The SOLAR IMPULSE aircraft has landed tonight at Phoenix, May 24^th, 23:46 UTC, bringing this mission to a safe and successful conclusion. Whilst we failed to achieve our original planned flight to Florida, the experience gained in being forced to carry out a significant diversion has been invaluable in the training of the mission team.

The simulation team will now further develop their extraordinary model, following performance analysis, to provide an even faster response regarding scenario options.

The meteorological forecasting was highly challenging given the severe storms which were developing and moving quickly on our planned track.

The air traffic advisors were naturally competent in organising clearances for the ever-changing needs of the flight, but the integration of their advice into the mission profile proved to be essential training for the team as a whole.

The team will remain in Geneva to carry out a comprehensive de-brief tomorrow, before finally retiring to their beds for a well earned rest!

2 minutes before landing !

The ground is 120 m under our aircraft.

Our last calculations show that our SOLAR IMPULSE Aircraft will land tonight, at 23:46 UTC, that is to say in 13 minutes from now.

See our next message for more details !!!

The aircraft is now flying its final approach to Phoenix Airport. Currently at altitude 1400 m, we are descending very slowly, and should land in approximately 50 minutes from now.

Another message will inform you about this event.

The weather forecast chart gives us a good opportunity for a smooth final leg en route for a landing at or near Phoenix. The simulation team are now calculating the position where we should initiate a long, slow descent for our landing at approximately midnight UTC. Top of descent is planned at 1855 UTC when the airplane will be at 7,800 m. The descent profile is unusual of course because our airplane is designed to behave like an exceptionally efficient glider with a low rate of sink.

Our air traffic advisors are investigating landing options in the Phoenix region where we could avoid any disruption to commercial flight traffic. However, the wind speed on the surface is forecast to be 10-12 knots which means that we must find a runway direction which will allow us to land into wind. The best runway direction happens to be at Phoenix International…

Following a long flight over the ocean, currently at 200 km from the closest Mexican coasts and flying at our floor altitude (around 3000 m), we are looking forward to the relative safety of flying over land. The aircraft should make landfall around 1200 UTC.

The weather systems are behaving as predicted and the original planned route across the Gulf of Mexico remains closed to us.

The team is now looking ahead to possible final landing places, and Las Vegas or Phoenix are the principal airports in the region for which we are heading. However this poses a major headache for our air traffic controllers who have the difficult job of negotiating landing permissions at extremely busy commercial airports. The solution is likely to be to use a less busy airport in the region, but of course we need one with a substantial size runway both in terms of width and length. We might need to talk very nicely to the American military!

Currently located at altitude 8 500 m, and position 23°05N, 114°44N, in the beginning of the night over North Pacific, our airplane is struggling with a strong wind from the West, at more than 100 km/h.

To prevent the aircraft from drifting toward East, where we would find a bad weather, we have decided to direct it to West, facing this wind. So, it’s energy is used to prevent it from drifting, rather than to really “move” toward a waypoint on our route.

This strategy will be applied in the next few hours, actually as long as we will not find a weaker wind, forecast at the altitude 5 500m.

You may have noticed that the online "Flight Datas" window is currently experiencing a failure in it's upgrade process. This has no consequence for our Virtual Flight, as involved computers are running under their own private network.

The next post will tell you more about the position and flight characteristics of the Solar Impulse Aircraft.

So now life is getting interesting here in the control centre. The meteorological forecast diagrams show that a very active weather system is moving southwards to block our path to Florida. It is possible that we could win this race with the weather, but it might leave us very vulnerable in the Gulf of Mexico with no diversion airfields available due to bad weather on the northern coast. If this were to happen and we experienced similar battery difficulties to this morning, we would be left with no option but to ditch in the water, certainly losing our airplane and risking the life of the pilot.

Our strategy therefore is to remain in the clear weather area and head much more to the North – towards Arizona. We have closed the option of Florida as a possible landing point and are re-assessing the situation on an hour by hour basis…

You may have noticed that we have run out of battery power and this has created precisely the kind of situation which the virtual flight was designed to highlight and gives the team valuable practice in dealing with scenarios which might otherwise come as an unwelcome surprise.

During the night the airplane experienced some greater than anticipated down-draughts which meant that extra power needed to be applied to the motors to compensate.

Also, for the mission team, sunrise is a relative term. Although we know of course the exact time at a given point the sun will rise over the horizon, the wings of the Solar Impulse are angled rearwards. This means that the amount of energy that the solar cells collect will vary depending on the direction in which the airplane is flying.

