ASN Wikibase Occurrence # 264923
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| Date: | Thursday 5 March 2020 |
| Time: | 13:45 UTC |
| Type: | DJI Phantom 4 Pro |
| Owner/operator: | Wessex Water |
| Registration: | Unregistered |
| MSN: | 0V2DGC6RA30282 |
| Fatalities: | Fatalities: 0 / Occupants: 0 |
| Aircraft damage: | Destroyed |
| Location: | Bristol Sewage Treatment Works, Kings Weston Lane, Avonmouth -
 United Kingdom
|
| Phase: | En route |
| Nature: | Survey |
| Departure airport: | Bristol Sewage Treatment Works, Kings Weston Lane, Avonmouth BS11 0YS |
| Bristol Sewage Treatment Works, Kings Weston Lane, Avonmouth BS11 0YS | |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
AAIB investigation to DJI Phantom 4 (UAS registration n/a): Controlled flight into wind turbine, Bristol sewage treatment works, Kings Weston Lane, Avonmouth BS11 0YS, 5 March 2020. The AAIB Final Report was published on 10 September 2020, ansd the following is an excerpt from it...
"The unmanned aircraft system (UAS) was being used to conduct an aerial survey of a sewage treatment works that contained four wind turbines in the survey area. The pilot was using the NATS Drone Assist app as part of the flight planning and risk assessment of the flight; however, the app did not mention the wind turbines, so the pilot looked up “wind turbine height” on the internet which returned a height of 328 ft.
A search was also made for any guidance material on flying in the vicinity of wind turbines, but none was found. The pilot had been made aware of aeronautical charts during UAS pilot training but did not use them when planning and risk assessing a flight.
The operator’s CAA Permission limited the height of the flights to 400 ft above the surface. It also limited the flying to greater than 50 m (164 ft) from any structure not under the control of the pilot; however, since the operator was also the owner of the wind turbines, this second limitation did not apply. Therefore, the pilot decided to fly the aircraft at 400 ft above the ground to provide clearance of 72 ft between it and the top of the turbine blades, which the pilot assessed to be a sufficient distance. However, the aircraft was destroyed when it flew into a wind turbine which had a height of 413 ft above the ground
=Analysis and findings=
The pilot was aware of the wind turbines at the site where the aerial survey was to be conducted but was unable to find any accurate information about the height of these either on the app used to plan the flight or from an internet search.
For a UAS pilot flying visual line of sight with the aircraft, tall obstacles may be obvious to see but their actual height is difficult to assess visually. All known ground obstacles greater than 300 ft in height are shown on aeronautical charts. These charts, and apps that use the same obstacle database, are one source of accurate information, and provide a clear indication of areas to avoid flying a UAS if limited to flying not above 400 ft.
However, for obstacles less than 300 ft, UAS pilots will need to determine their accurate heights from other sources. UAS pilots are responsible for flying their aircraft within the limitations imposed by their CAA Permission and so must ascertain the accurate height of any hazard or obstacle near the planned flightpath.
=Safety action=
Having been reminded of the obstacle and airspace information available on aeronautical charts or flight planning apps that have access to this information, the operator has amended its flight planning and risk assessment procedures to include reference to these.
=Damage To Airframe=
Per the above AAIB Report, the UAV was "destroyed".
Aditional: According to a contemporary local newspaper report ("Bristol Evening Post" 16 September 2020):
"A Wessex Water spokeswoman said a drone, operated by an experienced pilot, was taking aerial surveys of their Avonmouth site when it collided with a wind turbine. He added: 'No damage was caused to the turbine and the incident was recorded with the Air Accidents Investigation Branch (AAIB). While incidents of this nature are extremely rare, the AAIB has reminded us about the need to refer to obstacle and airspace information for future flights'".
Sources:
1. AAIB Final Report: https://assets.publishing.service.gov.uk/media/5f3cf8818fa8f51741ca5d87/DJI_Phantom_4__reg_na__09-20.pdf
2. https://www.bristolpost.co.uk/news/bristol-news/drone-crashes-wind-turbine-extremely-4521270
3. http://theuavdigest.com/tag/embry-riddle/
4. https://www.wessexwater.co.uk/community/education/avonmouth
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 30-Jun-2021 19:03 | Dr. John Smith | Added |
| 30-Jun-2021 19:05 | Dr. John Smith | Updated [Narrative] |
Corrections or additions? ... Edit this accident description
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