WPR11FA166

The pilot's failure to maintain directional control of the airplane during a momentary interruption of power from the left engine during the initial takeoff climb. Contributing to the accident was the power interruption due to water contamination of the fuel, which was likely not drained from the fuel tanks by the pilot during preflight inspection as required in the POH.

Witnesses reported that the airplane's takeoff ground roll appeared to be normal. Shortly after the airplane lifted off, it stopped climbing and yawed to the left. Several witnesses heard abnormal sounds, which they attributed to propeller blade angle changes. The airplane's flight path deteriorated to a left skid and its airspeed began to slow. The airplane's left bank angle increased to between 45 and 90 degrees, and its nose dropped to a nearly vertical attitude. Just before impact, the airplane's bank angle and pitch began to flatten out. The airplane had turned left about 100 degrees when it impacted the ground about 1,500 feet from the midpoint of the 10,000-foot runway. A fire then erupted, which consumed the fuselage. Review of a security camera video of the takeoff revealed that the airplane was near the midpoint of the runway, about 140 feet above the ground, and at a groundspeed of about 130 knots when it began to yaw left. The left yaw coincided with the appearance, behind the airplane, of a dark grayish area that appeared to be smoke. A witness, who was an aviation mechanic with extensive experience working on airplanes of the same make and model as the accident airplane, reported hearing two loud "pops" about the time the smoke appeared, which he believed were generated by one of the engines intermittently relighting and extinguishing. Postaccident examination of the airframe, the engines, and the propellers did not identify any anomalies that would have precluded normal operation. Both engines and propellers sustained nearly symmetrical damage, indicating that the two engines were operating at similar low- to mid-range power settings at impact. The airplane's fuel system was comprised of two separate fuel systems (one for each engine) that consisted of multiple wing fuel tanks feeding into a nacelle tank and then to the engine. The left and right nacelle tanks were breached during the impact sequence and no fuel was found in either tank. Samples taken from the fuel truck, which supplied the airplane's fuel, tested negative for contamination. However, a fuels research engineer with the United States Air Force Fuels Engineering Research Laboratory stated that water contamination can result from condensation in the air cavity above a partially full fuel tank. Both diurnal temperature variations and the atmospheric pressure variations experienced with normal flight cycles can contribute to this type of condensation. He stated that the simplest preventive action is to drain the airplane's fuel tank sumps before every flight. There were six fuel drains on each wing that the Pilot's Operating Handbook (POH) for the airplane dictated should be drained before every flight. The investigation revealed that the pilot's previous employer, where he had acquired most of his King Air 200 flight experience, did not have its pilots drain the fuel tank sumps before every flight. Instead, maintenance personnel drained the sumps at some unknown interval. No witnesses were identified who observed the pilot conduct the preflight inspection of the airplane before the accident flight, and it could not be determined whether the pilot had drained the airplane's fuel tank sumps. He had been the only pilot of the airplane for its previous 40 flights. Because the airplane was not on a Part 135 certificate or a continuous maintenance program, it is unlikely that a mechanic was routinely draining the airplane's fuel sumps. The witness observations, video evidence, and the postaccident examination indicated that the left engine experienced a momentary power interruption during the takeoff initial climb, which was consistent with a power interruption resulting from water contamination of the left engine's fuel supply. It is likely that, during the takeoff rotation and initial climb, water present in the bottom of the left nacelle tank was drawn into the left engine. When the water flowed through the engine's fuel nozzles into the burner can, it momentarily extinguished the engine's fire. The engine then stopped producing power, and its propeller changed pitch, resulting in the propeller noises heard by witnesses. Subsequently, a mixture of water and fuel reached the nozzles and the engine intermittently relighted and extinguished, which produced the grayish smoke observed in the video and the "pop" noises heard by the mechanic witness. Finally, uncontaminated fuel flow was reestablished, and the engine resumed normal operation. About 5 months before the accident, the pilot successfully completed a 14 Code of Federal Regulations Part 135 pilot-in-command check flight in a King Air 90. However, no documentation was found indicating that he had ever received training in a full-motion King Air simulator. Although simulator training was not required, if the pilot had received this type of training, it is likely that he would have been better prepared to maintain directional control in response to the left yaw from asymmetrical power. Given that the airplane's airspeed was more than 40 knots above the minimum control speed of 86 knots when the left yaw began, the pilot should have been able to maintain directional control during the momentary power interruption. Although the airplane's estimated weight at the time of the accident was about 650 pounds over the maximum allowable gross takeoff weight of 12,500 pounds, the investigation determined that the additional weight would not have precluded the pilot from maintaining directional control of the airplane.

