NTSB Identification: CEN13LA347
14 CFR Part 91: General Aviation
Accident occurred Saturday, June 08, 2013 in Arvada, CO
Probable Cause Approval Date: 02/10/2014
Aircraft: AEROSTAR INTERNATIONAL INC RX 8, registration: N7059U
Injuries: 1 Serious,2 Uninjured.

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

The pilot reported that, before the flight, he checked the weather forecast and received weather information from several sources. He and the other balloon pilots flying that day compared the weather information and agreed that the forecast weather provided suitable conditions for a safe flight that morning. However, because the wind conditions on the ground were light and erratic, they delayed taking off. The pilots continued monitoring the current and forecast weather using their wireless devices. The wind eventually calmed, and, after putting up additional pibals, they determined that the wind at altitude would take the balloons to the east-southeast and then south at 3 to 5 miles per hour. At takeoff, the wind was calm. The balloon traveled to the east-southeast and then, about 1,000 to 1,200 feet above ground level, the balloon turned toward the south. The first 30 to 40 minutes of flight were smooth, and the balloon traveled slowly to the southeast. About 40 minutes into the flight, at an altitude of 6,200 feet mean sea level, a wind gust buffeted the balloon. The pilot reported the condition to the other pilots who were flying in the area, and they responded that they were experiencing similar conditions at various altitudes. As he looked at the other balloons, the pilot noticed significant distortions in the envelopes indicative of high winds. The pilot briefed his passengers on a high-wind landing and landed in a cleared construction area. As the balloon touched down, he pulled the deflation lines, and the balloon deflated in seconds; however, the envelope concaved, and the balloon was dragged for several hundred feet until it came to rest on the side of a highway.

A review of meteorological data available at the time of the preflight briefing indicated, in part, that wind from the west existed at 10 knots or less before takeoff. The National Weather Service (NWS) terminal area forecast expected easterly wind shifting to the northwest at 13 knots during the anticipated flight with wind from the north gusting to 23 knots after 1000 mountain daylight time. The NWS area forecast did not expect any high winds across Colorado. The NWS Aviation Forecast Center had no advisories current for low-level turbulence or high winds over Colorado surrounding the anticipated flight. However, shortly after takeoff, a sudden increase in windspeed occurred across the region with wind gusts from 20 to 38 knots. The NWS misjudged the timing and underestimated the magnitude of the frontal boundary moving across the region. It is likely that, if the pilot had known about the gusting wind at the time of takeoff, he may not have chosen to fly that day.

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

The balloon's encounter with unforecast strong gusting wind, which resulted in a high-wind landing. Contributing to the accident was the National Weather Service's misjudgment of the timing and underestimation of the magnitude of the frontal boundary moving across the region.

Full narrative available

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