ERA22LA216 · Grumman AA1 C

The pilot had picked up the airplane from a maintenance provider after an annual inspection was completed the previous day. Prior to takeoff, the pilot performed an engine run-up with no anomalies noted, and the engine ran smoothly.

Shortly after takeoff, at an altitude of about 250 ft above ground level, the engine lost power and the airplane descended under control into trees. The engine did not “sputter” and the mixture control was set to full rich. The airplane impacted a wooded residential area about ¼ mile from the departure end of the runway and sustained substantial damage to the fuselage and wings.

The pilot recalled that the fuel selector was in the LEFT position for the flight. He stated that on previous flights he sometimes had to “fiddle” with the fuel selector when moving it to the LEFT position to ensure that it was in the detent. During the first postaccident examination of the fuel selector, the detent could not be felt and the associated “click” sound could not be heard when moving the selector from the OFF position to the LEFT position. It could be heard and felt when moving from the RIGHT to LEFT position. A lack of feel or click sound of the detent does not necessarily indicate that the fuel valve is not in the proper position, but it is the only means for the pilot to confirm the proper position.

A subsequent examination by a mechanic was arranged by the pilot/owner. The mechanic reported that the detent click sound could be heard as the fuel selector was moved to all positions, and fuel flowed through the valve when it was in the detents for the LEFT and RIGHT positions. The exact position of the selector at the time of the accident could not be confirmed, as it was moved to the OFF position after the accident. However, given the pilot’s familiarity with the operation of the fuel selector, it is likely that the fuel selector was correctly positioned in the LEFT detent.

The mechanic reported that the engine air filter element was found out of place, wedged between the carburetor heat valve/door and the top of the carburetor heat box. In that position, it prevented the carburetor heat control from moving to the ON position, and likely restricted or obstructed the air path to the carburetor. Given that the engine performed normally during the before takeoff run-up, takeoff roll, and initial climb, it was likely not in that position at those times. Additionally, it is unlikely to have been in that position during the engine-run up, as it would have prevented the application of carburetor heat, which should have been performed as part of the run-up procedure. Thus, it is likely that the air filter element was dislodged from its proper position sometime after takeoff.

Verbatim NTSB analysis and probable cause from the NTSB dataset