In mid-February 2012, an FAA inspector from the Long Beach Flight Standards District Office (FSDO) was giving a Part 135 check-ride to a line pilot employed by West Coast Charters, Santa Ana, California. The inspector noticed that, during the pilot's preflight of a King Air 200 airplane, he did not drain the airplane's fuel tank sumps. When he questioned the pilot about it, the pilot responded with "we [pilots] don't do that, the mechanics do that." The inspector pointed out to the pilot that the Pilot's Operating Handbook for the airplane requires that the King Air's 12 fuel tank sumps be drained during preflight before every flight. Follow-up communications between Long Beach FSDO inspectors and the Chief Pilot of West Coast Charters verified that this was standard practice. The DM for West Coast Maintenance said the King Air's fuel system has several tanks or cells, which feed the engine's nacelle inverted "L" shaped (57 gallon) fuel tank. He said maintenance personnel are required to open the nacelle tank every 24 months for inspection and cleaning. When this is done, it is common to find water, debris, and biomicrobial contaminants in the tank. He said the entire engine's fuel supply must flow to the bottom of this tank. The DM said that regular draining of the King Air's 12 fuel tank sumps would minimize the water and debris found in the nacelle tank upon inspection. The DM said that, during the accident airplane's departure, as the airplane rotated for takeoff, if water was present in the bottom of the nacelle tank, it would shift aft covering the fuel intake port to the engine. This "slug" of water would then flow to the engine's 14 fuel nozzles, where it could extinguish the engine's fire; the engine would stop producing power and its propeller would move from coarse to fine pitch. Subsequently, jet fuel would follow the water, and the engine's internal heat would likely be sufficient to relight the atomized fuel. The engines were equipped with auto ignition systems, and if they were in the on position, they may also have been triggered to relight the engine. The DM believes that the two pops he heard were attempts by the engine to relight the reintroduced fuel. He said that each pop would have been accompanied by grayish white smoke. The DM also said that water found in airplane fuel tanks does not necessarily come from contaminated fuel trucks. Airplane refueling trucks have stringent checks and documentation requirements of their filters and are subject to regular tank sump sampling. He believes that the biggest source of introduced water into fuel tanks is daily temperature variations and atmospheric temperature variations. That is, if a fuel tank is not completely full, there is a cavity of air above the fuel, and due to the tank's venting system, the air in that cavity will move in and out as daily temperature rise and fall, or as the airplane climbs to cruise altitude and descends at its destination. The United States Air Force has a fuels engineering research laboratory located at Wright-Patterson Air Force Base. One of their Senior Research Engineers stated that "the cavity above fuel in a partially filled fuel tank is vulnerable to aircraft fuel tank breathing through its vent system. This breathing of air, in-and-out, causes water to condense within the fuel tanks." He said that there are many variables which affect this phenomenon, including: diurnal temperature and pressure variations, flight altitude pressure variations, relative atmospheric humidity, fuel tank size and volume above the fuel, and fuel storage time. The senior engineer further stated that good housekeeping practices of an airplane's fuel source and regular draining of the fuel tank sumps is the simplest way to reduce the presence of water in aircraft fuel tanks. The FAA Advisory Circular number 20-43C, titled "Aircraft Fuel Control" states: "All aviation fuels absorb moisture from the air and contain water in both suspended particle and liquid form. The amount of suspended particles varies with the temperature of the fuel. Whenever the temperature of the fuel is decreased, some of the suspended particles are drawn out of the solution and slowly fall to the bottom of the tank. Whenever the temperature of the fuel increases, water is drawn from the atmosphere to maintain a saturated solution. Changes in fuel temperature, therefore, result in a continuous accumulation of water." "The presence of any contamination in fuel systems is dangerous. Laboratory and field tests have demonstrated that when water was introduced into the fuel tank, it immediately settled to the bottom. Fuel tanks are constructed with sumps to trap this water. It is practically impossible to drain all water from the tanks through the fuel lines, so it becomes necessary to regularly drain the fuel sumps in order to remove all water from the system." "If left undrained, the water accumulates and will pass through the fuel line to the engine and may cause the engine to stop operating." One of the airplane manufacturer's test pilots stated: "King Air fuel tanks must be drained before every flight, it seems like a little bit of water is always being drained off." The airplane was a twin engine, propeller-driven, eight seat, pressurized aircraft, which was manufactured in 1981 by Beech Aircraft Company. At the time of manufacture, the airplane was equipped with Pratt & Whitney Canada model PT6A-41 engines, each fitted with a Hartzell Propellers, Inc., three bladed propeller. Each engine was rated at a maximum takeoff rating of 850 shaft-horsepower. The airplane was later modified in accordance with Supplemental Type Certificates SA00433AT and SA2698NM-S, which installed Pratt & Whitney Canada model PT6A-42 turboprop engines, each fitted with a Hartzell Propellers, Inc., four bladed propeller. Each engine maintained the same maximum takeoff rating of 850 shaft-horsepower. The four-bladed Hartzell propellers were constant-speed, full-feathering, and reversible. They were manufactured in June 1999. The airplane was equipped with an automatic feathering system, which was designed for use during takeoff and landing, and should be turned off when the airplane is established in cruise climb. If the power output was reduced in either engine during takeoff, once the engine's torque dropped from 2,230 foot/pounds (ft/lbs) to about 220 ft/lbs, the propeller blades would move towards the feathered position. This system is operationally checked before every takeoff, as required in the Pilot's Operating Handbook, Before Takeoff (Run-up) checklist. The owner bought the airplane on August 12, 2009. It received its most recent annual inspection on August 9, 2010. According to airplane flight records, at the time of the accident, the airplane had flown 9,133 hours; the left engine had 5,695 total hours and 3,020 hours since its last overhaul; the right engine had 5,613 total hours and 3,325 hours since its last overhaul. The engine manufacturer recommends that the engines be overhauled every 3,000 flight hours. The propellers were installed about August 1999. The propeller manufacturer recommends that they be overhauled every 3,000 flight hours or every 6 years. The airplane's maintenance logbooks were not recovered, so an exact determination of the time on the propellers was not possible. The airplane's fuel system consisted of two separate fuel systems; one in each wing, and each feeding its respective engine via the nacelle (engine feed) tank. Each wing fuel system had a main fuel system composed of multiple interconnected fuel cells that gravity fed the 57-gallon capacity nacelle tank. Each wing had a 79-gallon capacity auxiliary fuel tank located inboard of the engine nacelle, which, if fueled would automatically feed the nacelle tank. Each wing fuel system, including the nacelle tank, had a total fuel capacity of 193 gallons, or a total fuel capacity of 272 gallons per wi