Solar-Powered Plane Forced to Land Due to Cloudy Skies on Round-the-World Trip

Remember that solar powered plane that's trying to fly all around the world? Well, it's just been forced to abort its record-breaking attempt to cross the Pacific, due to some dodgy weather conditions.

This may be a disappointing setback for both the on-ground crew and pilot, but Solar Impulse spokesperson Conor Lennon told me that what the aircraft's achieved thus far—it'll have been airborne for 40 hours when it lands prematurely in Nagoya, Japan—is still "a grand achievement".

The aircraft is currently on its seventh flight, and will complete 12 flights in total in an attempt to circumnavigate the globe. The Solar Impulse crew predicts that the aircraft will now complete its around-the-world trip in mid-August.

Solar Impulse 2's epically large, dragonfly-esque wings are covered in photovoltaic panels that produce solar energy which powers the vehicle's motors and is stored in its batteries. But bad weather can obviously block its ability to get enough sun power, jeopardising the aircraft's safety on longer flights.

The aircraft took off from Nanjing Lukou Airport at 2:39 am (local time China) on early Sunday. It was already 36 hours into its journey from China to Hawaii when the team based at the mission control centre in Monaco predicted that a spat of cloudy skies would affect the plane's trans-Pacific passage. This left Swiss pilot Andre Borschberg, who was flying the aircraft, with little choice but to turn back to Nagoya, Japan to wait until conditions cleared up.

"When we knew that the risk of landing in Nagoya was so much lower than carrying on, it was a relatively simple decision to make," said Lennon, who noted that this stretch of the journey had them constantly on the look out for hurricanes and typhoons, as well as cloudy conditions.

This was the aircraft's seventh and most-challenging aerial stunt to date, as it was set to cover a distance of 8,200 km from Nanjing (China) to Kalaeloa (Hawaii). The BBC lists that previous missions have included the vehicle's first successful attempt in March 9 2015, when it flew from Abu Dhabi to Muscat in Oman, covering 441 km in 13 hours and one minute, and the longest successful stage to date when it flew 1,468 km from Muscat to Ahmedabad in India in 15 hours and 20 minutes.

The plane is currently discharging its batteries, and there is no concern for the pilot's safety. "He could even have an extra hour or two of holding above Nagoya airfield, just to make sure we have perfect conditions for landing, and to ensure that all our guys in Nagoya can physically get there and look after the plane," said Lennon.

Had Borschberg pressed on with his journey he would have faced many risks. "We're talking about millions of cubic metres of water. There isn't any way you could have a support boat following the whole way, the plane can't land in the water because there is so much electrical equipment on board that there's a strong risk that the pilot would be electrocuted," explained Lennon.

In the worse case scenario, Borschberg would have had to bail out of the plane, activate his parachute, get rid of his parachute when in the water, then inflate his life raft and wait for the nearest boat to come and find him.

Lennon told me that the crew were slightly disappointed they had to land their plane now. However, he said the Solar Impulse still marked a first for solar aviation, and that they were keen on continuing to "push the limits of solar transport" and promote their green-friendly message.

"If we look back to the beginning of aviation when the Wright brothers built their first plane, people were asking what the point was and saying that the plane couldn't fly for very long distances. We're in the same situation now, but who knows where we'll be in twenty to thirty years time," said Lennon. "It's really the beginning of an adventure, and we've already managed to achieve pretty much what anyone thought was impossible."