West Caldwell, NJ, USA
N63TV
CESSNA T206H
The commercial pilot was departing in the turbocharged airplane to go to another airport and pick up the owner of the airplane. He contacted the air traffic control tower and received instructions from the controller to taxi to the active runway and hold short. The airplane taxied to the designated location and remained there for about 5 minutes. During this time, a student pilot heard the airplane's engine cycle from near idle to full power about five times and reported that the engine did not "sound right." The pilot requested and received clearance to takeoff, and, shortly after becoming airborne, advised that he had a "problem," declared an emergency, and requested to "return to the field immediately." The controller cleared the pilot to land on any runway, and the pilot reported that he was unable to maintain engine power. There were no other communications from the airplane. Review of security camera video revealed that the airplane was slow to accelerate and did not rotate until about 1,800 ft down the 4,552-foot-long runway from the point where the pilot initiated the takeoff roll. Once airborne, the airplane began to pitch slightly up and down while remaining in ground effect. Considering that the pilot was the only occupant of the six-seat airplane, the airplane should have become airborne much sooner. Further, there was adequate runway remaining at the point of rotation for the pilot to abort the takeoff and stop on the remaining runway. However, the pilot elected to continue the takeoff. The airplane climbed slowly, momentarily reaching an altitude that was just above the trees that surrounded the airport, then began to lose altitude, and turned left about 90°. The airplane then disappeared from view of the camera, and a smoke cloud was observed to rise from behind a tree line. Witnesses who observed the airplane just before impact saw the airplane gliding toward the ground "in slow motion" and heard no noise coming from the airplane. The witnesses reported that the airplane then rolled into a steep left bank, entered a nose dive, and exploded when it hit the ground. The witness observations were consistent with the pilot failing to maintain adequate airspeed, resulting in the airplane exceeding its critical angle of attack and an aerodynamic stall. Examination of the wreckage revealed signatures indicating that the propeller and the turbocharger's turbine wheel were not rotating during the impact sequence, which is indicative of a loss of engine power. The spark plug electrodes displayed evidence of black sooty deposits indicative of carbon fouling. The carbon fouling could have been the result of failure of the turbocharging system, which can result in an overly rich mixture condition so severe as to cause a total power failure. Examination of the turbocharging system revealed that it had been heavily damaged by the postcrash fire, and only the turbocharger and wastegate were recovered. Examination of the turbocharger revealed that the turbine and compressor wheels, which were interconnected by a shaft, could not be rotated by hand as the shaft had partially fused to the bearings likely as a result of exposure to the postcrash fire. The bearing radial holes were clear, and there were no excessive or abnormal scoring marks on the bearings as would be expected if they were contaminated, distressed, or subject to prolonged oil starvation. There was also no coking of oil in the turbocharger body that would have prevented lubrication of the bearings, and no definitive rotational rub marks that would have suggested excessive bearing wear or imbalance. Examination of the wastegate also did not reveal any anomalies, and the wastegate valve was free and could move through its full range of motion. The wastegate actuator body had been mostly consumed by the postcrash fire; only the valve housing assembly, actuator shaft assembly, springs, and retainer remained. X-ray examination of the oil supply line check valve, which was located upstream from the turbocharger and regulated the supply of oil that it received, showed that instead of being straight, the internal spring was slightly cocked about 5°. Review of the manufacturer's specifications revealed that no check valve leakage was allowed below 8 psi of oil pressure. However, flow testing of the check valve revealed that oil leaked from the check valve exit hole before 1 psi of pressure was reached, which indicated that the check valve was likely not preventing oil from draining into the turbocharger after shutdown and was pooling in the turbocharger body. During further examination of the check valve using computed tomography scanning and radiography, a small gap was found between the ball and the internal channel along the neck. Sectioning of the check valve revealed that the angled spring and the small gap between the ball and the internal channel were due to the presence of contamination in the internal channel on the upstream (inlet) side of the check valve and the presence of foreign material between the ball and the internal channel along the neck. The