AAE 451 – Aircraft Senior Design
Spring 2007
Continuous Area Coverage via Fixed-Wing Unmanned Aerial
Systems
System Requirements Review
Team 3
Sumitero Darsono
Charles Hagenbush
Keith Higdon
Seung-il Kim
Matt Lewis
Matt Richter
Jeff Tippmann
Alex Zaubi
I.
Description and overview of proposed system
The unmanned aerial system (UAS) will not be just one plane but will consist of a system
of multiple aircraft and support equipment that will work in conjunction to provide
continuous aerial coverage over about a five mile radius. The aircraft will house a small
payload consisting of a video camera, a thermo imaging camera, or a chemical detector.
The aircraft will either have a module payload or will carry all of the payload types
simultaneously depending upon the final payload weight and the weight of the cameras.
The aircraft itself will be a micro unmanned aerial vehicle (UAV) that is able to be hand
launched and carried in a military style backpack. The entire system will be transportable
by two or three people depending on the number of aircraft needed. The support
equipment is very limited and will consist of a small transmission unit and a laptop to
program waypoints and to view the incoming video feeds. The aircraft and transmission
equipment will both be portable so that they can be used anywhere that surveillance is
necessary.
II.
Customers, Competition, and Market
The proposed system will be geared toward a surveillance market, which includes mainly
military and law enforcement personnel. The military will deploy the system UAS out of
either a backpack when on foot or out of a Humvee when traveling. The main uses for the
UAS by the military will be for surveillance around a temporary base or convoy or for
forward reconnaissance. Law enforcement will deploy the UAS out of the back of a
squad car. The main use for law enforcement will be for assessing a hazardous situation
before committing personnel or to provide continuous surveillance of large groups.
Currently, there exist several vehicles of less than 10 pounds takeoff weight that have
proven successful and will compete with the proposed aircraft in the military sector.
Figure 1 below shows the capabilities of several successful vehicles in this class9.
1
Figure 1: Capabilities of the competition with pictures of each aircraft below
For law enforcement applications, there are a few vehicles of this class that are currently
in development, but none that have been as successful as the military UAVs. Farsight
Intelligence Systems and Octran are both developing systems for this market. Shown
below in Figure 2 are the Raider and the Marauder by Farsight and the Skyseer by Octran.
As these systems are currently in development, many of their capabilities are still
unknown or not disclosed.
Raider
Marauder
Skyseer
Figure 2: UAVs currently in development for law enforcement
Since the beginning of the War on Terror, the market for small Unmanned Aerial
Systems for the military sector has grown dramatically. Due advances in sensors,
materials and batteries the mission capabilities of small UAVs are ever increasing.
2
Combined with the changing scope of warfare, current small UA systems are seeing more
and more use in places such as Iraq and Afghanistan, and the United States military has
decided to invest substantially in similar systems. Shown below in Figure 3 is the
number of small UA systems, less than 10 pounds takeoff weight, which the United
States military plans to purchase, as of 20059.
Small UA Systems (<10 lb Gross Weight)
1400
1200
1000
Number of Systems
800
Number of Aircraft
600
400
200
0
Dragon Eye
FPASS
Pointer
\
Raven
Buster
Figure 3: Number of small UA systems to be purchased by US military (as of 2005)
From Figure 3, the Dragon Eye and the Raven, both made by AeroVironment, currently
dominate the military small UAV market. The success of these systems in Iraq and
Afghanistan has prompted the armed forces to allocate resources for the continued
development of small UA systems. Figure 4 below shows the Department of Defense’s
projected budget for procuring small UA systems9.
3
Projected Budget for Procurement of Small UA Systems
25
Budget ($M)
20
15
10
5
0
05
06
07
08
09
Fiscal Year
Figure 4: DoD budget for procuring small (<10 lbs) UA systems
As the capabilities and acceptance of these systems continue to increase, we can only
expect this market to grow and new markets to open. Foreign markets are opening as
well, as the Canadian and British militaries have seen the capabilities of the US UAV
systems and are looking to purchase systems for their forces8.
