WPR10FA473

A partial loss of engine power during approach for reasons that could not be determined because postaccident examination did not reveal any anomalies that would have precluded normal operation.

During a local flight, the airplane departed and climbed to over 8,000 feet mean sea level (msl) on the outbound leg to the north. About 44 minutes into the flight, the airplane began descending after a course reversal to the south on the return for landing. The pilot entered the landing pattern, however, due to multiple airplanes in the traffic pattern he extended downwind, and asked the controller in the air traffic control tower to call his turn to base leg. After getting established on a 3-mile final, the controller notified the pilot that the airplane appeared low. The pilot responded that he was having engine problems and would try to make it to the runway. Witnesses reported that the airplane was low on final approach and that the engine was sputtering and backfiring. The airplane subsequently collided with a building short of the runway. Postaccident examination of the wreckage found an engine monitoring unit on board. A download of the data indicated normal readings until the return descent where it appeared the pilot didn't enrich the mixture. As the pilot was turning onto the base leg, data on the engine monitoring system indicated that the engine revolutions per minute (rpm) started a gradual decrease, and the exhaust gas temperatures (EGT) for all six cylinders became erratic. The EGTs for cylinders one, two, and six dropped slightly, and stayed at higher values than the other cylinders. When the EGTs became erratic, the engine was likely losing combustion (power) in some cylinders. During the postaccident engine examination, the mixture lever was found loose on the throttle shaft but it could not be determined if it was functioning properly at impact. The reason for the partial loss of power could not be determined.

