Applied Mechanics and Materials Vol.

610 (2014) pp 97-100 Online: 2014-08-11

© (2014) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMM.610.97

Mini UAV Design and Manufacture with Bungee

Launched / Parachute Recovery
Lih-Shyng Shyu1, a *, Yung-Chia Hsiao1, b
1
Department of Electro-Optical and Energy Engineering, MingDao University, Taiwan.
a
lsshyu@mdu.edu.tw, bycshaw@mdu.edu.tw

Keywords: Mini-UAV, bungee launched, parachute recovery

Abstract. In the past ten years, the R&D of UAV (Unmanned Aerial Vehicle) is very popular and
has the trend to replacing with the manned aerial vehicle due to its low-cost and high-mobility.
According to the specifications, this project completes special contour and function of a mini-UAV
design and passes the strict fabrication, prototyping, and aerial test processes. With the advantages
of long flight endurance, speedy assembly/disassembly, simply contour, and portable, the developed
mini-UAV has the capabilities of bungee launch and parachute recovery. Thus, it makes much
progress in Taiwan’s mini-UAV area.

Introduction
In 2002, the ScanEagle, a mini unmanned aerial vehicle (UAV) was made its’ first test flight by
US army, and performed intelligence, surveillance, and reconnaissance (ISR) warfare in 2nd Iraq
war after 3-year research and development. By Image transmission, the US army can access the
intelligence of target area in time, and thus it makes this UAV more valuable in modern warfare.
Having similar contour of ScanEagle, the Israel’s Aeronautics also developed a mini UAV called
Orbiter with wing span of 2.2m, length of 1m, maximum take-off weight 6.5kg, controlled distance
15km, flight endurance of 1.5 hour, bungee launched, and parachute recovery.[1,2]

Project Specifications
As listed in Table 1, the specifications of this project adopts bungee launched and parachute
recovery function that requires enhanced strength structure during high-G take-off and lighter
structure for parachute recovery.

Table 1 Project Specifications

Function Specification
Flight Endurance 150min. or above
Vehicle Weight 15kg or below
Take-off /Landing method bungee launched /parachute recovery
Power Engine or Motor Power

Design Specifications
Referring available Mini-UAVs, the ScanEagle and Orbiter are selected in this project. So the
vehicle wing selects type of NACA3418, because this type has higher lift force and low drag
characteristic in low speed wind.[3] Taper ratio AR = 3.5，Ct/Cr = 0.75. Sweepback angle ≒ 40o,
considering flight vehicle’s sensitivity.[4] Fuselage contour is coned streamline-shaped. Bungee
launched design, vehicle speed = 25 kt (12.9 m/s) =VS (stall velocity). Ejection force (F)= 30.6
(kgw). Vehicle’s storage design 3parts, fuselage, centibar section and wings panel. Adopt quick
disassembly structure for easy storage. Engine is Saito FG-20, 20c.c. four-stroke fuel-efficient
gasoline engine. Fuel requirement≒3,000cc. Vehicle weight estimating range of 6-8 kg. Table 2
lists the primary specifications of the proposed mini-UAV.[1-5]

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98 Mechanics, Mechatronics, Intelligent System and Information Technology

Table 2 The primary spec. of proposed Mini-UAV

Length 1.1 m
Wingspan 2.8 m
Weight 7 kg
Endurance 150 min

Vehicle fuselage and centibar section structure design (Fig. 1), light-weight hollowed fuselage
structure as shown in Fig. 2.

Fig. 1 Fuselage and centibar section structure Fig. 2 Light-weight fuselage structure

Referring to ejection racks of ScanEagle and Orbiter Mini UAVs, the specifications of this
project’s ejection rack are acceleration distance 3m, deceleration distance 1m, acceleration 2.8G,
take-off speed ＞13m/s and acceleration time 0.3 sec..
Parachute applies lift force (air resistance) in the air to slow down the falling object. The larger
parachute area, the more air floatation (lift force) when landing. Force analysis of the parachute:[6]

mg − F = ma ( a : parachute downward acceleration ) (1)

Because force F is continues to increase until F=mg, acceleration a will be decreased to zero.
At this time, the parachute is falling in uniform velocity Vt called Terminal Velocity.
The vehicle’s velocity is zero after colliding ground (landing), and the collision force Fc on the
vehicle is：

0 − mVt
Fc = ( t : collision time, Parachute’s area = 4.6 m2 , safe Vt < 2 m/sec ) (2)
t

Fabrication and Verification

The vehicle structure is made of light-weight aeronautical material called Balsa according to the
blueprint. Then, the surface is covered with hot-plastic film, and several servo units and engine
are installed. As shown in Fig. 3, the prototype is made for testing the flight performance and
controllability with landing gear. To verify the vehicle, the Aerodynamic Force Center makes a 1/3
scale-down prototype vehicle (Fig. 4) that is lunched by hand for testing.[7]

