Cessna 750 accident near Jamestown, New York, August 5, 2024

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

Shortly after takeoff, while climbing to cruise altitude, the co-pilot of the business jet smelled an electrical burning smell. The pilot could not smell it, and the co-pilot reported that it dissipated. Shortly thereafter, both crew members smelled smoke, and multiple crew alerting system (CAS) messages began to appear. The pilots chose to divert to a nearby airport for a precautionary landing; however, while maneuvering toward the airport, the pilot struggled to maintain speed and pitch control, and radio communications were intermittent. During the subsequent landing approach, the airplane impacted the ground short of the intended runway, slid along the runway, and came to rest off the paved surface. A postimpact fire ensued, and the pilots egressed through the main cabin door. The airplane sustained substantial damage to the fuselage, empennage, and both wings during the accident sequence. A postaccident examination of the airplane revealed that the cockpit, cabin area, inboard sections of both wings, empennage, and the root section of the vertical stabilizer were consumed by postimpact fire. While the airplane was equipped with a cockpit voice recorder, it was not equipped with a flight data recorder (nor was it required to be), and no other devices that recorded parametric data were able to be recovered and downloaded. The upper portion of the vertical stabilizer and the horizontal stabilizers were intact. Control continuity was established from the cockpit to all flight control surfaces except for the left speed brake and spoiler cables, which displayed postimpact thermal damage. All primary control surfaces remained attached to the airframe in their respective locations. There were no signs of airflow-driven sooting or other thermal damage indicative of an in-flight fire with the exception of the left elevator, which showed a small amount of airflow-driven sooting. Most of the airplane’s remaining electrical wiring bundles were intact and showed no signs of electrical arcing. Several of the wire conductors, located aft of the rear pressure bulkhead, exhibited arcing, welding, and beading. An engine control system wiring harnesses recovered from the empennage sustained heavy thermal damage. The outer protective sleeving was missing and only metal braid mat remained, which precluded determination of whether chafing or rubbing damage was present on the outer sleeve. The metal braid mat exhibited signatures consistent with electrical arcing, and other areas with similar characteristics were observed nearby. Since the flight crew did not report any engine controllability issues during the accident flight, it is unlikely that this engine wiring harness was the source of the inflight smoke/fire. The No. 2 battery was located near the area of heavy thermal damage and exhibited evidence of arcing; however, further examination revealed that the arcing likely originated outside of the battery case. Additionally, the battery cable conductors exhibited features consistent with mechanical fracture. Given this evidence, the battery and its associated cables likely were not the source of the inflight smoke/fire. Based on the intermittent smoke smell reported by the crew, witnesses who reported not seeing visible smoke trailing the airplane during the landing approach, and the lack of extensive external airflow-driven soot patterns, the fire likely originated in the interior of the airplane and had not breached the fuselage before landing. Additionally, due to the lack of visible smoke or fire, the fire occurred in an area of the airplane that was inaccessible to the flight crew. The location of the damaged wiring and the lack of similar damage elsewhere in the airplane were indications that the fire likely originated in the lower portion of the airplane, aft of the rear pressure bulkhead. Two wiring bundles located in this area were identified as containing horizontal stabilizer trim system-related circuit wires. In addition, a coaxial cable that provided the antenna feed for the No. 2 very high frequency communication system was routed through this area; however, since some wiring was consumed in the fire or otherwise not conclusively identified, the actual ignition source could not be determined. According to the airframe manufacturer, the appearance of multiple CAS messages within a short period of time as reported by the crew was consistent with the way the installed avionics systems would respond to the loss of electrical power or data communication. Because several of these systems rely on wiring routed through the aft fuselage distribution corridor before branching into individual components, a localized disruption affecting that corridor may result in multiple systems detecting the loss of valid inputs simultaneously. Most of the wiring and electrical distribution components in this region were destroyed by fire, and only limited sections of the harness remained available for examination. Although a specific initiating conductor or failure point could not be identified, the location of the damaged wiring corresponded with the routing of electrical circuits associated with the flight deck indications and control difficulties reported by the crew.

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.

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