Pilot's Operating Handbook (POH) The POH states to enrich the mixture as required during descents. Before landing, the POH indicates that the pilot should select the full rich position. The emergency procedures section discusses loss of engine power. The POH tells the pilot to check fuel flow; if it is abnormally low, turn the auxiliary fuel pump on and lean as required. It says to turn the auxiliary fuel pump off if there is no improvement. CMI Service Bulletin SB08-03 On March 14, 2008, CMI issued service bulletin (SB) SB08-3 regarding throttle and mixture control levers. It noted that two types of throttle and mixture control levers were in use in the field. The original style control levers were manufactured from a bronze material, and featured a non-machined chamfer on one side, which mated to the machined chamfer on the throttle and mixture control shafts. Splines formed on the non-machined chamfer of the lever at installation. The control lever style in effect at the time of the SB were manufactured from stainless steel and featured a splined chamfer, which interlocked with the splined chamfer on the throttle and mixture control shafts. The SB provided inspection instructions at every 100-hour or annual inspection. The maintenance technician was to inspect the control lever for looseness, free play on the shaft, and proper installation. On July 30, 2010, CMI issued revision A for SB08-03, which was effective at the time of the accident. This revision stated that all bronze material control levers must be replaced when removed for any reason. A review of the maintenance logbooks for the airframe and engine did not indicate that the levers had been removed. Part 91 operators are recommended, but not required, to implement service bulletins. The airplane was a Beechcraft F33A, serial number CE-380. A review of the airplane's logbooks revealed that the airplane had an annual inspection on May 1, 2010, at a total airframe time of 6,950.4 hours. The tachometer read 702.9 at the last inspection. The engine was a Continental Motors, Inc. (CMI), IO-520-BA(8), serial number 280845-R. Total time recorded on the factory remanufactured engine was 702.9 hours at the last annual inspection. The Airport/ Facility Directory, Southwest U. S., indicated that runway 07L was 4,508 feet long and 75 feet wide. The runway surface was asphalt. The parallel runway 07R was 8,197 feet long and 100 feet wide; the displaced threshold was 917 feet long. The pilot was in contact with the Phoenix Deer Valley airport traffic control tower (ATCT). On September 27, 2010, about 1054 mountain standard time, a Beechcraft F33A, N1600W, collided with a building during landing at the Phoenix Deer Valley Airport, Phoenix, Arizona. The pilot/owner was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The private pilot sustained fatal injuries. The airplane sustained substantial damage to the wings, fuselage, and empennage from impact damage and a post-crash fire. The local personal flight departed Phoenix Deer Valley Airport about 0938. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot's family reported that he flew weekly to maintain proficiency, which was the purpose of this flight. The airplane had a Garmin GPSMAP 196 portable global positioning satellite system (GPS) unit installed. A National Transportation Safety Board (NTSB) specialist downloaded the recorded information and prepared a factual report, which is in the public docket for this accident. The data indicated that the flight lasted about 1 hour 16 minutes. The pilot departed to the east, turned north, and climbed to a peak recorded altitude of 8,123 feet mean sea level (msl) at 1020:34. He made a right turn to a southerly heading at 1021:13, and began descending. He turned to the southwest for a downwind entry to the north of runway 07L. A review of recorded air traffic control tower (ATCT) transmissions revealed that the pilot reported inbound for landing at 4,000 feet. He was cleared into the traffic pattern for a left downwind for runway 07L. There were several airplanes ahead of him, and he asked the ATCT to call his turn to left base for him. After his traffic called a 3 mile final, the ATCT advised him to turn, and he acknowledged. While on final, the ATCT advised the pilot that he appeared to be low. He responded that he was experiencing engine difficulties, and would try to make the runway. Witnesses reported that the airplane was very low, and the engine was sputtering and backfiring. Several witnesses, including a couple of certified flight instructors, stated that the airplane's wings were rocking, and the nose attitude was high. One witness looking head-on at the airplane noted that the nose pitched down just prior to the airplane colliding with a building. The airplane and building caught fire; one witness reported that the building's sprinkler system activated, and an alarm sounded. The Maricopa County Medical Examiner completed an autopsy, and determined that the cause of death was smoke inhalation. The FAA Bioaeronautical Science Research Laboratory, Oklahoma City, Oklahoma, performed toxicological testing of specimens of the pilot. Analysis of the specimens contained findings of 41 percent for carbon monoxide detected in blood, and no cyanide detected in blood. There was no ethanol detected in vitreous. The report contained the following findings for tested drugs: 67.87 (ug/ml, ug/g) acetaminophen detected in urine. A review of Federal Aviation Administration (FAA) airman records revealed that the 72-year-old pilot possessed a private pilot certificate with ratings for airplane single-engine land, single-engine sea, multiengine land, and instrument airplane. The FAA issued the pilot a third-class medical certificate on February 24, 2010. It had the limitations that the pilot must wear and possess corrective lenses for near and distant vision. On an insurance application dated September 3, 2010, the pilot reported that he had a total flight time of 1,872 hours as pilot-in-command. He had an estimated 647 hours in this make and model. He completed a biennial proficiency check in August 2009. Investigators examined the wreckage at Air Transport, Phoenix, on September 29, 2010. A complete report of the airframe and engine examination is in the public docket. Engine Investigators slung the engine from a hoist, and removed the top spark plugs. They rotated the crankshaft with a tool in an accessory drive gear. The crankshaft rotated freely through 360 degrees. The valves moved approximately the same amount of lift except for the exhaust valve for cylinder number two, which did not move at all. Cylinder number two sustained crush damage, had missing material, and a broken exhaust rocker arm. Investigators obtained thumb compression on all cylinders except cylinder number two. The fuel pump shaft rotated freely, and the gears in the accessory case turned freely. A borescope inspection revealed no mechanical deformation on the valves, cylinder walls, or internal cylinder head. The combustion chambers and piston heads had a layer of white and yellow colored deposits. The numbers one, three, and five cylinder sparkplug electrode areas had white deposits. Investigators manually rotated the magnetos, and both magnetos produced spark at all posts. The impulse couplings engaged. Throttle Body/Fuel Metering Unit CMI made the throttle body (part number 628528) and fuel metering (part number 629904-2) unit. The mixture control lever sustained damage; it was fractured at the control cable attachment. The fracture surface was jagged and angular. When manually manipulated, the mixture control lever slipped on the mixture control shaft, and moved independently of the shaft. Investigators removed the bronze control lever, and observed smearing of material at the beveled area of the lever.