Any pilot who’s had to land an airplane at its crosswind limit knows that each airplane has a point where its controls cannot overcome the sideways force, and one cannot perform the final level, straight-down-the-runway touchdown. Usually, pilots do a go-around or find a more wind-oriented runway. Solar Impulse’s explanation under the video tells why this is almost impossible under deteriorating conditions with a craft as huge and slow as SI2.
Take note of the control inputs test pilot Marcus Scherdel makes in the final moments of the August 30, 2014 flight.
The Solar Impulse team released this video in the last week, perhaps to explain why the crew is waiting for a positive “weather window” before embarking on a planned five-day epic voyage from Nanjing, China to Hawaii.
“Solar Impulse was still in flight test phase when Markus Scherdel, the experienced test pilot, was put to a challenge by strong crosswinds during landing. Si2 returned from a flight to Payerne Airfield and performed a planned low approach before landing. A go around and subsequent approach takes on average 20 minutes, during which the winds increased significantly and unexpectedly to 4 knots (4.6 mph) crosswind component. The pilot had no other option but to land despite the situation as the weather was rapidly deteriorating. Right before landing, the pilot got gust from the side, blowing the plane off the runway to the right. He then needed to correct back to the center line. Markus never lost his smile, although he was imposed a great work load, trying to avoid landing next to the runway or losing balance. This demonstrates how Solar Impulse is sensitive to turbulences.”