B412, vicinity Karlsborg Sweden, 2003

Summary: 

On 25 March 2003, the crew of a Bell 412 lost control of the aircraft as a result of pilot mishandling associated with the development of a Vortex Ring State.

Event Details
When: 
25/03/2003
Event Type: 
Day/Night: 
Day
Flight Conditions: 
VMC

18750

Flight Details
Aircraft: 
Type of Flight: 
Military/State
Flight Origin: 
Intended Destination: 
Take-off Commenced: 
Yes
Flight Airborne: 
Yes
Flight Completed: 
No
Phase of Flight: 
Manoeuvring
Location
Location - Airport
Airport: 
HF
Tag(s): 
Ineffective Monitoring, Manual Handling
LOC
Tag(s): 
Flight Management Error, Extreme Pitch
Outcome
Damage or injury: 
Yes
Aircraft damage: 
Hull loss
Non-aircraft damage: 
Yes
Non-occupant Casualties: 
No
Occupant Injuries: 
Few occupants
Occupant Fatalities: 
Few occupants
Number of Occupant Fatalities: 
1
Off Airport Landing: 
Yes
Ditching: 
Yes
Causal Factor Group(s)
Group(s): 
Aircraft Operation
Safety Recommendation(s)
Group(s): 
Aircraft Operation, Aircraft Airworthiness
Investigation Type
Type: 
Independent

Description

On 25 March 2003, the crew of a Bell 412 lost control of the aircraft as a result of pilot mishandling associated with the development of a Vortex Ring State.

Summary

This is the Summary from the report published by the Swedish Accident Investigation Board:

"During the concluding Swedish Army exercise for 2003…a military ambulance helicopter based on the Karlsborg base took part. In connection with a rescue exercise, air-sea rescue open water (LÖV), the helicopter performed repeated sorties to assist simulated emergency cases in lakes in the vicinity of Karlsborg. In the final phase of the ninth sortie, the pilots lost control of the helicopter which, with a high rate of descent, struck the ice on Bottensjön lake. The ice broke on impact, the helicopter turned over onto its back and sank nose-first towards the bottom of the lake and with the rear of the fuselage against the edge of the ice at water level.

Three crew members were able to leave the helicopter and make their way up to the surface of the water and onto the ice. A fourth crew member drowned in the accident…

…Investigation revealed no technical faults or shortcomings that could have caused the accident.

…The accident was caused by the helicopter being manoeuvred into an aerodynamic situation in which, as its speed was being reduced to IAS=0, sank into its own downwash located diagonally in front of and below the helicopter. This aerodynamic situation developed into a vortex ring state (VRS) which became noticeable in the measurement data approximately 8 s before impact on the ice, whereafter the helicopter’s rate of descent could not be prevented despite increasing input of collective pitch. A contributory cause of the accident was the two pilots’ simultaneous manoeuvring of the helicopter. This allowed small or no chance of discovering in time that they were approaching the helicopter’s limit for safe flight."

Related Articles

LOC

Further Reading

For further information see the full Report published by the Swedish Accident Investigation Board (SHK).

SKYbrary Partners:

Safety knowledge contributed by: