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Altran control screen in the MCC

This screen shows the Solar Impulse route, strassing winds and clouds to avoid.

During a flight, the blue curve represents the achieved route, and the yellow one shows the forecasted one. Between two flights, the only curve on the screen is the blue one, representing the effective route.

This is the result of  flight simulations run by the Altran team inside the MCC based in Monaco, which is the operational center of Solar Impulse flights.


Intensive computing made by the team leads to determine the forecasted journeys in real time, which allow the plane to avoid clouds and headwinds, and to benefit from downwinds.

Knots (kts): 1 knot = 1.1507 miles/hour or 1.852 km/hour

Feet (ft): 1ft = 30.48cm

EAS: Equivalent Air Speed

kWh: Kilowatt hour

Altitude and energy storage

During the day, Si2 stores energy in the form of electricity (in kWh) by charging its batteries, and in the form of potential energy by gaining altitude. When night falls, the first part of the night flight is carried out by gliding.


The temperatures drops around 10 degrees Celsius (18 degrees Fahrenheit) every 2,950 feet (900 metres). This exposes the aircraft to temperatures that vary between -40 and 40 degrees Celsius (-40 and 104 degrees Fahrenheit).

Position of the sun

The energy captured in a photovoltaic cell can vary greatly, depending on the angle of the sun’s rays, the incidence or position of the sun. The incidence depends in part on latitude and the time of day, as well as on the aircraft’s course.