design of uav systems uav system design 26-1 lesson objective - to complete the example uav system...

Design of UAV Systems

UAV System Design 26-1

Lesson objective - to complete the example

UAV System Design

Objectives

Expectations - You will better understand how to wrap up a pre-concept design project

2002 LM Corporation

26-2


UAV System Design 2002 LM Corporation

Review - surveillance UAV

• Predator follow-on type• Land based with 3000 foot paved runway

- Mission : provide continuous day/night/all weather, near real time, monitoring of 200 x 200 nm area

- Basing : within 100 nm of surveillance area- Able to resolve range of 1 sqm moving targets to 10m, and transmit ground moving target (GMT) data to base in 2 minutes

- Able to provide positive identification of selected 0.5m x 0.5 m ground resolved distance (GRD or “resolution”) targets within 30 minutes of detection

- Ignore survivability effects• Minimum required trades

- Speed- Operating altitude- Time on station

- All weather (SAR) vs. under weather (EO/IR)

- Size and numbers req’d

26-3



Surveillance UAV

200 nm

Loiter location?

100

nm

Surveillance area

200

nm

26-4



Defined requirements (from the customer)• Continuous day/night/all weather surveillance of 200nm

x 200nm operations area 100 nm from base • Detect 1 sqm moving targets (goal = 100%, threshold =

80%) and transmit 10m resolution GMTI data in 2 min.• Provide 0.5 m resolution visual image of spot targets

(goal = 100%, threshold = 80%) in 15 min.• Operate from base with 3000ft paved runway

Requirement refinement

Clear day, unrestricted10Kft ceiling, 10 nm

5Kft ceiling, 5 nm 1Kft ceiling, 1nm

Percent occurrence 50%30%15%05%

Ceiling and visibility (customer defined)

60%30%10%

Weather definition (derived)Good weather

Bad weatherUnflyable weather

• Five medium UAVs, four provide wide area search, a fifth provides positive target identification- SAR range required (95km)

• Only one UAV responds to target ID requests• No need to switch roles, simplifies ConOps• No need for frequent climbs and descents

• Communications relay req’d, distance = 158 - 212 nm• Speed requirement = 282 kts

• For target identification role• Operating altitudes different for each role• We will study other options as trades• Payload requirement : 707 lbm @ 26.55 cuft (including comm relay)

Initial system baseline

26-5



100 nm

200 nm x 200 nm

158 nm

17 Kft

10 Kft

17 Kft

17 Kft

17 Kft

26-6



Initial derived requirements

Derived requirements (from our assumptions or studies)• System element

• Maintain continuous WAS/GMTI coverage at all times• One target ID assignment per hour• Uniform area distribution of targets• Communications LOS range to airborne relay = 158 nm• LOS range from relay to surveillance UAV = 212 nm

• Air vehicle element• Day/night/all weather operations, 90% availability• Turboprop power• Takeoff and land from 3000 ft paved runway• Cruise/loiter altitudes = 10 – 17Kft• Loiter location = 158 nm (min) – 255 nm (max)• Loiter pattern – 2 minute turn• Dash speed =141 nm out and back @ 280 kts• Dash altitude 10 Kft

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• Air vehicle element (cont’d)• Payload weight and volume = 707 lbm @ 26.55 cuft• Payload power required = 4300 W• 18 hour WAS capability• Cruise L/D 24.5• Loiter L/D 25.6• Cruise TSFC 0.326• Loiter TSFC 0.31• T0/W0 = 0.121• W0/Sref = 40 psf• Bhp0/Weng 2.25• Leng/Deng 2.5• Engine density 22 pcf• Clto 1.5• Wlg/W0 0.05• etc.

