N - USA

The private pilot was continuing a cross-country flight after having stopped for fuel. About 20 minutes into the flight, the pilot said both engines started running rough, and he turned the airplane toward the nearest airport and descended. The pilot reported that he did not think the airplane would make it to the airport, and that due to the rugged terrain, he felt it was better to ditch the airplane in a large lake he was flying over. The pilot reported there were no mechanical anomalies prior to the loss of engine power. He said he felt that fuel contamination was the cause of the engine problem, and that not fueling during heavy rain might have prevented the problem. Fuel samples were taken from the fuel supply where he added fuel, and the equipment used to fuel the airplane. No other instances of fuel contamination were reported, and according to the FAA inspector the fuel samples were tested, and found to be clean. The airplane was not recovered from the lake, and has not been examined by the NTSB.

The first officer was flying the Area Navigation, Global Positioning System, approach to runway 22. During the approach, the airplane was initially fast as the first officer had increased engine power to compensate for wind conditions. Descending below the minimum descent altitude (MDA), the first officer momentarily deployed the speed brakes, but stowed them about 200 feet above ground level (agl), and reduced the engine power to flight idle. The airplane became low and slow, and developed an excessive sink rate. The airplane subsequently landed hard on runway 22, which drove the right main landing gear into the right wing, resulting in substantial damage to the right wing spar. The first officer reported intermittent airspeed fluctuations between his airspeed indicator and the captain's airspeed indicator; however, a subsequent check of the pitot-static system did not reveal any anomalies that would have precluded normal operation of the airspeed indicators. About the time of the accident, the recorded wind was from 190 degrees at 11 knots, gusting to 24 knots; and the captain believed that the airplane had encountered windshear near the MDA, with the flaps fully extended. Review of air traffic control data revealed that no windshear advisories were contained in the automated terminal information system broadcasts. Although the local controller provided windshear advisories to prior landing aircraft, he did not provide one to the accident aircraft. Review of the airplane flight manual (AFM) revealed that deploying the speed brakes below 500 feet agl, with the flaps in any position other than the retracted position, was prohibited.

According to the flight crew, they exited the clouds approximately 250 feet above ground level, slightly left of the runway centerline. The pilot not flying took control of the airplane and adjusted the course to the right. The airplane rolled hard to the right and when the pilot corrected to the left, the airplane rolled hard to the left. The airplane impacted the ground in a right wing low attitude, resulting in substantial damage. Further examination and testing revealed anomalies with the yaw damper and spoileron computer. According to the manufacturer, these anomalies would not have prevented control of the airplane. Greater control wheel displacement and force to achieve a desired roll rate when compared with an operative spoileron system would be required. The result would be a slightly higher workload for the pilot, particularly in turbulence or crosswind conditions. An examination of the remaining systems revealed no anomalies.

The airplane was loaded to within a few hundred pounds of its maximum gross takeoff weight, and departed from an airport located in a valley, surrounded by rising terrain. Although visual conditions prevailed at the accident airport, fog was present in the adjacent valleys. During the initial climb after takeoff, the right engine lost partial power due to a failure of the number one cylinder exhaust valve. The pilot secured the right engine; however, he was unable to maintain a climb with only the left engine producing power. The airplane was manufactured in 1964. Review of weight and performance data published at the time of manufacture, revealed that the airplane should have been able to climb about 400 feet-per-minute with a single engine producing power. No current weight and balance data was recovered, and due to impact and fire damage, the preimpact power output of the left engine could not be determined. Both engines were last overhauled slightly more than 12 years prior to the accident, and flown about 310 hours during that time. For the make and model engine, the manufacturer recommended overhaul at 1,200 hours of operation, or during the twelfth year.

The pilot was returning a group of skydivers to their home base after a weekend of skydiving. He flew several jump flights, and then stopped early in the afternoon to prepare the airplane for the flight home. The flight was planned into an area of clouds, turbulence, and icing, which the pilot had researched. He delayed the departure until he decided that he could complete the planned flight under visual flight rules (VFR). The accident occurred at night with little illumination of the moon, and the airplane was in an area of layered clouds. A detailed analysis of the weather conditions revealed that the flight probably encountered broken to overcast layers both below and above its flight altitude. The satellite and sounding images suggested that it was possibly in an area of mountain wave conditions, which can enhance icing. The recorded radar data indicated that the pilot was likely maneuvering to go around, above, or below rain showers or clouds while attempting to maintain VFR. The airplane likely entered clouds during the last 3 minutes of flight, and possibly icing and turbulence. It was turning when it departed from controlled flight, and a performance study showed that the angle-of-attack at this point in the flight was increasing rapidly. The study determined that the
departure from controlled flight was consistent with an aerodynamic stall. The unpressurized airplane was flying at over 14,000 feet mean sea level for more than 1 hour during the flight. It reached 15,000 feet just prior to the accident in sequential 360-degree turns while climbing and descending. Supplemental oxygen was not being used. At these altitudes, the pilot would be substantially impaired by hypoxia, but would have virtually no subjective symptoms, and would likely be unaware of his impairment. The pilot had logged over 2,000 hours of total flight time, with nearly 300 hours in this make and model of airplane. He was instrument rated, but had only logged a total of 2 hours of actual instrument flight time. Company policy was to fly under visual flight rules only, and they had not flight-checked the pilot for instrument flight.