Alaska

The float equipped airplane was attempting to cross a mountain pass, following two other company airplanes. The first two pilots, and passengers, described five to seven miles visibility, 700 feet ceilings, clouds hanging on the mountainsides, and misty rain. The route of flight required several turns in the pass. The pilot had not flown through the pass in marginal Visual Flight Rules (VFR) weather before this flight. After the first two airplanes went through the pass, they lost radio contact with the accident pilot, and did not see or hear from him again. The wreckage was later located at the head of an intersecting canyon, two miles before the correct pass. The airplane had been modified with a Short Take Off and Landing (STOL) kit. Canadian certification flight tests had determined that this modification eliminated aerodynamic warning of impending stalls, and therefore required an audible stall warning. Company pilots indicated it was common for the stall warning system to activate at an airspeed 10-15 miles per hour above the actual stall. At the time of the accident, the airplane did not have the ventral fin installed, and a takeoff flaps setting was selected. The audible stall warning circuit breaker was found in the pulled (disabled) position.

The pilot departed from an intersection 2,100 feet from the approach end of the 6,700 feet long runway. Immediately after takeoff the right engine failed. The pilot told the NTSB investigator-in-charge that he feathered the right propeller, and began a wide right turn away from terrain in an attempt to return to the airport. He stated the airspeed did not reach 90 knots, the airspeed and altitude slowly decayed, and the airplane was ditched into smooth water. After recovery, the cowl flaps were found in the 50% open position. No anomalies were found with the fuel system. The airplane departed with full fuel tanks, at a takeoff weight estimated at 6,606 pounds. The right engine was disassembled and no mechanical anomalies were noted. The best single engine rate of climb airspeed is 106 knots, based on cowl flaps closed, and a five degree bank into the operating engine.

The commercial pilot departed under special VFR conditions on a CFR part 135 flight for a remote lake. During the flight, low clouds, rain, and fog were present in an area of mountainous terrain along the route of flight. The pilot stated that he intended to utilize a narrow mountain pass to transit the area, and as he entered the mountain pass, discovered that the ceiling and visibility would not allow safe passage. He said that he made an emergency 180 degree turn in an attempt to exit the pass, and subsequently collided with terrain. After initial impact, the airplane slid downhill about 100 feet, and came to rest on a 35 degree slope. The pilot stated that weather conditions at the time of the accident consisted of: Ceiling, 500 foot overcast; visibility, 2 miles with rain and fog; wind 360 degrees, at 8 knots. The pilot noted that there were no pre accident anomalies with the airplane.

The flight departed Anchorage, Alaska, and was en route to Saint George, Alaska, to pick up passengers for a return flight to Anchorage. The pilot-in-command (PIC) was seated in the right seat, and the copilot was seated in the left seat. This was the copilot's third flight in this make and model airplane, and he was not qualified as a crewman in it under 14 CFR Part 135. There was no record of when the copilot last performed a non directional beacon (NDB) approach. The NDB indicator in the cockpit was on the left side of the left control column, partially blocked from the view of the PIC. The minimum altitude for the segment of the approach prior to the final approach fix (FAF) was 1,700 feet. The Minimum Descent Altitude (MDA) for the final segment of the approach was 880 feet. The reported ceiling was 100 feet overcast. The Air Route Traffic Control Center radar altitude readout for the airplane revealed that the airplane descended below 600 feet prior to reaching the FAF. The radar ground track revealed the airplane on course prior to the course reversal procedure turn on the published approach. The radar ground track showed that after the course reversal, the airplane continued through the published final approach course, and turned to parallel the inbound track three miles north of course. The radar plot terminates about the location of the 550 feet high cliffs where the airplane was located. Weather at the time of the accident was reported as 100 foot overcast. This location was 5.5 miles (DME) from the airport. A review of radar tapes from the day prior to the accident, show the same airplane and PIC tracking the published course outbound and inbound, and descending below the published approach minima to below 500 feet. This flight successfully landed at the airport. An interview with the copilot from the successful flight revealed that the PIC intentionally descended to 300 feet on the approach until he acquired visual contact with the ocean, then flew to the airport to land. An aircraft flying on the published inbound final approach course at 5.5 DME is over water, approximately three miles from the nearest terrain.

The captain/operator, the first officer and one passenger, departed on a cross-country positioning flight. The airplane contained about 300 gallons of fuel. After 3.9 hours en route, the flight was cleared for a visual approach to the destination airport. During the approach, both engines lost power about 2,000 feet mean sea level. The pilot stated the right fuel tank was empty. He estimated that 50 to 60 gallons of fuel remained in the left fuel tank. While the airplane was descending toward an area of open water, he attempted to restart the engines without success. He then lowered the landing gear, and made a right turn toward a small airstrip, located about 5 miles northwest of the destination airport. The airplane touched down in an area of soft, marsh covered, terrain. During the landing roll, the airplane nosed down and received damage to the forward, lower portion of the fuselage. An inspection of the airplane by an FAA inspector revealed the left fuel tank contained about 1 inch of fuel. The right fuel selector was positioned on the right auxiliary fuel tank. The left fuel selector was positioned between the left main, and the left auxiliary fuel tanks.

