Table of Contents

Executive summary

Management summary

Plan chart

Conceptual design summary

Mission requirement

Design requirements

Preliminary design

Analysis Methodology

Initial Concepts

First Designs

CFD

Trade Offs

Mission Model

Performance Estimates

Detail design

3d Drawings

Manufacturing plan

Gantt Chart

Testing plan

Check list

Performance Result

Bibliography

The aim of this project is to create two remote controlled aircraft that will meet the key mission requirements and associated design features. These requirements include creating two unconventional aircraft designs which can perform an unassisted take off, flight time for at least two minutes, house a payload consisting a dollar coin and a ping pong ball and perform a figure 8 manoeuvre. Aside from the mission requirements, the aircraft’s structural components will consist of a specified material. The first prototype aircraft will be made of foam whereas the second will be from 3D printed plastic, and the substitution for another material will be penalized. To meet the mission requirements, our team researched on existing remote-controlled aircraft designs and the type of structural design types incorporated.

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Our team decided to use a conventional rectangular wing for our first prototype. The rectangular wing provides a good amount of lift without having much disadvantages. A H-tail design was used for the tail assembly. The H-tail will provide the aircraft with superior yaw control, increasing its ability to perform a figure 8, however, the downside is it will be tail heavy and bring the centre of gravity towards the rear. The problem was minimized by adjusting the tail boom accordingly and positioning the heavy components such as the battery, motor and payload towards the front of the aircraft. The aircraft flew and met the mission requirements, but there were existing issues that almost prevented it from succeeding.

After analysing the performance of prototype one, our group decided to create a highly manoeuvrable aircraft, a flying swept wing. The reason for changing it was to reduce weight and the centre of gravity issue the H-tail brought. Coincidentally, a tailless aircraft was our solution. A flying wing aircraft is theoretically the most aerodynamically efficient as it offers the lowest drag and would mainly consist of the wing’s surface area, which provides high lift. However, the lack of conventional stabilizing surfaces and the associated control surfaces would make the aircraft unstable and difficult to control. To minimize the instability, we positioned the heavy components at the middle of the aircraft and had our pilot frequently practise with the aircraft to familiarize with the controls. Prototype two also flew well and was able to perform the necessary tasks despite being difficult to control.

Overall, both aircraft designs had their respective disadvantages but proved to be successful as they both met the design criteria and the set mission requirements.

Our group completed a conceptual design report at the beginning of this project, which included a plan chart to track our progress. Our team distributed the task evenly during planning and manufacturing stage to ensure we can complete the project on time. This included different members completing different part assemblies. There were many instances which structure parts were damaged and had to be remade, which caused us to fall behind schedule. During the prototype two stage, we decided to take a lot of precaution by printing multiple repeats of a structure part to ensure time will not be wasted. By planning and assuming there will be set-backs we achieved additional time or the damage to our progress was reduced. Our manufacturing improvement during prototype two was evident by the time spent was a lot less than prototype one. Overall, a plan chart is significant to help track progress, but foreseeing setbacks and working on prevention improved our development.

Plan chart

How work was distributed among members

Mission requirement

Fly 30 seconds

Fly 2 minutes

Carry a Ping-pong ball

Convention design and unconventional design

Design requirements

Wing loading about 5 to 6

COG place at 1/4 chord line

Choose the smooth airfoil at 10 to 20ms^-1

Base on wing loading calculate the theoretical dimensions for the plane and try to Manufactory

During the Manufactory find the problems (for example :too much weight or COG is place at wrong place ,design is not thick enough to print in the 3D printer, worst situation— wrong wing loading)

Gathering experience and try not to make same mistake.

Analysis Methodology

Initial Concepts

To serve as a solid jumping point for our 2nd design it seemed researching current and past flying wing designs would allow us to get a rough idea on what wing shapes would provide us with decent stability and lift.

Image1

The fuselage was heavily inspired from birds of prey due to the incredibly low drag they have when diving, this later proved to be a very good base point to design from.

First Designs

Stability in a flying wing is dependent on where the CG is placed relative to the Aerodynamic Centre, so we swept the wings back to position the AC towards the rear of the aircraft without compromising aerodynamic performance. The best way to rapidly test these ideals were to produce and test several small-scale wing designs, until a sweep angle with the optimum performance, then simulating these dimensions into Solid works to get the area for the wing loading calculations.

