Wake turbulence is a disturbance in the atmosphere that forms behind an aircraft as it passes through the air, and air traffic control requires more spacing behind larger jets like the A380 in an attempt to avoid the phenomenon.
Wake turbulence incidents are uncommon and typically involve a larger jet and a smaller aircraft rather than two super-jumbos.
The U.S. Federal Aviation Administration (FAA), which handled air traffic control during the Qantas incident, does not specify a minimum distance of separation between two A380s during flight due to wake turbulence risks.
It specifies that Boeing 747s require 4.5 nautical miles of separation and smaller jets up to 8 nautical miles.
No passengers were injured and there was no aircraft damage from the incident which involved an A380 flying from Los Angeles to Melbourne behind another Qantas A380 flying from Los Angeles to Sydney, a Qantas spokesman said.
“The trailing airplane, the Qantas 94 encountered some wake turbulence from the Qantas 12, and that caused a jolt to the airplane for a short period of time,” Qantas Chief Technical Pilot Alex Passerini told a Sydney radio station.
“The airplane climbed maybe 100 feet or so and descended back to its cruising altitude, and the captain took action to avoid the further exposure to the wake vortex.”
Australian television presenter Eddie McGuire, who was on board the flight, said the incident had lasted about 10 seconds.
“It did have that feel of, you know when you go over the top of a rollercoaster and you just get a little bit of a feeling, and the plane did bank to port, to the left-hand side, a little bit,” he said on Channel 9.
“But it steadied up after about 10 seconds, and I have to say that what the most reassuring part of the situation was that the Qantas pilot came on immediately and said we’d gone in to the back of the turbulence of the Sydney plane.”
Qantas said it has notified the Australian Transport Safety Bureau of the incident.
An Airbus spokesman said Qantas had reported the incident to the manufacturer. “The situation was handled fully in accordance with procedures and the aircraft performed as designed,” he said.
In January 2017, wake turbulence behind an Emirates A380 sent a business jet into an uncontrolled descent, with the smaller airplane losing nearly 9,000 feet of altitude before the crew was able to gain control, according to an interim report by German investigators.