I read that the amazing Solar Impulse back in 2015 had circulated around the globe for 500 hours. It flew with speed 70 km/h and altitude of cruising 28000 ft. My questions are below

  1. Did it fly in the commercial airspace? if yes then did it have kind of type 23 certification for small aircraft?

  2. I have searched about the system of it such as flight control system and autoflight, but found nothing. What kind of the system was used in solar impulse? Did it have typical system with small aircraft such as Dassault Falcon or Pilatus?

  3. Maybe anyone has detailed information related to solar impulse system such as flight control, autoflight, etc?

Thank you

  • $\begingroup$ I won't call an ATR a small aircraft. A bizjet such as a dassault falcon is smaller, not to mention GA. $\endgroup$
    – Manu H
    Commented Apr 6, 2020 at 5:38
  • 2
    $\begingroup$ You'd be amazed to learn how far you get with an experimental certification if you create enough publicity about that flight you try to accomplish. $\endgroup$ Commented Apr 6, 2020 at 5:49
  • 1
    $\begingroup$ @PeterKämpf so the experimental certificate allows the aircraft to fly in commercial busy airspace? $\endgroup$
    – Zahi Azmi
    Commented Apr 6, 2020 at 6:34
  • 3
    $\begingroup$ There isn't really such thing as commercial airspace. $\endgroup$ Commented Apr 6, 2020 at 7:11
  • $\begingroup$ @ZahiAzmi: Yes, all you need to do is to apply for a special permission and get that accepted. Publicity helps with that acceptance. A lot. $\endgroup$ Commented Apr 6, 2020 at 8:53

2 Answers 2


To answer the question presented in the title, I looked to Wikipedia for details on the flight(s) of Solar Impulse. According to Wikipedia, Solar Impulse 2 (HB-SIB) circumnavigated the Earth’s Northern Hemisphere in 17 legs/flights. Of those 17 legs, 14 legs had maximum altitudes above 18,000 feet MSL. In the U.S., Class A airspace is between 18,000 and 60,000 feet MSL. It is not considered “commercial” airspace. It is accessible to any aircraft with a Mode C transponder and ADS-b, including experimental aircraft. And, even this requirement can be waived with prior approval.

91.135 Operations in Class A airspace.

Except as provided in paragraph (d) of this section, each person operating an aircraft in Class A airspace must conduct that operation under instrument flight rules (IFR) and in compliance with the following:

(a) Clearance. Operations may be conducted only under an ATC clearance received prior to entering the airspace.

(b) Communications. Unless otherwise authorized by ATC, each aircraft operating in Class A airspace must be equipped with a two-way radio capable of communicating with ATC on a frequency assigned by ATC. Each pilot must maintain two-way radio communications with ATC while operating in Class A airspace.

(c) Equipment requirements. Unless otherwise authorized by ATC, no person may operate an aircraft within Class A airspace unless that aircraft is equipped with the applicable equipment specified in §91.215, and after January 1, 2020, §91.225.

(d) ATC authorizations. An operator may deviate from any provision of this section under the provisions of an ATC authorization issued by the ATC facility having jurisdiction of the airspace concerned. In the case of an inoperative transponder, ATC may immediately approve an operation within a Class A airspace area allowing flight to continue, if desired, to the airport of ultimate destination, including any intermediate stops, or to proceed to a place where suitable repairs can be made, or both. Requests for deviation from any provision of this section must be submitted in writing, at least 4 days before the proposed operation. ATC may authorize a deviation on a continuing basis or for an individual flight.

For further details about the aircraft, it’s custom autopilot and flight controls, and the actual flight Itself, visit https://aroundtheworld.solarimpulse.com/adventure .


For the solar impulse system:(question3)

The photovoltaic cell is made from two layers of Silicon (semiconductor material): - a layer doped with Boron which has fewer electrons than Silicon, this zone is therefore positively doped (zone P). - a layer doped with Phosphorus which has more electrons than Silicon, this zone is therefore doped negatively (zone N). When a photon(= smallest indivisible measure of energy associated with electromagnetic waves, ranging from radio waves to gamma rays) of light arrives, its energy creates a rupture between a silicon atom and an electron, modifying electrical charges. This is called the photovoltaic effect. The atoms, positively charged, then go to the P zone and the electrons, negatively charged, to the N zone. A difference in electric potential , that is to say an electric voltage, is thus created.

On the Solar Impulse, there are exactly 17,248 silicon solar cells on a surface of 269.5m², capable of capturing up to 340kWh of solar energy per day. The energy created by these cells is stored in four high-performance lithium polymer batteries , located in nacelles isolated from the aircraft. The only drawback is the weight: they alone represent ¼ of the total weight of the aircraft.

These batteries power engines that have an average power over 24 hours of 15hp, comparable to a small motorcycle, and its maximum power is 70hp. The four engines are fixed under the wings, with a two-blade propeller four meters in diameter. The total efficiency of this set of engines is 94%, which makes it a record of energy efficiency. The speed of the Solar Impulse varies between 36km / h and 140km / h, which is equivalent to the speed of a car

For the flight i think there is no rules ...see this:

us look at what happens during a 24 hour flight. For the solar panels, the day begins late and ends early: enough light to sustain flight is limited to just 10 hours per day! It’s a race against time...

6am: The sun has just risen. The airplane is on the runway. Its batteries, charged by the sun on the previous day, are nearly full. So it can take off using that stored energy... 6am-6pm: It gains altitude. The four motors turn at maximum power as the plane must create lift (the force that allows the plane to climb) to reach a thinner layer of air where there are fewer clouds. Despite the steady energy consumption, the batteries are charging. Nearing 6pm: It reaches 9000 meters (29,500 feet), its maximum altitude. The sun’s rays fade. The motors are throttled down and the plane starts to glide down to an altitude of 1500 meters (5000 feet), which takes about 4 hours, during which time it consumes almost no electricity... Nearing 10pm: At 1500 meters (5000 feet) of altitude, the pilot powers up the motors again, but this time they will take their energy from the batteries. The airplane flies like this until daybreak when solar energy again feeds power to the motors and recharges the batteries. A new cycle begins.

To determine the flight path that Solar Impulse will take in the sky, many factors must be considered: weather, air traffic areas, also the height of the land to be flown over and the performance of the airplane. A team of engineers and meteorologists based in Monaco Mission Control Center (MCC) determines the best route for the plane and then prepares the flight plan. Once the route is chosen, overflight and landing clearances must be negotiated for each country

system The numbers in the picture are the energetic efficiency http://solarimpulsemmktpe.e-monsite.com/pages/i-le-fonctionnement-et-la-conception.html

For more information :https://aroundtheworld.solarimpulse.com/adventure/technical-challenge-1

  • 1
    $\begingroup$ How does this answer the question about type 23 certification? $\endgroup$
    – Bianfable
    Commented Apr 6, 2020 at 9:15
  • $\begingroup$ It is an awnser for the question 3 $\endgroup$
    – L'aviateur
    Commented Apr 6, 2020 at 9:20
  • $\begingroup$ I am so sorry for not detailed question, by system, I mean "typical" aircraft system such as flight control or autoflight $\endgroup$
    – Zahi Azmi
    Commented Apr 6, 2020 at 9:30
  • $\begingroup$ Ah, sorry, I only read the title and the beginning of the question body. As stated, the question is way too broad though. $\endgroup$
    – Bianfable
    Commented Apr 6, 2020 at 9:30
  • $\begingroup$ Question not clear $\endgroup$
    – L'aviateur
    Commented Apr 6, 2020 at 9:34

Not the answer you're looking for? Browse other questions tagged .