Tecnam P2002 SIERRA N308TA accident near Watsonville, California

Probable cause

A partial loss of engine power during initial climb due to the blockage of the carburetor’s main jet by deteriorated float material. Contributing to the accident was an inadequate maintenance inspection by maintenance personnel.

NTSB analysis

During the initial climb, the airplane's engine started to vibrate violently and lost significant power. The flight instructor performed an emergency descent and landing to an open field. Postaccident examination of the engine's dual carburetors found that 30 to 50 percent of the No. 2 main carburetor's left main carburetor jet was blocked by foreign material. The float inside the carburetor float chamber showed signs of flaking on the corner edges; the material was consistent with that found in the carburetor jet.

Engine test runs conducted with the main jet reduced to about 50 percent of its original size revealed that the blockage resulted in the partial loss of engine power, indicating that the accident engine's power loss directly resulted from the blockage of the left carburetor's main jet. Manufacturer Service Instruction 912-021 states that the engine's carburetors are to be removed and inspected every 200 hours due to several carburetors previously being found with contamination in the float chamber. The instruction warns that such contamination could possibly cause a partial or complete blockage of the idle or main jet or other ducts vital for operation and lead to poor performance or stoppage of the engine. Maintenance records revealed that the required 200-hour carburetor removal and inspection had been completed 2 days before the accident. During the inspection, maintenance personnel should have seen and replaced the visibly deteriorated carburetor float, removed the carburetor main jet, and blown air through the jet channels with compressed air to ensure that the passage was clear, which most likely would have prevented the accident.

Text from the NTSB. Open the NTSB docket for WPR12LA281 for the full record.