MOONEY M 20G near Phoenix, AZ — 2015-07-10

Probable cause

The pilots' failure to apply carburetor heat during the approach for landing, which resulted in a total loss of engine power due to carburetor icing.

NTSB narrative

The private pilot receiving instruction reported that, abeam the runway threshold on the downwind leg of the traffic pattern, he reduced engine power to idle to conduct a practice 180o power-off landing. The pilot maintained glide speed until about 40 ft above the ground then noticed that the airplane was slightly below the intended glide path. The pilot applied throttle to initiate a go-around; however, the engine sputtered and power did not increase. The pilot executed a forced landing short of the runway; the airplane touched down hard and bounced. The right main and nose landing gear collapsed, and the airplane came to rest to the right of the runway. The flight instructor reported that, upon the pilot's decision to conduct a go-around, he ensured that the throttle, propeller, and mixture were in the correct position, but made no reference to carburetor heat. During a postaccident examination, the engine was started, operated, and shut down normally with no anomalies noted. Data from the engine monitoring system revealed that, shortly before the engine lost power, it was operating at idle power for about 1 1/2 minutes, during which the cylinder exhaust gas temperatures were decreasing. At the end of the 1 1/2 minutes, in the engine rpm increased and the the exhaust gas temperatures showed a small spike, then continued to decrease. The rpm then decreased to zero, and the manifold pressure adjusted to barometric pressure, consistent with a total loss of power. The reported temperature and dew point at the time of the accident were conducive to carburetor icing at glide and cruise power settings. It is likely that the carburetor collected ice during the time the engine was at idle power. When the pilot increased power, the engine responded momentarily, but was unable to continue operation with the restricted airflow through the carburetor. The airplane's pilot operating handbook stated that full carburetor heat should be applied when reducing power for descent or landing.

Analysis

Primary failure mode

Engine power loss

First missed decision gate

Pilot could have aborted the practice landing earlier to avoid power loss.

NTSB coding

• Fuel related · Landing
• Carburetor Icing Conditions

Evidence available

• FDR / data
• 5 docket documents

Docket documents5

• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
• Record of Email - Certified Flight Instructor Statementinterview
• Data from the Engine Monitoring Systemother
• Record of Conversation - Lycoming Enginesother
• Record of Email - FAA Regarding Postaccident Engine Runother

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