Red Bluff, CA, USA
C-GOBC
Cessna A150M
The airplane experienced a loss of engine power after takeoff, made a forced landing, touched down on uneven terrain, and came to rest inverted. The pilot was on the fourth leg of a cross-country flight when the engine lost power on the initial climb-out about 200 feet agl. Investigators inspected the engine and found the exhaust valves for two of the cylinders stuck in the open position, with dark combustion deposits in the combustion chambers. Both of the exhaust valves exhibited purple discoloration consistent with thermal overheating damage. All four cylinders exhibited pink discoloration of the head and cooling fins in the vicinity of the exhaust ports, which is consistent with thermal overheating. The pilot reported that the engine had been running rough during the approach phase of the flight prior to the accident. The pilot flew the airplane a total distance of approximately 567 nm on the day of the accident. The previous 19.8 hours of the airplane were flown exclusively by the accident pilot. Just prior to the accident, the engine had undergone a 50-hour inspection, and had had a major overhaul 185 hours ago.
HISTORY OF FLIGHT On August 18, 2006, at 1642 Pacific daylight time, a Canadian-registered Cessna 150M, C-GOBC, experienced a loss of engine power after takeoff, and nosed over during a forced landing in an open field near Red Bluff Municipal Airport (RBL), Red Bluff, California. The pilot operated the family-owned airplane under the provisions of 14 CFR Part 91 as a personal cross-country flight. The airplane sustained substantial damage. The private pilot, the sole occupant, received minor injuries. Visual meteorological conditions prevailed for the flight that originated from Boundary Bay (CZBB), British Columbia, Canada, at 0625. The flight was destined for San Jose Municipal Airport (SJC), San Jose, California. A Federal Aviation Administration (FAA) visual flight rules (VFR) flight plan had been filed. The National Transportation Safety Board investigator-in-charge (IIC) interviewed the pilot. The pilot reported that he was working towards his Canadian commercial license, which required a 300 nm cross-country flight. He had planned refueling stops at Bellingham International Airport (BLI), Bellingham, Washington, Portland International Airport (PDX), Portland, Oregon, Rogue Valley International Airport (MFR), Medford, Oregon, Red Bluff Municipal Airport, and San Jose International Airport. On the accident portion of the flight, he had refueled at RBL, and readied the airplane for takeoff. There were no discrepancies with the takeoff roll. About 200 feet above ground level (agl) the engine lost partial power; moments later the engine lost all power. He forced landed the airplane in an open field with uneven terrain. After the main landing gear touched down, the nose "dropped suddenly and dug into the ground." At that point the airplane nosed over and came to rest inverted. The pilot was able to extricate himself from the airplane and flagged down an officer from the Red Bluff Police Department. A responding officer from the Red Bluff Police department took a statement from the pilot. The pilot reported that the engine had recently been rebuilt and maintained in accordance with the Transport Canada regulations and standards. The officer stated that the airplane landed in a vacant field that had varied terrain levels. The first identified point of contact was a large dip where the officer believed the nose landing gear separated after the airplane touched down. The airplane skidded a short distance before it nosed over and came to rest inverted. A witness from RBL airport reported to the Red Bluff Police department that he had spoken to the accident pilot at the fuel island between 1530 and 1600 the day of the accident. The pilot told him that the engine was running rough when he came in to land. The pilot checked the oil and told the witness that the oil was low. The witness observed the accident pilot adding oil that the pilot had in the airplane. The witness did not observe the airplane takeoff, or the accident. The IIC interviewed the airport manager. The airport manager indicated that two other airplanes refueled after the accident airplane, and departed RBL without incident. In a written report the pilot stated that prior to flight he had completed a preflight engine run-up check in accordance with the Cessna 150M Pilot Operating Handbook. The Safety Board IIC reviewed the pilot's route of flight and estimated the total distance flown on the day of the accident to be approximately 567 nm. TEST AND RESEARCH The Safety Board IIC examined the wreckage along with a representative from Teledyne Continental Motors (TCM), a party to the investigation, at Plain Parts, Pleasant Grove, California, on September 5, 2006. The propeller