Accident Overview
On December 3, 2010, at approximately 1740 central standard time, a twin-engine Beech 95-C55 airplane, registration N211DS, was substantially damaged during a forced landing near Claremore Regional Airport (KGCM) in Claremore, Oklahoma. A post-impact fire ensued. Night visual meteorological conditions prevailed at the time. The personal flight was conducted under 14 Code of Federal Regulations Part 91 on an instrument flight rules flight plan. The pilot sustained serious injuries; his passenger sustained minor injuries. The flight departed Jacksonville, Texas, at approximately 1610 and was en route to KGCM.
Pilot Account
In a written statement, the pilot reported that he had just reduced engine power while turning to final for runway 17 when the left engine lost power. As he began preparing for single-engine operations, the right engine also lost power. The pilot stated that insufficient airspeed and altitude remained to reach the airport, so he performed an off-field landing. Prior to the power reduction, the fuel selector valves were selected to the main tanks, the fuel boost pumps were off, the mixture was set to rich, and all four fuel tanks indicated "adequate fuel."
Examination Findings
A Federal Aviation Administration (FAA) airworthiness inspector reported that the left wing had separated from the airplane and was burned. The empennage had separated from the airframe and was found in the debris field. The recovery team noted that the right main fuel tank was full of fuel, while the left main fuel tank was burnt with signatures consistent with a fuel-fed fire. Both auxiliary fuel tanks were empty.
Examination of the right engine revealed residual fuel in the fuel lines and spark plug signatures consistent with normal operation per the Champion Spark Plug chart. The engine was rotated by hand, and valve movement and air movement were observed on all six cylinders. Both magnetos rotated manually and produced a blue spark at all leads. The right fuel tank and fuel system showed no anomalies. The right fuel selector valve exhibited tight, specific detent positions and functioned properly when tested with shop air.
The left engine sustained extensive impact and fire damage, preventing rotation of the engine and magnetos. Its spark plugs also displayed normal operation signatures. The left fuel tank and fuel system were fire-damaged and could not be examined for continuity. The left fuel selector valve did not demonstrate specific detent positions but functioned as designed when tested with shop air. Further inspection revealed tape securing one ball bearing within the valve's yoke assembly; the second ball bearing was missing.
The airplane was equipped with a fuel flow indicator, two oil pressure and temperature gauges, and an engine monitor, all containing non-volatile memory. Data recovery showed that the fuel flow indicator recorded 66.8 gallons of fuel remaining based on pilot-loaded information. The engine monitor indicated a decrease in exhaust gas temperature (EGT) on the right engine approximately one minute before a decrease in EGT on the left engine. The oil pressure and temperature gauges recorded decreases toward the end of the data, but a correlation could not be performed due to the lack of a time stamp.
Prior Incidents
The pilot reported having experienced two previous events of loss of engine power on both engines within the preceding few months. One event occurred at 18,000 feet, the other below 2,000 feet. Both were preceded by reduction of engine power under rich mixture conditions. The pilot believed that the root cause was never identified and was related to "fuel delivery that exceeds that required for stable combustion." Both engines were modified with a Merlyn Products turbonormalizing system (Supplemental Type Certificate SA01663SE).
Conclusion
The reason for the loss of engine power on both engines could not be factually determined.