United States of America

The pilot departed on a night multiple-leg flight series with full tanks. On approach for the second landing, the green landing gear lights extinguished. The pilot discovered that if the landing gear was extended the circuit breaker would stay in and if the landing gear was retracted the circuit breaker would pop. The circuit breaker controlled the landing gear lights, the engine oil pressure, and both fuel quantity gauges. The pilot continued on four additional flights in that condition. The fourth flight terminated 5 miles from the runway with a double power loss. Examination revealed the fuel tanks were empty. The pilot had flown the airplane 4.3 hours including 6 takeoffs, one missed approach, and a 20 minute ground run prior to departure with both engines running on the final flight.

The air tanker pilot was on a fire suppression mission with fire retardant chemicals aboard, and had made two previous drops on the fire line. Another tanker and spotter pilot witnessed the last drop approach, and reported that the pilot was turning from base leg to the westerly drop heading downwind while in a 60-degree left bank. The aircraft suddenly rolled left to 90 degrees, and at that point the left wing tip struck the terrain. The winds were estimated by the tanker pilots to be 25 to 30 mph with gusts to 40 plus from the east. The pilots also reported turbulence and bad air. Airmet Tango was issued for turbulence and isolated severe conditions mainly below 10,000 in the vicinity of canyons and passes.

While departing on a local area aircraft checkout flight the aircraft stayed low and the pilot advised the tower that he had a fuel problem. The aircraft had been fueled with aviation grade 100LL twice the day before in preparation for a trip. The pilot attempted to return to the airport, but collided with power lines 1.5 miles north. Examination of the engines revealed severe detonation had occurred. A fuel sample was obtained from the aircraft and tested negative for jet fuel contamination. The aircraft had been modified by installation of higher horsepower engines and turbochargers with manual wastegates. During postaccident examination of the aircraft systems the manual wastegates were found partially closed; a position that can provide additional manifold pressure. The engines are restricted to a maximum of 29.5 inHg.

For unknown reasons, the twin engine airplane belly landed at Myrtle Beach and was damaged beyond as a result. The pilot, sole on board, escaped uninjured.

After takeoff while over the departure end of the runway, deep gray colored smoke was observed by the tower controller trailing the right engine. The pilot was alerted of this and advised the controller the flight was returning. Witnesses reported seeing smoke trailing the right engine and that the airplane rolled to the left, pitched nose down, impacted trees, and then the ground. A fatigue crack was detected in the exhaust aft of the No. 6 cylinder of the right engine; and incomplete fusion of a weld repair was also noted. Heat damaged components from the right engine were replaced and the engine was started and found to operate normally. A foreign object of undetermined origin was found in the intake area of the No. 3 cylinder. Analysis of the voice tape revealed both engines/propellers were operating near full rated rpm when the pilot acknowledged the transmission that smoke was trailing the right engine, one engine/propeller rpm then decreased to about 2,160 rpm. Examination of the flight controls revealed no evidence of preimpact failure or malfunction. Flap positions at impact could not be determined. Calculations indicate that the airplane was approximately 55 pounds over the maximum certificated takeoff weight at takeoff.

The airline transport pilot departed on a CFR Part 135 cargo/mail flight for a remote coastal village. When the flight did not reach the destination, an aerial search was initiated. The wreckage was located the following day in mountainous terrain, 21 miles from the departure airport. The airplane had collided with rising terrain. An AIRMET for mountain obscuration in clouds and precipitation was issued for the pilot's planned route of flight. A pilot that departed about 20 minutes after the accident airplane's departure, had a similar route of flight. He characterized the weather conditions along the accident airplane's route as 'very low visibility with rain, fog and varied layers of cloud cover.' This pilot stated that he changed his route in order to avoid the worsening weather conditions. He added that with satisfactory weather conditions, and given the intended destination of the accident airplane, the standard route of flight would be directly over the mountain that the accident airplane collided with.

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 airplane was on an IFR flight plan, level at 16,000 feet, when radar and radio contact was lost. The tops of the clouds in the area of the accident were reported to be at 18,000 feet. A pilot who was flying in the area of the accident site at the time of the accident stated that the cloud tops of 'the buildups' were from 16,000 to 20,000 feet. The pilot additionally stated that moderate unexpected turbulence was encountered and 'Obviously, the updrafts in the area were very strong.' Satellite imagery data revealed that an east-west cloud band, about 10 miles wide, was located in the area of the accident. The ground track of the airplane was traversing the cloud band during the minutes prior to and around the accident time. The onboard weather radar was found in the off position. According to Advisory Circular -00-6A, 'Do avoid by at least 20 miles any thunderstorm identified as severe or giving an intense radar echo. Do clear the top of a known or suspected severe thunderstorm by at least 1,000 feet altitude for each 10 knots of wind speed at the cloud top.' The airplanes calibrated airspeed (KCAS) was calculated at 141 knots, and the indicated airspeed (KIAS) was 139 knots. According to the POH, the maneuvering speed at gross weight was 135 KCAS and 133 KIAS.

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 airplane departed at night after maintenance was performed on the left engine. The pilot attempted to return to the airport and while on base leg struck the ground inverted and nose down. The left engine propeller was found feathered. On the left engine, the # 5 cylinder was off the engine and the # 5 piston with the connecting rod still attached were found nearby. Interviews revealed that during maintenance, the # 1,3,5,and 6 cylinders had been removed and reinstalled; however, the # 5 cylinder had not been tightened. Several people had worked on the airplane at various stages of the work. The maintenance facility did not have a system to pass down what had been accomplished, and the FAA did not require the tracking of work accomplished in other than 14 CFR Part 121, or 14 CFR Part 145 facilities.