Date:	Wednesday 2 December 2020
Time:	12:09
Type:	DJI Phantom 4 RTK
Owner/operator:	Network Rail
Registration:	Unregistered
MSN:	0V2GDC6RA30246
Fatalities:	Fatalities: 0 / Occupants: 0
Other fatalities:	0
Aircraft damage:	Destroyed
Location:	Newtongrange railway station, Newtongrange, Dalkeith, Midlothian -   United Kingdom
Phase:	En route
Nature:	Survey
Departure airport:	Newtongrange, Dalkeith, Midlothian
Destination airport:	Newtongrange, Dalkeith, Midlothian
Confidence Rating:	Information verified through data from accident investigation authorities

Narrative:
AAIB investigation to DJI Phantom 4 RTK, (UAS registration n/a): Written off (damaged beyond economic repair) when crashed due to loss of control caused by a detached propeller, Newtongrange railway station, Newtongrange, Dalkeith, Midlothian, 2 December 2020. The AAIB Final Report was published on 20 May 2021, and the following is an excerpt from it:

"Synopsis:
The UAS, a DJI Phantom 4 RTK, was being operated in an automated flight mode to survey a railway track and surrounding infrastructure when one of the four propellers detached whilst in-flight. The aircraft rapidly descended from a height of 70 metres (230 ft) where it struck the ground in the rear garden of a house. No persons were injured.

This investigation has reviewed the new UAS regulations introduced on 31 December 2020 concerning the safe overflight of people and data available to assist in risk assessments. Two Safety Recommendations are made to the UK CAA.

Safety Recommendation 2021-023
It is recommended that the Civil Aviation Authority collate up to date information regarding the failure rates per flying hour for unmanned aircraft systems operating in the Specific category, or previously under a CAA Permission for Commercial Operations, to facilitate effective risk assessments.

Safety Recommendation 2021-024
It is recommended that, until an analysis of failure rates per flying hour has demonstrated an acceptable level of safety, the Civil Aviation Authority should consider prohibiting the overflight of uninvolved persons for those unmanned aircraft operating in the Specific category which rely solely upon their propulsion system for lift that would, following a failure of the propulsion system, impact the ground with a kinetic energy exceeding 80 Joules

AAIB Conclusion
The DJI Phantom 4 RTK struck the ground in the rear garden of a house whilst conducting an aerial survey. The manufacturer stated that the accident had been caused by the left rear propeller detaching from its motor. Failure of UAS aircraft that then fall to the ground pose a risk of injury to people on the ground which is not mitigated by the current UK regulations or the published guidance and policy material. Information on the failure rate of UAS are also not available on which to determine the risk of overflying uninvolved persons.

Safety action
In January 2021, Network Rail precluded the use of DJI Phantom 4s in support of its survey activities. Furthermore, they advised that they intend to carry out trials using a UAS with a MTOM (Maximum Take Off Mass) of less than 250 grams for when there is a need for UAS operations over uninvolved persons. The FMS is also being updated to provide a ‘risk map’ to include information on areas having known hazards, such as transmission masts that could affect UAS communications

Damage to Airframe
Per the above AAIB report "Damage to motors, propellers, arms, landing gear and fuselage". The UAS sustained damage that was "beyond economic repair", and was scrapped.

1. AAIB Final Report: https://assets.publishing.service.gov.uk/media/609cf2d98fa8f56a39f36210/DJI_Phantom_4_RTK_UAS_reg_N-A_06-21.pdf
2. https://www.edinburghnews.scotsman.com/news/transport/drone-fell-230ft-into-back-garden-in-midlothian-village-when-propeller-detached-while-in-flight-3244378
3. https://www.walesonline.co.uk/news/uk-news/official-report-calls-ban-drones-20641274
4. https://www.suasnews.com/2021/05/aaib-investigation-to-dji-phantom-4-rtk/
5. https://www.msn.com/en-gb/travel/news/drone-fell-230ft-into-back-garden-in-midlothian-village-when-propeller-detached-while-in-flight/ar-AAKcmsP
6. https://www.yorkshireeveningpost.co.uk/news/people/drone-ban-must-be-considered-after-rail-survey-aircraft-falls-in-garden-3244555
7. https://www.expressandstar.com/news/uk-news/2021/05/20/drone-ban-must-be-considered-after-rail-survey-aircraft-falls-in-garden--report/
8. https://www.dji.com/uk/support/product/phantom-4-rtk
9. https://en.wikipedia.org/wiki/Newtongrange_railway_station

A DJI Phantom 4 RTK unmanned aircraft system (UAS) was being operated in an automated flight mode when one of the four propellers detached whilst in-flight. The aircraft rapidly descended and struck the ground.

Read the AAIB report: https://t.co/PSVALDdFCx pic.twitter.com/buToYn6XMN

— AAIB (@aaibgovuk) May 20, 2021

Date/time	Contributor	Updates
22-May-2021 15:44	Dr. John Smith	Added
22-May-2021 15:48	Dr. John Smith	Updated [Source, Embed code, ]
01-Jul-2021 20:43	Dr. John Smith	Updated [Cn, Source, Category, ]
30-Nov-2024 18:24	Dr. John Smith	Updated [Registration, Source, Narrative, Category, ]