ASN Wikibase Occurrence # 200762
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| Date: | Friday 3 February 2017 |
| Time: | |
| Type: | Thales Watchkeeper WK450 Mk 1 |
| Owner/operator: | |
| Registration: | WK042 |
| MSN: | |
| Fatalities: | Fatalities: 0 / Occupants: 0 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Cardigan Bay -
 United Kingdom
|
| Phase: | En route |
| Nature: | Military |
| Departure airport: | Aberporth Airport (EGFA) |
| Aberporth Airport (EGFA) | |
| Confidence Rating: |  Accident investigation report completed and information captured |
The Thales Watchkeeper WK450 Mk 1 was lost in the sea when being flown from its ground station by a combined crew of Thales and UAV Tactical Systems (UAVTS) operators who were testing de-icing equipment. Historical weather data for Aberystwyth shows that temperatures on the day averaged about 9°C.
DSA report:
SECTION 1.4.9 - SUMMARY OF FINDINGS
1.4.9.1. The Panel concluded that the cause of the crash was aerodynamic stall
due to inaccurate air speed being used by the FCS within the VMSC. This air
speed was calculated by the VMSC, which was reacting to inaccurate pitot total
pressure measurements caused by pitot blockages from flying in cloud and
precipitation over a prolonged period. The FCS response to the erroneous air
speed included pitching oscillations and FEP manoeuvres, over speeding and
unstable flight near-stall speed, which may have caused physical damage to the
left V-tail. Using the Reason's Swiss Cheese Analysis56, the causal, contributory
and aggravating factors are shown in figure 1.4.9.1.
Accident investigation:
 |
|
Sources:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/654737/DSA_AAR_16-17_-_RT.pdf
http://www.theregister.co.uk/2017/11/01/thales_watchkeeper_crashes/
DSA_____________________________
Final accident report:
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/792947/20190402-WK042_SI_Final_Report-_Redacted__RT-OS.pdf
Media:
NEW: The @DefenceHQ investigation into the cause of a Watchkeeper crash in February 2017 has been published.
— Henry Jones (@hthjones) 11 avril 2019
It has identified "aerodynamic stall due to inaccurate air speed" as the principle cause for the crash. pic.twitter.com/VlmbPnpZZ0
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 01-Nov-2017 12:08 | harro | Added |
| 11-Apr-2019 10:57 | Iceman 29 | Updated [Departure airport, Destination airport, Source, Embed code, Narrative] |
| 12-Jun-2019 09:47 | harro | Updated [Embed code, Accident report, ] |
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