Diamond Aircraft Ind INC DA 40 NG accident near Sanford, North Carolina, May 7, 2025

The NTSB's narrative final · quoted from the NTSB record

The purpose of the accident flight was for the pilot and the mechanic, who was the passenger on the accident flight, to go on a short test flight after the airplane’s most recent annual inspection. The pilot reported that he performed one circuit of the airport traffic pattern, which was uneventful. During the second circuit, he decided to perform a touch-and-go landing, but the airplane bounced, so he decided to abort the landing. During the initial climb the mechanic heard a “pop,” and shortly thereafter the pilot noticed the engine speed decreased and the airplane lost partial engine power. To avoid trees, the pilot attempted to return to another runway and land, but the airplane descended and impacted a field short of the runway. Postaccident examination of the airplane revealed that the turbocharger air discharge duct had separated from the engine (this duct provided turbocharged intake air to the diesel engine). One of the two worm drive clamps that would have secured the duct to its mating hose was found separated and unsecured. The worm drive’s screw was worn and loose in the clamp housing, consistent with reuse. No evidence of any other preaccident mechanical malfunctions or failures of the engine were found during the examination. Data recovered from the engine control unit (ECU) revealed that the engine boost pressure dropped to ambient pressure during the initial climb, about the same time that the mechanic reported hearing the “pop.” Because the diesel engine relied on turbocharged intake air for power, disconnection of the turbocharger air discharge duct would have resulted in a significant loss of engine power consistent with the partial loss of engine power described by the pilot. The mechanic stated that during the airplane’s most recent annual inspection, he had removed the turbocharger air discharge ductwork, and that when he reinstalled it, he reused the worm drive clamps (rather than using new clamps as prescribed by the airplane’s maintenance manual). Given the worn and loose condition of the unsecured clamp’s worm drive found during the wreckage examination, it is likely that the reused clamp loosened during the accident flight, resulting in the turbocharger air discharge duct’s separation and the partial loss of engine power during the initial climb.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.

Photographs from the investigation 3 pictures from the NTSB's docket, as the NTSB released them

Photograph 1 – main wreckagePhotograph 2 – Main wreckagePhotograph 3 – Engine, note: Air discharge duct missing.

The NTSB's photographs with the NTSB's captions, at screen size. Open a picture to see it full size or to report one that should not be shown.