N15LMGrumman American Avn. AA-1C · 1977

On May 2, 2022, at 1853 eastern daylight time, a Grumman American AA-1C, N15LM, was substantially damaged when it was involved in an accident near Seneca, South Carolina. The pilot sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

Maintenance personnel at Eagle Ridge Airport (SC24), Seneca, South Carolina, completed an annual inspection of the airplane the day before the accident. On the day of the accident, the pilot picked up the airplane from the maintenance facility. He reported that the airplane had “plenty of fuel” on board and the fuel selector was set to the LEFT tank.

The pilot performed an engine run-up prior to takeoff, which he described as “thorough.” He checked the magnetos and the oil pressure, which were normal. The engine ran smoothly, and when he applied full power the engine ran well.

Shortly after takeoff from runway 23, at an altitude of about 250 ft above ground level, the engine lost power and the airplane descended under control into trees. The pilot was unsure if the engine stopped completely before the airplane struck the trees. He recalled it 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.

A witness located next to the accident site reported that the airplane “was low” and the engine stopped suddenly with “no backfire.” First responders reported an odor of fuel at the accident site. The mechanic who performed the annual inspection responded to the accident site and reported that he turned off the master switch and moved the fuel selector to the OFF position. He did not recall what position the selector was in before he moved it to OFF, or how far he moved the handle, and did not recall if he felt or heard a detent click when he moved it. He stated that he rotated the handle toward the OFF position as far as it would move.

The pilot reported that typically when moving the selector to the LEFT position, he sometimes had to “fiddle with it” to get the valve into the detent. The detent is a mechanical “notch” in the fuel valve (connected to the selector handle) that can be felt, and an associated “click” heard, when rotating the selector handle into the desired position; this is to confirm that the fuel valve is fully seated in the proper position. If the valve is not in the detent, fuel flow may be restricted or obstructed.

A postaccident examination of the airplane by a Federal Aviation Administration inspector revealed substantial damage to both wings and the fuselage. When the fuel selector handle was rotated clockwise from the OFF position to the LEFT position, no detent “feel” or click sound was noted. When the handle was rotated from the LEFT position to the RIGHT position, and from the RIGHT back to LEFT, a click was heard, and a detent was felt.

The throttle control was found in a near idle position and the mixture control was near the full rich position. The primer was in and locked. The carburetor heat control was in the closed position. The throttle and mixture controls moved smoothy throughout their operating ranges. Both magnetos produced spark on all towers. The magneto-to-engine timing was measured, and both were found to be within specifications. The carburetor inlet screen was unobstructed. About 2 ounces of fuel were observed in the carburetor bowl, about 1 ounce of fuel was observed in the electric fuel pump, and a trace of fuel was observed in a fractured fuel line leading to the left wing. About 1 cup of fuel was observed in the remnants of the right main fuel tank, and no fuel was found in the remnants of the left main fuel tank. However, both main fuel tanks were impact damaged and appeared to have been breached. All the fuel samples were blue in color (consistent with 100LL aviation fuel) and free of contaminants.

A subsequent examination of the airplane by another mechanic was arranged by the pilot/owner. The mechanic reported that he found the air filter element out of place, inside the carburetor heat box between the carburetor heat valve and the top of the box. He believed that the filter would have, in that position, obstructed or restricted the airflow into the carburetor. He did not attempt to blow air through the filter. He also noted that the carburetor heat control would not operate properly, due to the air filter element’s location obstructing movement of the carburetor heat valve/door. When he attempted to pull the carburetor heat control to the ON position, it would only move slightly, and when he released it, it moved to the OFF position. Additionally, the mechanic operated the fuel selector valve and reported that it clicked into the detent for all positions (LEFT, RIGHT, and OFF). Using an external fuel supply, he noted that fuel flowed through the selector valve when it was in the RIGHT and LEFT positions. Further, he reported that when energized, the electric fuel pump operated, and the fuel pressure gauge indicated fuel pressure. No federal investigative oversight was present for this examination.

A review of the last 3.5 years of the airplane’s maintenance records revealed that the air filter was replaced during each annual inspection, including the one completed the day before the accident. There were no entries related to the fuel selector during the period reviewed.

At 1854, the weather reported at Oconee County Regional Airport (CEU), Clemson, South Carolina, about 2 miles east of the accident site, included a temperature of 28°C and a dew point 13°C. The calculated relative humidity at this temperature and dewpoint was about 40 percent. Review of the icing probability chart contained within Federal Aviation Administration Special Airworthiness Information Bulletin CE-09-35 revealed the atmospheric conditions at the time of the accident were "conducive to serious icing at glide [idle] power."