Horseshoe Bay, TX, USA
N224TB
RAYTHEON AIRCRAFT COMPANY G36
About six weeks before the accident, the pilot aborted a takeoff when the airplane’s engine did not develop the expected manifold pressure required for takeoff. After the aborted takeoff, the pilot completed several engine runups to troubleshoot the engine issue. The fuel flow to the engine would suddenly decrease when the engine power was increased above 24 inches of manifold pressure. The pilot’s aviation mechanic was unable to replicate the engine issue on two subsequent occasions. On the day of the accident, the pilot completed an uneventful before-takeoff engine runup. The airplane then had a loss of engine power during the takeoff run when the pilot increased the engine power to about 25 inches of manifold pressure. The pilot immediately reduced engine throttle, and the engine resumed normal operation at a lower manifold pressure. The pilot aborted the takeoff, taxied off the runway, and attempted to troubleshoot the engine issue. However, he was unable to replicate the engine issue during a subsequent engine run-up, during which the engine ran normally at 28 inches of manifold pressure. He also verified proper operation of the fuel selector, magnetos, battery and alternator, engine-driven fuel pump, auxiliary fuel pump, and mixture control. The pilot decided that he would fly the airplane to another location where it could be further examined by his aviation mechanic. The pilot selected 30 inches of manifold pressure and 33 gallons per hour (gph) for the takeoff, but the engine power decreased to 25 inches of manifold pressure and 12 gph at some point during the takeoff roll. The pilot stated that he believed the airplane would have departed the end of the runway if he had aborted the takeoff and that, despite the partial loss of engine power, he thought he could save the airplane by continuing the takeoff. The pilot was unable to restore full engine power and a forced landing was completed to a nearby highway. The airplane was subsequently destroyed by a postimpact fire. A mobile phone video showed the airplane began its takeoff roll about 175 ft from the start of the runway. The airport manager reported that the airplane did not appear to accelerate normally during the takeoff roll. Video of the takeoff showed the airplane became airborne about 3,560 ft down the runway from where it started its takeoff roll. Takeoff performance calculations determined that about 1,250 ft of the 5,977 ft-long asphalt runway was required for a normal takeoff at maximum gross weight and with the wing flaps retracted. Based on the available information, the pilot was aware of the partial loss of engine power during the takeoff run and should have aborted the takeoff before liftoff, which required about 3 times the expected runway distance. After liftoff, the airplane was observed in a shallow climb before it rolled to the left and descended into trees and terrain. The airplane was subsequently destroyed during a postimpact fire. Postaccident examination of the engine and its accessories did not reveal any mechanical malfunction that would have resulted in a loss of engine power. However, the engine, fuel system, and turbo-normalizing components sustained extensive damage that precluded the additional testing required to determine why the engine lost power.
On May 28, 2015, about 1343 central daylight time, a Raytheon Aircraft Company G36 airplane, N224TB, was destroyed when it was involved in an accident near Horseshoe Bay Resort Airport (DZB), Horseshoe Bay, Texas. The pilot sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. About 6 weeks before the accident, the pilot aborted a takeoff at DZB when the airplane’s engine did not develop the expected manifold pressure required for takeoff. After the aborted takeoff, the pilot completed several engine runups to troubleshoot the engine issue. The pilot reported that the fuel flow to the engine would suddenly decrease when the engine power was increased above 24 inches of manifold pressure. The pilot verified proper operation of the fuel selector, mixture control, magnetos, and the auxiliary fuel pump, but he was unable to resolve the engine issue. The pilot contacted his aviation mechanic, located at Burnet Municipal Airport (BMQ), who traveled to DZB and examined the airplane the same day. The mechanic was unable to replicate the engine anomalies that the pilot had encountered earlier that day. On a subsequent day, the pilot flew the airplane to BMQ where the mechanic still could not replicate the reported engine issues. The pilot then flew the airplane back to DZB. On the day of the accident, the pilot completed an uneventful engine runup before he attempted a takeoff on runway 17 at DZB. The airplane had a partial loss of engine power during the takeoff run when the engine power was increased to about 25 inches of manifold pressure. The pilot immediately reduced engine throttle and the engine resumed normal operation at a lower manifold pressure. The pilot aborted the takeoff and taxied off the runway where he attempted