"The pilots will need brawny arms and muscles of steel" - Flight Envelope Tests "The pilots will need brawny arms and muscles of steel to work the controls" jokes Bertrand Piccard when referring to the pilotability of the Solar Impulse prototype: in order to avoid any superfluous power requirement of the limited solar energy, the prototype's controls have been re-sized and will now be direct and unassisted. This means that the pilots will need a lot of strength to move them. "We already know that the aircraft will be difficult to pilot", André Borschberg underlines, explaining furthermore the additional challenges the pilots are going to face: "It will need a great amount of attention to get it to fly, taking care to avoid any departure from the neutral horizontal position.