What aircraft was involved and where did it happen?

The accident on 2010-02-05 involved a Bell 427, registration OK-AHB, at 1 km NE Horní Olešná, CZ.

What was the probable cause of the accident?

The accident was caused by the pilot's decision to continue the mission into weather conditions that were likely below the established operational minimums for a single-pilot HEMS flight, resulting in a loss of visual ground references over snow-covered terrain and an inability to maintain safe altitude.

HEMS Bell 427 crashes in snowy terrain near Horní Olešná

A medical helicopter crashed in a field near Horní Olešná after the pilot encountered visibility conditions likely below operational minimums.

What happened

On February 5, 2010, a Bell 427 helicopter, registration OK-AHB, operated by ALFA-HELICOPTER, was performing a HEMS (Helicopter Emergency Medical Service) mission. The crew, consisting of a pilot, a doctor, and a flight nurse, was flying from the Hosín base toward Jihlava to perform a secondary patient transport.

During the flight, the pilot encountered deteriorating weather conditions. While the pilot initially observed visibility between 3 and 5 km, the visibility dropped to approximately 2 km near Jindřichův Hradec and further decreased to roughly 1.5 km near Horní Olešná. In response to the worsening weather, the pilot reduced speed and altitude, eventually deciding to abort the mission to Jihlava.

While flying at a very low altitude over a snow-covered field, the pilot encountered 22 kV electrical lines. Despite maintaining power, the aircraft's uncontrolled descent led to a collision with the ground at a low forward speed. The impact caused the landing skids to break and the helicopter to overturn onto its left side, resulting in the destruction of the main rotor blades and the tearing of the gearbox from the fuselage. The crew escaped the overturned aircraft without injuries.

The investigation

An investigation by the ÚZPLN established that the pilot was properly qualified for VFR flight and was medically fit. The aircraft was airworthy and had sufficient fuel for the mission.

The investigation focused on the pilot's decision-making and the loss of visual references. It was noted that the pilot had set the radio altimeter's low-altitude warning at 200 ft, even though operational procedures for landing at unexamined sites required a setting of 35 ft. Furthermore, the investigation examined the meteorological conditions, noting that the visibility in the area of the accident was likely below the HEMS operational minimums for single-pilot operations.

Findings

The primary cause was the pilot's decision to continue the flight until conditions had likely deteriorated below HEMS operational minimums for single-pilot operations.
The loss of sufficient visual references over the snow-covered terrain led to an inability to safely control the aircraft's height above the ground.
The pilot failed to set the radio altimeter warning to the required lower altitude, which could have prevented the uncontrolled descent.
The terrain was rising toward the electrical lines, contributing to the impact despite the pilot's attempt to maintain altitude.