Another interesting factor is that when the airplane flies towards the east, it’s speed affects the length of it’s day as it is effectively accelerating the sun’s passage relative to itself.

So this morning (airplane local time) we were faced with a situation due to the above anomalies where the aircraft batteries will be depleted before the sun is able to effectively run the motors. An added complication is that we are flying towards an area of high cloud which will further diminish the charging efficiency.

The night-time minimum altitude of 3,000 m is designed to allow a reasonable safety margin in the event that efficient charging does not occur as the sun rises, and so the airplane is not likely to be in a critical situation where a ditching in the ocean may be envisaged.

However, we can take action to further mitigate against such a prospect. So we intend to turn the aircraft onto a westerly heading reversing the angle of the wings to the rising sun in order to maximise the charging potential. This directional change should only last as long as is necessary to take maximum advantage of the sun’s low angle.

Apparently, we have a severe server failure!

We will not be able to provide you images from the Mission Room before breakfast time (around 7:00 GMT).

We apologize for this inconvenience.

"We have just entered our first night abord the plane, after almost 900 km since our departure from Honolulu. The plane is flying towards East, and we use now the batteries to maintain the engines running".

"We have now reached or maximum altitude of the day, that is to say almost 12 000 m, for more than two hours. Flying at 105 km/h along the 20 th parallel, our batteries are full. The sun is just behind us, 12° above the horizon, and will be set in one hour. The solar energy is now not sufficient to maintain the plane at the maximum altitude, and we are about to begin our very slow descent above the Pacific Ocean"

At 16h20 GMT, after a last check of all the actors of the Solar Impulse Team, we have started the four electrical engines of the plane, thrusting them at the maximum power. The 2007 Solar Impulse Virtual Flight was beginning !

After a few hundred meters on the runway, facing the ocean, the airplane has slowly taken off, 20 minutes after the dawn. The weather forecast is quite good, but in the next hours, we’ll have to follow a route, almost along the 20th parallel, so as to avoid some clouds, north-east of Honolulu. Approximately 1h15 minutes later, we should be at the altitude 3000 m, and able to climb entirely with the sole energy provided by the sun.

Then, tonight at midnight (GMT), we should arrive at the altitude 9 700 m, and, less than two hours later, at our maximum altitude (approximately, 12 500 m).

The sun will rise above Honolulu in 70 minutes from now, and the Solar Impulse team is now ready to start the Virtual Flight.

Let me introduce all the persons involved in this adventure:

- As Flight Director, Raymond Clerc is working with a highly specialized and motivated Team whose mission is to achieve a safe and successful flight.

- Brian Jones, partner of Bertrand Piccard during the Orbiter Round the World Balloon Flight in1999 was also involved in the Mission Control of Orbiter 1 and 2. With his huge experience in such missions, he will be the coordinator of the mission team, also observing the human aspect of the team.

- Christophe Béesau, Director of the Altran Simulation Team, expert in simulation, is in charge of the simulation tool. Assisting him are Robin Ladmiral and Bertrand Cahuzac, both Modeling specialists, simulating the behavior of the airplane during the flight. All the information describing the Virtual Flight is provided by this simulation.

- Luc Trullemans is our Meteorological Expert, working with multiple models in order to advise us about the route to be flown.

- From Brussels, David Dehenauw is ensuring that the world data feeding the models is precise and accurate.

- Niklaus Gerber and Greg Moegli are former ATC controllers from Skyguide, both part of the Orbiter Round the World Ballon Mission. They have the task to coordinate the crossing of all the different airspace, with the respective controllers on duty along the route. They also provide permanent update of possible alternates in case of unexpected problems.

- Phil Mundwiller and Selina von Schack are responsible for providing up to the minute information to the media.

 
The whole Solar Impulse Team is currently preparing to take off, for our Virtual Flight 2007!

This year, we will be flying from Honolulu to Miami.

Currently settled in the premises of the “Geneva Airport”, we are computing the last details of this flight. The weather forecast meeting, a few minutes ago, has confirmed us the decision to take-off today. So, we’ll leave the runway of the Honolulu International Airport, (157° 55' W    : 21° 19' N), at 4h20 pm GMT, 5 minutes after sunrise (6h20 pm in Geneva). As you can see on this map, Honolulu is in the night, for 4 hours more.