Table of Contents
I.
II.
III.
IV.
V.
Introduction
A.
Team AWESOME
B.
Mission Requirements Analysis
C.
Design Rationale
D.
Expected Performance
E.
System Overview
Airframe Systems Design, Development & Testing
A.
Airframe
B.
Autopilot
Payload Systems Design, Development & Testing
A.
Video System
B.
Camera Gimbal
C.
Wi-Fi Repeater
Ground Station Design, Development & Testing
A.
Air Vehicle Control
B.
Mission Payload Control
Safety, Testing & Airworthiness
A.
Aircraft Testing
B.
Flight Line Command and Control
C.
Checklists
D.
Frequencies Used
Team AWESOME, ERAU Prescott AZ
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I. Introduction
A.
Team AWESOME
Embry Riddle- Prescott’s Team AWESOME is a multidisciplinary team comprised of three
aerospace engineers and three aeronautical science majors, formerly military unmanned
aerial systems operators. Combined, the team has over 300 manned and over 3,000
unmanned hours of flight experience. The team was established January 2011 and started
with a donated Senior Telemaster aircraft. Since then the team has test flown 11 aircraft of
increasing complexity, and now designs and builds lightweight composite electric aircraft.
B.
Mission Requirements Analysis
The primary objective of the SUAS mission is to gather ISR as quickly, safely, and
autonomously as possible. Specifically, the sub-objectives are to:







C.
Set up the system in 40 minutes or less
Autonomously navigate from takeoff to landing
Obtain real-time intelligence of targets with 50 ft. accuracy, identifying five
characteristics
Dynamically re-task the aircraft for adjusted waypoints and search areas
Relay data from the Simulated Remote Intelligence Center (SRIC)
Complete the mission in 20-40 minutes
Implement an effective and dynamic safety/training program
Design Rationale
After analyzing the mission requirements, the team identified the Key Performance
Parameters that would be realistically attainable, and established the values and
competencies of the team. The goals the team set were to:







Achieve all the objective Key Performance Parameters of the SUAS Competition
Implement a real-time digital video payload in a two-axis gimbal
Make the system rugged, field deployable, and reliable
Make the system independent of runways
Make the aircraft lightweight
Make all aircraft modular with interchangeable parts
Design the entire system for simplicity
Many of the design decisions made by team AWESOME are largely motivated by the team’s
practical experience. The team’s early systems were large, fragile balsa wood aircraft with
unreliable gasoline engines. These aircraft were difficult to operate, and were limited by
Team AWESOME, ERAU Prescott AZ
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runway availability and environmental factors. In addition, the team’s former military UAS
experience drives the group to build simple, rugged, and dependable systems.
D.
Expected Performance
At the outset, the team expected to build a single aircraft, purchase a single autopilot, and
complete the systems integration by March 2012. Since then the team has designed and
built three different aircraft, purchased six autopilots, crashed two aircraft, built and tested
a deep-stall/airbag recovery system, redesigned the wings, designed and flight tested a
new empennage, built a digital video system, reverted to analog, and went over budget. In
the last year, all sections of the project have gone through multiple iterations of the
systems engineering process, and the team has now produced an aircraft ready to complete
the SUAS mission.
E.
System Overview
The Goose II UAS (G2) is an electrically powered, composite construction airplane. The
fuselage is made of a carbon fiber tube, and the mission dependent equipment is housed in
a fiberglass pod fuselage attached to the bottom of the aircraft. The wings and tail surfaces
are fiberglass over EPS foam, reinforced with carbon fiber spars. All of the aircraft sections,
including the pod, are attached without tools. When disassembled, the aircraft is small
enough to fit into a suitcase. The G2 has an 80” wingspan and weighs only 6 pounds empty,
and can carry 6 pounds of payload. The G2 can fly roughly 20 minutes for every pound of
batteries it carries. It has a carbon fiber two-axis gimbal, weighing less than 5 ounces. The
plane is hand-launched, and lands on its replaceable skid plate belly. The plane uses an
Ardupilot Mega 2.0 autopilot for autonomous navigation and camera control, and features
an easy to use operator interface that allows for simple point-and-click flying. The Wi-Fi
system on board can rebroadcast networks in its range up to 1 mile.