CFD

After basic design has been completed we used Solid works CFD analysis to gather data and to refine our design for the best optimal wing. This involved the endplate design and in deciding in any twist in of the wings airfoils along its length (we opted none for a more predictable flight performance). This also allowed us to gather essential data of the aircraft including Lift, Drag, Moment and Dynamic Pressure, all of which was used to help design the aircraft and determine the final dimensions of the wing when combined with the fuselage.

Left: Flow Trajectory at Zero Lift AOA Right: Streamlines of flow viewed from above

Trade Offs

In the design process many compromises had to be made to make sure that the aircraft worked at its absolute best, the biggest of which was the removal of the fuselage altogether to help reduce weight. This compromise meant we lost some aerodynamic efficiency, wing span, our motor mount and a large portion of our structural rigidity.

Original Design of the FFMk3

We did however rectify some of our structural integrity problems by adding some carbon rods to the underside of our wings at the cost of some weight. This benefit far outweighed the loss as the aircraft was far lighter than we had designed the wings to deal with meaning we lost very little aircraft performance.

Mission Model

There were several aspects of the aircraft needed to be considered to achieve the project goals, these included; Endurance, Turn Rate, Stability and Take Off Performance.

Take off performance was the most vital of these and thus was the focus of the aircraft, this in turn meant we had to have a high wing loading to achieve a low velocity take off.

Stability was always going to be the most difficult due to the inherent instability of a flying wing design, however due to the research, analysis and testing done it was achieved in time for the flight day. However, after some unexpected damage the aircraft received before the 3rd flight we were uncertain where our cg sat with respect to our aerodynamic centre. This turned out to be problematic due to the sensitivity the design has with regards to the CG.

Lastly one uncertainty we had was the speed of the actual aircraft, due to its extreme light weight and aerodynamic design it was entirely possible that the aircraft would not be able to be properly tested before the final flight day (due to restrictions in flying space at other venues) Fortunately we could counter this problem in small areas by climbing, this allowed us to maintain TAS while lowering our speed relative to the ground, allowing us to fully test the aircrafts performance.

Performance Estimates

Theoretically the Aircraft has the stability, Battery life, take off performance and the manoeuvrability characteristics to complete the mission effectively. Since the aircraft weighs only 0.11kg (110g with battery and motor) and the Wing Area is 0.12m the total wing Loading is 0.91667 (0.11/0.12). The aircraft should easily take off and gain altitude quickly. However, since the aircraft has Neutral Stability it does require more input from the Pilot to keep it in the air thus making it harder to fly.

Parameters

Dimension

Wing Span

800mm

Wing area

0.12m2

Length

200mm

Wing Loading

0.91667

Sweep Angle

300

Sweep Distance

215.35mm

Height

95mm

Angle of attack

100

Root Chord

200mm

Tip Chord

70mm

Wing Span/2

400mm

Distance of Root Chord to Aileron

160mm

Distance of Tip  Chord to Aileron

40mm

Aileron length

200mm

Aileron width

30mm

Length of Aerofoil

200,160,80,70mm

Landing gear height

70mm

Weight

110g

CG distance

126mm

MAC length

145.4mm

MAC distance

167.9mm

Flight performance for the flying fish was to fly with the speed with 15-25m/s while covering the minimum distance of the basketball court and to fly for 2 minutes.

Mission performance for the flying fish was to design an unconventional UAV design which is able to carry specified payload. Can perform a figure 8 manoeuvre while having endurance for 2 minutes. Finally able to take-off unassisted.

3d Drawings

With the process of manufacturing the aircraft we had broken the aircraft parts into each little segments such as the wings, landing gear strut, fuselage, ailerons. Once all the parts such as wing ailerons of the aircraft were covered with skin than all the group members worked together to place the aircraft together. This took us roughly about 3-4 hours. Further this plan has helped us to fix the aircraft with any problems that we had encounter during flight, glide and balance test. 

At the start of 4 major parts of the flying fish which were fuselage, wing, landing gear and ailerons.

