Piper PA-24-250 N7500P accident near Colorado Springs, Colorado

Probable cause

The pilot’s failure to use the carburetor heat during a descent that resulted in the loss of engine power due to carburetor icing.

NTSB analysis

The pilot reported that after a cross-country flight at 10,500 ft mean sea level (msl), he had descended and was approaching to land. When the airplane was abeam the runway numbers on the downwind leg of the traffic pattern, about 7,500 ft msl, he noticed that the engine sounded as if it was no longer producing power. He attempted to restore power but was not successful and executed a forced landing to a field which resulted in substantial damage to the fuselage and right wing.

Postaccident examination revealed no preimpact anomalies that would have precluded normal operation. First responders stated that the airplane’s wing contained fuel, the fuel selector was positioned for the left main fuel tank, and that the left fuel gauge read just over ½ tank of fuel remaining. The recovery company confirmed the presence of fuel in the airplane but could not provide a detailed report of how much fuel each fuel tank contained.

The pilot reported in a telephone interview that he did not use carburetor heat at any time during the accident flight or during troubleshooting procedures. When he was about 20 minutes from his destination, he descended to about 9,000 ft. msl, and switched to the fullest fuel tank. He also adjusted settings as appropriate for the approach. When in the traffic pattern, once he realized that the engine had lost power, he said attempted to restore engine power using the emergency procedures from the pilot’s operating handbook (POH), including switching fuel tanks, and activating the airplane’s electric fuel boost pump. When engine power was not restored, he switched back to the previous tank as it should have contained the most fuel.

Review of the POH revealed that the normal approach and landing procedures state:

“Carburetor heat should not be applied unless there is an indication of carburetor icing, since the use of carburetor heat causes a loss in engine power which may be critical in the event of a go-around, and can induce detonation in this situation.”

The POH stated in the “Emergency Procedures” section that in the event of an engine failure the first step would be to switch fuel tanks, and if this did not restore engine power the pilot should:

Check fuel pressure and turn on electric fuel pump, if off.

Push Mixture control to full rich.

Apply carburetor heat.

Check ignition switch.

The temperature and dewpoint at the accident airport were conducive to serious icing at glide power settings. Given the lack of mechanical anomalies found and the recorded temperature and dewpoint being within a range conducive for carburetor icing, the likely reason for the loss of engine power was due to carburetor icing.

Text from the NTSB. Open the NTSB docket for CEN24LA206 for the full record.