Their story, in their words…
The plan
Our initial plan for the project was to challenge ourselves both physically and mentally. Due to our collective interest in engineering, we had the idea to build a remote-controlled plane that we could run and/or cycle for a set distance with.
After multiple days of brainstorming, we decided to build a 2-metre wingspan plane that could fly on an autopilot along a pre-determined route as we cycled on the roads beneath it. The primary concern with this idea was the legal implications with operating such a plane.
After looking on the websites of the CAA, BMFA, and UAVhub, we discovered our project would be classed as a Small Unmanned Aircraft (SUA), and therefore could not be flown over main roads or in residential areas, which made it difficult if we wanted to run or cycle underneath.
Ashton spent days on footpath and drone buddy finding a route that would work by avoiding main roads and airfields, Matthew then found transport there as well as selecting a place to get a cargo bike from, in which someone would sit to monitor the plane at all times.
Matthew also got in contact with National rail and Southeastern to ensure that we could take such a bike on their trains, unfortunately they only replied to us days before we were set to go, telling us we couldn’t have cargo bikes on trains, forcing us to select Richmond Park as the location instead. This didn’t affect the core idea of our plan, but it did change the location.
The build
Having finished the design and our GCSE exams, building started on the 19th of June with laser cutting the foamboard panels of the fuselage and the balsa wing ribs (which we had nested in our design to minimise the waste from the laser cutting).
Once completed, we began to assemble the fuselage with hot glue and epoxied the ribs onto carbon fibre rods using a jig to ensure they were correctly spaced, however as we were about to epoxy the second wing it got stuck in a tight section of the jig, while removing it one side came out very suddenly, leaving the other still stuck and shattering all of the ribs and forcing us to re-cut and epoxy the ribs.
Dowels were then cut to size and glued along the front of the wing to prevent distortion to the leading edge when they were covered by the plastic film, ensuring good aerodynamics. The control surfaces were then cut and bevelled to allow them to move, and holes were cut for the metal servos to be put in.
Finally, we soldered the motor and ESC together, and Morgan soldered the lithium ion cells in series. Once this was done, all we had to do was plug everything in, trim the servos, plot our route, and we were ready to fly.
The autopilot software we chose to use is called Ardupilot as it is very customisable and allows us to program in any variables which we need to customise for our plane, such as decreasing responsiveness to improve glider-style efficiency.
It is also extremely popular; being used by a range of people from hobbyists like us to government-funded tech start-ups, as a result it has a very large community and extensive wiki which was referenced throughout the project to fix problems.
First attempt
We had initially planned to fly on the 6th of July and we showed up to the park excited and ready, but things did not go as planned. Due to a calibration error the flight controller was giving out an incorrect input to the motor, making it unable to arm, we only discovered this to be the cause weeks later, however as we sat in the field, trying to understand the cause of the beeping we looked up and saw the sky darken, we were then pelted with hail (in July) and as we ran for shelter with the plane a sudden gust of wind gave the wings so much lift that they broke their enclosure, putting an end to the day. While this was a good sign for the aerodynamics of the plane, it was still disheartening and led to a complete re-design of the central wing hub, as well as great programming changes.
Time for Round 2.
Final attempt
We arrived at Richmond Park on the 31st of August at 9am with the cargo bike, plane, and repair equipment. It was quite sunny at first and the wind was very calm… at first, unfortunately it soon picked up, we were also soon informed that we were in fact not allowed to cycle on any of the green paths in the park, a rule which we had not come across in our research, this led us to decide to scrap the cycling part of the project and go instead for aircraft distance endurance, not human endurance.
Having assembled the plane we threw it into the air, at which point it nosedived into the ground due to a glitch in the software. Undeterred, we spent the next hour bending the motor shaft back and using hot glue to re-secure the nose, and fixing programming errors, however, the motor shaft remained slightly bent, causing vibrations in the aircraft.
Despite this we sent it up anew to begin autonomous flight and this was a complete success, we observed it fly fully autonomously for 8km overall, varying between speeds of 2m/s and 20 m/s because of the wind. Suddenly, on our 8th lap of the field the plane was caught by a gust of wind and pushed into a tree.
Conclusion
Despite this heartbreaking and rather abrupt ending to our project, we are all very proud of what we have achieved. We have designed and built a fully functioning UAV (overcoming snapped ribs and burnt holes in the wing), learnt from our attempt on the 6th of July to improve our plane’s ability to withstand stress on the wings, raised £715 for the Mark Evison Foundation (names of those who donated can be seen on the fuselage), gained a very good understanding of the ardu-pilot software, got very good at repairing damage and overcoming problems, and most importantly we managed to get the plane to fly 8 kilometres fully autonomously, without any human input, in weather that was much worse than what it had been designed for.
We have also gained important research, communication, and problem-solving skills over the course of this project and are extremely grateful to the Mark Evison Foundation for allowing us to complete this project, it was an absolute blast.