26-8



• Payload element• Installed weight/volume/power 707 lbm/26.55 cuft/4300W• SAR/GMTI

• Range/FOR /resolution/speed = 95 km/45/1 m/2 mps• Uninstalled weight/volume/power 350 lbm/8 cuft/3000W

• EO/IR • Type/range/resolution = Turret/13.3 km/0.5 m• Uninstalled weight/volume/power 100 lbm/1 cuft/700W

• Communications • Range/type = 212nm/air vehicle and payload C2I

• Uninstalled weight/volume/power 57 lbm/5.9 cuft/300W• Range/type = 158nm/communication relay

• Uninstalled weight/volume/power 57 lbm/5.9 cuft/300W• Control Station element

• Waypoint/flight path control• 6 control consoles [air vehicle/EO/IR (2), SAR (1), C3I (1),

product process/dissemination(1), launch and recovery(1)] plus provision for back-up/jump seat (1)

Support element• To be determined


26-9



WAS requirement resolution

• Because our weather criteria defines 10% of the days as unflyable, we can no longer use 80% target area coverage to meet the 80% threshold requirement• Area coverage will have to increase to 89%

• WAS SAR range/target width required goes up to 0.55 nm or WAS range = 55nm (102 Km)

Range

Target width

center

mid-side corner

Square target area coverage

0

20

40

60

80

100

0.4 0.6 0.8 1 1.2 1.4 1.6

Sensor range/target w idth

Are

a co

vera

ge

(%)

From centerFrom mid sideFrom corner

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SAR sizing considerations

A number of factors affect SAR range (minimum and maximum) and resolution- Power (how much RF energy is reflected from the target)

- Even though transmitted power required vs. radar range is typically expressed as a 4th power relationship, our parametric data (based on total input power required) shows a nominal linear relationship

- Geometry (minimum and maximum depression angles)- Absolute minimum angle defined by the radar horizon- Typical minimum “look down” angle about 5 degrees- Typical maximum “look down” angle about 60 degrees

- Dwell time (how long energy stays on the target)- Function of platform speed and/or antennae pointing

- Signal processing timeTo keep things simple, we resize using only the range-power parametric and geometry (ignoring curvature)

26-11



SAR geometry

With additional power this SAR should be able to increase WAS and GMTI range to 226 Km• Beyond 226 Km, higher altitude would be required

Long Range SAR Profile

0

10

20

30

40

50

60

70

0 100 200 300

Range (km)

Alt

itu

de

(Kft

)

5.6 deg

5 deg

Max range(from spreadsheet)

Min range(from spreadsheet)

44.7 deg

20.8 deg

Earth curvature effects have been ignored

26-12



SAR geometry (cont’d)

With additional power these SARs should be able to increase WAS and GMTI range to 52 - 87 Km• The 102 km WAS requirement means that we have to

loiter at a higher altitude, 30 Kft vs. the previous 27.4Kft

Other SAR Profiles

0

10

20

30

0 25 50 75

Range (km)

Alt

itu

de

(Kft

)Medium Range SAR

Short Range SAR8.7 deg

20.8 degMax range at 5 degree lookdown = 52 - 87 km

17 –27 deg

This plot also ignores earth curvature effects

26-13



ID requirement

• A different logic applies to the ID mission• We required 100% area coverage because we operate at 10Kft and have ceilings 10 Kft 20% of the time• Now we have to deal with 90% availability

• Our only option to increase overall ID mission capability to 89% is to operate at lower altitude

• We plot ceiling altitude vs. percent occurrence and estimate that a 7 Kft operating altitude will increase overall target coverage to the required value of 89%

Ceiling statistics

80

85

90

95

100

0 2.5 5 7.5 10Ceiling (Kft)

Pe

rce

nt

oc

cu

ran

ce

(%

)

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Other ID issues

• We did not take advantage of EO/IR range to decrease ID mission fly out distance• But this was offset by the fact we ignored time and distance to ID the target and turn back to base

• To ensure we have taken all ID requirements into account, we need to model the engagement geometry• We assume the UAV flies directly at the target and upon initial detection (in the spot mode) turns away to intercept a point that will allow a 45 degree lookdown

• It then turns into the target flying a constant radius turn and goes back to the initial detection location• Essentially flying a tear drop pattern

• During this entire time, the UAV can see the target at a resolution equal to or better than the requirement• Making it a good ID mission sensor figure of merit

26-15



ID geometry assessment

Initial EO/IR detection

Ground distance for 45 degree look down(distance = altitude)