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Aircraft
Servos
Aircraft
Sensors
ArduPilot
Mega 2.0
Camera
Gimbal
Safety Pilot
Air Vehicle
Operator
Video
Transmitter
Payload
Operator
Figure 1: System Command and Control Architecture
II. Airframe Systems Design, Development & Testing
A.
Airframe
The aircraft built for the competition is the Goose II, the third generation of systems
engineering processes to construct the optimal platform. At the time of the initial Request
for Proposal (RFP) the team was in a transitional phase, utilizing two aircraft. The first,
Skywalker, was an electric, EPO foam RC airplane, which was reinforced with fiberglass to
stiffen the fuselage, and Kevlar to protect the belly during skid landings. The platform was
highly robust, and has survived several crashes. The second, WhitePlane I, was the team’s
first attempt at building a composite aircraft. It had a carbon fiber tube fuselage, an
aluminum pod underneath for payload carrying and skid landings, and used fiberglassed
Skywalker wings with compartments cut out for lithium batteries. WhitePlane I was a
successful platform, and helped to identify the center section as the weak point in the
carbon tube fuselage design. The team decided to use WhitePlane I to explore a deepstall/airbag recovery method, in which the horizontal stabilizer rotates up and stalls the
plane, and a ducted fan inflates an airbag out of the pod to cushion the landing. The
recovery system was designed, built, and tested. However, the project was cancelled after
three iterations of marginal results and repeated aircraft damage.
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Figure 2: WhitePlane I, Deep-Stall/Airbag Test
The team began designing a new aircraft, the Goose I, which would have a newly designed
center section, modular and interchangeable parts, custom designed flight surfaces, and an
upgraded, more efficient propulsion setup. In early stages, the Goose I was designed to
carry the batteries in its wings, like WhitePlane I. However, the new propulsion setup
included larger batteries, and the new wing design was too thin to accommodate them.
Figure 3: Goose I
The wing for Goose I was designed to create maximum endurance as well as a stable
platform. This design was done in two phases, the first was the selection of a twoTeam AWESOME, ERAU Prescott AZ
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dimensional airfoil shape, and the second was the selection of the three-dimensional wing
geometry. To start the airfoil selection a large array of NACA 4 digit, Selig and Eppler
airfoils were analyzed in a program called XFLR 5, and example of this analysis can be seen
in Fig. Four. The seven airfoils with the highest lift to drag ratios were then taken and
given a weighted score based on their lift coefficient, pitching moment and lift over drag.
The results of this weighted score can be seen in Table One, the result of this scoring
demonstrated that the best airfoil choice was Selig 4110. Also the two dimensional
coefficients can be seen plotted in Fig. Five, as well as the lift over drag ratio in Fig. Six.
Figure 4: Airfoil Analysis
Airfoil
Lift over Drag L/D Weighted Score
Eppler 216
82.15
8.22
Eppler 214
72.33
7.23
Eppler 212
67.39
6.74
Selig 4022
66.02
6.60
Selig 4110
65.67
6.57
NACA 4515
60.42
6.04
NACA 5515
63.87
6.39
Moment about the quarter chord Weighted Moment Score
-0.18
0.75
-0.13
2.73
-0.11
3.72
-0.15
2.01
-0.09
4.40
-0.12
3.14
-0.15
2.11
Lift Coefficient
0.94
0.77
0.64
0.83
0.62
0.73
0.84
Weighted Lift Score
4.70
3.86
3.22
4.13
3.11
3.67
4.18
Total Score
13.66
13.82
13.69
12.74
14.07
12.86
12.68
Table 1: Airfoil Weighted Score
Team AWESOME, ERAU Prescott AZ
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Figure 5:Two Dimensional Coefficients
Figure 6: Lift to Drag Ratio
Once the two-dimensional wing shape had been chosen, XFLR 5 was used again to analyze
several different variations of three-dimensional wing geometry. This analysis gives 3D lift,
drag, moments as well as pressure distribution. An example of this analysis can be seen in
Fig. Seven. The aspect ratio, taper ratio and wing area were varied in order to find a
geometry that would yield the most efficient wing possible, the three dimensional
coefficients can be seen in Fig. Eight as well as the lift over drag in Fig. Nine.
