, which sustained thermal damage to its skin on the inboard side. The outboard skin of the right float was unremarkable. No flame pattern or scotching was visible beyond three feet in any direction.

Investigators found the left float diagonally under the fuselage and that float's mounting struts to be impaled into the fuselage underbelly. At the location of that impingement, centered at the location of the center under-belly and lube oil tank, a concentration thermal damage was found to have melted aircraft framework structure.

Investigators found the fuel tank selector switch in the debris of the cockpit. The selector switch was within the