Accident pattern · EMS-configured twin and single turbine helicopters (general)
HEMS night CFIT in degraded visual conditions — helicopter-type lesson
Report: NTSB Special Investigation Report on EMS Operations, SIR-06/01
What happened
A night HEMS flight is accepted into deteriorating weather over dark, featureless terrain. The crew continues visually, loses outside visual references, and the helicopter strikes terrain or water under control (CFIT) with no prior warning to the crew.
Chain of causes
- 1Pressure to complete the mission for the patient influences the go/no-go decision
- 2No formal risk-assessment tool used before departure
- 3Single-pilot flight into reducing visibility without an autopilot upper-modes flown, or without reverting to instruments early enough
- 4No terrain awareness warning system, or crew did not react to it
Lessons
- Use a formal pre-flight risk matrix and empower any crew member to stop the flight
- Transition to instruments and use the 4-axis autopilot/AFCS upper modes early if visual references degrade, rather than pressing on visually
- Night unaided flight over unlit terrain should be treated as an IMC risk
- Terrain awareness and warning systems (HTAWS) must be fitted and heeded
What changed afterwards
FAA and EASA HEMS rules now push operators toward NVG use, HTAWS fitment, formal risk assessment, and instrument-capable aircraft such as the H145 with Helionix 4-axis AFCS.