Figure 7: Wing Analysis
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Figure 8: Three Dimensional Coefficients
Figure 9: Lift to Drag Ratio
For a truly modular design, all of the pieces of the aircraft (outboard wings, tail tube, motor
tube, and pod) would need to attach in one place- the center wing section. The team needed
to make the skeleton of the center wing as strong as possible, but still remain lightweight.
To do this, the center wing of Goose I was designed to be built with carbon fiber tubing and
plates in an interlocking fashion. The motor and tail tubes were designed to slide over the
center section tubes and lock with push-button clips. The wings were designed with
protruding carbon spars that would slide into the center section and hold in place with
friction. The pod was designed to attach to the center section using bolts. The design of the
skeleton is also where wing dihedral and incidence angle are built in. The skeleton was
built, but the carbon plates were observed to be flimsy, so the plates were doubled to add
rigidity.
Team AWESOME, ERAU Prescott AZ
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Figure 10: Goose I Carbon Skeleton
To build the wings and tail surfaces, the team researched composite construction
techniques by watching instructional videos, talking to experimental composite aircraft
builders, visiting local UAS manufacturer Brock Technologies, Inc, as well as a great deal of
trial and error. The team used an inverse mold technique to make the flight surfaces. First,
the end-point airfoils are printed 1:1 scale on paper, and used to cut out carbon fiber
guides. Then, the guides are adhered to EPS foam and guide a hotwire that cuts the flight
surface. Placement of the guides can facilitate wing taper, sweep, and washout. Then, the
wings are drilled laterally and hotwired inside to form hollow sections and carbon fiber
spar channels. The wings are fitted with carbon spars, carbon end-caps, and fiberglassed
with lightweight cloth and resin.
Team AWESOME, ERAU Prescott AZ
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Figure 11:Goose I, First Flight
Goose I flew on March 20, 2012. The aircraft was observed to be overly maneuverable on
pitch, and marginally stable on roll. Goose I also required a large angle of attack to maintain
level cruise flight. The pitch control throw was reduced, and a 60 polyhedral was built into
the three wing sections with brackets to add roll stability, with good results. The angle of
attack required for straight and level flight produced undesirable drag, and would have to
be corrected with a modified incidence angle. This would require a new wing and center
section. The team decided then to design a new aircraft, Goose II, with a higher incidence
angle and built-in dihedral. Goose II would also have a V-tail empennage for lower weight,
simplicity in manufacturing, and ground clearance during landing. Other modifications
included building an autopilot tray on the top of the center wing for easy access, and
changing the pod attachment to a Picatinny scope rail for easy tool-less attachment and
center of gravity adjustment.
Team AWESOME, ERAU Prescott AZ
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Figure 12: Goose II with V-Tail, First Flight
The first flight of Goose II was on May 15, 2012. The aircraft was stable in roll, and had a
level pitch attitude in cruise. However, the V-tail made the aircraft unstable in yaw, and the
aircraft entered several spins, which nearly crashed it. The Goose line of parts were made
to be interchangeable, so the T-tail from Goose I was placed on Goose II. The flight test of
Goose II with the T-tail was very successful, and it will serve as the competition aircraft.
B.
Autopilot
The autopilot is solely responsible for autonomous UAS navigation. In order to find the best
solution for the mission, the team evaluated several small UAS autopilots. At the initial RFP,
the team was using the Uthere RUBY autopilot. RUBY has a 3 axis IMU, GPS, and a
pitot/static system. It supports autonomous takeoff, waypoint navigation, and landing. The
system did not yet support telemetry and waypoint adjustments at that time, so it was a
poor choice for the SUAS competition. Shortly thereafter, the team had a MicroPilot 2028
LRC donated to the university, and the team decided to use it for the competition. The first
problem with the 2028 was its large size and weight. The Long Range Communications
modules would be unnecessary for the SUAS competition, and added a great deal of weight.
