ZENAIR CH2T near Woodland, CA — 2014-03-06

Probable cause

A total loss of engine power during approach due to carburetor icing, which resulted in an off-airport landing into trees.

NTSB narrative

The flight instructor reported that the airplane entered clouds as it was descending during the training instrument approach. The flight instructor suggested that the student pilot increase the descent rate to pass through the clouds more quickly. After about 1 to 2 minutes in the clouds, the student reduced the engine power and pitched the airplane slightly down to increase the descent rate. Immediately thereafter, the engine speed dropped to between 800 and 1,000 rpm, and the propeller sounded as if it were windmilling. The flight instructor took control of the airplane and completed a mental emergency checklist with the student confirming the steps, which included applying carburetor heat; however, the instructor's attempts to restore engine power were unsuccessful. The airplane exited the cloud layer between 1,500 and 2,500 ft. The flight instructor declared a Mayday with approach control as he and the student completed the emergency checklist again with no results. The flight instructor initiated an off-airport landing, and, during the landing roll, the airplane collided with trees. A postaccident examination of the airframe and engine revealed no anomalies that would have precluded normal operation. The weather conditions encountered at the time of the accident were conducive to the formation of serious carburetor icing at cruise power. It is likely that carburetor ice formed during the descent and that the extended low-power setting prevented the engine temperature from getting high enough to melt the ice.

Analysis

Primary failure mode

Engine power loss

First missed decision gate

Student pilot should have maintained power during descent to prevent engine issues.

NTSB coding

• Loss of engine power (partial) · Approach-IFR initial approach
• Carburetor Icing Conditions

Evidence available

• 5 docket documents

Docket documents5

• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
• Student Statementinterview
• Flight Manual Excerpt, Pre Landing Checkother
• PIC and Flight Instructor J Witwer Reportreport
• Sierra Academy of Aeronautics Accident Reportreport

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