III. Concept of Operations
a. Military
Current unmanned vehicles of this size, the Dragon Eye and Raven for example, provide
simply “over the hill” type missions where they observe a target location for a few
minutes and then return; whereas, our system provides the capability to observe a
location or multiple locations for hours at a time. The system is designed to be deployed
with the infantry at the squadron or platoon level. Similar to other systems of this size,
the aircraft is simply launched by hand and does not require a runway. In addition, the
entire system: aircraft, laptop, and supporting equipment would be transported via
backpack or a small container in a Humvee.
In order to best describe the planned capabilities and operations of the vehicle, there is a
listed description provided of a situation encountered by the military and how the vehicle
aids in response to the situation. Figure 5 shows a schematic of this scenario.
4
Figure 5: Concept of operations in a military role
In a rural, rugged area of Iraq, the commanding officer of a communication relay station
is notified of rising levels of insurgency near the station and that the station may come
under attack. He instructs a soldier to remove one of the UAVs from its container in the
supply building and deploy it. After assembling the vehicle and setting the flight path
waypoints via a laptop, the soldier launches the aircraft by hand to begin its mission. The
soldier operator then activates the visual and IR cameras, and data is streamed back to the
user in real-time. Two more vehicles wait in the supply building should the officer
determine that the desired surveillance area would require multiple aircraft, or if only one
aircraft’s surveillance was needed but beyond the endurance of a single plane.
As depicted in Figure 5, this system can work with conventional security and patrols.
The aircraft provides several features that Humvees or foot soldiers cannot provide, such
as surveillance of difficult terrain and extended range without risk of casualties.
5
b. Law Enforcement
Increase in national threats such as terrorism and crime along with budget pressure has
caused law enforcement agencies to seek more effective, efficient, and less costly ways to
perform their mission. The idea of using a remotely operated vehicle system, whether it
is ground or air, has begun to interest law enforcement. Currently, law enforcement
already utilizes remote control ground vehicles to perform some missions, such as those
used by the bomb squad and the SWAT (Special Weapons and Tactics) team. However,
the idea of unmanned aerial vehicles for law enforcement is relatively new.
The concept of continuous coverage using an unmanned aerial vehicle that is small, light,
portable, cheap, and that an officer can operate has great appeal to law enforcement
personnel. This vehicle will provide mobility to sensors systems, and in doing so, can
assist police agencies in obtaining evidence, providing surveillance and much more.
Figure 6: A UAV in front of police officers5
Typically, police agencies can use the UAV to provide overhead surveillance in assessing
hazardous situations before committing personnel. Similar to the military, police officers
need to gather information on each mission before performing their actions. Usually, the
law enforcement personnel carry out these missions. However, placing a police officer in
a situation that is relatively unknown and high risk may jeopardize the police officer’s
safety. Currently, the alternative method is aerial surveillance provided by helicopter.
6
Unfortunately, helicopters are very expensive to buy and operate, require dedicated pilots,
and their availability is limited. Law enforcement agencies can use UAVs as a perfect
substitute for a helicopter in the aerial surveillance role5.
In addition to a surveillance camera, the UAV can carry a chemical or radiation sensor.
This allows law enforcement personnel to search for suspected drug manufacturing sites
as well as monitor hazardous chemical spills. With this information, police agencies can
coordinate a better plan in order to perform a given mission. Furthermore, the UAV can
search for missing people in difficult terrain. This allows officers to save time in located
missing people and minimizes the risk to rescuers.
Currently, several law enforcement agencies around the world have started to use UAVs
in performing their missions. In South Africa, tactical UAV systems such as Kentron
Seekers operate for the purpose of crowd monitoring and urban surveillance. The UAV
monitors large crowds that have gathered legally and peacefully for demonstration. This
ensures that the law enforcement agency can obtain real time information about the
situation and fewer personnel are required on duty. Similarly, Pakistani law enforcement
agencies use the Pakistan built Bravo tactical UAV to perform border patrol. However,
these systems are relatively large, making their mobility limited.
Figure 7: Police Officer Holding the SkySeer UAV
When BBC News approached the Los Angeles Police Department (LAPD) and Los
Angeles Sheriff Department (LASD) in an article that was published on June 6, 2006, the
sheriff made several comments regarding the SkySeer UAV (See database in appendix).
