A passenger plane had to alter course to avoid colliding with a weather balloon the size of a house as he came in to land on Shetland, an official probe has revealed.
The Saab 2000 was coming in to land at Scatsa Airport when the crew observed a white balloon about five miles away.
The pilot turned 20 degrees to avoid the balloon, which passed down their right-hand side at a distance of 400 metres. He assessed the risk of collision as “high.”
Lerwick Met Office told the UK Airprox Board – which probes near misses – that weather balloons are launched twice daily.
Before launch the balloon is as large as a person and it expands as it gains height – before it bursts it can be as big as a house. A parachute ensures it falls to the ground safely.
At the time of the incident on January 21 the wind was gusting 25 knots.
The board said the weather balloon did not show on radar, but the pilot saw it and was able to take avoiding action.
“The board noted that the UK Aeronautical Information Publication clearly states that Lerwick launches Radiosonde weather balloons twice a day and, as such, crews flying in the area should be alert to the possibility of such an encounter,” it said, commending the Saab pilot for his “good lookout” in spotting the balloon.
“In discussing the subsequent actions of the Saab pilot, the board opined that, having reported seeing the balloon from five nautical miles away, he therefore had plenty of time to make a decision on how best to avoid it. They acknowledged that the Met balloon was relatively large, and that it could have been a surprise to the crew if they weren’t expecting to see something of its size.
“However, members thought that perhaps the pilot could have taken earlier, more positive action to ensure that he didn’t fly close enough to the balloon to cause concern. That said, they acknowledged that action had been taken and, because of this, the board thought that the aircraft wasn’t in any danger.”