Fig. 3 The prototype vehicle Fig. 4 Scale-down verification vehicle

 Applied Mechanics and Materials Vol. 610 99

The first flight testing of this prototype found that the wind would make the wings vibrate and
hard to control, because the outside wings’ structure was too weak. This problem is solved by
enhancing the wing structure. The first prototype makes 5 flights of 2.1 hrs.
As shown in Fig. 5, the ejection rack are weight 30 kg, max. elevation angle 250°, acceleration
distance 3m, acceleration time 0.7sec., and take-off velocity over 20m/s.
To verify the functions of ejection rack, the spring cords are applied as many as 6. A dummy
model of 7.16 kg was launched with take-off velocity of 21m/sec, and thus met the requirement.
Testing the original 2m-length parachute by helicopter at height about 100m with load of 7kg
lead found that the Terminal (landing) velocity was 4-5 m/sec due to not calculating the effect of
top air outlet that made the parachute stable. Therefore, the parachute length is enlarged to 3.2m,
and the test result meets the requirements of 1.5 m/s (Fig. 6).

Fig. 5 Ejection Rack Fig. 6 Parachute testing (parachute in the box)

The System Testing

After individually testing vehicle and ejection rack, the whole system tests were under way. As
shown in Fig. 7, the prototype was ejected three times, the functions of vehicle and ejection rack are
met the requirements. The ejections of prototype with parachute recoveries were executed. The
servo ejected the cover connected with ropes that pulled out the main and second parachutes, when
vehicles reached 150m height. The vehicle is safely landed as shown in Fig. 8.

Fig. 7 The prototype ejection Fig. 8 The parachute recovery of prototype

Discussion
1. No-tail UAV’s R&D of vehicle design, bungee launched, and parachute recovery has not
displayed in Taiwan until this project. This project completes mini-UAV design and passes the
strict fabrication, prototyping, and aerial test processes to verify the system’s easy controllable,
safety, and stable.
100 Mechanics, Mechatronics, Intelligent System and Information Technology

2. The wings can be quick assembly/disassembly. Electric is connected by a plug, while the
connection of middle wing and outer wing is by a screw bolt. Thus can meet the mobile and
fast demands.
3. Ejection rack consists of modules and can be easily assembly/disassembly. The spring cords
designed with combined type can adjust the number of cords according to the size of vehicle,
that meets multi-vehicle ejection requirements.
4. Parachute’s design meets the project requirement with landing velocity less than 2 m/s.
5. The mini-UAV has bottom cabin design for installing optic devices. The center of weight is
also considered in the design.
6. After checking the fuel tank, the high-thrust fuel-efficient engine can meet 2.5 hrs flight
endurance.
7. Only having two separated parts of fuselage and wings, vehicle can be packed in a bag of
50x60x120 (cm) and easily carried by single person in high mobility.

Conclusions
This project spent only 8 months from idea, fabrication, prototyping, to test flight, and met the
requirements. In the process, we had fully communication with demander to understand the purpose
of this project, not merely designed and fabricated a conventional UAV for meeting the bungee
launched and parachute recovery requirements. This project completes special contour and function
of a mini UAV design and passes the strict fabrication, prototyping, and aerial test processes. With
the advantages of long flight endurance, speedy assembly/disassembly, simply contour, and
portable, the developed mini MAV has the capabilities of bungee launch and parachute recovery.
Thus, it makes much progress in Taiwan’s mini MAV area.

References
[1] Information on
http://www.aerovironment.com/aera-aircraft/unmanned.htm1
http://www.auvsi.org/
http://www.puav.com/
http://www.uavforum.com/
http://www.vectorsite.net/avuav.htm1
http://wwwuvonline.com/
[2] D. A. Fulghum and J. D. Morrocco, Israel Air Force to Grow in Size, Power and Range,
Aviation Technology, sept. 2000.
[3] Ira H. Abbott and Albert E. Von Doenhoff, Theory of Wing Sections, USA Dover Publication,
Inc. New York, 1959
[4] Lian, Y., Shyy, W., Viieru, D. and Zhang, B., “Embrace Wing Aerodynamics for Micro Air
Vehicle”, Progress in Aeronautical Sciences, Vol.39, 2003.
[5] Roskam, J., “Airplane Design”, Roskam Aviation and Engineering Corporation, 1985.
[6] Hsian, F. B. and Lee, M. T., “The Development of Unmanned Aerial Vehicle in
RMRL/NCTU”, 4th Pacific International Conference on Aerospace Science and Technology,
Kaohsiung, Taiwan, May, 2001.
[7] Luo ya-hui, Shyu lih-shyng, Chang wu-chung, "Development and application of unmanned
aircraft," The New Quarterly vol. 32, No.3 2005.
Mechanics, Mechatronics, Intelligent System and Information Technology
10.4028/www.scientific.net/AMM.610

Mini UAV Design and Manufacture with Bungee Launched / Parachute Recovery
10.4028/www.scientific.net/AMM.610.97