The head of the LASD technology exploration project Charles Heal said, "It (Skyseer)
7
provides several things that we can't get other ways." Commander Heal also provided
sample applications for the UAV. For example, when burglaries occur, the conventional
approach is to call the fire department to bring in ladder trucks, allowing officers
physically to climb onto the top of a building. However, the SkySeer can provide an
aerial view of a building where someone has broken in through the roof. He also
commented, "If the suspect really wants to hurt you, your head is the first thing that he
sees. Now we'll have the ability to actually to fly this over and see if it is even worth
doing containment." Currently, the LASD department only has one prototype Skyseer.
Heal said that when the prototype does go into service, it will deploy with the SWAT unit
to carry out initial evaluations in real life situations1.
The market potential of a UAV in law enforcement is huge and relatively untapped.
Ideally, each police station could have one UAV. With the large number of law
enforcement organizations in the United States, Europe and around the world, the future
of UAVs in law enforcement operations is very bright.
IV. Customer Attributes/House of Quality
As the business plan stated, the primary customers for the UAS would be either military
or law enforcement personnel. These two customers have several similarities and
differences. They both are at risk from attacks by enemy forces, and both desire
knowledge of their surroundings. Military personnel would operate in much harsher
environmental areas with significantly long lasting operations, while law enforcement
personnel often operate in urban areas that require high maneuverability. Below are the
most important attributes for both the military and law enforcement, though the level of
importance is not necessarily the same for military and law enforcement. The complete
house of quality is provided in the appendix.
Performance:
Continuous coverage during day and night
Long range
Long endurance
8
Hand toss launch
Resolution of sensor
Ability to fly during harsh weather
Accessibility:
Packable into backpack
Easy to retrieve
Interchangeable Sensor/Diverse Sensor package
Easy to pilot
Easy to assemble
Available fuel source
Durability:
Withstand skid landing
Shelf life
Easy maintenance
Water proof
Manufacturing
Low material cost
Off the shelf items
After proposing the above questions, the list was narrowed down to the most important
aspects for both potential clients. Military and law enforcement received separate pools
to decide the importance of each individual attribute in the house of quality. After
averaging the total score, military customers considered long endurance, hand toss launch,
and the ability to pack in backpack as important traits, while law enforcement considered
hand toss launch and simple piloting system as the most important traits. Since many law
enforcement agencies on a limited budget, they have also listed low cost as higher
importance.
Then a list of engineering traits that related to the UAS was developed. Each engineering
trait received a relationship with the questions asked of the customer, and with each other
engineering trait to see which traits were highly related and which were completely
independent (see house of quality in appendix). Last, each engineering trait received a
9
relative and weighted score so that a trait focus could be determined. Since the UAV’s
primary focus is small size and light weight, its take off gross weight (TOGW) is the
most important engineering trait to both military and law enforcement customer. In
addition, operative cost is highly important. Since the goal is to provide one UAS per
platoon for military customers and per team of officers for law enforcement agencies,
operative cost must be low enough to have a large number of systems affordable.
Payload weight and number of aircrafts are the next important engineering traits for both
customers. We can therefore focus on the UAV’s weight, payload weight, and cost
issues. Since the target TOGW and payload weight are close to thresholds, cutting down
cost will be the main focus.
V.
Initial Trade Studies on Design Requirements
Now that the customers important attributes have been determined and a general feel has
been developed based on current airplanes in service, initial design-to requirements for
the aircraft design are listed below in Table . The table consists of only the important
variables to which the design will be most dependent on.
Table 1 – Design Requirements
Target Threshold
TOGW (lbs)
Endurance (hrs)
Range (nmi)
Loiter Speed (kts)
Stall Speed (kts)
Payload Weight (lbs)
Power Density (W-hrs/kg)
We/W0
10
4
20
30
7
2
350
0.4
12
2
10
40
15
4
200
0.5
The major design requirements are the TOGW, loiter speed, stall speed, and endurance.
The limit on the weight for hand launch capable UAV is 12 lbs. The loiter speed based
on sensor requirements is 40 knots. The stall speed needs to be 7 knots for a hand launch
takeoff. Finally, the endurance target is 4 hours in order to out perform the competition.
