Amateur-built AVENTURA II N932MC accident near West Pittsfield, Maine

Probable cause

The pilot's failure to maintain airplane control after a total loss of engine power due to carburetor icing, which accumulated because the carburetor heat was not functioning.

NTSB analysis

The airline transport pilot departed in his amateur-built airplane and planned to stay in the airport traffic pattern to conduct a functional test of the retractable landing gear. He stated that, as he was turning the airplane left to the final leg of the airport traffic pattern, he noticed that the controls were "very stiff" when he tried to roll the airplane level and needed two hands to move the control wheel. The airplane then began to descend. The pilot was unable to level the airplane, and during the continued descent, it collided with trees. After the accident, two witnesses told the pilot that the engine had stopped producing power before the airplane impacted the trees; however, the pilot said he was unaware that the engine had lost power.

Postaccident examination of the flight controls revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. Postaccident examination of the engine revealed that the engine exhaust was positioned too close to fuel lines, which did not have heat shielding protection, and that a mandatory fuel return line was not installed, both of which could result in vapor lock to the engine. However, when the engine was test-run, it ran continuously for several minutes without hesitation. Given the successful engine test-run, it is unlikely that vapor lock caused the loss of engine power. Despite the noted deficiencies with the engine's installation, no preimpact mechanical functions or failures of the engine's powertrain were found that would have precluded normal operation.

Examination of the airplane also revealed that the carburetor heat was not functional. Given that the atmospheric conditions at the time of the accident were conducive to carburetor icing at glide engine power settings, the carburetor likely accumulated ice. If the engine lost total power due to the accumulation of carburetor ice and the pilot inadvertently allowed the airplane to slow, then the effectiveness of the airplane's flight controls would have been degraded and likely would have resulted in the loss of airplane control, as reported by the pilot. Therefore, it is likely that the carburetor accumulated ice because the carburetor heat was not functioning, which led to the total loss of engine power.

Text from the NTSB. Open the NTSB docket for ERA16LA247 for the full record.