Solar Impulse: Zero-fuel plane makes forced Japan landing

Solar Impulse, the zero-fuel aeroplane, has landed in Japan after being forced to abort a Pacific crossing due to deteriorating weather ahead of it.

The aircraft, which set off from China on Saturday local time, had hoped to reach Hawaii by the end of the week.

But a developing cold front over the ocean is blocking its path and pilot Andre Borschberg has decided to play safe by putting down in Nagoya.

He will now wait in Japan for a new weather opportunity to present itself.

Solar Impulse is attempting to make the first circumnavigation of the globe by an aeroplane powered only by the sun.

The 17,000 photovoltaic cells on its wings drive propellers during the day but also charge batteries that sustain flight during the night.

The China-Hawaii stint was to be the seventh leg in the quest that began back in March from Abu Dhabi, UAE.

Mr Borschberg brought Solar Impulse into Nagoya airfield at 23:49 local time (14:49 GMT). A line of brilliant LEDs on the front edge of the plane's wings announced his approach to the runway.

Because Japan was never a scheduled stop, the project has had to scramble to get its ground crew and equipment to the airport to meet the vehicle.

This saw the Swiss adventurer having to circle above Nagoya while preparations were made beneath him.

Solar Impulse will now be tied down and protected from the elements in a mobile hangar while meteorologists and flight strategists look for a new possibility to cross the Pacific.

LEG 1: 9 March. Abu Dhabi (UAE) to Muscat (Oman) - 772km; in 13 hours and 1 minute

LEG 2: 10 March. Muscat (Oman) to Ahmedabad (India) - 1,593km; in 15 hours and 20 minutes

LEG 3: 18 March. Ahmedabad (India) to Varanasi (India) - 1,170km; in 13 hours and 15 minutes

LEG 4: 18 March. Varanasi (India) to Mandalay (Myanmar) - 1,536km; in 13 hours and 29 minutes

LEG 5: 29 March. Mandalay (Myanmar) to Chongqing (China) - 1,450km; in 20 hours and 29 minutes

LEG 6: 21 April. Chongqing (China) to Nanjing (China) - 1,241km; in 17 hours and 22 minutes

LEG 7: 31 May. Nanjing (China) to Kalaeloa, Hawaii (USA) - 8,200km; journey aborted, plane diverted to Nagoya, Japan

Flying the more than 8,000km from Nanjing in China to Kalaeloa in Hawaii was always considered the big test in the round-the-world flight.

Bertrand Piccard, who has shared the pilot duties in the single-seater plane over the past three months, told BBC News: "When we started a project like this one, we knew it would not be easy. If it was easy, somebody else would have done it before.

"When we took off from China two days ago, we thought we could go through the front and reach Hawaii. Now, we see the front has closed. It's active. There's rain, there's icing - everything that's dangerous for our aircraft. So we've decided to stop in Nagoya and wait for better weather to continue."

The LEDs on the front edge of the plane's wings announced its approach to the Nagoya runway

Although disappointed at having being forced to make a stopover, the team is nonetheless delighted with the performance of its aircraft.

Just the journey from Nanjing has covered more than 2,850km - a new distance world record for a manned solar-powered plane. The time in the air, also, 44 hours, is a record in the same aviation class.

And in completing a full day-night cycle on Sunday into Monday, Solar Impulse has proven its credentials as an "eternal plane". That is, given the right weather conditions, the vehicle has the ability to stay aloft indefinitely (even if that is not a practical option for the pilot).

Quite when the aeroplane will now get to go to Hawaii is anyone's guess at the moment. It is unlikely to get a chance before next week. Mr Borschberg will need some time to rest, as will his ground crew.

But there is some urgency in that further delays have an impact on later stages of the circumnavigation.

Ideally, the team needs to cross America, and then the Atlantic, before the hurricane season starts to peak in August.

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