ASN Wikibase Occurrence # 270371
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| Date: | Wednesday 3 February 2021 |
| Time: | 11:38 UTC |
| Type: | UAVE Prion Mk 3 (UAS) |
| Owner/operator: | UAVE Ltd |
| Registration: | Unregistered |
| MSN: | 3-007 |
| Fatalities: | Fatalities: 0 / Occupants: 0 |
| Aircraft damage: | Substantial |
| Location: | MoD Area 7, Salisbury Plain, Chitterne, Wiltshire -
 United Kingdom
|
| Phase: | En route |
| Nature: | Training |
| Departure airport: | MoD Area 7, Salisbury Plain, Chitterne, Wiltshire |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
AAIB investigation to UAVE Prion Mk 3, (UAV, registration n/a): Loss of power followed by stall and spin, Salisbury Plain, Wiltshire, 3 February 2021. The AAIB final report into the incident was published on 9 December 2021, and the following is the summary from it:
"During a training flight at a height of 400 ft agl the engine lost some power and the aircraft started to descend. The operator sent a command to limit the throttle but this did not resolve the issue. The autopilot was in a mode whereby the throttle was used to control airspeed and elevator used to control altitude. The loss of altitude caused the autopilot to pitch the unmanned aircraft nose-up until it stalled, entered a spin, and then hit the ground.
The loss of power was determined to have been caused by a loose spark plug cap. After the accident the engine was modified with a safety feature which provides additional security to ensure the plug cap is fitted correctly. This modification has been embodied fleet wide.
=AAIB Conclusions=
The UAS accident was the result of a combination of factors:
● The engine suffered a loss of power due to a loose spark plug cap.
● The attempt to resolve the power issue by limiting the throttle did not work.
● Limiting the throttle caused the autopilot to remain in a mode that would result in the autopilot stalling the UA.
● The system design did not permit the operator to change autopilot modes in-flight.
● There was insufficient time to take manual control when the airspeed started reducing towards the stall speed.
=Safety Actions=
Following this accident the engine has been modified and the operator has changed their training and operational procedures to help mitigate the risk of recurrence.
=Damage sustained to airframe=
Per the above AAIB Report: "Substantial damage to forward fuselage, front skids, both wings, propeller and rear boom"
Sources:
1. AAIB Final Report: https://assets.publishing.service.gov.uk/media/618a9775d3bf7f5601cf3246/Prion_Mk_3__UAS_registration_n_a__12-21.pdf
2. https://www.uave.co.uk/prion.php
3. https://en.wikipedia.org/wiki/Salisbury_Plain#Military_use
Media:
UAVE Prion Mk 3 (UAS) recovered post accident (top left picture):
AAIB December Bulletin now publishedhttps://t.co/a5ML1GcqwA pic.twitter.com/dP8e1aBK2v
— AAIB (@aaibgovuk) December 9, 2021
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 09-Dec-2021 23:13 | Dr. John Smith | Added |
| 09-Dec-2021 23:14 | Dr. John Smith | Updated [Embed code, Narrative] |
Corrections or additions? ... Edit this accident description
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