A serious incident involving controlled flight into terrain (CFIT) during a night vision goggle (NVG) operation offers critical lessons for pilots. NVG flights remain among the highest-risk categories in aviation, often conducted at low altitudes in uncontrolled environments. Each situation brings its own unique set of threats that demand careful assessment and mitigation. This case highlights the risks and reinforces key strategies for safer NVG operations.
The incident
On Nov. 6, 2020, an Airbus EC135 helicopter emergency medical services (HEMS) crew —comprising a commander, a technical crew member (TCM), and a doctor — was flying at night from an industrial site in Slagelse, Denmark, back to Ringsted Airport (EKRS), their HEMS base.
The crew was aware of increasing ground fog in the area, including near EKRS, but they felt comfortable with the visual references available.
In the final stage of their approach, the commander suddenly saw only a bright white light through his NVGs, lost visual references, and initiated a go-around. During this maneuver, the helicopter unexpectedly struck the ground in a farm field before climbing away. Initially, the crew believed they had impacted the aerodrome itself — but they were actually 210 meters (690 feet) short of the helipad, in a ploughed field.
The crew had departed Slagelse at around 7 p.m., deep into a 14-hour shift. They used NVGs on departure, climbing to 1,200 feet (366 meters) above mean seal level (AMSL) en route to EKRS. Along the way, they observed shallow fog to the south and increased halos and glare around vehicle and building lights — indicating high humidity and worsening fog conditions.
They approached EKRS from the west and activated the runway and helipad lights via the aerodrome radio frequency. Pre-landing checks and a landing briefing were completed — but no go-around criteria were discussed. The commander stated he would conduct a “shallow approach to obtain good references.”
The helicopter entered a left-hand downwind for Runway 23 at 600 ft. (183 m) above ground level (AGL). Turning base, with a groundspeed of about 45 kts (83 km/h), the commander lowered his NVGs and reported that everything appeared clear. However, he also noticed fog patches below.
Crossing 200 ft. (61 m) AGL, groundspeed decreased to 15 to 20 knots (28 to 37 km/h). Suddenly, without warning, the commander saw only bright light through his NVGs. Startled, he initiated a go-around, but the helicopter impacted the ground almost simultaneously, leaving visible impact marks.
During the climb-out, the crew heard a maximum power aural warning. The TCM began calling out airspeed and altitude while the helicopter ascended. Visual references were regained, and the climb continued, though the crew noticed a slight increase in vibration.
Believing they had struck the aerodrome, they were unaware the actual impact site was a nearby farm field. They aborted their plan to land at EKRS and diverted safely to Slagelse Hospital (EKSE).
Photos taken after the incident showed a bent crossbeam on the airframe from the impact.
Investigation findings
So, what caused this CFIT incident? The investigation concluded:
• The flight crew did not adequately identify low-visibility threats due to fog.
• A shallow approach reduced vertical clearance from the ground fog layer.
• Visual illusions contributed to reduced situational awareness on final.
• Fog patches likely caused an NVG whiteout around 100 ft. (30 m) AGL.
• The startle effect delayed the go-around initiation.
• Maximum power application could not prevent ground impact.
• A possible subconscious desire to return to base (“get-home-itis”) may have influenced decision-making.
Key takeaways
1. Integrate threat and error management (TEM) into briefings
Actively incorporating TEM in your briefings helps the crew identify threats and strategies to mitigate them. Without this, it becomes difficult to respond effectively when things go wrong.
2. Don’t let NVGs and shallow fog fool you
Vertically, you may see through shallow fog, but horizontally, visibility can drop sharply. NVGs amplify light, sometimes giving the illusion of better visibility than actually exists. Scan underneath your goggles regularly for a gross error check.
3. Shallow approaches reduce visual references in fog
The report noted the commander’s choice to fly a shallow approach “seems irrational” given the fog. Staying above fog as long as possible — within legal and operational limits—provides better visual references.
4. The black hole effect
When there are few light sources in your peripheral vision, you may misjudge your altitude. Refer to your instruments and use pilot monitoring to avoid falling into this illusion.
5. Managing the startle effect
Surprise is inevitable when reality doesn’t match expectations. The best defense is prevention — proactively identify threats and discuss response strategies to maintain situational awareness.
6. Communicate go-around criteria
Without clear go-around criteria, it’s hard to judge whether to continue an approach. In multi-crew ops, both pilots need to share the same mental model and agree on what conditions call for a go-around.
Conclusion
Shallow fog, NVGs, and night HEMS operations are a potent combination of risk factors. Hopefully, this incident summary offers better insight into how deceptive shallow fog can be — and why it should never be underestimated.