10
With the endurance being 4 hours, this directly affects the amount of power needed to fly
the mission.
a. Database Regression
Trade studies on the design requirements show the feasibility and sensitivity of the
chosen initial design requirements. Two approaches were used to look at the effect of
these variables.
The first was a power regression line fit to a database of 22 UAV’s no larger than 200 lbs.
There are 6 parameters that are record in the database, the gross weight, empty weight,
payload weight, maximum endurance, cruise velocity and altitude. Weight fraction is
calculated as a ratio between the gross weight and empty weight.
To find relation between the six parameters and the weight fraction of the UAV, data
regression is used to create a predictor equation. The predictor equation used the least
square approach and the resultant equation will provide the weight fraction of the UAV.
The equation derived from the database is:
Equation 1 – Regression Curve Fit





We
0.1566
0.3014
 1.243Wo
Payload 0.0806 Endurance 0.0975 Vcruise
Altitude 0.0174
Wo

11
Weight Fraction Regression for Small UAVs
0.9000
0.8000
0.7000
We/Wo
0.6000
0.5000
0.4000
0.3000
0.2000
We/Wo =1.2429654Wo^0.1566*Payload^-0.0806*Endurance^0.0975*
Velocity^-0.3014*Altitude^-0.0174
0.1000
0.0000
0
50
100
150
200
250
Wo
Wo vs. We/Wo
Regression
Figure 8 – Regression Curve Fit
Under the regression obtained from Equation 1 and Figure , the predicted weight fraction
is approximately 0.5458 using a TOGW of 10 lbs, payload of 2 lbs, endurance of 4 hours,
cruise velocity of 39.2 knots, which is 1.32 times the loiter speed of 30 knots, and an
altitude of 7000 ft.
b. Trade Study Plots from Initial Sizing
The second trade study method used initial sizing methods to calculate the predicted
takeoff gross weight by estimating some aircraft characteristics such as L/D ratios,
propeller efficiencies.
i.
TOGW
The TOGW is the most important aspect of our design as it what our market is
determined upon. A soldier can not hand launch a 30 lb plane. Also, 30 lb plane will
also have a hard time landing without a clear ground path. For example, the Institu
ScanEagle is 40 lbs and has a rail launch system and a unique cable catch landing system9.
12
These both require large pieces of equipment to set up and transport with the UAS. With
a TOGW of 10 lbs, the plane can be hand launched and transported relatively with ease.
We ight F ra c tion a s a F unc tion of Gros s We ight
0.9000
0.8000
We ight F ra c tion
0.7000
0.6000
0.5000
0.4000
0.3000
0.2000
0.1000
0.0000
1
51
101
151
201
Gros s We ight (lbs )
We ight F ra c tion P re dic tion
Da ta ba s e
Figure 9 – Database Regression: Empty Weight Fraction vs. TOGW
From the data obtained, it shows, as the gross weight of the UAV, becomes heavier, the
weight fraction of the UAV will increase for a given set of other variables. This trend is
also seen in the code predicting the takeoff gross weight, Figure . The graph shows an
increasing gradient in weight as the empty weight fraction is increased. The goal of
We/W0 of 0.4 for a 10 lb plane would be more than sufficient.
13
Figure 10 - Trade study on empty weight fraction on Takeoff Gross Weight
ii.
ENDURANCE
The endurance of our plane is a key factor derived from the mission goals of our plane.
Because continuous coverage is wanted, rather than “see what you need and come back”
approach, the plane needs to stay up in the air longer. Also, because the most planes in
the market for hand launched aircraft have endurances of maximum endurance of 2 hours,
designing a plane with an endurance of twice, 4 hours, what the current competition has
gives this design an edge in the market9.
14
We ig h t Fra ctio n a s a Fu n ctio n o f E n d u ra n ce
0 .9 0 0 0
0 .8 0 0 0
We ight Fra ction
0 .7 0 0 0
0 .6 0 0 0
0 .5 0 0 0
0 .4 0 0 0
0 .3 0 0 0
0 .2 0 0 0
0 .1 0 0 0
0 .0 0 0 0
0
1
2
3
4
5
6
E n d u ra n ce (h r)
We ig h t Fra ctio n P re d ictio n
Da ta b a s e
Figure 11 - Database Regression: Empty Weight Fraction vs. Endurance
The trend line shows the longer the UAV is flying, the bigger the weight fraction is
needed. The longer the UAV needs to fly, the more power the UAV takes, which also
leads to a higher gross weight. An increase in gross weight leads to an increase in the
denominator of weight fraction, hence increase in weight fraction.