Constant radius turn

Top View

45 degree look down angle

Slant range defines initial target detection

Profile View

Turret Type ISpot slant range (SLR) for 0.5m

detection = 10KmTurn radius = 1.15 nmG’s required = 1.41Total Imaging time = 3.2 minRadius extension req’d = 2.2 nm

Turret Type IISpot SLR for 0.5m detection =

13.3 KmTurn radius = 1.15 nmG’s required = 1.41Total Imaging time = 3.94 minRadius extension req’d = 2.1 nm

280 Kts

280 Kts

280 Kts

7 Kft

Conclusions • Even Turret Type I exceeds

threshold requirements• Minimum SLR required

for ID 3 km• Need to add 2 - 3 nm to

required dash distance

26-16



Requirement refinement

Refined WAS SAR range = 102 km at 30 Kft- From our parametric data, for a 55 nm (102 km) range

- Power required = 3400W; Weight (uninstalled) = 370 lbm; Volume (uninstalled) = 9.25 cuft

Refined ID EO/IR resolution required = 0.5 m at 3 km - We have no EO/IR range parametrics but from optics, range and resolution should vary primarily with focal length which in turn should vary with turret diameter - We estimate diameter required at 4 inches, well

below the smallest sensor in our database- Therefore, we select the smallest EO/IR sensor listed in our database (See Lesson 11):- Turret diameter =9 in; height = 14 in; Weight and

volume (uninstalled) = 40 lbm at 572 cuin; Power required = 450W

ID radius for 100% coverage = 141nm + 3 nm = 144nm

26-17



Refinement (cont’d)

• Another issue is “requirement creep”- We have not strictly adhered to our threshold strategy

• For example, our UAVs carry SAR and EO/IR sensors- Although operationally advantageous (one payload for both missions), it exceeds our threshold definition

• Therefore, we will size for interchangeable payloads - But power and volume available must meet the most stringent requirements for each module

• Since the ID mission has the smallest payload but requires the most fuel, we assume that unused payload volume can be used for fuel- We will also retract the EO/IR sensor to reduce drag - Later we can do a cost effectiveness trade study to verify these benefits but for now it is intuitively obvious

• However, we will continue to assume that any WAS UAV can function as a communication relay- Another intuitively obvious requirement to test later

26-18



WAS payload requirement

• WAS mission payload- SAR weight (installed) = 370lbm1.3 = 481 lbm- SAR volume (installed) = 9.25(1.25^3) = 18 cuft- SAR power required = 3400W- Basic communication payload (ADT) = 221.3 = 28.6 lbm at 500cuin1.95 = 975 cuin installed at 300W

- Relay communication payload = 221.3 = 28.6 lbm at 500cuin1.95 = 975 cuin installed at 300W

- Two communication antennae = 2251.3 = 65 lbm at 221.95 = 7.8 cuft

• Total WAS mission payload requirement- Weight = 603.2 lbm- Volume = 26.9 cuft- Density = 22.4 pcf- Power required = 4000W

At $5000/lbm WAS payload unit cost = $3M

26-19



• ID EO/IR mission payload- EO/IR weight (installed) = 40lbm1.3 = 52 lbm- EO/IR volume (installed at h = 14 in) = 1.0 cuft- EO/IR power required = 450W- Basic communication payload (ADT) = 221.3 = 28.6 lbm at 500cuin1.95 = 975 cuin installed at 300W

- ADT antennae = 251.3 = 32.5 lbm at 21.95 = 3.9 cuft

• ID Auxiliary fuel- Fuel volume available = 26.9cuft – 5.5cuft = 21.4 cuft- Allowable fuel weight = 603.2 – 113.1 = 490lbm- Required fuel volume (at PF = 0.7) = 14 cuft

• Total ID mission payload requirement• Weight with zero fuel = 113 lbm• Weight with fuel = 603 lbm• Volume = 26.9 cuft• Power required = 450 W

ID payload requirement

At $5000/lbm ID payload unit cost = $0.6M

26-20



Modular payloads

Consolidated payload requirement• Weight = 603 lbm (max)• Volume = 26.9 cuft• Power required = 4000 W (max)