presence of contamination in the check valve indicated that contamination was likely present in other components of the turbocharging system. Because the controller and the wastegate use engine oil and pressure for operation and control of the turbocharger, if either one is contaminated, system performance can be compromised. Maintenance records indicated that two repairs requiring replacement of major components of the engine took place about 2 years before the accident. The first repair occurred following a report by the owner of high oil consumption, and it entailed replacing a cracked air/oil separator, leaking oil dipstick gaskets, a leaking fitting on the turbocharger wastegate actuator, and the turbocharger "due to oil leaking past shaft seal intake system." The second repair occurred about 4 months later, when the owner again reported high oil consumption. This resulted in replacement of the Nos. 3, 5, and 6 cylinders because the oil control rings stuck in the pistons of these cylinders, which indicated debris had been deposited in the ring grooves. Although these repairs provided evidence that suggested the oil system was contaminated, the maintenance records did not show that any reused oil lines, the turbocharger oil supply line check valve, or turbocharger system components such as the controller and wastegate were flushed. Further, review of the engine manufacturer's guidance revealed that it did not include instructions for checking or replacing the check valve during inspections, flushing of any reused oil lines, the check valve, and components such as the turbocharger, controller, and wastegate whenever a turbocharger leak was detected, following an engine test run after cylinder replacement, after replacing lubrication system components, or when doing any type of maintenance where contamination or foreign debris could be introduced into the system. If the engine manufacturer had included these instructions and the mechanics had performed actions such as flushing the check valve and turbocharger system components following either of the two engine repairs, it is likely the contamination found in the check valve (and likely present in other components of the turbocharging system) would have been removed. The presence of contamination in the check valve, the airplane's maintenance history, and the carbon fouling of the spark plugs, strongly suggest that the engine lost power due to contaminated oil compromising the performance of the turbocharger system. The National Transportation Safety Board asked the Federal Aviation Administration in 2008 to require manufacturers to amend their pilot operating handbooks (POHs) to include emergency procedures for turbocharger failures (Safety Recommendation A-08-21). However, the FAA did not take this action, and review of the POH for the airplane revealed that it did not include an emergency procedure for turbocharger failure. Under the emergency procedure for an engine failure, the POH called for advancing the mixture control to the rich position if restart does not occur, but review of the airplane manufacturer's supplementary information revealed that a failure of the turbocharger system would cause either an overboost condition or some degree of power loss and that, if a turbocharger system failure resulted in power loss, it may be further complicated by an overly rich mixture. According to the supplementary information, this rich mixture condition may be so severe as to cause a total power failure. It could not be determined whether the total loss of engine power in this case was due solely to failure of the turbocharger system or whether it was the result of a partial loss of power due to failure of the turbocharger system that was exacerbated by an overly rich mixture.
HISTORY OF FLIGHTOn August 15, 2015, at 1002 eastern daylight time, a Cessna T206H, N63TV, impacted trees and terrain after a loss of engine power during initial climb at Essex County Airport (CDW), Caldwell, New Jersey. The commercial pilot was fatally injured, and the airplane was destroyed. The airplane was registered to Stalactite, LLC, and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the positioning flight, destined for Teterboro Airport (TEB), Teterboro, New Jersey. According to a friend of the pilot, the pilot planned to fly to TEB, pick up the owner of the airplane and fly with him to South Hampton, where the owner had a residence. The friend owned a Cessna 182 and was interested in purchasing a Cessna 206 like the one the pilot was flying, so the pilot invited him to come to CDW before the flight and see the airplane. The friend arrived at the airport about 0930 and noticed that the pilot had already completed the preflight inspection of the airplane. The pilot appeared to be "fine, his usual self, and doing good that morning," The pilot's friend was in the fixed base operator's (FBO) lobby when he heard the airplane's engine start. The airplane stayed on the ramp for a few minutes and then taxied out. About 10 minutes later, the pilot's friend saw the airplane as it passed by a window in the FBO. The airplane seemed