Pilot Debrief

CESSNA 172M near Clearbrook, MN — 2024-04-29

Final reportCEN24LA168
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Date
2024-04-29
Location
Clearbrook, MN, USA
Aircraft
CESSNA 172M
Registration
N12805
Category
Airplane
Highest injury
Serious
Fatalities
0
Phase of flight
Descent

Probable cause

The pilot’s delayed use of carburetor heat which resulted in the loss of engine power due to carburetor icing.

NTSB narrative

The pilot reported that he had just been cleared to fly the GPS approach in night instrument meteorological conditions when the engine rpm decreased. The pilot turned on the carburetor heat, enrichened the fuel mixture, and advanced the throttle forward in order to troubleshoot the loss of engine power; however, there was no change in the engine operations. The pilot did not recall the accident sequence. Security video footage showed that the airplane touched down on the top of a one-story building, then impacted a retaining wall and the ground. The airplane sustained substantial damage to the engine mounts and forward fuselage. A postaccident examination of the engine revealed no mechanical anomalies that would have precluded normal operation. The investigators determined that there should have been adequate fuel to complete the flight. The temperature was about 37° F and the dew point was about 35° F. According to the carburetor icing probability graph conditions were conducive for serious icing at cruise power. The loss of engine power was likely due to the accumulation of carburetor icing during the flight. While the pilot did activate the carburetor heat, it is likely that the ice had already accumulated to a point that the carburetor heat was insufficient to melt the ice and restore full engine power.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have diverted to an alternate airport before engine issues arose.

NTSB coding

Evidence available

  • Video
  • Photos
  • 10 docket documents
View NTSB final reportView NTSB docket

Docket documents10