Accident Aérospatiale AS 350BA Ecureuil ZK-HEX,
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ASN Wikibase Occurrence # 221917
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Date:Sunday 17 February 2019
Type:Silhouette image of generic AS50 model; specific model in this crash may look slightly different    
Aérospatiale AS 350BA Ecureuil
Owner/operator:Reid Helicopters Nelson Ltd.
Registration: ZK-HEX
MSN: 1654
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Written off (damaged beyond repair)
Location:Eves Valley, Nelson -   New Zealand
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Fire fighting
Departure airport:
Destination airport:
Confidence Rating: Information verified through data from accident investigation authorities
The helicopter crashed while battling a wild fire. The pilot sustained minor injuries.

According to TAIC: "The circumstances reported to date are that the... helicopter was operating with a monsoon bucket over the Pigeon Valley area near Nelson. Something caused the pilot to conduct an emergency landing. The helicopter landed heavily and the sole pilot received moderate injuries. The nature of damage to the helicopter is yet to be established".

A preliminary report issued by the NZ Helicopter Association and CAA said their was a sudden yaw to the left followed by one to the right and a pitch up. The pilot immediately jettisoned the monsoon bucket, and made a forced landing. Their investigation found the most likely scenario was that the top ring through which the monsoon bucket was attached to the helicopter, partially collapsed.

TAIC concluded:

After dropping a load of water on the target area, the helicopter was returning to a nearby pond to refill the monsoon bucket. The lifting line suspending the monsoon bucket made contact with and disabled the helicopter’s tail rotor, resulting in a loss of directional control.

A tubular, segmented, stainless-steel ring was held in place at the top of the bucket with hook-and-loop fastener tabs. This ring was intended to maintain the circular shape of the top section of the bucket when it was being filled.

It was likely that during the accident flight, one or more of the hook-and-loop fastener tabs came undone, allowing the ring to become insecure and the bucket to lose rigidity. This likely resulted in a sudden change to the aerodynamic stability of the bucket in the airflow, leading to the bucket trailing behind the helicopter and the lifting line contacting the tail rotor. The reason for the hook-and-loop fastener tabs coming undone could not be determined.

The bucket manufacturer had developed design improvements to reduce the likelihood of the hook-and-loop fastener tabs coming undone, but the modification was not mandatory. Therefore, the Transport Accident Investigation Commission (Commission) has made a recommendation that the Cloudburst monsoon bucket manufacturer ensure that all Cloudburst monsoon buckets with this hook-and-loop fastener system are modified with the design improvements.

The monsoon bucket lifting line was of a length that likely increased the risk of the external load coming into contact with the tail rotor. The Commission found that at the time of the accident, there was insufficient guidance available to pilots on the appropriate line length for monsoon bucket operations. The aircraft manufacturer has since published a Safety Information Notice on this issue and the operator has incorporated this guidance into its operating procedures.

Sources: (p4)


Revision history:

17-Feb-2019 07:00 gerard57 Added
17-Feb-2019 07:53 gerard57 Updated [Source]
17-Feb-2019 07:58 Anon. Updated [Location]
17-Feb-2019 14:15 Iceman 29 Updated [Location, Source, Narrative]
18-Feb-2019 15:53 Anon. Updated [Aircraft type, Source]
18-Feb-2019 15:54 harro Updated [Aircraft type]
18-Feb-2019 20:35 Aerossurance Updated [Source, Narrative]
22-Feb-2019 15:31 RobertMB Updated [Aircraft type, Registration, Cn, Operator, Source]
22-Feb-2019 15:32 RobertMB Updated [Operator]
16-Dec-2019 20:51 Aerossurance Updated [Source, Narrative]
16-Dec-2019 20:55 Aerossurance Updated [Source]
04-Jan-2021 10:50 Aerossurance Updated [Source, Narrative]
15-Jan-2021 17:45 Aerossurance Updated [Source]
16-Jan-2021 12:02 Aerossurance Updated [Embed code]
25-Jan-2022 07:07 Ron Averes Updated [Location, Embed code]
22-Jul-2023 05:23 Ron Averes Updated [Aircraft type]

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