SARADT Comm.relay

ADTantennae

Relayantennae

EO/IRADT Auxiliary fuelADT

antennae

WAS payload

ID payload

26-21



Assessment results

• Removing the SAR from the ID mission payload and adding an auxiliary fuel tank significantly increased ID mission capability and drastically reduced cost- Much of the cost saving, however, is due to the reduction in ID payload cost (from $3.5M to $0.6M)

• This occurred despite putting a second UAV plus payload on alert to have replacements for both SAR and EO/IR equipped UAVs if needed- This increased the number of UAVs plus payloads required but still traded favorably at the system level

• Removing the EO/IR from the WAS payload had some, but not significant, cost and performance benefit - Probably offset by the additional backup requirement

• The most cost effective size is now a 18hr WAS endurance vehicle that now can conduct 6 IDs vs. 4 IDs with the original 18 hr baseline

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Baseline comparisons

Air Vehicles Required(initial baseline)

0

2

4

6

8

10

6 12 18 24 30 36 42 48

Operational endurance capability (hrs)

Nu

mb

er

WAS missionID mission

Air Vehicle + Payload Cost(initial baseline)

0

20

40

60

80

6 12 18 24 30 36 42 48


Pro

cure

men

t c

ost

($M

)

WAS missionID missionCombined

Air Vehicle + Payload Cost(threshold baseline)

0

10

20

30

40

50

60

6 12 18 24 30 36 42 48


Pro

cure

men

t c

ost

($M

) WAS missionID missionCombined

Air Vehicles Required(threshold baseline)

0

2

4

6

8

10

6 12 18 24 30 36 42 48


Nu

mb

er

WAS missionID mission

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Threshold requirements

With two exceptions, the new baseline now meets only threshold requirements- 89% WAS target area coverage 90% of the time (the specified flyable days)

- Covers 100% ID target area for ceilings at or above 7Kft (for 89% coverage) 90% of the time (the flyable days)

One capability that exceeds threshold is that all WAS UAVs can function as communication relays- This capability trades favorably since at least 2 UAVs need this capability for redundancy and yet a 3rd UAV would still have to be on standby as a replacement

The other capability that exceeds threshold is the ability to provide simultaneous WAS and ID coverage- Without this capability, the system would be of limited operational use (especially at one ID per hour)

- No capability to do WAS much (or all) of the time

26-24



Threshold baseline

W0 =3776 lbmEW = 2101 lbmAR = 20Sref = 94 sqftSwet = 455sqftPayload = 603 lbmFuel = 1039 lbmPower = 362 Bhp TBPropMax endurance = 14.5 hrsMax speed = 280 kts

This air vehicle can stay on station for 18 hours at 30 Kft or perform 6 ID missions at 7Kft in 6 hours

7 WAS and 5 ID air vehicles are required

Approximately to scale

43.4

1.9’

7.7’

21.3’

3.0’

26-25



Goal requirements

Even though our strategy is to design to threshold requirements to minimize cost, we still need to determine the cost of meeting goal requirements- It might turn out to be cost effective and competitively smart

Goal performance, however, will not be 100% capability- 10% of the days are unflyable, and 90% capability will be the best we can do

Achieving goal performance is simple, we have to cover 100% of the WAS area and ID targets from 1Kft- WAS SAR range required is 71 nm (131 Km)

- From our parametric plot, SAR power and uninstalled weight and volume are 4000W, 450 lbm and 11 cuft

- Installed weight and volume, therefore, are 585 lbm and 21.5 cuft

- And required loiter altitude increases to 37.6Kft

26-26



Goal WAS payload

• WAS mission payload- SAR weight (installed) = 450lbm1.3 = 585 lbm- SAR volume (installed) = 11(1.25^3) = 21.5 cuft- SAR power required = 4000 W- Basic communication payload (ADT) = 221.3 = 28.6 lbm at 500cuin1.95 = 975 cuin installed at 300W



• Total WAS mission payload requirement- Weight = 707 lbm- Volume = 30.4 cuft- Density = 23.3 pcf- Power required = 4600W