The process of manufacturing began with 3d printing the parts on the 3d printers using ABS plastic material. We usually used to print 2 or more copies of the same parts so while manufacturing or the while testing if something breaks we could easily replace that part with its copy so that much time would not be consumed).

Cut out any excessive parts on it by sanding or scissors.

Skin was put the fuselage, wing and the ailerons. We used ____ paper for the skin.

Hot glue was used to put all the parts together while putting the parts together we saw that landing gear was had to stick to the aircraft and was making the plane. Therefore we decided to replace the landing gear design and make new design for the landing gear where we will used carbon rod of 9mm as strut for landing gear and stick them to the root chord of the wings.

Then placed the parts together, when all the parts were paced together including electrical we had done the glide test and everything was working good.

Hence we decided to do flight test in which the plane didn’t lift off due to being heavy as it weight around 150grams.

Therefore we decided to cut of the excessive parts which were not necessary for this design (we got fuselage, under skin and small rods out)

Then we stick the parts together again using hot glue and checked the weight and it was around 110grams. Hence we checked the glide and balance test. Which also went alright. Lastly we also tested the flight test which also went smooth.

Gantt Chart

For a finish project we need to do some check such as Wing loading is it same as what we plan (about 5.5 to 6.7). For the Centre of gravity is it at the C/4 chord length. if it is behind the right place it may not fly.

We also need to check the weight is it at the acceptable range if its over we need to decrease or change our plan. For the Motor and control device we just need to make sure we set up right and it works when we need

Finally for the Maintenance we need do some back up work ,for example if we have time we need to make as more back-up as we can then we should feel comfortable when we break some part.

Check list

Working well

Not working

Testing date

Wing loading

 Week 10-13

Centre of Gravity

Week 10-13

Actual weight

 Week 7-13

Motor

 Week 13

Control devices

 Week 13

Maintenance

 Week 9-13

Gross weight

 Week 9-13

Prop

 Week 13

Engine no.

 Week 13

During the flight test of prototype one, we noticed a list of issues affecting its performance. These issues included: the centre of gravity moving towards the rear leading to difficulties controlling the aircraft, structure instability and weight asymmetry from constant patching of the aircraft with tape from the damage build up and horizontal stability issues from the elevator incorrectly aligned to the body. Despite these problems, our aircraft was able to perform an unassisted take off and carry out the mission requirements. We predicted that our aircraft would have the manoeuvrability a H-tail entailed, but we did not consider what the damage build up could cause.

After analysing the performance of prototype one, our group decided to create a new design, for prototype two, a flying swept wing aircraft.

The decision to change designs was to reduce the aircraft’s weight by removing the tail assembly and increasing lift through a larger wing surface area. We predicted the flying swept wing design to have great manoeuvrability and more lift with a downside of control instability. Upon completion of manufacturing, we realized our aircraft was a lot heavier than planned and would not take off, despite having a bigger wing area.

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To fix this, we decided to remove the fuselage and excess plastic supports then fuse the wings together. This solved our weight issue but compromised our structure stability. During flight day, the aircraft performed within our expectations. The change to a larger wing area decreased the take-off distance and improved the aircraft’s flight performance and showed great manoeuvrability, however, the pilot struggled to control the aircraft. We did not anticipate that the weakened structure will be strong enough to withstand numeral amount of crashes.

To conclude, both aircraft designs have proven to be successful as they both met the design criteria and the set mission requirements.

Fwcg.3dzone.dk. (2018). Flying wing CG calculator. [online] Available at: https://fwcg.3dzone.dk/?wing_span=81&root_chord=21.7&tip_chord=7&sweep_type=0&sweep=30.84&cg_pos=20&show_mac_lines=1 [Accessed 26 Oct. 2018].

Ichef.bbci.co.uk. (2018). [online] Available at: http://ichef.bbci.co.uk/wwfeatures/wm/live/1280_640/images/live/p0/3h/bq/p03hbqcv.jpg [Accessed 26 Oct. 2018].

Image 1: Theaviationist.com. (2018). [online] Available at: https://theaviationist.com/wp-content/uploads/2013/03/B-2-by-morther-nature-comparison.jpg [Accessed 26 Oct. 2018].