What happened
On 21 July 2006, a group of five hot air balloons prepared for a mass takeoff at a school sports field in Henley on Thames, Oxfordshire, as part of a corporate event. The crew and passengers for the Ultramagic N-250, registration G-BZJX, were on board and ready for departure at 1815 hrs.
As the pilot began the takeoff sequence, an unexpected gust of wind blew the balloon toward another aircraft, G-CBFY, which was positioned nearby. The pilot attempted to increase the rate of climb by applying maximum heat, but was unable to gain sufficient altitude to clear the stationary balloon. Consequently, the basket of G-SBJX struck the canopy of G-CBFY, causing the latter's canopy to tear and deflate. The flight of G-CBFY was subsequently aborted. There were no injuries to the 11 people on board G-BZJX or the crew of the other balloon, and while the basket caused damage to the other canopy, G-BZJX itself sustained no damage.
The investigation
The investigation examined the meteorological conditions and the positioning of the balloons prior to the incident. While the pilot had attempted to contact the pilot of the downwind balloon via radio without success, the investigation focused on the wind variability. Meteorological data from nearby stations, including Farnborough and Heathrow, showed winds generally consistent with forecasts. However, records from High Wycombe indicated a gust of 12 kt at 1800 hrs, confirming that wind direction and speed were subject to sudden changes.
Findings
- The primary cause of the contact was an unexpected gust of wind in a direction not anticipated by pre-flight planning.
- The wind direction during the takeoff was approximately 70 degrees different from the expected direction.
- The pilot was unable to achieve a sufficient rate of climb to avoid the collision despite applying maximum heat.
- The incident occurred during a mass takeoff, where the proximity of multiple balloons increases the risk of contact.