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The team contacted MicroPilot to ask if the autopilot could be removed and used
standalone. The company was unable to help, saying that technical support must be
purchased at $1,500 per year. The other problem was that the license for the ground
control station software, Horizonmp, was expired and would have to be purchased for an
additional $1,500. The team decided that an investment of $3,000 was unwise, considering
the functionality of the autopilot was unknown, and the team would be unable to replace
the autopilot in the event of a crash.
Figure 13: Uthere RUBY autopilot (left) MicroPilot 2028 LRC (right)
Several autopilots were then evaluated for their cost, functionality, ease of use, and opensource architecture. Procerus Kestrel, Cloud Cap Piccolo, and MicroPilot 2128 were
immediately ruled out for their high cost. The team then evaluated the inexpensive, open
source Paparazzi and ArduPilot Mega, and chose the latter for its easy to use ground
station. The team bought four ArduPilot Mega 1.4 autopilots, and later two ArduPilot Mega
2.0 autopilots all for less than $3,000.
Figure 13: ArduPilot Mega 1.4 (Back) and 2.0 (Front)
Team AWESOME, ERAU Prescott AZ
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The ArduPilot Mega 2.0 is the most powerful open-source IMU based autopilot available
today. It supports full mission scripting, autonomous takeoff, landing, and waypoint
navigation, simple “fly-to-here” commands, geo-fencing, area search path planning, and
airborne PID tuning. Its sensors include 3-axis IMU, GPS, pitot/static, barometric altimeter,
volts/current, and 3-axis magnetometer. The capability is outstanding for the price. After
extensive flight-testing, the team believes the autopilot is well suited for the SUAS
competition.
One capability that the team had to add to the Ardupilot software was air vehicle flight
termination. Utilizing the Ardupilot’s open-source architecture, the team wrote the
necessary code to command the air vehicle to return home after 30 seconds of lost link, and
terminate its flight after 3 minutes of lost link.
III. Payload Systems Design, Development & Testing
A.
Video system
The aircraft’s payload is a crucial system in completing the SUAS mission, and the team has
concentrated much of its resources to advancing the payload capability and usefulness. The
team initially planned to use a digital video system over Wi-Fi for the benefit of combining
the video and SRIC payload. The team purchased an Arecont Vision IP Megapixel Camera,
and two Engenius 300Mbps routers with 3-way Multiple In/Multiple Out (MIMO)
technology. The system was assembled and field-tested with Omni-directional antennas
and reached approx. 500 feet. Building on this success, the team purchased three bidirectional amplifiers and directional antennas and conducted field-testing. The team
expected range of over 2 miles with this setup, but range was only increased a small
amount, and video was unreliable at 1,000 ft. The cause is still not completely known, but
is suspected to be losses in cabling and connectors.
When the digital video system did not work as anticipated, the team decided to use analog
video and a commercial-off-the-shelf Wi-Fi repeater. The current system uses a 2.4 GHz
video transmitter and receiver, and a 720 line analog video camera. The system was
ground tested at 2,500 ft. with good results. A signal amplifier was added to the receiver,
with excellent results. Next the team plans to purchase and test a 10 db Omni-directional
antenna.
B.
Camera Gimbal
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Many of the team members have a great deal of UAS operating experience. Thus as a matter
of preference, a two-axis camera gimbal was required. The team could not find a
satisfactory gimbal for a low price, so one had to be constructed. The method of
construction proved to be a difficult area, along with difficulty finding suitable hardware
and parts. A gimbal was designed in CATIA so that the parts could be printed 1:1 scale and
cut out of carbon fiber, and assembled with metal risers. Standard RC servos were
insufficient to move the gimbal in the range and accuracy required, so the servos were
modified with miniature chain/sprocket drives and external geared potentiometers.