quieter than it should have to him, and he thought that it did not seem to be moving very fast. About 10 minutes later, a line service agent entered the FBO and said that there had been an airplane accident. According to information provided by the Federal Aviation Administration (FAA), the pilot contacted the CDW air traffic control tower, requested to taxi, and advised the controller that he had the current weather that was being transmitted by CDW's automatic terminal information service. The controller subsequently instructed the pilot to taxi to runway 22 and to hold short of the runway at intersection "November," which was normally used for airplanes departing on runway 22. The airplane taxied to the designated location and remained there for about 5 minutes. According to FAA inspectors, during the time that the airplane remained stationary, a student pilot heard the airplane's engine go from near idle to full power about five times and reported that the engine did not "sound right." The air traffic controller cleared the pilot for takeoff with a left turnout. Shortly after becoming airborne, the pilot advised that he had a "problem," declared an emergency, and requested to "return to the field immediately." The controller cleared the pilot to land on any runway, and the pilot reported that he was unable to maintain engine power. There were no other communications from the pilot. Review of security camera video revealed that, during the takeoff, the airplane appeared to accelerate slowly and rotated about 1,800 ft. after the pilot initiated the takeoff roll." Once airborne, the airplane began to pitch slightly up and down while remaining in ground effect and then slowly climbed. The airplane momentarily reached an altitude that was just above the trees that surrounded the airport, then began to lose altitude, and turned left about 90°. The airplane disappeared from view of the camera, and a smoke cloud then rose from behind a tree line. According to witnesses who saw the airplane just before impact, the airplane was at the same height as the trees and appeared to be gliding toward the ground. One witness stated that the airplane appeared to be "in slow motion;" it then banked sharply to the left and pitched steeply down. Another witness reported that the airplane made "a hard-left turn, went into a nose dive, and exploded when it hit the ground." Three additional witnesses reported similar observations. The witnesses heard no noise coming from the airplane before the impact. PERSONNEL INFORMATIONAccording to FAA and pilot records, the pilot held a commercial pilot certificate with ratings for airplane single-engine land and instrument airplane, a flight instructor certificate with a rating for airplane single-engine, and a ground instructor certificate with an advanced ground instructor rating. His most recent FAA third-class medical certificate was issued on March 30, 2015. He had accrued about 1,941 total hours of flight experience, 16 hours of which were in the accident airplane make and model. AIRCRAFT INFORMATIONThe airplane was a 6-place, single-engine, high-wing monoplane of conventional metal construction. It was equipped with fixed-tricycle-type landing gear and was powered by a turbocharged, 310-horsepower, Lycoming TIO-540-AJ1A engine, driving a three-blade, McCauley, controllable pitch propeller. According to FAA and maintenance records, the airplane was manufactured in 2009. Its most recent annual inspection was completed on April 17, 2015. At the time of the inspection, the airplane and engine had accrued 1,155.4 total hours of operation. According to the maintenance provider who had maintained the airplane since December 2011, anything that bothered the owner about the airplane would get fixed. Most of the items that were addressed by the maintenance provider were cosmetic or routine maintenance, such as oil and filter changes, gauges, starter replacement, lights, accessories, battery replacement, and compliance with airworthiness directives and service bulletins. The maintenance provider reported that the owner's landings could be a little rough, so they had also replaced some tires as he had experienced a few flat tires, and, as a result, the owner would keep a spare set in the airplane in case he blew a tire on landing. Review of maintenance records revealed that the airplane's engine had been receiving regular oil changes since new as well as spectrometric oil analysis. Review of oil analysis reports provided by the maintenance repair organization indicated that a sample of the engine's oil that was taken on March 5, 2012, contained elevated levels of iron, nickel and chromium. Another sample taken on December 19, 2013, contained elevated levels of aluminum, chromium, iron, and nickel. In a report dated March 9, 2015, the laboratory commented about an oil sample that had been taken on March 4, 2015, stating that: "These numbers are a lot easier to take than the high aluminum, chrome, iron, and nickel we saw last time. The shorter oil run obviously helped, but most of the metals are lower on a ppm/hour basis too, meaning that the engine really did wear better. If anything, nickel could still stand to be lower. 