What happened
On October 13, 1963, the gas balloon HB-BIU, known as "Emil Messmer," departed from Schlieren, Switzerland. Although the pilot had received weather reports suggesting low surface winds, the balloon encountered significantly stronger and more gusty conditions than anticipated during the flight.
As the balloon approached the Kaufbeuren area in Bavaria, the pilot attempted a landing at an inactive airfield. However, due to intense gusts, the balloon was unable to land safely and was instead driven into the bed of the Wertach River. During this period of uncontrolled movement, the basket struck vegetation, causing the pilot to lose temporary control of the vent line.
Following the river crossing, the balloon continued to drift, striking fences and eventually colliding with the roof of a building. The envelope made contact with a 380V electrical line, which snapped. The resulting short circuit ignited the escaping gas, causing the balloon to burn rapidly. The pilot ordered all passengers to evacuate the basket onto the roof before jumping to safety. While the passengers escaped with minor injuries, the fire caused significant damage to the building's structure.
The investigation
Investigators examined the flight logs, weather charts from the German Sea Weather Office, and eyewitness accounts from the scene. The investigation focused on why the pilot was unable to utilize the rip cord to rapidly deflate the balloon during the high-wind event.
While the pilot reported that the rip cord had become entangled with the vent line due to contact with trees, investigators noted that this could not be definitively proven. The investigation also reviewed the meteorological data, which showed that while initial reports suggested calm surface winds, the actual conditions at the time of the accident involved severe gusts capable of blowing hats off bystanders.
Findings
- The primary cause of the accident was an uncontrolled ground drift caused by wind conditions that deviated sharply from the pilot's pre-flight weather information.
- The pilot's decision to proceed with the flight was based on inaccurate wind forecasts that did not account for the sudden increase in wind speed and turbulence.
- The balloon's contact with a high-voltage power line caused a short circuit, which served as the ignition source for the gas.
- The pilot's lack of experience in managing such extreme wind conditions contributed to the inability to execute an effective emergency landing or utilize the rip cord effectively.