Incident AgustaWestland AW139 5Y-NPS,
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ASN Wikibase Occurrence # 189908
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Date:Thursday 8 September 2016
Time:13:15 UTC
Type:Silhouette image of generic A139 model; specific model in this crash may look slightly different    
AgustaWestland AW139
Owner/operator:Kenya Police Air Wing
Registration: 5Y-NPS
MSN: 31717
Fatalities:Fatalities: 0 / Occupants: 4
Aircraft damage: Written off (damaged beyond repair)
Location:Mathare North, Nairobi -   Kenya
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Aerial patrol
Departure airport:Nairobi-Wilson Airport (WIL/HKNW)
Destination airport:Nairobi-Wilson Airport (WIL/HKNW)
After a brief flight of approximately 9 minutes, the helicopter established hover above the Mathare area in Nairobi, at approximately 5700ft barometric altitude. Witnesses from the ground reported that the aircraft spent about 2 minutes in HOGE above Mathare, before suddenly losing altitude and crashing inside the perimeter of the National Youth Service Engineering Institute, while spinning around the vertical axis with a significant yaw rate at 13.15 UTC, consistent with videos posted on social media. Three POB suffered serious injuries and one minor injuries.

At 13:14:49, the following chain of events occurred:
The pilot significantly increased the collective.
The torque limiter logic prevented the engines from exceeding 110% torque.
The Nr drooped to 96% with the “ROTOR LOW” Aural Warning.
The pilot compensated for the right yaw with left pedal.
The pilot lowered the collective 20% in about 2.5s.
Nr returned to 100%, descent rate increased, and the aircraft started to yaw left.
Aircraft reached 20°nose-down, 4000ft vertical speed, and 60kts ground speed.

At 13:15:03, the following occurred:
A sudden rise in collective input without any pedal compensation; the yaw rate increased.
The aircraft crashed with a spiraling motion.



Revision history:

08-Sep-2016 14:32 harro Added
08-Sep-2016 15:46 CTYONE Updated [Registration, Cn, Operator, Total occupants, Source]
08-Sep-2016 16:48 CTYONE Updated [Aircraft type]
08-Sep-2016 19:50 Aerossurance Updated [Phase, Nature, Narrative]
09-Sep-2016 05:27 Iceman 29 Updated [Embed code]
09-Sep-2016 09:01 TB Updated [Damage]
10-Sep-2016 06:31 Anon. Updated [Departure airport, Destination airport, Embed code, Photo, ]
10-Sep-2016 14:36 Iceman 29 Updated [Embed code]
11-Sep-2016 10:26 Aerossurance Updated [Source, Narrative]
20-Sep-2016 07:09 Aerossurance Updated [Source]
11-Oct-2018 19:39 Aerossurance Updated [Time, Departure airport, Destination airport, Source, Narrative]
27-Oct-2019 18:02 Aerossurance Updated [Embed code]
27-Oct-2019 18:04 Aerossurance Updated [Embed code]
27-Oct-2019 18:13 Aerossurance Updated [Source, Embed code, Narrative]

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