Hot Air Balloon Strikes Power Lines in Porvoo

Casualties unknown • FI

A Lindstrand A-120 hot air balloon struck 20 kV power lines during landing near Porvoo, causing the basket to detach and the envelope to sustain burn damage.

What happened

On the evening of June 5, 1998, a Lindstrand A-120 hot air balloon, registration OH-GSM, experienced a significant damage event while attempting to land at the Kokonniemi Ski Center near Porvoo. The flight, which carried one pilot and five passengers, had been operating under varying wind conditions, leading the pilot to change takeoff locations several times to ensure a landing on mainland Finland.

As the pilot approached the chosen landing site, the balloon descended rapidly toward a 20 kV power line situated approximately 70 meters from the edge of a nearby forest. Despite the pilot's attempt to increase lift by activating both burners, the basket struck the lines. The impact caused a short circuit, and the intense heat from the electrical discharge caused three of the four basket suspension cables to snap. The basket detached from the envelope, causing the balloon to surge upward to approximately 1,500 feet.

During the separation, the burners remained open, and the resulting flames caused significant burn damage to 42 panels of the balloon's envelope. The pilot, demonstrating remarkable skill, climbed to the edge of the basket to manually close the gas valves and reignite the burners. After approximately 10 minutes of continued flight, the pilot successfully performed a controlled landing in a nearby field. There were no injuries to the crew or passengers.

The investigation

The investigation examined the flight preparation, weather conditions, and the mechanical sequence of the impact. Investigators noted that the pilot had utilized a quick-deflation system, indicating the selection of a tight landing area. The investigation also reviewed the aircraft's maintenance status, finding the OH-GSM to be airworthy and the pilot highly experienced in both passenger and instructional flights.

Findings

The pilot selected a landing site that was too small for the prevailing weather conditions.
The approach altitude was insufficient to safely clear the 20 kV power lines located at the edge of the landing zone.
The basket struck the power lines due to an inadequate approach height relative to the obstacle.
The electrical short circuit caused the sudden failure of the suspension cables and subsequent envelope damage from burner flames.

Probable cause

The primary cause of the accident was the pilot's selection of a landing area that was too small for the existing wind conditions, which necessitated an approach altitude that was too low to clear the 20 kV power lines.

Frequently asked questions

What happened in the 1998-06-05 aircraft accident near FI?

A Lindstrand A-120 hot air balloon struck 20 kV power lines during landing near Porvoo, causing the basket to detach and the envelope to sustain burn damage.

What aircraft was involved and where did it happen?

The accident on 1998-06-05 involved a aircraft, registration OH-GSM, at FI.

What was the probable cause of the accident?

The primary cause of the accident was the pilot's selection of a landing area that was too small for the existing wind conditions, which necessitated an approach altitude that was too low to clear the 20 kV power lines.

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