# NTSB CEN23LA135: Bell Helicopter Textron APT70, N314AL, Mineral Wells, TX, March 14, 2023 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: March 14, 2023, 10:00 local (15:00 UTC) - Place: Mineral Wells, TX - Coordinates: 32.8932, -98.2332 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=32.8932&lon=-98.2332&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: Federal Aviation Administration, Bell Helicopter - NTSB case key (mKey): 106895 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN23LA135 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/106895/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=106895 - Page: https://openairdocs.org/ntsb/CEN23LA135 ## Probable cause The flight crew’s loss of control of the unmanned aircraft due to software limitations. Contributing to the accident was the overly restrictive low voltage threshold limits. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Electrical power system](https://openairdocs.org/ntsb-findings/01022400): Aircraft › Aircraft systems · Related operating info (probable cause); cases with it: [Bell Helicopter Textron APT70, 1 case](https://openairdocs.org/ntsb-findings/01022400/cases.md?model=061014W), [All aircraft, 48 cases](https://openairdocs.org/ntsb-findings/01022400/cases.md) - [Indicating/recording systems](https://openairdocs.org/ntsb-findings/01023100): Aircraft › Aircraft systems · Related operating info (probable cause); cases with it: [Bell Helicopter Textron APT70, 1 case](https://openairdocs.org/ntsb-findings/01023100/cases.md?model=061014W), [All aircraft, 18 cases](https://openairdocs.org/ntsb-findings/01023100/cases.md) - [Auto flight system](https://openairdocs.org/ntsb-findings/01022200): Aircraft › Aircraft systems · Design (probable cause); cases with it: [Bell Helicopter Textron APT70, 1 case](https://openairdocs.org/ntsb-findings/01022200/cases.md?model=061014W), [All aircraft, 8 cases](https://openairdocs.org/ntsb-findings/01022200/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Fuel exhaustion](https://openairdocs.org/ntsb-events/192); cases with it: [Bell Helicopter Textron APT70, 1 case](https://openairdocs.org/ntsb-events/192/sequence.md?model=061014W), [All aircraft, 804 cases](https://openairdocs.org/ntsb-events/192/sequence.md) - [Maneuvering: Electrical system malf/failure](https://openairdocs.org/ntsb-events/332); cases with it: [Bell Helicopter Textron APT70, 1 case](https://openairdocs.org/ntsb-events/332/sequence.md?model=061014W), [All aircraft, 182 cases](https://openairdocs.org/ntsb-events/332/sequence.md) - [Landing-flare/touchdown: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490) (defining event); cases with it: [Bell Helicopter Textron APT70, 1 case](https://openairdocs.org/ntsb-events/490/sequence.md?model=061014W), [All aircraft, 1,309 cases](https://openairdocs.org/ntsb-events/490/sequence.md) ## Analysis During a flight test, the unmanned aircraft’s flight control computer registered a low battery voltage reading and entered an automatic land in place flight maneuver. The aircraft was hovering over a large bush at the time and the ground station operator (GSO) attempted to override the system, but the system rejected the commands. The GSO attempted to change the land in place waypoint, but the system again rejected the command. The aircraft performed its land in place maneuver and collided with the bush, which resulted in the aircraft tipping over and coming to rest inverted. The operator reviewed the aircraft systems and found the low voltage threshold to be overly restrictive. In addition, software prevented the flight crew from overriding the land in place command and regaining control of the aircraft by changing the waypoint. ## Factual narrative On March 14, 2023, about 1030 central daylight time, a Bell Textron APT70 unmanned aircraft, N314AL, was substantially damaged when it was involved in an accident near Mineral Wells, Texas. The aircraft was operated under the provisions of Title 14 Code of Federal Regulations Part 91 as a flight test. During the flight test, the aircraft returned to base and was in a transition to hover when the flight control computer registered a low battery voltage reading and went into an emergency automatic land in place flight command. The GSO attempted to override the system, but the system rejected the commands. The crew then noted the “F BATT CRIT LOW VOLT” warning illuminated, which initiated a descent for the aircraft to land at its present position. At the time, the aircraft was in a hover at an altitude of about 100 ft above the ground over a large bush when the Land Failsafe command was activated. A command was sent to the vehicle to override the landing command, but the ground control station indicated that the override command was rejected. The GSO then attempted to change the land in place waypoint, but the system again rejected the command. The aircraft performed its land in place maneuver and collided with a shrub, which resulted in the aircraft tipping over and coming to rest inverted. Substantial damage was sustained to the lower left wing section. The operator reviewed the aircraft systems and found the low voltage threshold to be overly restrictive. In addition, a software limitation prevented the crew from overriding the land in place command by changing a waypoint. ## Aircraft - Registration: [N314AL](https://openairdocs.org/deregistered/N314AL-2023-10-09), registration cancelled 2023-10-09, S/N 002, built 2019 (OpenAirDocs) - Reported make and model: BELL HELICOPTER TEXTRON INC APT70 - Registry model: [Bell Helicopter Textron APT70](https://openairdocs.org/model/bell-helicopter-textron-apt70) (registry code 061014W) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Powered-lift, unmanned - Serial number: 002 - Year built: 2019 - Airframe hours: 17.6 - Engines: Proprietary 5 horsepower electric; Proprietary 5 horsepower electric; Proprietary 5 horsepower electric; Proprietary 5 horsepower electric - Damage: Substantial damage - Flight: Flight test, Part 91 - Operator: Bell Textron Inc - Registered owner: Bell Textron Inc - Airworthiness certificate: Special, Experimental (Special) - Airport: NA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; injuries: none; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review August 16, 2022; seat: none; flight hours: 1,500 total, 1,400 as pilot in command, 36 in the last 90 days, 12 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 130° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 52 °F, dew point 27 °F - Altimeter: 30.31 inHg - Observed at: KMWL, 3 nm away - METAR: KMWL 141553Z AUTO 13009KT 10SM CLR 11/M03 A3031 RMK AO2 SLP260 T01111028 ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20230314013269A](https://openairdocs.org/incident/20230314013269A), Mar 14, 2023: Bell Helicopter Textron Inc APT70, Graford, TX, Substantial damage. UAS was conducting a flight test. UAS rejected the command of the ground control computer and landed in a scrub and tipped over after contact and hit the… ## Docket (5 files) The files NTSB released with the investigation on March 28, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=106895. 8.4 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 6.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16169087&FileExtension=pdf&FileName=6120_1%20N314AL%20CEN23LA135_Redacted-Rel.pdf - Memorandum of record, bell (item 2, PDF, 1 page, 94 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16862365&FileExtension=pdf&FileName=MOR,%20Bell-Rel.pdf - Photo (item 3, PDF, 1 page, 1 photo, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15304747&FileExtension=pdf&FileName=CEN23LA135%20Photo%201-Rel.pdf - Statement of party representatives to NTSB investigation (item 4, PDF, 1 page, 132 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15304288&FileExtension=pdf&FileName=Signed_party_form_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 5, PDF, 1 page, 153 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16094063&FileExtension=pdf&FileName=N314AL%20Release_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.