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ASN Wikibase Occurrence # 76234
Last updated: 13 September 2021
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Date:05-JUN-2006
Time:12:20
Type:Silhouette image of generic BK17 model; specific model in this crash may look slightly different
Eurocopter EC 145 (BK 117C-2)
Owner/operator:Sécurité Civile
Registration: F-ZBPB
MSN: 9007
Fatalities:Fatalities: 3 / Occupants: 4
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Category:Accident
Location:Gavarnie, Hautes-Pyrénées -   France
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Ambulance
Departure airport:
Destination airport:
Investigating agency: BEAD
Narrative:
Crashed in mountains (west slope of Petit Astazou).

Causes of the event
The accident resulted from a loss of yaw control.
The investigation identified two possible hypotheses as to the cause of the loss of control:
- a rock fall(s) damaging the CARs or the main rotor:
- the occurrence of a long-term stationary flight, in an area unfavourable to this risk, may have been a determining factor.
- reaching the efficiency limit of the RAC during the clearance manoeuvre :
The absence of a flight-parameter recorder did not make it possible to determine the circumstances and determining factors for this hypothesis. However, it was considered that :
- the theoretical margin available could have been consumed by the cumulative effects:
- of unfavourable local aerology (turbulence, downdrafts);
- the installation of yaw inertia;
- of the clearance trajectory used (straight translation);
- weak right tailwind.
- The absence of a reconnaissance passage did not allow the pilot to assess the local aerology and may have contributed to an overestimation of the available margin;
-the pilot's lack of expertise in the mountain rescue mission on BK117 C2 may have led to a lack of comfort which contributed to reaching this limit:
-by overdosing the power control;
-by a difficulty to identify the foot margin and to control the yaw rate under autopilot;
-by incomplete and/or late rudder action, allowing yaw inertia to build up.
-the phenomenon of "false foot stop" (forces felt on the rudder pedals in transit) may have been encountered and contributed to a momentarily incomplete rudder action;
-it is likely that the yaw rotation was initiated by the pilot; late detection by the pilot of the yaw control problem encountered is then likely the cause of the lack of backup manoeuvring when the aircraft first found itself facing the valley (engagement of forward translation). Second, the margins in relation to the terrain did not allow the pilot to apply the control magnitudes required to stop the rotation, or, if they were applied, the impact with the terrain could not be avoided.


Sources:

http://www.aerosteles.net/fiche.php?code=gavarnie-ec145
https://www.defense.gouv.fr/english/content/download/105576/1032042/Rapport%20public%20BEAD-air-S-2006-013-A.pdf

Accident investigation:
cover
  
Investigating agency: BEAD
Status: Investigation completed
Duration:
Download report: Final report


Revision history:

Date/timeContributorUpdates
11-Aug-2010 10:30 TB Added
01-Nov-2012 11:26 TB Updated [Aircraft type, Location, Source, Narrative]
23-Nov-2012 09:56 TB Updated [Aircraft type]
13-Sep-2017 08:47 harro Updated [Total occupants]
27-Jul-2020 15:04 KagurazakaHanayo Updated [Time, Source, Narrative]
27-Jul-2020 15:36 harro Updated [Phase, Nature, Narrative, Accident report, ]
24-Oct-2020 12:21 Aerossurance Updated [Aircraft type, Accident report]

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