WPR13LA317

The pilot reported that, shortly after leveling the airplane for cruise during the night flight, he adjusted the fuel mixture control, and the engine lost all power. He performed troubleshooting procedures and discovered that by cycling the throttle forward and aft the engine would produce intermittent bursts of partial power. He subsequently landed the airplane on a road short of a runway and then the airplane slid along the shoulder and down an embankment, which resulted in substantial damage to both wings and the lower cabin structure. Postaccident examination revealed that the outer sheath of the fuel mixture control cable had become detached from its clamp on the carburetor body and that the cable's sheath exhibited signatures consistent with movement. As a result, movement of the mixture control within the cabin resulted in unpredictable movement of the mixture control arm. When the pilot adjusted the mixture just before the loss of engine power, the detached cable likely allowed the mixture to become excessively lean. According to maintenance records, maintenance personnel tightened the clamp during the last annual inspection; however, it could not be determined if maintenance personnel improperly tightened the clamp during the inspection. No other mechanical anomalies were noted that would have precluded normal operation. Data extracted from the airplane's engine monitor indicated that the pilot's continued throttle control movements following the power loss would have activated the carburetor's accelerator pump, which resulted in sufficient quantities of fuel being delivered to the engine to produce partial power.

On July 8, 2013, about 2320 Pacific daylight time, a Cessna 182H, N2062X, landed on a road following a loss of engine power near Hesperia, California. The airplane was registered to, and operated by, the pilot under the provisions of 14 Code of Federal Regulations Part 91. The commercial pilot and passenger sustained minor injuries; the airplane sustained substantial damage during the accident sequence. The cross-country personal flight departed Apple Valley Airport, Apple Valley, California, about 2300, with a planned destination of French Valley Airport, Murrieta/Temecula, California. Night visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported that having departed to the south he leveled the airplane for cruise at 7,500 feet mean sea level. As he approached Lake Arrowhead, California, he began to lean the fuel mixture, and the engine lost all power. He reduced the airplane's airspeed to best glide, and cycled the fuel selector valve from the "both," to "right," and then "left" positions, with no change. He set the mixture control to full rich, and realizing he would not be able to glide the airplane over the adjacent ridgeline and into the Los Angeles Basin, he initiated a shallow left turn. He continued to troubleshoot, and discovered that by cycling the throttle control forward and aft, the engine would produce intermittent bursts of partial power. The airplane continued to descend at a reduced rate towards the unlit desert terrain. Shortly thereafter, the landing lights illuminated a boulder field, and his GPS system began to issue terrain warning alerts. He was unable to see the surrounding terrain, so maneuvered the airplane towards Hesperia Airport utilizing his GPS for guidance, while continuing to "pump" the throttle control. The airplane continued to descend, and as it came to within about 2 miles of the airport, the right main landing gear struck the chimney of a house. The airplane continued a further 1/4 mile, and the pilot spotted a flashing stop light. He aimed for the light, aware that a new 4-lane road had been recently constructed in that area. The airplane landed in the center of the road, and rotated to the right as soon as the damaged right main landing gear made contact with the ground. The airplane subsequently slid along the shoulder, and down an embankment, where it came to rest against a power distribution pole. The airplane sustained substantial damage to both wings and the lower cabin structure during the accident sequence. Examination The airplane was recovered and examined by the NTSB investigator-in-charge and an inspector from the Federal Aviation Administration (FAA). The engine appeared undamaged; the gascolator was full with clear blue-colored fuel, and all fuel lines between the gascolator and the carburetor inlet were intact, with their fittings tight. The carburetor drain plug was removed and fuel flowed from the bowl. The engine mixture control inner cableremained attached to the mixture control arm; however, the outer spiral sleeve had become detached from its clamp on the carburetor body. Movement of the mixture control within the cabin resulted in unpredictable movement of the mixture control arm. The cable and associated carburetor clamp were coated in oily residue and black debris, and the spiral sleeve exhibited polishing and flattening of its surface in the area which would have been bound by the clamp. Rotation of the throttle lever resulted in squirts of fuel issuing from the accelerator pump discharge tube. The carburetor was dissembled and examined along with the engine. No anomalies were noted which would have precluded normal operation; a complete report is contained within the public docket. Engine Monitor The airplane was equipped with a JPI EDM-700 Engine Monitor. The unit was removed from the instrument panel, and sent to the National Transportation Safety Board Office of Research and Engineering for data extraction. The EDM-700 recorded exhaust gas and cylinder head temperatures (EGT, CHT), oil temperature, fuel flow, and fuel used at 6-second intervals. The data revealed that about 8 minutes after engine start, EGT and CHT for all six cylinders rose to about 1,300 and 330 degrees F, respectively, with a corresponding fuel flow rate of 21 gallons per hour. These values remained relatively constant for another 8 minutes. Over the next 90 seconds, fuel flow gradually reduced to 3 gallons per hour, with a corresponding temporary rise and then drop in EGT to 375 F, along with a decline in CHT to 180 F. For the next 2 minutes, fuel flow increased to 6 gallons per hour, and the EGT began a gradual increase, recovering to the pre-anomaly temperatures. Over the next 7 minutes EGT began to rapidly fluctuate with a temperature spread across all cylinders of between 1,100 and 1,375 F, during which time the cylinder head temperature remained constant at about 275 F. Thirty-seconds later the EGT dropped to 750 F, and the recording ended. Carburetor The airplane was equipped with a Precision/Marvel Schebler MA-4-5 series carburetor. The carburetor was equipped with an accelerator pump connected to the throttle linkage. The pumps fuel was supplied by the main fuel bowl via a check valve, and its operation was independent of the mixture control position. The design of the accelerator pump was such that repetitive movement of the throttle linkage forced a small amount of fuel to continually flow through the discharge tube, and into the carburetor throat. Maintenance records revealed that the last maintenance event was an owner/operator assisted annual inspection, performed on March 11, 2013, about 30 flight-hours prior to the accident. The following entries were documented at that time: " 6. LUBE CARB MIXTURE CABLE 1. TIGHTEN MIXTURE CABLE ATTACH POINTS, PANEL/CARB .... 3. INSPECTED All CONTROLS FOR SECURITY AND TRAVEL" No other entries were observed indicating the cable or clamp had beenreplaced since the engine was installed, 1,021.08 flight hours prior in August 2001.