CEN23LA388 · Cessna 210B

The flight instructor and private pilot receiving instruction reported that their first two attempts to depart were aborted due to engine roughness discovered during the engine run-ups, which was subsequently determined to be an ignition issue that was addressed by replacing a spark plug. After a satisfactory engine run-up check, they initiated the takeoff. During the initial climb, when the airplane reached about 150 ft above ground level (agl), the tower controller informed them that the airplane was trailing smoke. About that time, the engine lost all power, and the flight instructor executed a forced landing to a field where the airplane sustained substantial damage to both wings, fuselage, and left horizontal stabilizer. Postaccident examination revealed that the oil sump contained only 4 quarts of oil with a total oil capacity of 12 quarts. No evidence of an external oil leak was found. Examination of the top spark plugs found that the electrodes were dry, black, and sooty, indicating an overly rich fuel mixture. The airplane was equipped with a fuel flow transducer installed at the firewall, upstream of the engine driven-fuel pump and downstream of the electric fuel pump. According to the maintenance records, the transducer was installed in conjunction with an avionics upgrade and in accordance with a supplemental type certificate (STC). The installation manual associated with that STC stated that the placement of the transducer was at the discretion of the installer but that a common location was downstream of any electric boost pumps but upstream of the engine-driven fuel pump. However, the transducer manufacturer’s installation manual provided conflicting information, stating that the transducer must be installed after any fuel pumps and that installation upstream of any fuel pumps could result in vapor lock. Although a vapor lock condition would result in a lean mixture that could result in a loss of engine power, the spark plug indications and the in-flight smoke were not indicative of a lean mixture condition. Additionally, although vapor lock can result in hard starting, it generally does not manifest as a loss of power once the engine is operating. The oil sump contained less oil than specified for its minimum operating capacity. However, postaccident examinations found no evidence of oil leakage and no condition that would result in the engine burning oil. Further, the engine was not seized, and the spark plugs did not appear to be oil fouled. Thus, there was no evidence that the low oil level contributed to the loss of engine power. A fuel line fitting that extended from the engine-driven fuel pump to the mixture valve was loose and moved freely when slight finger pressure was applied. Blue staining was evident at the fitting location, potentially consistent with fuel leakage. The fuel injection mixture control valve screen contained substantial debris and fibers. However, postaccident testing of the fuel control unit (with the contaminated screen installed), fuel pump, and fuel flow sensor revealed no functional deficiencies. The loose fuel fitting could result in leakage of fuel and, in conjunction with the obstructed fuel filter, could result in a lean mixture. Under certain conditions, fuel leakage in an airplane can result in a fuel spray that may appear as a cloud of white fuel vapor, which could be mistaken for smoke. However, the investigation was not able to determine the amount of fuel leakage from the loose fitting, and, as stated previously, the spark plug indications were inconsistent with a lean fuel condition. The reason for the loss of power could not be determined.

Verbatim NTSB analysis and probable cause from the NTSB dataset