Yesterday, for the first time at 13:47 the Solar Impulse HB-SIA taxied down the runway powered by its own engines.

At the controls of the HB-SIA, Solar Impulse test pilot Markus Scherdel cautiously took to the runway under the watchful eyes of the whole team, with computers monitoring the plane's behaviour online via the embedded telemetric devices.

This inaugural day out on the runway allowed low-speed runway testing with the prototype going through a series of acceleration and breaking manoeuvres, checking that the calculated and simulated strains are not being exceeded.

"The runway tests are necessary and involve a certain amount of risk for the landing gear. The chances of damaging the plane are greatest during low-speed ground manoeuvres. The faster the plane goes the more lift it gets from its wings, meaning that there is less load on the wheels", explains André Borschberg, co-founder and CEO of Solar Impulse.

A foam rubber safety trolley accompanied the HB-SIA during these initial ground exercises. Should the landing gear have malfunctioned, this trolley would have been there to secure the aircraft without damage.

The results of these initial tests have fully met expectations of the Solar Impulse team and the decision has been taken to carry on with further tests today, successfully doubling the speed up to 10 knots and removing the safety trolley.

The next stage will involve taking the prototype up to its 35 km/h take-off speed and having it do its first few "flea hops". This will be a critical stage. The objective will be to record numerous unknown parameters as the aircraft will be operating in an unexplored flight domain.