What happened
On June 1, 2003, a commercial hot air balloon flight carrying 13 people was conducting a landing near Dorfen, Bavaria. The flight had departed from an external launch site near Zangenberg/Emerkam approximately 90 minutes earlier. As the Schröder / Fire G balloon approached the landing site at a low sink rate, it made contact with the edge of an unpended path. Due to an embankment sloping downward to the right of the path, only one-third of the basket's width made contact with the ground.
This uneven contact caused the basket to decelerate on one side, resulting in a 90-degree rotation. As the balloon envelope continued to deflate, the basket tipped forward onto its narrow side. The shifting weight and the pulling force of the deflating envelope caused the basket to overturn completely, with the burner assembly striking the ground with significant force. The impact trapped the passengers upside down within the basket. During the process of deflating the envelope, a fire ignited beneath the basket, fueled by escaping propane. The fire led to the destruction of the aircraft and the explosion of two stainless steel gas cylinders.
The investigation
The BFU investigation examined the sequence of the landing, the mechanical state of the aircraft, and the meteorological conditions. Investigators found that the pilot was properly licensed for commercial passenger transport and possessed extensive experience. The aircraft was maintained according to regulations and was operating within its design limits. Meteorological data indicated wind speeds of 8–10 knots with gusts exceeding 12 knots at the time of the accident.
Technical analysis of the site showed that no gas hoses or connections were forcibly severed by the overturning of the basket. Investigators also examined the behavior of the stainless steel gas cylinders, noting that while some valves were open, others remained closed. Research into the cylinder explosions suggested that extreme localized heating from the flames caused the material strength of the steel to fail before the safety valves could relieve the internal pressure.
Findings
- The primary cause of the accident was the uncontrolled release of propane following the basket's overturn.
- The basket overturned because it landed on the edge of an embankment, causing asymmetric braking and a 90-degree rotation.
- The fire was likely ignited because the pilot flames had not been extinguished prior to landing, providing a continuous ignition source for the escaping gas.
- The passengers and the pilot sustained injuries, with 3 persons seriously injured and 3 persons lightly injured.
- The structural integrity of the gas cylinders failed due to intense, localized heat from the fire, leading to explosions.