13 ppm is almost high enough to get a mark, so that's one we'll be monitoring next time. There's a trace of fuel to report this time, but that's not anything to worry about. It's likely just from normal use. Much better at 1,151.6 hours S[ince ]New." In a report dated August 12, 2015, for an oil sample that was taken on August 4, 2015 (11 days before the accident), the laboratory commented that: "Steady as she goes for this sample out of N63TV. If we're being picky you could say that iron should have come down as a result of the shorter oil run, but 39 ppm isn't bad at all for one of these engines after 20 hours on the oil. Everything else is in good shape, so we'd be surprised if the extra iron on a per-hour basis turned out to be an issue. No problems with the oil itself were found, making for a very nice report overall." Maintenance records indicated that two repairs requiring replacement of major components of the engine had been accomplished. The first repair followed a report from the owner that the engine was experiencing high oil consumption. According to a maintenance entry dated January 21, 2013, and the associated work order, this resulted in the maintenance provider inspecting for the cause of the oil leaks by first washing down the engine, and then after a test flight, tightening loose rocker box return line coupling clamps, replacing a cracked air/oil separator, replacing leaking oil dipstick gaskets, and replacing a leaking fitting on the turbocharger wastegate actuator. During this inspection and maintenance action, maintenance personnel noticed oil on the inlet scroll of the turbocharger and oil on the belly of the airplane, so they replaced the turbocharger "due to oil leaking past shaft seal intake system." The second repair occurred about 4 months later, when the owner again reported high oil consumption. According to a maintenance entry dated May 22, 2013, and the associated work order, this resulted in the maintenance provider checking the compressions and borescoping the cylinders. During this inspection and maintenance action, maintenance personnel found pooled oil in the Nos.3, 5, and 6 cylinders. Per guidance from a Lycoming representative, they attached an airspeed indicator to a modified oil dipstick cap and then ran the engine. No excessive crankcase pressure was found. Next, they ran the engine to get the temperature up and shut down the engine at 1,300 rpm. Then they borescoped the cylinders again and found that all of the pistons were damp, all of the spark plugs were dry, and there was pooled oil in the Nos. 3, 5, and 6 cylinders. After these tests, maintenance personnel removed the Nos. 3, 5, and 6 cylinders and found the oil control rings stuck in the pistons. They installed new Nos. 3, 5, and 6, cylinder assemblies. The maintenance records did not indicate that the check valve on the turbocharger oil supply line was cleaned or replaced following either of these engine repairs. Turbocharger System Information The airplane was equipped with a turbocharging system manufactured by Hartzell Engine Technologies (HET) that forced air into the engine's combustion chamber, allowing the engine to maintain sea-level manifold pressure as altitude increased. The turbocharging system consisted of a turbocharger, controller, wastegate, and pressure relief valve. The turbocharger converted wasted energy, in the form of hot exhaust gases from the engine exhaust, into increased manifold pressure to increase power available from the engine. After air and fuel were burned in the cylinders, the exhaust gases from combustion were used to spin a turbine wheel at high speeds. The turbine wheel was connected to a compressor wheel that compressed induction air supplied through an opening in the lower cowl, that was ducted through a filter and into the compressor, increasing its density. The pressurized induction air would then pass through the throttle body and induction manifold into the engine cylinders, completing the cycle. The controller sensed manifold pressure to maintain sea level horsepower at altitude, without over-speeding the turbocharger or over-boosting the aircraft's engine. It did this by controlling pressurized engine oil to hydraulically actuate the wastegate. The wastegate (exhaust bypass valve), used speed or compressor discharge pressure (boost) during certain conditions of a flight. Managed through the controller, the wastegate opened to allow exhaust gas to bypass the turbocharger, limiting speed and boost. The pressure relief valve acted as a supplementary safety device in the airplane turbocharger system. The valve was set to open at a pressure slightly above the maximum turbocharger discharge pressure, should the controller or wastegate not adequately limit the boost pressure. According to HET, the turbocharger operates at speeds over 100,000 rpm and at temperatures exceeding 1,650ºF, and oil is required at the correct flow rate and pressure to lubricate the bearings, stabilize the rotating shaft and bearings, and act as a coolant. The system's