June 13 was not a good flying day for Solar Impulse. Hoping to finish this epic journey between continents, Andre Borschberg ran into stiff winds and severe turbulence. Although in the air for 16 hours and 6 minutes while covering 780 kilometers (484 miles), the flight did not make it to its destination of the solar plant at Quarzazate, but returned to Rabat after battling winds and extreme turbulence. Since the airplane cruises at around 30-35 miles per hour, its average ground speed for the flight of 55 kilometers per hour (34.1 mph) seemed normal enough, but didn’t show the wild swings in groundspeed experienced by Borschberg, a strong contrast to the uneventful leg between Madrid and Morocco.
At one point, ground speed was around 10 km/h, or 6.2 mph. At another, ground speed exceeded 140 km/h, or 87 mph. Unfortunately the good tailwinds were all blowing away from the destination and at 14:34 Greenwich Time (UTC) after over seven hours in the air, the decision was made to return to Rabat.
Borschberg made a safe landing at 23:14 UTC, another night descent that shows the batteries on board are capable of keeping the craft aloft – even at the end of a rough and disappointing day.