At $5000/lbm WAS payload unit cost = $3.5M

26-27





• ID Auxiliary fuel- Fuel volume available = 30.4 cuft – 5.5cuft = 24.9 cuft- Allowable fuel weight = 707 – 113.1 = 594 lbm- Required fuel volume (at PF = 0.7) = 17 cuft


Goal ID payload

No change in ID payload unit cost of $0.6M

26-28



Goal assessment

• Increasing SAR size and WAS loiter altitude increased air vehicle size required- Gross weight = 3482 lbm vs. 2993 lbm for threshold- Empty weight = 1996 lbm vs. 1716 lbm for threshold- Unit air vehicle cost = $798K vs. $686K for threshold

• WAS payload size and cost also increased- WAS payload = 707 lbm vs. 603 lbm for threshold- WAS payload cost = $3.5M vs. $3.0M for threshold

• ID payload was unchanged at 113 lbm- ID auxiliary fuel increased to 594 lbm vs. 490 lbm

• The number of air vehicles required was unchanged• The procurement cost of achieving goal (90%) vs. threshold (80%) increased by $5.9M (17%)- 87% of the increase was the paylaod

• Goal capability cost $590K per additional % coverage vs. the threshold average of $425K per %

26-29



Alternate concepts

The alternatives are resized versions of the baseline1. Two (2) air vehicles consisting of 1 WAS UAV and 1 ID

UAV2. Twenty (20) air vehicles consisting of 16 WAS UAVs

and 4 ID UAVsFrom experience, we now know what drives the answer- The size and number of payloads (at $5K per pound)

For 89% area coverage, alternative 1 requires one 110 nm (204 km) WAS SAR (uninstalled cost = $6.5M)- Power = 6000 W, Weight = 650 lbm, Volume = 15 cuft

For 89% area coverage, alternative 2 requires sixteen 27.5 nm (51 km) WAS SAR (uninstalled cost = $19.2M)- Power = 1900 W, Weight = 240 lbm, Volume = 6.5 cuft

It is obvious from this simple comparison that the 2nd alternative will not be a cost effective solution- We only need to evaluate alternative 1 (1 WAS, 1 ID)

26-30



Alternate 1 WAS payload

• WAS mission payload- SAR weight (installed) = 650lbm1.3 = 845 lbm- SAR volume (installed) = 15(1.25^3) = 29.3 cuft- SAR power required = 6000 W- Basic communication payload (ADT) = 221.3 = 28.6 lbm at 500cuin1.95 = 975 cuin installed at 300W



• Total WAS mission payload requirement- Weight = 967 lbm- Volume = 38.2 cuft- Density = 25.3 pcf- Power required = 6600W

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Alternate 2 ID payload



• ID Auxiliary fuel- Fuel volume available = 38.2 cuft – 5.5cuft = 32.7 cuft- Allowable fuel weight = 967 – 113.1 = 854 lbm- Required fuel volume (at PF = 0.7) = 14.9 cuft


No change in ID payload unit cost of $0.6M

26-32



Alternate 2 mission profile

The increased 204 km WAS SAR range requirement requires an increased WAS loiter operating altitude of 58.6 Kft (for a 5 degree look down angle)- Cruise speed must also be increased to compensate

- Nominally to 280 kts (5 kts above best loiter speed) At 58.6 Kft the TBProp is no longer sized by takeoff- Bhp0/W0 must be increased to 0.287 just to reach initial

cruise altitude (see Mperf output Hdot4)- Using a standard ceiling altitude definition of 100 fpm

- It is also necessary to ensure excess power is available to meet cruise and high speed requirements- See Mperf outputs Hdot4 through Hdot17

The alternate UAV is larger and more expensive- W0 = 12328 lbm; EW = 7344lbm; Bhp0 = 3489 Hp- 3 WAS, 5 ID air vehicles @ $2.9M ea.; 3 WAS

payloads @ $4.84M ea.; Total cost = $40.8M vs. $34M

Make sure you check these on your projects

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Remaining baseline tasks

Our assessments, therefore, show that the baseline ConOps (1 ID and 4 WAS air vehicles) with the refined air vehicles and modular WAS and ID (with auxiliary fuel) payloads meet our threshold (and goal!) mission requirements at the lowest overall procurement cost- This refined baseline will become our “Preferred Baseline

System Concept”…….. if it meets our risk assessment criteria

- The best overall system concept we have found even though conceptual design studies may find better solutions for the individual system elements to include better air vehicle designs, better payloads, etc.