In addition, the gimbal’s standard pulse width modulation (PWM) control was undesirablethe gimbal always moved back to the center position when the joystick was released. To
correct this behavior, an Arduino sketch was written and implemented into the ArduPilot
software that interprets joystick distance from center, and changes servo PWM at a
correlated rate and direction.
C.
Wi-Fi Repeater
To address the challenge of the Simulated Remote Intelligence Center (SRIC), the team will
use an off-the-shelf Wi-Fi repeater with an external antenna. The team will purchase the
Amped Wireless 600mW Pro Smart Repeater. The system is simple and requires the user to
attach the unit to a laptop via LAN, connect to the primary network, and then set up a
secondary repeater network.
Figure 14: Amped Wireless 600mW Pro Smart Repeater
IV. Ground Station Design, Development & Testing
A.
Air Vehicle Control
For the ArduPilot system, there are three ground stations available. Our team selected
the APM Mission Planner program for its ease of use, simple HIL simulator interface,
and operator preference.
Team AWESOME, ERAU Prescott AZ
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Figure 15: APM Mission Planner
The Mission Planner program required no modification from our team to be a usable
interface. The team has used the program extensively for flight-testing, and found it to be
suitable for completing the SUAS competition mission. The operator can command the
aircraft to autonomously takeoff, fly to selected waypoints, right-click the map and select
“fly to here,” define no-fly zones, create a geo-fence, create a search area, enter camera
parameters and generate a search path, adjust the search area in flight, and autonomously
land.
The Ardupilot Mega uses telemetry radios from 3D Robotics that are capable of 250 kbps at
100 mW. With omni antennas, the team has flight-tested the range up to 1,500 feet with
90% signal strength. These antennas are a replacement for the Xbee radios the team used
before, which were unreliable and faulty.
B.
Mission Payload Control
For the mission payload operator, the team needed to determine the camera stare point
coordinates as the gimbal moves. To that end, the team created a program in Microsoft
Excel to calculate the trigonometry angles and distance/coordinate formulas. The operator
inputs aircraft height/location and gimbal position, and the program calculates target
coordinates. The system has been ground tested with good results. The next steps are to
test the system in the aircraft, then write a program to auto-populate the aircraft’s
telemetry data into the program.
V. Safety, Testing & Airworthiness
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A.
Aircraft Testing
Testing new unmanned aircraft always involves some inherent risk. To mitigate that risk,
all of Team AWESOME’s aerial systems undergo rigorous physical inspection and lab
testing. The systems are modeled in X-Plane and put through an extensive Hardware-inthe-Loop (HIL) test, whence PID gains are set for the model. All new aircraft are flown
manually to determine airworthiness, stability, controllability, and stall/spin
characteristics. Then the autopilot is installed and simulation PID gains are carefully tested
and refined.
B.
Flight Line Command and Control
The team captain is the Pilot-in-Command and is responsible for, and the final authority on,
safety of flight. The Air Vehicle Operator programs the autonomous flight paths of the air
vehicle. As per the Academy of Model Aeronautics safety documents, a Safety Pilot keeps
the air vehicle in unaided visual range, and is always prepared to take manual control of the
aircraft. A See-and-Avoid Spotter is charged with looking for manned aircraft and giving
directions to the Safety Pilot to give the manned aircraft right-of-way.
C.
Checklists
Team AWESOME develops checklists that are intended to assist flight line personnel to
perform flight operations safely and efficiently. The checklists change with the dynamic
nature of flight-testing, and are meant to assist. Flight line personnel do deviate from
checklists to the extent necessary to complete the mission. The Pilot in Command is the
final authority on flight line procedures.
Team AWESOME, ERAU Prescott AZ
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Figure 16: Goose II Operating Checklist
D.
Frequencies Used
433 MHz-
Safety Pilot RC control
72 MHz-
Payload control
2.4 GHz-
Analog Video
2.4 GHz-
Wi-Fi re-transmitter
900 MHz-
Autopilot telemetry and control
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