AAE 451 – Aircraft Senior DesignSpring 2007

Continuous Area Coverage via Fixed-Wing Unmanned Aerial Systems

System Requirements Review

Team 3

Sumitero DarsonoCharles Hagenbush

Keith HigdonSeung-il KimMatt LewisMatt Richter

Jeff TippmannAlex Zaubi

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I. Description and overview of proposed systemThe 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 MarketThe 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.

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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.

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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.

\ 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.

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Small UA Systems (<10 lb Gross Weight)

0

200

400

600

800

1000

1200

1400

Dragon Eye FPASS Pointer Raven Buster

Number of Systems

Number of Aircraft

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. MilitaryCurrent 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.

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Projected Budget for Procurement of Small UA Systems

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5

10

15

20

25

05 06 07 08 09

Fiscal Year

Budg

et ($

M)

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.

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b. Law EnforcementIncrease 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.

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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)

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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 QualityAs 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

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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

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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 RequirementsNow 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 ThresholdTOGW (lbs) 10 12Endurance (hrs) 4 2Range (nmi) 20 10Loiter Speed (kts) 30 40Stall Speed (kts) 7 15Payload Weight (lbs) 2 4Power Density (W-hrs/kg) 350 200We/W0 0.4 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.

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With the endurance being 4 hours, this directly affects the amount of power needed to fly

the mission.

a. Database RegressionTrade 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

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Weight Fraction Regression for Small UAVs

0.00000.1000

0.20000.30000.4000

0.50000.60000.7000

0.80000.9000

0 50 100 150 200 250Wo

We/W

o

Wo vs. We/Wo Regression

We/Wo =1.2429654Wo 0.1566*Payload -0.0806*Endurance0.0975*Velocity -0.3014*Altitude-0.0174

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 SizingThe 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

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system9. 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.

Weight Fraction as a Function of Gross Weight

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.6000

0.7000

0.8000

0.9000

1 51 101 151 201

Gross Weight (lbs)

Weig

ht F

racti

on

Weight Fraction Prediction Database

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.

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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.

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Weight Fraction as a Function of Endurance

0.00000.10000.20000.30000.40000.50000.60000.70000.80000.9000

0 1 2 3 4 5 6

Endurance (hr)

Weig

ht F

racti

on

Weight Fraction Prediction Database

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.

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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.

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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

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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

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.6000

0.7000

0.8000

0.9000

0 10 20 30 40 50 60 70 80 90Payload Weight (lbs)

Weig

ht Fra

ction

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

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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

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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

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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.

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Appendix

VI. Initial Aircraft design-to requirements

a. Trade studies to show realistic requirements

b. Investigations into payloads/batteries/etc.

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UAV DATABASE

Vehicle Name Empty Weight (lbs)

Gross Weight (lbs)

Payload Weight (lbs)

Maximum Endurance

(hrs)Cruise Velocity Altitude We/w0

Azimuth 14.3 5.5 4.4 2 31.1 985 0.3846AEROS 4.994 7.194 2.2 0.75 20.02 3000 0.6942Pointer FQM-151A 4.994 8 2.002 1.5 40 12500 0.6243Swift - Eye 3.96 14.08 6.6 0.67 29.92 14000 0.2813Javelin 8.69 18 6 2.5 55 3000 0.4828azimut 2 5.5 19.8 4.4 2 65 984 0.2778Biodrone 15.4 22 6.6 1.5 70 984 0.7000Aerosande 4 19.8 33 11 24 24.3 19880 0.6000Seascan 24.25 33.95 7.054 15 56.38 16000 0.7143MKY 66 35.2 30.8 2 67 9840 0.5333Luna X-200 66 44 6.6 3 43.73 9800 0.6667Phantom 88 50.6 18.04 3 56.4 9800 0.5750MKY2 132 57.2 74.8 3 80.5 13120 0.4333APID-2 121 77 44 4 62.1 985 0.6364Mini- Vanguard 84.7 104.72 20.02 2.5 40.27 3000 0.8088Tern 44.88 125 29.92 5 75 10000 0.3590Dakota 70.84 132.66 49.94 3.4 126.585 15000 0.5340Fox Tx 264 143 66 5 56.4 11500 0.5417Futura UCAV 44 154 33 1.1 195 984 0.2857Chacal 2 66 165 44 4 173 9840 0.4000MK-105 Flash 105.6 198 59.4 3 50 10000 0.5333Vixen/ Hellfox 139.7 199.54 49.94 4 64 2500 0.7001

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