Severe turbulence likely tore wing off plane in fatal crash

Severe turbulence was the most likely culprit in a fatal plane crash in Bronkhorstspruit, Gauteng, in early December.

The pilot died in the crash, which also destroyed the aircraft.

According to the SA Civil Aviation Authority (CAA), the Evektor light sport aircraft was on a sightseeing flight with another aircraft when its left wing separated from the fuselage, sending the plane spiralling rapidly into the ground at the edge of Bronkhorstspruit Dam.

The pilots of both planes had planned to fly from the base at Springs airfield to a dam near Nigel but decided to head north instead as a large thunderstorm cell was building to the southeast.

The pilot of the other aircraft told investigators that both planes flew northwards in loose formation and that visibility was good. The weather over the dam was also clear. 

Witnesses on the ground saw the accident aircraft flying from north to south over the dam when something broke off the aircraft.

“The eyewitnesses saw something (blue in colour) breaking off the aircraft fuselage while it was flying over the dam, whereafter the pilot most probably lost control of the aircraft,” a CAA report said.

“The aircraft was seen twirling in the sky while descending before it impacted terrain (open field) on the southern side of the dam.”

The outer section of the left wing was located about 100m from the main wreckage.

While the preliminary investigation carried out by the CAA into the accident did not specifically list turbulence as the cause of the crash, eyewitnesses told investigators that a strong easterly wind began blowing in the area about the same time as the accident, lasting for between five and 10 minutes.

Meanwhile, the pilot of the accompanying aircraft, having been informed by his passenger that he had seen “something fall from the sky”, was unable to circle the crash scene due to excessive turbulence.

“The pilot flying the [other] aircraft stated that while flying over the dam, they (him and the passenger) encountered extremely turbulent flying conditions and could see waves (ripples) on the water surface,” the report said.

“He was unable to orbit (circle) the accident site as it felt like the aircraft was going to overturn.”

The Evektor Sportstar is a two-seat, all-metal, light sport aircraft manufactured by Evektor-Aerotechnik in the Czech Republic.

Hundreds of the popular plane are in service about the world.

The crash was widely discussed in the flight safety section of local aviation Avcom where posters, many of whom are also private pilots, speculated that the two aviators had encountered turbulence from a storm front building east of the dam.

One poster noted that he had previously witnessed weather conditions changing rapidly at the dam with a gale suddenly starting to blow on an otherwise windless day.

The US Federal Aviation Administration (FAA) warns pilots to avoid flying through or even near thunderstorms.

“As nature’s uncontrolled ‘heat engine’, the thunderstorm can create some of the worst weather hazards known to aviation,” the US aviation watchdog said in a briefing document on the dangers of thunderstorms for aircraft.

“Never go closer than 5-miles (8km) to any visible storm cloud with overhanging areas, and strongly consider increasing that distance to 20-miles (30km) or more,” it said, pointing out that hail and violent turbulence from strong thunderstorms could be encountered even at that distance.

Pictures taken by a witness and used in the SACAA’s accident report appear to show a rapid change in weather conditions as a thunderstorm builds to the east of the dam.

“I see reason for caution in all those photos but particularly No.6, with that sharp-edged almost boiling cloud, and the darkness behind,” a former flight instructor wrote on Avcom.

“That is shouting massive thunderstorm.”

TimesLIVE