lubricating oil comes directly from the engine's oil system, so shutting down the engine immediately stops the flow of oil to the turbocharger. If the turbocharger is still turning at a high rate of speed when oil flow is cut off, the turbocharger bearings can be damaged. In addition, any stagnant oil remaining around the extremely hot turbine shaft will overheat and "coke" or burn. The controller and the wastegate also use engine oil and pressure for operation and control of the turbocharger. If either one is contaminated by oil, does not receive the correct oil flow rate, or lacks sufficient oil pressure to function, system performance is compromised. In the event of malfunction of a turbocharged engine, HETs experience is that maintenance personnel assume that the turbocharger is at fault and replace it. Frequently the replacement unit fails, which prompts an investigation into the real cause of the initial failure. According to HET, the major cause of turbocharger failures is faulty lubrication systems. The accident airplane was equipped with a check valve on the turbocharger oil supply line, which was located upstream from the turbocharger and regulated the supply of oil that it received. HET does not require the use of check valves, and the check valve installed on the airplane was supplied by the engine manufacturer. The check valve was used to prevent oil from draining into the turbocharger after shutdown and pooling in the turbocharger body. According to HET, this pooling can result in stagnant oil remaining around the extremally hot turbine shaft and coking or burning. Along with coking, bearing damage can occur that causes the bearings to orbit instead of spin, which can lead to turbine and/or compressor rub, wear, and failure. If a check valve sticks in an open or partially open position, this allows the turbocharger's center body to fill with oil; the oil then leaks past the seals because the oil cannot drain and is not being scavenged. The absence of turbo air pressure (both in the compressor and turbine housings) also does not assist in preventing oil leakage past the piston rings, which can result in the presence of oil in the compressor/induction system (evidence of oil in the combustion chambers) and/or the turbine/exhaust system (resulting in smoking during engine start). METEOROLOGICAL INFORMATIONThe recorded weather at CDW, at 1012, about 10 minutes after the accident, included: variable winds at 3 knots, 10 miles visibility, clear skies, temperature 28°C, dew point -17°C, and an altimeter setting of 30.13inches of mercury. AIRPORT INFORMATIONThe airplane was a 6-place, single-engine, high-wing monoplane of conventional metal construction. It was equipped with fixed-tricycle-type landing gear and was powered by a turbocharged, 310-horsepower, Lycoming TIO-540-AJ1A engine, driving a three-blade, McCauley, controllable pitch propeller. According to FAA and maintenance records, the airplane was manufactured in 2009. Its most recent annual inspection was completed on April 17, 2015. At the time of the inspection, the airplane and engine had accrued 1,155.4 total hours of operation. According to the maintenance provider who had maintained the airplane since December 2011, anything that bothered the owner about the airplane would get fixed. Most of the items that were addressed by the maintenance provider were cosmetic or routine maintenance, such as oil and filter changes, gauges, starter replacement, lights, accessories, battery replacement, and compliance with airworthiness directives and service bulletins. The maintenance provider reported that the owner's landings could be a little rough, so they had also replaced some tires as he had experienced a few flat tires, and, as a result, the owner would keep a spare set in the airplane in case he blew a tire on landing. Review of maintenance records revealed that the airplane's engine had been receiving regular oil changes since new as well as spectrometric oil analysis. Review of oil analysis reports provided by the maintenance repair organization indicated that a sample of the engine's oil that was taken on March 5, 2012, contained elevated levels of iron, nickel and chromium. Another sample taken on December 19, 2013, contained elevated levels of aluminum, chromium, iron, and nickel. In a report dated March 9, 2015, the laboratory commented about an oil sample that had been taken on March 4, 2015, stating that: "These numbers are a lot easier to take than the high alu
A loss of engine power due to a malfunction of the turbocharging system likely due to contaminated oil. Also causal were the pilot's decision to continue the takeoff although the airplane was not performing normally and his failure to maintain adequate airspeed following the loss of engine power, which resulted in the airplane exceeding its critical angle of attack and an aerodynamic stall. Contributing to the accident was the engine manufacturer's inadequate guidance regarding inspection and maintenance of its turbocharged engines.
Source: NTSB Aviation Accident Database
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