ERA15FA191

The total loss of engine power for reasons that could not be determined due to thermal damage and because postaccident examination of the engine revealed no anomalies that would have precluded normal operation.

The commercial pilot fueled the airplane with 20 gallons of fuel before departing on the 1-hour cross-country flight. While on final approach to the destination airport, the pilot advanced the throttle lever; however, the engine did not respond. The pilot attempted to restore engine power but was unsuccessful and subsequently conducted a forced landing to a small clearing. The airplane impacted terrain, trees, and a gate before coming to rest about 1 mile short of the runway and was largely consumed by postcrash fire. Based on the minimal rotational damage to the propeller and propeller assembly, it is likely that the airplane experienced a total loss of engine power before impact. Due to the significant postcrash fire it was unlikely that the loss of engine power was the result of fuel exhaustion. Postaccident examination of the airframe and engine, including the fuel and ignition systems, revealed no evidence of mechanical malfunctions or abnormalities that would have precluded normal operation. Although functional testing of the engine-driven fuel pump and the throttle body was precluded due to thermal damage, disassembly of the units revealed no anomalies.

Throttle and Mixture Cable The as found positions of the throttle and mixture cable were noted at the accident site. The cables and their respective assemblies were then sent to the NTSB Materials Laboratory in Washington, D.C. for further examination. Both control assemblies exhibited significant heat damage; however, no pre-existing binding or obstruction to operation was observed on either of the controls. The throttle cable position was measured at 3.75 inches, which correlated to 74% open. According the airplane manufacturer, the full-closed (idle) position would measure 1.3 inches, and the full (open)-throttle position would measure 4.620 inches. The mixture cable position measured 6.70 inches, about 57% rich. According to the manufacturer, the full idle-cutoff position would measure 5.35 inches, and the full-rich mixture position would measure 7.70 inches. The throttle control cable could not be easily moved, likely due to heat damage to the liner. The mixture control release rod was bent and unable to be moved, likely due to thermal damage. Magnetos and Fuel System Component Examination The ignition and fuel system components were examined at the manufacturer's facility under NTSB oversight. The magnetos could not be functionally tested due to thermal damage. Rotation of the drive shafts resulted in a coinciding rotation of the distributor gears (as observed through their respective housing ports). Disassembly of the magnetos revealed that the internal timing of each magneto was correct. The internal wires sustained thermal damage and some components were corroded. The cam follower opened and closed the points appropriately during drive shaft rotation. The engine-driven fuel pump sustained thermal damage that precluded functional testing. The pump was disassembled and no pre-accident anomalies were noted with the internal components. The mixture control shaft o-ring was in place, but was thermally damaged. The throttle body was disassembled and no pre-accident anomalies were noted with the internal components. The o-rings were in place. The fuel manifold valve was disassembled and the diaphragm was intact with the plunger secured. The screen was clear with no debris or obstructions noted. A test was conducted with an exemplar engine-driven fuel pump on an exemplar engine. The mixture control shaft o-ring was omitted to induce a known leak from the engine-driven pump. During priming operation, fuel was observed leaking from the mixture control shaft. The exemplar engine was started and run throughout production test parameters (idle to full power) with no misses or engine stumbling noted. Throttle Body The throttle body could not be functionally tested due to thermal damage; however, the manufacturer provided a new, exemplar throttle body for testing purposes. The valve's o-rings were removed to simulate a leak in the throttle body assembly. The assembly was then connected and bench-tested on a fuel test stand and subsequently attached to an exemplar engine and tested under the supervision of NTSB personnel. The throttle body operated within the acceptable range of a new unit and no anomalies or hesitations were noted. Similar Previous Accident A review of the NTSB database revealed an accident involving a similar airplane and engine that occurred on May 10, 2014, in San Antonio, Texas (NTSB accident number CEN14LA234). In that case, the pilot also advanced the throttle lever while operating in the airport traffic pattern and the engine stopped producing power. Postaccident examination of the engine revealed no anomalies, and the reason for the loss of engine power could not be determined. The airplane wreckage was moved before the investigative team's arrival; however, photographs revealed that the airplane was engulfed in flames shortly after impact. A video taken by the pilot immediately after he exited the airplane showed fire beginning predominantly forward of the wings but engulfing the wings within a few seconds of the start of the recording. The initial impact point was indicated by three tire markings in the grass, corresponding to each of the airplane's three landing gear, which extended about 20 ft. The tire marks ended, and the airplane subsequently impacted a palm tree about 5 ft agl, then a 15-ft-tall archway over an entrance gate before impacting another tree and the ground. The debris path extended about 200 ft on a heading about 060° from the initial impact point, and the airplane came to rest on a heading about 260°. The forward fuselage exhibited extensive thermal damage. The empennage was intact and not affected by the postcrash fire. The engine remained attached to its mounts and the firewall; however, all of the mounts displayed varying degrees of impact damage. The propeller remained attached to the crankshaft flange and the propeller spinner was secured to the hub. The spinner exhibited no rotational scoring or signature marks around its circumference. The three propeller blades remained attached to the hub. One blade exhibited leading edge gouging, one blade tip was bent aft, and the other blade exhibited chordwise scratching and was bent aft about midspan. Engine Observations Examination of the engine revealed extensive thermal damage to the rear accessory pad and top of the engine. The turbo controller was not observed and was presumed to be destroyed by the postimpact fire. The No. 5 cylinder exhibited impact damage on the cooling fins. All spark plug leads remained attached to their respective plugs and to their respective magnetos. The fuel injector lines remained attached. Portions of the lubrication line system were thermally destroyed. No external anomalies were noted. The crankshaft was rotated by hand at the propeller flange, and thumb compression was obtained on all cylinders except No. 5 as a result of impact damage that restricted movement of the valves. Crankshaft continuity was observed from the propeller flange aft to the crankshaft gear bolts and the accessory end. Camshaft continuity was also confirmed. Removal of the oil pump housing cap revealed that the oil pump gears were intact with no signs of hard particle passage throughout the housing. The oil filter was in place and safety-tied. The oil filter was removed and cut open for examination. The filter element was thermally damaged but otherwise unremarkable. The engine oil dipstick was present; the oil level was about 7 quarts, within the normal operating range, and the oil appeared normal in color and was free of contaminants. The propeller governor remained attached to the front side of the engine, and the cable remained secured and attached to the propeller lever. Ignition System The ignition wiring was thermally destroyed. The magnetos were secure on their mounting pads. The pressurization lines to the magnetos were secured in place but were destroyed by fire. The ignition harness was destroyed; however, the terminal leads to the sparkplugs were secured and in place. All spark plugs were secured and in place. The top spark plugs were removed and the cylinders were inspected with a borescope. All cylinders appeared normal in color and no abnormalities were noted within the cylinder barrels, intake valves, or exhaust valves. The sparkplugs appeared to be in new condition with little-to-no combustion deposits on the electrodes or insulators. During crankshaft rotation, the magneto impulse couplings were audibly observed. Removal of the vent plug on each magneto revealed the distributor gears were intact and the left magneto showed signs of thermal distress. The magnetos were removed for further testing. The shafts and gear rotated freely by hand. Removal of the ignition harness from the distributor towers did not show any signs of arcing or cracking. Turbocharger System The left and right turbochargers were manufactured by Hartzell. The slope control was not located during the