The certificated commercial pilot was departing on a 14 CFR 135 cargo flight. The airplane lifted off and climbed to about 200 feet. Instead of turning right toward the intended destination, the airplane began a left turn toward the runway. The angle of bank increased to about 45 degrees. The airplane then nosed down, and descended into snow covered terrain, about 200 yards north of the runway. Examination of the engine revealed the number six cylinder head was fractured, and slightly separated from the cylinder barrel. The area around the point of separation was blackened and oily. Similar discoloration was noted on the inside of the engine cowl. A metallurgical examination of the cylinder head revealed a fatigue fracture along a large segment of the thread root radius between the 5th and 6th threads. The engine's cylinder compression is part of the operator's approved airworthiness inspection program. The number six cylinder compression, recorded 121 hours before the accident, was noted as 60 PSI. The last engine inspection, 27 hours before the accident, did not include a record of the engine compression.

The pilot departed in visual meteorological conditions of three to four miles visibility with high ceilings. He stated the airplane encountered freezing rain about five miles south of the airport while in cruise flight at 1,200 feet msl, and rapidly accumulated ice on the airframe, wings, and windshield. The pilot said he initially changed altitude in an attempt to exit the icing conditions. Ice accumulation continued, so he elected to return. While maneuvering to land at the airport, the airplane was unable to maintain altitude at full engine power. He said that any angle of bank resulted in the onset of pre stall buffet, so he decided to land on a frozen lake south of the airport. He said that the airplane did not reach the lake, 'mushed into the ground,' and during the flare/touchdown, the left wing stalled. The pilot did not have access to the official weather prior to departure. The National Weather Service contracted observer, made his observation from a location about five miles south of the official weather station at the airport. The FAA AWOS-3 was inoperative. Examination of the airplane after the accident revealed a 1/2 inch layer of clear ice covering all the upper and lower airfoil surfaces of the airplane, from leading edges to between 1/3 and 1/2 of the chords. All antennas were coated with approximately 1/2 inch of clear ice. The airplane was not equipped with ice protection equipment except for pitot heat and windshield heat.

During the takeoff roll, while passing 45 knots indicated airspeed, ice formed between the inner and outer panes of the airplane's windshield, obscuring the crew's vision. The flight crew aborted the takeoff, the airplane drifted off the left side of the snow covered runway, and caught fire. The crew reported the airplane and windshield were cold soaked and the temperature was -10 degrees Fahrenheit. The windshield anti-ice system blows air from a combustion heater between the windshield glass panes. The air source for the heater, once the airplane has forward airspeed, is two leading edge wing scoops. The crew told the NTSB investigator that the taxi time was too short for the windshield to warm up, and that during the taxi, snow was circulated around the airplane and into the wing scoops.

The pilot, who was also the station manager, arrived at the airport earlier than other company employees to prepare for a scheduled commuter flight, transporting seven passengers and cargo to another village during hours of arctic, predawn darkness. Heavy frost was described on vehicles and airplanes the morning of the accident, and the lineman who serviced the airplane described a thin glaze of ice on the upper surface of the left wing. The pilot was not observed deicing the airplane prior to flight, and was described by the other employees as in a hurry to depart on time. The pilot directed the lineman to place fuel in the left wing only, which resulted in a fuel imbalance between 450 and 991 pounds (left wing heavy). The first turn after takeoff was into the heavy left wing. The airplane was observed climbing past the end of the runway, and descending vertically into the water. No preimpact mechanical anomalies were found with the airplane or powerplant. The aileron trim indicator was found in the full right wing down position. Postaccident flight tests with left wing heavy lateral fuel imbalances, disclosed that approximately one-half of right wing down aileron control deflection was used to maintain level flight, thus leaving only one-half right wing down aileron control efficacy. Research has shown that frost on airfoils can result in reduced stall angles of attack (often below that required to activate stall warning devices), increases in stall speeds between 20% and 40%, asymmetric stalls resulting in large rolling moments, and differing stall angles of attack for wings with upward and downward deflected ailerons (as when recovering from turns).

The float equipped airplane was observed taking off in light winds and calm water, and obtaining a steep climb and nose high attitude. Witnesses described hearing no reduction of engine noise from takeoff power to climb power. The airplane entered a steep left bank about 200 feet above the water, then rolled rapidly to the right and impacted at a steep angle into the water. The airplane had been modified with a Short Take Off and Landing (STOL) kit. Certification flight tests had determined that this modification eliminated aerodynamic warning of impending stalls, and therefore required an audible stall warning. Test results also required the addition of both a ventral fin, and horizontal stabilizer finlets, to meet directional stability certification. These tests determined that the least stable condition was in the takeoff flap configuration, during climb. The Supplemental Type Certificate (STC) for the modification required the ventral fin, and an audible stall warning system be installed. The manufacturer provided a marketing video, produced prior to the STC approval, which stated the stall warning system was not required in the U.S. The company indicated this tape was used for training, and was a basis for pilots routinely disabling the stall warning horn by pulling the circuit breaker. At the time of the accident, the airplane did not have the ventral fin installed, a takeoff flaps setting was selected, and the audible stall warning circuit breaker was in the pulled (disabled) position. The local FAA Flight Standards Office had inspected the accident airplane 14 times in the previous 29 months, and made no mention of the ventral fin not being installed.