Piccard (one “c”) came in from the west. It looked like he was setting up for a right downwind runway 14R at Moffett (KNUQ). I was a bit disappointed. Though it was certainly cool to see Solar Impulse 2 flying, it was dark (about 11:30 pm), and all I could really see where SI2’s lights—and I’d been hoping to be right under the final approach path. But, with a 14 landing, I be looking all the way down a long runway to see the landing.
Solar Impulse 2 was on its way to Moffett Federal Airfield, with Bertrand Piccard flying, was nearing completion of a truly epic leg on an epic journey. The journey: fly around the world in an airplane completely powered by electricity, generated by 17,000 solar cells atop (mostly) the wings, stored in on-board batteries to last the night (when coupled with slowly gliding down from over 25,000′). The leg: Hawai’i-California.
I started moving to another part of the fence between us, on the sidewalk of the frontage road that runs between the US-101 highway and the light rail tracks the run past the approach end of Moffett’s runways 32, to find what I hoped would be a good vantage from which to watch the landing across the airfield. As I looked for SI2, turning base-to-final or on final approach, I saw that Piccard was not landing on either of the runways 14: he was heading for the right downwind runways 32—probably 32R, since it’s the longer, and has an ILS for additional guidance.
I got excited, and headed back to where I’d been, or near there. Solar Impulse 2 was going to fly right past me—past us, the dozens of people congregated along the frontage road—on short final!
SI2 is a remarkable airplane. It’s among the ultimate form-follows-function craft, designed with one purpose in mind: to fly for as long as a pilot can fly, using no fossil fuels, powered only by electricity generated from photovoltaic cells.
- Wingspan: 71.9 meters (236 feet), bigger than a 747-400’s wingspan by over 7 meters, and 6½ times bigger than my Mooney’s.
- Length: 22.4 meters (73.5 feet), just shy of three times longer than my Mooney.
- Energy source: 17,238 PV cells, atop the wings, fuselage, and tailplane, able to generate 66 kW.
- Energy storage: 4 batteries, each with a capacity of 41 kWh.
- Maximum weight: 2,300 kg (5,100 pounds)
- Power: 4 electric motors, each producing 13 kW (17.4 HP), driving propellers 4 meters in diameter.
The cockpit’s unpressurized, and unheated, to save weight. At altitude Piccard wears an oxygen mask and uses a delivery system like the one we have in the Mooney (pulse-demand, from Mountain High): it allows for much longer oxygen duration from a given volume, and also dehydrates the user much less (compared with conventional continuous-delivery systems).
The general pattern with SI2 is to take off with fully charged batteries, during the day, then slowly climb to 7,500-8,500 meters (about 25,000-28,000 feet), keeping the batteries charged. As the sun sets and the electric generation wanes, manage the power output of the motors, and the electricity needs, and slowly descend, ending up between about 1,000 and 1,500 meters (3,000-5,000 feet) as the sun rises and the PV cells begin to generate electricity again. Climb slowly and charge the batteries, and repeat as needed.
I started to get the camera ready as Piccard flew right downwind. With a ground speed of about 30 knots and the leading edges of the wings sporting 16 LED landing lights, it was very easy. Piccard completed his base leg, and turned final. I took a few pictures.
By tracking SI2’s ground track relative to me, I could tell Piccard was lining up with the runway a bit to my right (as I was facing away from the runways, watching SI2). I moved to position myself better.
It was almost eerie as Piccard flew Solar Impulse 2 just a few dozen meters, perhaps a hundred feet, above my head. I could barely hear any noise from the props as the slowly turned and Piccard descended. Passing us, above the frontage road, he turned off the two outboard motors, I expect so he’d have less thrust to contend with as SI2 entered ground effect and the drag lessened.
Then, they were down. 60 hours of flying, non-stop from Hawai’i.