Editors Note: New posting at HB-SIA website:
“At the end of the day there is a big reward, mixed with awe and the intense satisfaction of seeing what one has dreamed up actually takes shape.” After five years of hard work, Solar Impulse will proudly present the prototype “Solar Impulse HB-SIA”, on June 26, 2009.
MendoCoastCurrent, Solar Impulse Newsletter, September 2, 2008
Parts have been arriving in large numbers since early summer. Small or large, each plays a vital role and is of fundamental importance. Tail or engines, wing panel or horizontal stabiliser, all have in common that they have been manufactured at least once. These elements are the fruit of years of research, calculations, simulations, and real scale tests, leading to products that are both the lightest and the most resistant possible. In their final form they are all “ready to fly” once validated. “At this stage of realisation we have no more doubts about the technologies and the construction techniques”, comments Solar Impulse CEO André Borschberg.
Manufactured by the ETEL company, the four motors (plus two in reserve) have been assembled and tested. Special attention has been paid to their cooling system to make sure that they will still continue to function properly in the thermal zones foreseen. In comparison with the initial prototypes, they have improved in both weight and efficiency. One of the gondolas in which they will be podded has been assembled around its chassis. The lithium batteries and the cabling have been tested. Mounted on a vehicle, this gondola with its engine and propeller have undergone trial runs at flight speed.
The final-form tail and cockpit have been assembled and have undergone major load testing: one 900kg block of lead at cockpit level and three 300kg blocks, one for each axis, at the aircraft’s tail. As employees all held their breath, you could have heard a pin drop as loading was done successively, first 20%, then 50, 70 and finally 100%. There was great satisfaction – and relief – when the structure passed the final test. And when the fuselage passed its final validation test, giving the green light needed to continue the programme, there was a huge round of applause.
During last May’s simulated flight, the pilots noticed that the flight controls were no way as stiff as they would be when actually flying. As a result they have been re-sized on the simulator, their effectiveness tested and the strength needed to move them re-evaluated. To avoid any superfluous power requirement, the controls will be direct and unassisted. “The pilots will need brawny arms and muscles of steel to work them”, joked Bertrand Piccard.
André Borschberg went one step further: “We already know that the aircraft will be difficult to pilot. It will need a great amount of attention to get it to fly, taking care to avoid any departure from the neutral horizontal position.” Two special devices will be assisting the pilot in this tricky task:
- the Omega instrument, a flight control instrument supplementing the artificial horizon giving the pilot a more precise indication of the aircraft’s bank angle and flight vector,
- the man-machine interface, capable of transmitting vibrations to the pilot to warn him aware of potentially dangerous situations.
The next stage will involve the main wing with its 61m span. Made up of three 20m “box” beams, it is due for delivery in November. Following assembly, it too will undergo vibration tests in explore the aircraft’s aero-elasticity. At the same time, the wing’s subsystems, like the landing gear and the flight controls (flaps, spoilers, elevators, transmission rods and bars) will be put together and similarly subjected to final evaluation. Once tested, these elements will be integrated one by one. HB-SIA, our first prototype, will slowly take the shape we have planned for it.