Skip to content

2 Seater BlackFly with Fuel Cells : Bigger, Meaner Flying Machine

in this video we are going to look at the engineering of two seater version of the Opener’s BlackFly and how a fuel cell can increase its flight time by more than 5 times.

In this video we’re going to explore the design of opener’s blackfly using its existing design as a template we will make modifications and create different iterations of it such as a larger two-seater version and one that can be powered by fuel cells so without further ado let’s begin one of the most iconic aircraft of the present era is no doubt the black fly

From opener its beauty lies in its simplicity it’s a tandem wing configuration that doesn’t have a vertical stabilizer and doesn’t even have a landing gear it looks like a canoe with wings and yet the aircraft can take off vertically seamlessly transition to cruise and also land vertically unlike any other aircraft out there we’ve had tail sitter veto aircraft

In the past that were simple and functionally similar but trying to board them was a challenge to say the least and ground infrastructure was required which is why the idea failed to prevail the opener’s blackfly on the other hand touches an unparalleled level of simplicity with no requirement of ground infrastructure at all it can land and take off from paved

Surfaces grass asphalt and even snow or ice it can even land on water the present design developed by opener falls under part 103 a faa part 103 legal aircraft can be sold without the need to go through a rigorous certification process but this also severely restricts the role of the aircraft to being just a recreational one it also limits the occupancy to just

One person and the empty weight limit to 115 kilograms the black fly weight is slightly over that threshold that is the aircraft weighs 142 kilogram but because it is an amphibious ultralight it still qualifies for the part 103 as the weight restriction for amphibious aircraft is higher furthermore it is also restricted to the type of airspace it can fly in while

Falling under part 103 has its advantages and one of them is no requirement of pilot’s license to fly the aircraft but as mentioned it has several limitations the blackfly’s design has so much potential particularly if a larger version of it is made at present it has a compact footprint of just 4.16 meters by 2.5 meters it can fit in a garage and occupy space less

Than that of two cars parked side by side but what if we enlarge it slightly to increase the maximum take-off weight what if we make it a two-seater what if we make it run on a fossil fuel system and see how much its flight time can be increased what if we don’t restrict the aircraft to the ultralight category and modify it to a utility aircraft comparable to the

Cessna 172 to explore all this let’s start our what if journey the iteration of black fly we will explore will have a longer wing size the wing size is increased from 4.16 meters to 6.16 meters on both the wings we will also have to add four extra propellers two on each wing to increase the take-off power and maintain the same distributed propulsion intensity as the

Original model this will allow us a higher value of maximum take-off weight and also maintain the same flight characteristics the fuselage can be extended to increase the space inside of the aircraft bear in mind that this extended design has a smaller footprint than a cessna 174 and yet it can take off from and land in your back garden which the cessna cannot from

The specs we find that each propeller of the black fly can give a thrust of 59 kilograms with four additional propellers we will get an additional 236 kilograms of thrust of which we will leverage only around half that is 118 kilograms for the additional payload this will be done to have a similar lift authority of the original aircraft with this allowance we can

Either choose to add an extra passenger or can add a fuel cell system bear in mind that the original black fly has just 8 kilowatt hour of battery almost a fifth of the battery energy is set aside for reserve flight another fifth of the total capacity is kept in accessible to protect the battery this leaves us with just around 5 kilowatt hour for hover and cruise

The black fly has one of the lowest energy consumption of just 245 watt hour per mile with two people on board the energy consumption per mile would increase particularly if the disc loading doesn’t remain the same if we maintain the same design of having one kilowatt hour battery behind every propulsor then the upscale design would have an extra four kilowatt

Hour of battery making it 12 kilowatt hour in total from calculations it was found that the original black fly consumes about 42 kilowatts of maximum power and gives us about 15 minutes of flying time with the maximum allowable weight in the extended version we can add another seed behind the pilot’s seat with the added seed the extra weight of the airframe the

Motors the batteries and an extra person the power required would be 68 kilowatts considering the disc loading of not just 8 but 12 propellers the calculations reveal that the flight time reduces in the two-seater version despite the additional batteries to just 12.5 minutes nonetheless the two-seater version with the single occupant and the extra seat removed

Has an estimated flight time of 20 minutes so there is an improvement there is some merit in developing the two-seater version with batteries and specially with more powerful batteries on the horizon it would however require the aircraft to clear a very stern certification process but this design template is simply too good to ignore the real change in flight time

Can come with the use of fuel cells note that one kilogram of hydrogen has 33.3 kilowatt hour of energy content or calorific value even with a 60 efficient fuel cell one kilogram of hydrogen would still provide 20 kilowatt hours of electricity the fuel cells vehicle have been around for over a decade the technology has matured and cost reduction is being achieved

Through economies of scale for the fuel cell version of the black fly we can use toyota mirai’s fuel cell the specs of which are as follows the fuel cell stack weighs about 52 kilograms the combined space that the two hydrogen tanks occupy is 122 liters they can store hydrogen at 70 mega pascals the tanks have a combined weight of 87.5 kilograms and can hold five

Kilograms of hydrogen in total this fuel cell can provide power of up to 136 kilowatts and needs a battery as a buffer which is already present in the black fly now there is little margin to add extra weight of the fuel cell in the normal backfly we can however add it to our extended version with the 12 props calculations reveal that with a single tank the flight

Time will increase to 54 minutes with two tanks of hydrogen and with the extra weight of the system considered the flight time will increase to 1 hour and 24 minutes but bear in mind that these flight time values with fuel cells are based on just a single occupant not two if we increase the occupants to two then with a single tank of hydrogen the flight time comes

Out to be 39 minutes the disc loading increases though which means a lot more load on the propellers for two tanks of hydrogen and with two people on board the flight time is 65 minutes the max power required will be increased to 87.5 kilowatts the disc loading is 30 percent higher than the normal flight which will alter the flight characteristics and the aircraft

Will not be flying as nimble as seen in the videos so with the fuel cells the flight time increases significantly bear in mind that the fuel cell stack used here can produce up to 136 kilowatts even in our most loaded condition we are well below that number therefore a lighter fuel cell can be used similarly with a fuel cell system on board the amount of battery

Can be also reduced to save weight so there we go to recap the black fly is one of those aircraft that anyone would like to own the design is amazing and lends itself well for larger utility scale aircraft the fuel cell system such as the one used here for calculations costs about 40 000 us dollars nonetheless as the price drops it’s certainly worth looking at

The black fly with a fuel cell system for the extended range and performance and with this the video is concluded if you learned something from it then do give it a thumbs up thank you for your attention

Transcribed from video
2 Seater BlackFly with Fuel Cells : Bigger, Meaner Flying Machine By Electric Aviation