What happened
During the preparation for a sightseeing flight near the Hazelmere trailer park in Surrey, British and Columbia, an Aerostar S77A hot air balloon, registered C-GTRU, was subject to an intense, uncontrolled propane fire. The aircraft, operated by SRP Adventure Tours Limited, was being inflated when a sudden explosion and fire erupted in the basket.
As the fire spread, the pilot and ground crew attempted to evacuate the 12 passengers from the basket. Because the emergency deflation system was not activated, the balloon began to rise while passengers were still jumping from the basket. The basket was tethered to a trailer by a synthetic strap, which eventually failed due to heat and tension. This released the balloon, which continued to climb until the envelope collapsed. The burning wreckage subsequently fell into a nearby residential area, igniting three mobile homes and two vehicles.
The investigation
The investigation focused on the fuel system and the circumstances leading to the fire. It was determined that the pilot had modified the balloon's configuration by adding a fourth fuel cylinder to increase lift and flight duration, as the aircraft was operating significantly above its maximum allowable gross weight.
Investigators examined the fuel lines and found that the line from the fourth cylinder was not secured in a protective sleeve like the other lines. The investigation also looked into the maintenance of the envelope, finding that repairs to the fabric exceeded 65 percent of the total surface area, which violated manufacturer airworthiness instructions. Additionally, the investigation reviewed the regulatory oversight of the operator's Special Flight Operating Certificate.
Findings
- The primary cause of the fire was the disconnection of the fuel line at the tank valve of the fourth cylinder, likely due to wear and handling from the pilot's practice of coiling the line around the cylinder.
- The fire was fed by continuous propane discharge because the aircraft lacked an emergency fuel shut-off valve.
- The balloon's ascent and subsequent crash were caused by the failure of the synthetic tether strap under heat and tension.
- The aircraft was operating at a weight substantially greater than its maximum allowable gross weight.
- The safety briefing provided to passengers failed to explain emergency exit procedures.
- A lack of regulatory oversight allowed unauthorized modifications and deviations from airworthiness instructions to persist.
Safety action
Following a separate incident involving a Firefly 12B balloon, the TSB issued two recommendations:
- A08-01: The Department of Transport should ensure that commercial passenger-carrying balloon operations meet safety and oversight standards equivalent to other aircraft of similar capacity.
- A08-02: The Department of Transport should ensure that all balloons carrying fare-paying passengers are equipped with an emergency fuel shut-off.