remained attached to the crankshaft. One propeller blade displayed aft bending at the mid-section. Scratches were observed on the front of the blade progressing from the mid-section bend towards the tip. The other propeller blade was found with chordwise abrasions along its entire length. Investigators removed the engine. They placed it on a stand, attached it to a hoist, and removed the upper and lower spark plugs. The spark plug electrodes for cylinder number two had light grey deposits. The spark plug electrodes for cylinder number four had no deposits. The lower spark plugs for cylinders number one and three were oil-soaked. The upper spark plugs for cylinders number one and three had heavy dark deposits. Oil was noted between the electrodes of the upper number three cylinder spark plug. Investigators observed pink discoloration of the head and cooling fins in the vicinity of the exhaust ports on all four cylinders, which the TCM representative stated was consistent with thermal discoloration. Crankshaft rotation was achieved by manual rotation, and thumb compression could not be obtained for cylinders number one and two. The exhaust valve for cylinder number one was found to be in the open position; dark deposits were noted on the valve head, seat, and stem. The rocker arm moved freely by hand. The cylinder was removed and the combustion chamber was found to have dark deposits and oil residue. The exhaust valve for cylinder number two was found to be in the open position; the rocker arm moved freely by hand. The cylinder was removed and dark deposits were observed in the combustion chamber; the rocker box cover contained oil residue. The exhaust valve head displayed dark purple discoloration, which the TCM representative stated was consistent with thermal discoloration. Cylinder number three was removed and dark deposits were observed in the combustion chamber; the rocker box cover contained oil residue. Cylinder number four was removed; the combustion chamber had light combustion deposits and the rocker box cover contained oil residue. The piston heads for all of the cylinders were inspected and showed dark combustion deposits. The piston skirts were free of damage, and all of the piston rings were intact and free in their grooves. All piston pin plugs were found to be intact and undamaged. The left and right magnetos were removed and manually rotated; the impulse couplings were noted to engage, and sparks were observed at all four terminals. The ignition leads were undamaged. The carburetor sustained impact damage and separated at the induction manifold flange. The lower drain plug was removed and a rust material was found in the cavity. The mixture linkage arm sustained impact damage, but moved freely when manually manipulated; the throttle valve linkage arm and throttle valve moved freely by hand. The carburetor was disassembled and no anomalies were noted. The oil pump rotated freely by hand; the oil pickup tube screen was free of debris and unrestricted. The oil was drained from the sump and found to be dark in color. Investigators removed the starter and flange from the engine and no damage was observed. The starter rotated freely by hand. Investigators removed the alternator from the engine and no damage was observed. The alternator rotated freely by hand. The accessory gears were covered in residual oil, and continuity was established through to the crankshaft by hand rotation. The TCM representative stated the thermal discoloration exhibited by the engine could have been caused by either an incorrect leaning technique, an extended ground run with inadequate airflow over the cylinders, or a lack of engine oil. AIRCRAFT INFORMATION The engine was a Teledyne Continental Motors O-200-A, serial number 255453. The airplane logbooks were inspected and found to contain both airframe and engine inspection records, as well as pilot and flight time information. A review of the airplane's logbooks revealed that the airplane had a total airframe time of 7,352.8 hours on the day of the accident. A logbook entry stated that the engine was overhauled at a total airframe time of 7,167.8 hours. At 7,306.3 hours, the airplane received a 50-hour inspection. Logbook entries indicated that the previous 19.8 hours of the airplane were flown exclusively by the accident pilot, and took place over a period of 93 days. PERSONNEL INFORMATION The pilot reported that he held a Canadian issued private pilot license, with ratings for airplane single engine land. He reported that his total flight time as pilot-in-command was 59.8 hours, of which 26.4 hours were in same make and model as the accident airplane.
The pilot's improper mixture leaning technique, which lead to thermal damage and seizure of the exhaust valves.
Source: NTSB Aviation Accident Database
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