Solar Impulse To Unveil New Aircraft in April

By Thierry Dubois
Source: Aviation Week & Space Technology

To alleviate the pilot's workload, and even allow him to sleep, a stability augmentation system (SAS) has been designed. It can act on all control surfaces but, as the aircraft is already very stable on the pitch axis, most important are the electric actuators on the ailerons and the rudder, says CEO and pilot Andre Borschberg. “The SAS can hold a heading or an attitude but can't navigate,” he explains.

The upper-level system providing higher-level control is the monitoring and alerting system (MAS), which Borschberg describes as a “virtual copilot.” The MAS oversees the aircraft, SAS and pilot. Borschberg emphasizes that it uses other sources of data than does the SAS. In case of a deviation from usual attitudes, it warns the pilot early enough for him to react, even if he had been taking a nap.

Sleep is a major issue, but pilot Bertrand Piccard, who is also company chairman and founder, appears to be confident. He was due to spend 72 hr. in a mission simulator in Dubendorf to fly virtually from New York to Seville, Spain, last month. The idea is to take 10 naps of 20 min. each over a 24-hr. period. Piccard is working with sleep experts on sleep lead-in and wake-up transitions. Moreover, in case sleeping is ruled out because of tough flight conditions, methods for keeping awake will be tested. Caffeine pills will be used only in emergencies. “I want to surf on sleep waves when I feel them coming,” Piccard says. He was trained as a psychiatrist and thus wants to use hypnosis techniques. The impact of fatigue on pilot reaction time will be measured throughout the simulated flight.

On the ground, short- and mid-term weather forecasts will be available to the team to decide when to take off and possibly work out a diversion, if required. A notable level of optimization, although not actually a forecast, is to statistically determine the best route between two stopovers, finding a trade-off between sunny areas and tailwinds. In this regard, the flights across the U.S. were a rehearsal for those around-the-world, says Christophe Beesau, an Altran simulation expert. In 2003-15, the project's budget is 150 million Swiss francs ($170 million).

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