Blocked carburetor brings down Tecnam

Aircraft: Tecnam P2002 Sierra. Injuries: None. Location: Watsonville, Calif. Aircraft damage: Substantial.

What reportedly happened: The flight instructor and student were on an instructional flight. During the initial climb, the engine started to vibrate violently and lost significant power. The CFI performed an emergency descent and landing to an open field.

The post-accident examination of the engine’s dual carburetors found that 30% to 50% of the 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%  of its original size revealed that the blockage resulted in the partial loss of engine power, indicating that the 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 two days before the accident.

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 Identification: WPR12LA281

This June 2012 accident report is are provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.

Comments

  1. Tom says

    This is ridiculous. Any carb that has to be taken apart every 200 hours for inspection is a badly engineered carb – plain and simple. By the way, once you get all the AD’s handled on the Marvel Schelbler there isn’t any reason you can’t put 2000 hours on one without problems. Just clean the fuel screen every annual and drain the fuel on every preflight. Watch out for the “new fangled” stuff.

    • Keith says

      Guys I know with MS carbs who lost their good (original) venturis have reprofiled the junk (new) venturis to get rid of the poor vaporization problem. In other words, they undid what was done by the now-rescinded AD. They have also come out with a couple of different composite float designs.

      I’ll keep my metal floats.

  2. Keith says

    Metal floats don’t disintegrate in gasoline.

    Carb makers don’t use them because they also aren’t expendable parts which need to be replaced.

    As Marvel Schebler proved with their disastrous venturi-swap scheme, actual SAFETY is not as important as finding a way to get carb owners to pay for new parts.

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