Appleby NIEUPORT 28 accident near Paso Robles, California, April 23, 2017

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

The airline transport pilot of the experimental amateur-built World War I fighter replica departed from a private airstrip for a local flight. The airplane climbed, turned left, and entered the downwind leg for the runway. Shortly thereafter the airplane descended in a steep nose down attitude until it impacted terrain. Signatures observed at the accident site and the damage to the airplane were consistent with a near vertical impact attitude into terrain. Postaccident examination of the airplane revealed that an elevator flight control cable rod end had separated from its turnbuckle connection, which resulted in the pilot losing pitch control of the airplane. No safety wire was found at the connection of the turnbuckle and the separated cable rod end, even though it should have been safety wired according to proper maintenance procedure. A review of the airplane's maintenance logbook revealed no maintenance documented for work performed on the elevator or elevator cables. It could not be determined when or by whom the elevator turnbuckle was connected without being properly safety wired. It is likely that the unsecured connection gradually loosened over time until it finally disconnected during the accident flight. According to the airplane's mechanic, the flight control cables and turnbuckle assemblies that were contained in the interior of the airplane's fuselage (including the section of elevator cable found disconnected) were not accessible during routine inspections. The mechanic further stated this portion of the flight control cable and turnbuckle assemblies would even be difficult to inspect with the fuselage's fabric covering removed, due to the plywood paneling and wood stringers in that area. A window in the empennage allowed for inspections of the elevator control attachments only in the tail, and the rudder control attachments could be inspected externally. Therefore, the mechanic was unable to inspect the cables and turnbuckle assemblies contained in the interior of the airplane's fuselage.

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.