# NTSB DCA24LA200: Aergility Atlis 1, N237KG, Dunnellon, FL, May 24, 2024 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 4 · Limited · Final report - Date: May 24, 2024, 10:22 local (14:22 UTC) - Place: Dunnellon, FL - Coordinates: 29.067728, -82.382497 - Nearby events: https://openairdocs.org/map.md?lat=29.0677&lon=-82.3825&mi=10 - Phase of flight: [Uncontrolled descent](https://openairdocs.org/ntsb-phases/650) (OpenAirDocs' grouping) - Defining event: [Uncontrolled descent: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 4 - Basic report with no Prelim publish - NTSB office: Major Investigations Division - Parties: FAA, Aergility/ VP of research and development - NTSB case key (mKey): 194380 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DCA24LA200 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194380/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=194380 - Page: https://openairdocs.org/ntsb/DCA24LA200 ## Probable cause An intermittent electrical failure that switched two motor controllers off, resulting in a loss of hover capability and impact with the ground. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine controls: eng cntl sys wiring](https://openairdocs.org/ntsb-findings/01057697): Aircraft › Aircraft power plant · Malfunction (probable cause); cases with it: [All aircraft, 4 cases](https://openairdocs.org/ntsb-findings/01057697/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Uncontrolled descent: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) ## Analysis An Aergility ATLIS 1 experimental unmanned aerial vehicle (UAV), operated by Aergility Corporation and registered as N273KG, sustained substantial damage during a hard landing at Marion County Airport, Dunnellon, Florida. The flight was operated by Aergility as a flight test within airport property and was conducted under the provisions of Title 14 Code of Federal Regulations Part 91 and a Federal Aviation Administration Certificate of Authorization (COA). There were no injuries. The ATLIS is a vertical takeoff and landing (VTOL) cargo UAV currently under development by the Aergility corporation. The Aergility ATLIS UAV is equipped with six rotors with electric motors powered by batteries for vertical take-off and landing, and a turboprop propulsion engine and propeller for forward flight (see figure 1). Rotor speed (RPM) is always controlled by the autopilot to manage attitude and altitude control. The turboprop engine provides the power for forward flight and an engine driven starter/generator provides power for recharging the batteries. The accident occurred during the 16th test flight of the test program, and the fourth flight of the day. At this point in the flight test program, only hover and very slow forward flight testing had been performed with the UAV. The purpose of this flight was to examine the performance of hover when incorporating a change in center of gravity (c.g.) location within the c.g. range of the UAV. The turboprop engine for forward flight was not in use for this test, and the propeller was strapped in the “X” position. According to the operator, the UAV was being piloted in manual mode, where pilot inputs command roll angle, pitch angle, yaw rate, and vertical rate. Approximately 45 seconds into the flight, while hovering at about 15 feet above ground level (AGL), the UAV executed a planned 90-degree clockwise heading change over the takeoff location. Shortly afterward, an audible reduction in rotor RPM was noted, and the UAV began to descend. The pilot immediately input control to increase vertical rate, but the descent continued. The UAV remained level and maintained heading throughout the descent to the ground. Despite the pilot’s input to counter the descent, the descent rate was not arrested. Autopilot sensor data showed the aircraft contacted the ground at 6.8 meters/second descent rate. Figure 1. Atlis Aergility UAV. (Source: Aergility Corporation) Upon contact with the ground, the landing gear skids collapsed, and the wings deflected downward about 10-15 degrees from the normal dihedral, breaking the spars just outside the fuselage spar box. After the wing spars had broken, the wingtip rotors lifted each wing, rotating vertically around the spars until they collided directly above the fuselage, causing significant damage to the rotors, wings and booms. The fuselage experienced only minor damage. The turboprop engine was undamaged, and one of the 4 blades of the turboprop propeller was damaged. Examination oftelemetry data logs and systems information revealed that all motor controllers were operating in the normal range, when the front right and left rear motor controllers simultaneously switched to the “OFF” state. The autopilot had not yet incorporated an algorithm to detect and react to a motor controller shutdown and increase thrust, and the autopilot was prioritizing roll, pitch and yaw control. As a result, the UAV was unable to maintain hover with 2 of the 6 motors shut down, yet did impact the ground in a stable pitch, roll and yaw attitude. Examination of onboard data logs and telemetry data logs of the systems information showed the data recording was active through the engine 2 and 6 shutdown, the subsequent ground impact and the resulting wing structural failure. However, the data did not reveal any error message or anomalous data related to the simultaneous shutdown of the 2 motor controllers. Examination of the hardware and electrical circuits of the accident aircraft did not reveal any evidence of failures or electrical shorts in any of the electrical systems, wiring, connections, or busses. Several conditions were identified that could have caused the motor electronic speed controllers to switch to “OFF”. The two motor controllers correctly transmitted telemetry messages following the switch to the “OFF” state indicating they were still functioning, and subsequent testing of the two motor controllers found no fault or failure in either of the two motor controllers. A short intermittent open condition could cause both controllers to switch to “OFF”, but there was no evidence in either the flight logs or hardware to conclusively identify the cause of the open condition in this accident, indicating the condition that switched off the controllers was a very brief transient electrical event. As a result of this accident, the operator/manufacturer implemented improvements to the motor controller logic to help prevent a similar event by increasing sampling of any error conditions before issuing a command to switch the motor off. For non-transient events, the controller will now reduce power before depowering when appropriate, and to re-evaluate command thresholds values. Additionally, for future flights telemetry data will include comparison with error thresholds, and multiple reporting messages when thresholds are exceeded. ## Aircraft - Registration: N237KG (not matched to a registry record) - Reported make and model: Aergility ATLIS 1 - Category: Powered-lift, unmanned - Serial number: A000001 - Year built: 2024 - Airframe hours: 2 - Engines: Turbotech SAS TP-R90 120 horsepower turbo prop; EMRAX electric (x6) 2280HV+42%-1UVW electric - Damage: Substantial damage - Flight: Flight test, Part 91 - Operator: Aergility - Registered owner: Aergility - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, April 29, 2024 - Destination: Same as departure - Airport: X35, Marion County Airport - Equipment: Auto-pilot, Data recorder ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 26; injuries: none; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review September 21, 2023; seat: none; flight hours: 94 total, 2 in this make and model - Co-pilot; age 65; injuries: none; commercial; airplane ratings: single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review May 15, 2023; seat: none; flight hours: 447 total, 0 in this make and model ## Weather - Conditions: Visual (VMC), Day - Lowest ceiling: none - Temperature: 80 °F ## Docket (1 files) The files NTSB released with the investigation on September 3, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=194380. 2.3 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18532942&FileExtension=pdf&FileName=Aergilty%20ATLIS%201%20Accident%20-%20May%2024,%202024%20-%20NTSB%20Form%206120_Redacted-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.