This is also shown in
the trade study with the code, Figure . In this graph, as the endurance goes up, the
gradient of the TOGW increases. With the current parameters, the endurance level could
increase slightly, but the target will stay at 4 hours as many other parameters will change
this graph.
15
Figure 12 - Trade Study - TOGW vs. Endurance
iii.
LOITER SPEED
The loiter speed of the aircraft is a variable controlled by the sensor payload. Some
cameras cannot operate at speeds larger than 40 knots2. Plus, with the low-resolution
cameras, images become blurry at fast speeds. A fast loiter speed ensures multiple
aircraft can cover a larger area, while a smaller loiter speed helps with the more focused
point monitoring and resolution. The loiter speed does not have as great of an effect on
the TOGW, as seen in. This will allow some variation in the final loiter speed chosen.
16
Figure 131 - Trade Study - TOGW vs. Loiter Speed
iv.
STALL SPEED
The takeoff and landing of the aircraft is where the stall speed comes into play. For a
takeoff, the stall speed needs to be at the speed at which the person launching the plane
can throw it at. The values for the stall speed need to be calculated based on studies on
how fast a person can throw a 10 lb airplane. Since this parameter doesn’t effect the
initial sizing, but the aerodynamics and wing characteristics, an approximation of 7 knots
is the target value for the stall speed. Also the plane needs to come in very slow on
approach to ensure the landing will not damage any parts on the airplane.
v.
PAYLOAD
The payload weight incorporates the sensor and communication equipment. Looking at
sensors of the low resolution type have weights around 2 – 4 lbs. The UAV will carry a
system of visual and infrared cameras to provide day and night surveillance. Although a
trade study was not done, many visual and infrared cameras were researched to find the
17
best set of cameras. The chosen cameras were picked because of their light weight and
their resolution. The FLIR Photon EOM core with at 37.5mm lens was chosen for the
infrared camera3. This infrared camera is used in many UAVs and is designed
specifically for that purpose. The Matrix MB-1250HRVF with 4 to 8x zoom was chosen
for the visual camera6. This camera was chosen because of its small size and weight with
enough zoom to fit our chosen pixilation. The cameras will be either interchangeable or
will both be on the aircraft at the same time depending upon the final payload weight and
volume available.
Weight Fraction as a Function of Payload Weight
0.9000
0.8000
Weight Fraction
0.7000
0.6000
0.5000
0.4000
0.3000
0.2000
0.1000
0.0000
0
10
20
30
40
50
60
70
80
90
Payload Weight (lbs)
Weight Fraction Prediction
Database
Figure 14 - Database Regression: Empty Weight Fraction vs. Payload Weight
Figure 14 shows the heavier the payload weight, the smaller the weight fraction. It is
important to note that weight fraction is a ratio between the gross weight and empty
weight. Assuming the UAV only consisted of three weights (empty, gross and payload),
an increase in payload weight leads to a decrease in either empty weight or gross weight.
However, gross weight is assumed to be constant, therefore, empty weight has to
18
decrease. Decrease in empty weight means smaller value of the numerator, hence smaller
weight fraction.
Looking at the trade study plot, Figure , of the payload weight with an unfixed TOGW,
the graph shows the TOGW will increase nearly linear with the payload weight for the
same empty weight fraction. However, a pound of payload does not increase the TOGW
by a pound, but by about three pounds.
Figure 15 - Trade Study - TOGW vs. Payload Weight
c.
POWER DENSITY
Power density has a large impact on how far the plane can fly. Essentially it is the fuel
weight of an electric airplane, but constant during flight. With power density, the more
power that can be packed into the weight of the battery the longer and lighter the plane
can fly. The trade study plot from the code shows the effect of the power density, Figure
162. Most lithium polymer packs lie in the range of 200 W-hrs/kg. New fuel cells have a
19
power density of 350 W-hrs/kg. With a new fuel cell, the aircraft could fly for an
extended period of time.
