Many people are fantasizing to simply fly away when they are stuck in traffic. In one of our PAL-V videos, Marco van den Bosch explained that you need to drive to an airstrip and transform from car to airplane. This sounds simple but I can imagine that it took a lot of research and innovation to develop it like this. Can you explain the technology behind it?
This is actually one of the key elements to make a flying car successful, the “trick” is to combine both aircraft and car into one vehicle, making the conversion from one mode to the other which is needed to comply with both air and road regulations. We have patented our folding rotor system that uses a unique hinge in the middle of the rotor. Furthermore, we have implemented a hydraulic lift system to raise the height of the vehicle by 35 centimetres when transitioning from drive to flight mode. This was needed to ensure that the propeller doesn’t hit the ground while also making the car more stable on the road, which we managed to do by lowering the centre of gravity when lowering the complete cabin/fuselage.
The PAL-V uses two motors, both 100 hp. For a sportscar, it does not sound like a lot. How are these engines capable of driving and flying in such a sporty manner?
Indeed, 100 horsepower doesn’t sound like an enormous amount but remember that the vehicle weighs only 664 kg, which is half of the weight of a small hatchback so our power to weight ratio is pretty good. Additionally, add in an aerodynamic body. Looking closely at the lines of the PAL-V Liberty, you may notice it looks a bit like a water droplet, aerodynamically that is a very good profile to use, reducing drag-resistance for driving and especially in flight mode.
PAL-V selected the gyrocopter principle, in one of the videos Hans Joore showed us how safe this really is, very impressive, but what other technical arguments were considered in order to choose this principle?
Apart from all the safety (highest priority) and then the ease of use arguments, a gyroplane in general is a very simple mode of flight. There are no complex mechanics involved, you have an engine that is connected to the propeller and you have a rotor that is powered by the wind or passage through the air, simple! So, there is no complex mechanical connection between the engine and the rotor as you see on helicopters. This allows us to use for example a foldable rotor system and create a flying car that is lightweight, easy to operate, and with low operational cost. The less moving parts you have, the less to maintain, the cheaper it is to fly.
The PAL-V Liberty uses a traditional fuel system, why didn’t you use an electrical system running on batteries?
Of course, we studied the possibility of using electrical propulsion for the PAL-V Liberty, actually we have a design for it already, however, this design is only feasible when the battery technology has improved significantly. To give you an example of the energy density of a battery, a chocolate bar contains more than 5 times the amount of energy than the current batteries you find in electric cars. If we were to install batteries in our PAL-V Liberty, our flight range would be so low that our customers could only make short hops from maybe their town to the next town but not any further. To make matters worse, the aviation regulations say that you should be able to fly another 30 minutes after you have arrived at your destination. This is because sometimes the airport is busy or not available, and you need for example to wait in the air for a while or fly to the next landing area. So, the PAL-V Liberty can actually fly 400-500 kilometres plus an additional 30 minutes which you are not allowed to use when planning for your flight as this is called your reserve. Imagine that our maximum range with batteries would be 150 kilometres and our cruise speed is 140 km/h. Of the 150 km, 70 would need to be reserved giving a usable range of only 80 km. This is also assuming you started with fully charged batteries. This is the problem that we currently have with batteries, their energy density is still too low for aviation.
What about Hydrogen?
Hydrogen could be a good alternative, but it is not mature enough for aviation yet and not as widely available as petrol. In the end, our customers want to use their PAL-V Liberty for flying all over the world, we certainly don’t want to have them worried that they will not find the right fuel at their destination to fill up their PAL-V Liberty.
Can you tell us what your team’s biggest technical challenge was in developing a flying car?
We have faced many challenges over the last years and most people -assume that the biggest challenge is the regulations. I am not sure if I agree with that. We have built up a good relationship with EASA and the Dutch RDW (Regulation Authorities) and the regulations that are in place guide us to develop a safe vehicle, building an aviation company and a high-quality manufacturing company. Of course, these regulations set a very high bar for our team, but in the end, we will have a very safe vehicle that can be enjoyed by our customers.
It is not about a single biggest challenge. Arriving at a low weight, compact design, user-friendly conversion from drive to fly, and performance are also important factors.
What’s next? What projects are you running on the background that we are not aware of yet?
As mentioned, we are looking into new forms of propulsion systems, but these are long term plans. In the background, we also teamed up with NLR to develop an eVTOL (electrical Vertical Take-Off and Landing). This eVTOL is for the Urban Air Mobility market, but please be aware this is a project that will take another 10 years to complete. One of the reasons for that is because we will use electric propulsion in this vehicle, and we don’t expect high-density batteries to become available soon for the aviation industry.
What will the future bring for you?
I’m looking forward to the time ahead and all the challenges that we will face, we have built a great team and I’m sure that we can manage to make PAL-V a big success! In the end, it’s all a team effort.