NTSB Identification: DEN99IA154.
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Incident occurred Wednesday, August 11, 1999 in HARTSEL, CO
Probable Cause Approval Date: 06/22/2000
Aircraft: Balloon Works FIREFLY 9, registration: N2570E
Injuries: 6 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

As he approached the touchdown point, the pilot flared the balloon and pulled the deflation line. The line broke and fell into the basket. The pilot was unable to deflate the balloon because the line had broken inside the envelope near the parachute harness. The ground crew secured the balloon long enough for the passengers to exit, then the wind dragged it across the ground. Holes were cut in the middle portion of the envelope to gain access to the deflation valve, and the balloon was deflated. Examination of the deflation line by NTSB's Materials Laboratory disclosed glazing damage to the outer cover, typical of heat damage. According to the manufacturer, the Kevlar braided inner core chars at 890 degrees F. The nylon or polyester braided outer covering has a stick point of 430 degrees F. and a melting point of 492 degrees F. A new line has a nominal strength of 4,000 pounds.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

Total failure of the deflation line due to heat damage (as evidenced by glazing), most likely caused by the improper use of the flight controls (burner system) by person(s) unknown.

Full narrative available

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