to troubleshoot the engine issue. He was unable to replicate the engine issue during a subsequent engine runup, during which the engine ran normally at 28 inches of manifold pressure. He also verified proper operation of the fuel selector, magnetos, battery and alternator, engine driven fuel pump, auxiliary fuel pump, and mixture control. The pilot decided that he would fly the airplane to BMQ where his mechanic could further troubleshoot the engine issue. He intended to takeoff from runway 17 and then climb to 5,500 ft mean sea level while remaining over the airport before flying direct to BMQ (about 14 nautical miles). He selected 30 inches of manifold pressure and 33 gallons per hour for the takeoff. The engine power decreased to 25 inches of manifold pressure at some point during the takeoff, but the pilot elected to continue the takeoff because he felt committed at that point. He retracted the landing gear, adjusted the throttle position, and selected the auxiliary fuel pump switch to the low setting. After seeing no improvement in engine power, the pilot selected the auxiliary fuel pump to the high setting and the airplane had a total loss of engine power. He then returned the auxiliary fuel pump to either the low or off setting and the engine regained some power, but not enough to sustain a climb. The pilot attempted to establish best glide speed and entered a left turn toward a nearby highway where he intended to complete a forced landing; however, the airplane descended into trees while it was in the left turn and then impacted the highway. The pilot reported that the cockpit became engulfed in flames almost immediately after impact with the highway. The pilot did not recall if he repositioned the fuel selector to off or if he moved the throttle/mixture controls before he exited the airplane with serious injuries. When interviewed by Federal Aviation Administration (FAA) inspectors, the pilot was asked why he chose to continue the takeoff after the airplane experienced a partial loss of engine power. The pilot replied that he believed the airplane would have departed off the end of the runway if he had aborted the takeoff, and that despite the partial loss of engine power he thought he could save the airplane by continuing the takeoff. The pilot told the FAA inspectors that he had flown the airplane for at least a year, and that he was familiar with the engine’s turbo-normalizing system. The pilot postulated that perhaps the engine-driven fuel pump had malfunctioned, which had resulted in the loss of engine power. The pilot told the FAA inspectors that the airplane’s auxiliary fuel pump was initially turned off for the takeoff, but he repositioned the auxiliary fuel pump switch from off to the low setting while he attempted to restore engine power. When the engine operation did not improve, the pilot then briefly repositioned the auxiliary fuel pump switch to the high setting. The pilot further acknowledged to the FAA inspectors that he knew that the engine was not designed to operate with the auxiliary fuel pump on the high setting but noted that the fuel flow had decreased to about 12 gallons per hour when the engine lost power. On the day of the accident, the airport manager reported seeing the airplane abort a takeoff on runway 17 after it did not accelerate normally during the takeoff run. After the aborted takeoff, the airplane taxied to the north end of the airport for another takeoff attempt on runway 17. She recalled that the airplane did not come to a stop before it turned from the taxiway onto runway 17 where it immediately made another takeoff attempt. She reported that on the second takeoff attempt, the airplane did not appear to accelerate normally and that she became concerned when it was still on the runway after it passed the fixed base operator building that was located about midfield. She estimated that the airplane did not become airborne until at least 4,000 ft into the takeoff run. After liftoff, the airplane continued in a shallow climb before it rolled to the left and descended into trees and terrain. Two motorists, who were driving westbound on Highway 71, reported seeing the airplane descend in a left-wing-down attitude into trees and the roadway. After impact, the airplane caught fire and the pilot was observed to exit the right side of the airplane. One of the motorists assisted the pilot away from the airplane which had become fully engulfed in flames. A mobile phone video showed the airplane taxi onto the runway and start its takeoff roll about 175 ft from the runway threshold. Surveillance video showed the airplane lifted off the runway with about 2,242 ft of runway remaining, or about 3,560 ft from where it began the takeoff roll. At 1335, about 8 minutes before the accident, the DZB automated surface observing system reported the surface wind direction was 140° true at 9 knots with no gusts, and an outside temperature of 31° C. Moderate thunderstorm activity with lightning had been detected in the distant east thru the southeast; however, according to weather radar and video