For the aircraft propulsion system, a large number of lithium polymer batteries were
organized into a database for comparison, but the power densities for all of the batteries
were found to be too low for the aircrafts threshold time airborne. As an alternative, fuel
cell technology was compared to the batteries and exceeded the lithium polymer batteries
in power density as well as total power output. The largest power density for any of the
batteries was 250 watt hours per kilogram by the Venom Group 15c 11.1v 3 cell lithium
polymer battery10. The fuel cell, produced by Protonex, has a power density of 350 watt
hours per kilogram7. Although fuel cells are still a relatively new technology, by the time
the aircraft is put into production, technology should have gone above and beyond the
current data.
Figure 162 - Trade Study - TOGW vs. Power Density
20
References
1. Bowes, Peter. “High Hopes for Drones in LA Skies”. February 15, 2007.
http://news.bbc.co.uk/2/hi/americas/5051142.stm
2. CONTROP-Precision Technologies LTD. http://www.controp.co.il/
PRODUCTS/SPSproducts.
3. FLIR Systems Indigo Operations. http://www.flir.com
4. Murphy, Douglas. Cycon, James. “Applications for mini VTOL UAV for law
enforcement”. January 15, 2007. http://www.spawar.navy.mil/robots/
pubs/spie3577.pdf.
5. “Law Enforcement UAVs”. Aeronautics Defense System Ltd. January 25, 2007.
http://www.aeronautics-sys.com/Index.asp?CategoryID=116&ArticleID=
280&Page=1.
6. PolarisUSA Video. http://www.PolarisUSA.com.
7. Protonex Technology Corporation. http://www.protonex.com/procoreuav.html.
8. Raven UAVs Winning Gold in Afghanistan’s ‘Commando Olympics’,” Defense
Industry Daily [online], November 2005, http://www.defenseindustrydaily.com/
2005/11/raven-uavs-winning-gold-in-afghanistans-commando-olympics/
index.php [retrieved 17 February 2007]
9. “Unmanned Aerial Systems Roadmap 2005-2030,” Department of Defense, August
2005, pp 39-51.
10. Venom Group International. http://www.venom-group.com.
21
Appendix
VI.
Initial Aircraft design-to requirements
a.
Trade studies to show realistic requirements
b.
Investigations into payloads/batteries/etc.
22
UAV DATABASE
Vehicle Name
Azimuth
AEROS
Pointer FQM-151A
Swift - Eye
Javelin
azimut 2
Biodrone
Aerosande 4
Seascan
MKY
Luna X-200
Phantom
MKY2
APID-2
Mini- Vanguard
Tern
Dakota
Fox Tx
Futura UCAV
Chacal 2
MK-105 Flash
Vixen/ Hellfox
Empty Weight
Gross
(lbs)
Weight (lbs)
14.3
4.994
4.994
3.96
8.69
5.5
15.4
19.8
24.25
66
66
88
132
121
84.7
44.88
70.84
264
44
66
105.6
139.7
5.5
7.194
8
14.08
18
19.8
22
33
33.95
35.2
44
50.6
57.2
77
104.72
125
132.66
143
154
165
198
199.54
Maximum
Payload
Endurance Cruise Velocity
Weight (lbs)
(hrs)
4.4
2
31.1
2.2
0.75
20.02
2.002
1.5
40
6.6
0.67
29.92
6
2.5
55
4.4
2
65
6.6
1.5
70
11
24
24.3
7.054
15
56.38
30.8
2
67
6.6
3
43.73
18.04
3
56.4
74.8
3
80.5
44
4
62.1
20.02
2.5
40.27
29.92
5
75
49.94
3.4
126.585
66
5
56.4
33
1.1
195
44
4
173
59.4
3
50
49.94
4
64
Altitude
We/w0
985
3000
12500
14000
3000
984
984
19880
16000
9840
9800
9800
13120
985
3000
10000
15000
11500
984
9840
10000
2500
0.3846
0.6942
0.6243
0.2813
0.4828
0.2778
0.7000
0.6000
0.7143
0.5333
0.6667
0.5750
0.4333
0.6364
0.8088
0.3590
0.5340
0.5417
0.2857
0.4000
0.5333
0.7001
23