Accident Details
On August 20, 2009, at approximately 1600 Eastern Daylight Time, a Cessna A188B, registration N4842R, was involved in an accident near McRae, Georgia. The airplane sustained substantial damage after a forced landing into a soybean field. The pilot, a certificated commercial pilot, was not injured. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed for the local aerial application flight. The flight was operated under 14 Code of Federal Regulations Part 137. The flight originated from Telfair-Wheeler Airport (MQW) in McRae, Georgia, at 1545.
Pilot and Flight Description
According to the pilot, while spraying chemicals on a field, the engine oil temperature began rising while the oil pressure dropped. The pilot exited the field and noticed that the engine was rapidly losing power. The oil pressure dropped to zero, and the engine subsequently lost all power. The pilot initiated an emergency dump of the spray solution and attempted to climb but was unable due to low airspeed. A forced landing was then executed in a soybean field. The nose and engine compartment came to rest in the dirt, and the landing gear collapsed. The pilot reported that fuel leaked from the right fuel tank.
Aircraft Damage and Initial Examination
Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the aircraft was resting on its belly. Substantial damage was noted to the firewall, engine mounts, fuselage attachments, and the left wing. The airplane was recovered for further examination.
Engine Examination
Initial engine inspection found that the engine remained attached to the airframe and sustained light impact damage to the front of the oil sump. Some heat damage was observed on the crankcase vent tube. The top spark plugs were removed, and the crankshaft was rotated using the propeller. Compression was confirmed on all cylinders, and continuity was confirmed to the rear of the engine and the magneto drives. Both magnetos were in place and undamaged. When rotated at high speed, no spark was observed on any magneto terminal. Disassembly revealed that the points on both magnetos had severe wear and burning damage, and the points would not separate when the drive shafts were rotated. Evidence of arcing was observed inside both magnetos.
The top spark plugs exhibited normal wear compared to the Champion Check A Plug comparison chart, with dark deposits in the electrode areas. The oil filter had light impact damage and was opened; metallic particulates were found in the filter element.
Post-Accident Engine Run Attempts
An attempt was made to run the engine after replacing both magnetos with operational Slick-6310 units, both ignition harnesses, and the spark plugs on the right side with Champion RHB-32E spark plugs. The oil filter was replaced, and after several start attempts, the starter was also replaced. The airplane battery was replaced for the run attempts. Despite numerous attempts using two different starters and several batteries, the engine would not start. The engine was subsequently sent to the manufacturer for further examination.
Manufacturer Examination
At the manufacturer, the throttle body and mixture control assembly was tested and found to have abnormal flow through the return fitting at the full rich setting, with a leak at the mixture shaft. The unit was disassembled, revealing scoring on the interface surfaces of the mixture control shaft and fuel metering plug. Disassembly of the engine showed that the number 1 and 4 piston heads exhibited thermal erosion consistent with a pre-ignition/detonation event.
Maintenance History
A review of the engine logbooks indicated that the engine was overhauled on May 3, 2006. The last 100-hour inspection was completed on October 3, 2008. The airplane flew 105 flight hours since that inspection.