footage of the accident, there was no rain or thunderstorm activity at the airport when the accident occurred. According to takeoff performance data contained in the manufacturer’s Pilot Operating Handbook, the airplane operating at maximum gross weight with the wing flaps retracted and the reported wind direction/speed and temperature would require about 1,250 ft of runway to achieve liftoff and about 2,100 ft of runway to clear a 50 ft obstacle. According to airport data, the asphalt runway 17 at DZB was 5,977 ft long. Based on available information, the airplane was below maximum takeoff weight when the accident occurred. The airplane wreckage was recovered to a secured storage facility where it was examined. Most of the fuselage and the right wing had been destroyed during the postimpact fire. The left wing and empennage exhibited various levels of impact-related and fire damage. The fuel system could not be tested due to extensive fire damage. The fuel selector position could not be reliably determined due to fire damage. The fuel tank caps were installed on each wing fuel tank. The fuel strainer assembly was free of debris. The left flap, nose landing gear, and both main landing gear were found retracted. The right main landing gear had separated from the wing structure. The landing gear selector switch was found in the gear-up position. The engine, a turbo-normalized Continental IO-550-B, serial number 569820, exhibited significant fire damage and the intake pipes were crushed and melted toward the rear of the engine. Engine and propeller control continuity could not be verified due to extensive impact-related damage. The propeller remained attached to the crankshaft; propeller blade No. 1 rotated freely in the hub and was bent toward the cambered side, propeller blade No. 2 was damaged near the tip and bent toward the non-cambered side near the tip, propeller blade No. 3 exhibited impact-related damage at the tip. The engine crankshaft was rotated by hand, which confirmed continuity to each cylinder, rear accessory gearing, and the oil pump. Examination of each cylinder with a lighted borescope revealed normal combustion deposits on the pistons and cylinder bores and confirmed that all valves were present. The upper spark plugs were removed and exhibited normal wear signatures. The upper spark plugs for cylinders Nos. 1-4 exhibited light gray deposits of their respective electrode areas. The electrode area of the upper No. 6 spark plug had darker deposits when compared to the other spark plugs examined. The lower spark plugs were covered in engine oil. Both magnetos remained attached to the top of the engine case and exhibited various levels of excessive heat damage and/or melting. Both magnetos produced spark at all terminals when rotated using an electric drill motor. The engine-driven fuel pump exhibited significant fire damage that precluded a bench test. The drive coupling for the engine-driven fuel pump was intact and undamaged. Further disassembly of the engine-driven fuel pump revealed additional heat and fire damage. The propeller governor remained in place and oil was discharged when the drive shaft was rotated by hand. The oil pump remained in place and appeared undamaged, and the internal gears were covered in oil and rotated freely. There were no metal particles observed in the oil filter element. The fuel metering unit had separated from the engine and exhibited significant fire and impact-related damage. The fuel screen for the fuel metering unit was clear of debris. The fuel manifold remained in place on the upper engine case, and when disassembled revealed the diaphragm and spring were undamaged. A small amount of water was observed inside the fuel manifold. The fuel injector nozzles were removed and examined by visual inspection. Several of the fuel injector nozzles were initially obstructed by moisture and were cleared out by blowing air through the injectors. The No. 2 fuel injector nozzle was obstructed by two small particles that fell out of the injector when it was tapped against a workbench. The particles exhibited similar characteristics to the dirt found on the exterior of the engine. The turbocharger remained partially attached to the engine and exhibited impact-related damage. The turbocharger was disassembled, and no oil leaks were observed. The shaft rotated and both the turbine and compressor blades exhibited impact-related damage. The wastegate had partly separated and exhibited significant fire damage. The wastegate valve was found in the open position and moved freely. The manifold pressure controller and pressure relief valve were not located during the investigation and are believed to have been destroyed during the fire. The engine examination did not reveal any mechanical failures that would have resulted in a loss of engine power.
The pilot’s failure to abort the takeoff after the partial loss of engine power before liftoff, and the partial loss of engine power for undetermined reasons.
Source: NTSB Aviation Accident Database
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