Balloon Works FIREFLY 11 N7021U

Summary

On 19 August 1999 at about 14:10 local time, a Balloon Works FIREFLY 11 registered N7021U, operated by HOT Air Expeditions, Inc., was involved in an accident near Cave Creek, Arizona, United States. 13 people were on board and one was seriously injured, 4 had minor injuries. The aircraft was slightly damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

19 August 1999 at 14:10

Classification

Accident

Location

Cave Creek, Arizona, United States

Coordinates

33.6802, -112.0400

Aircraft

Balloon Works FIREFLY 11

Registration

N7021U

Category

Balloon

Operator

HOT Air Expeditions, Inc.

Operating rule

Part 91: General Aviation

Purpose of flight

Unknown

Phase of flight

Not recorded

Aircraft damage

Minor

Weather

VMC

Light

Day

NTSB number

LAX99FA273

1 person was seriously injured.

An unforecast encounter with a low level microburst that resulted in a distortion of the balloon envelope, an excessive outflow of hot air (loss of lift), creating an excessive rate of descent that was beyond the performance capability of the balloon to recover in the altitude available. The failure of a passenger to follow the emergency procedures directives of the pilot was a factor in this accident.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

While attempting a high wind landing, the balloon hit hard and one passenger sustained serious injuries. The pilot checked weather prior to departure, and said that at 0610, the weather was mostly cloudy with surface winds from the south at 3 to 5 mph. About 0635, the nearby Deer Valley airport ATCT told the pilot that surface winds were 12 knots from 220 degrees. In addition, another company pilot told him by radio that surface winds in his location were now 25 mph. The pilot's ground crew also confirmed that surface winds had increased substantially. The pilot said that he was 3,000 feet msl when the change in wind velocity was reported, and he selected an alternate landing site and briefed his passengers on high wind landing procedures. The approach was initiated at a descent rate of 700 fpm. During this time he told the two standing passengers to sit down because they would be experiencing a very rough landing. After descending through 500 feet agl at 700 fpm, the balloon's vertical sink rate suddenly increased substantially. He said this encounter had caused distortion in the envelope that resulted in the envelope losing hot air (lift), and increasing his rate of descent. His attempt to slow the descent in the time remaining was unsuccessful and the balloon landed short of the intended site, rebounded into the air, and then skidded about 100 yards before coming to a stop with the carriage lying on its side. Another balloon pilot, who saw the landing, said that the balloon appeared to have encountered a sudden microburst that resulted in an inadvertent hard landing. Other witnesses described the final descent as rapid, and noted that the envelope was distorted (flattened) downward as if the balloon was being pushed down. According to the FAA approved performance data sheet, terminal velocity (Vt) of the balloon under maximum gross weight conditions is 1,200 fpm with a recovery time to equilibrium 90 seconds, and altitude lost during recovery (from application of burner to equilibrium) to be 1,000 feet. The POH states that should weather conditions deteriorate while in flight, the pilot should land immediately, and "to risk damage if necessary to land while the flight is still under control." The manufacturer reported that the maximum demonstrated wind speed at landing during certification testing was 7 knots.

Quoted verbatim from the NTSB record.