However, the baseline is still not completely defined - We still need to (1) assess risk, (2) determine operations

and support requirements, (3) determine manpower requirements and (4) estimate life cycle cost

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Risk assessment

Since we have already compared our initial baseline air vehicle against other aircraft in our parametric database, a quick check of the new baseline should verify that our performance is achievable (i.e. low risk)

Maximum L/D trends

0

5

10

15

20

25

30

35

0 2 4 6 8

(L/D

)ma

x

Wetted AR = b^2/Swet

Manned aircraftGlobal Hawk (est)

Manned aircraft data: LM Aero data handbook

Model estimate

Airframe Weight Comparisons - (data from Roskam and Janes)

0

5

10

15

20

25

0 25 50 75

GTOW/Sref (psf)

Waf

/Sre

f (p

sf)

Biz Jet

SE Piston Prop

ME Piston Prop

Reg TurboJet Trans

Jet fighters

Mil Train

TR-1

This and the SFC data checks but we still have risk

26-35



Air vehicle risk

materials or active flutter suppression

2.Reduce AR to max. demonstrated value (12)

3.Design a fix (e.g., a quick change wing or removable outer wing panel for the ID mission)

Our wing aspect ratio (AR) is well above that of any known air vehicle that has to fly at an equivalent air speed (EAS) of 250 Kts (280 KTAS @ 7Kft )• High AR wings are susceptible to flutter at high speeds

We have three options for dealing with this risk1. Assume someone can solve the problem later, e.g. new

Aspect Ratio Comparison

5

10

15

20

25

30

100 150 200 250 300 350 400

EAS (kts)

As

pe

ct

rati

o

IC PropTB PropSmall JetsHeavy JetsUAV

Our baseline

Global Hawk

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Assessment of options

Option 1 is viable if solutions are in work or we are willing to fund the required technology programs- Otherwise we are simply kicking the problem down stream

Option 2 is viable if we can stand the penalty- Spreadsheet analysis shows that at AR=12 we can achieve the same level of mission performance at W0 = 4372 lbm (+596 lbm) and EW = 2369 lbm (+268lbm)- Overall cost increases $1.3M to $35.3M

Option 3 is viable if the design fixes cost < $1.3M- Designing and testing a second wing optimized for the ID mission could easily exceed this cost

- A removable outer wing panel might be less complex but (1) attachment provisions will increase wing weight and (2) either more takeoff power or flap performance will be required to offset the reduced wing area

We will use our spreadsheet model to assess Option 3

26-37



Option 3 assessment

Optimized ID mission wing will not be cost effective- ID mission performance essentially will be unchanged but development program will involve design and test of second wing on one additional flight test vehicle - Vehicle cost alone $3M

Removable wing panel may also not be cost effective- Assuming 5% wing weight penalty for non-optimum wing but no increase in Clto, Bhp0/Sref = 0.142 (vs. 0.121), W0 = 4081 lbm (+305 lbm), EW = 2325 lbm (+224 lbm) and overall mission cost = $35.1M (+$1.1M)

- With 23% increase in Clto (and additional 5% wing weight penalty), W0 = 3929 lbm (+153 lbm), EW = 2216 lbm (+115 lbm) and overall mission cost = $34.6M (+$0.6M)

- Assuming development cost proportional to weight of additional wing, development goes up 15% ($13M)

Unless increased O&S cost offsets development, the most cost effective option will be a AR = 12 wing design

26-38



Risk abatement plan

We identify the issue of high-speed vs. high-AR as high risk and document a requirement for a conceptual design trade study to determine the best option - We select the AR=12 concept as our preferred baseline to ensure “margin” on our air vehicle cost estimates to cover the projected unit cost increase

- We will also increase our development cost estimate to cover the cost of additional design, test and evaluation required by removable wing panels- We put an upper limit on development cost of $2M- If it is higher, a better option would simply be to

decrease AR to 12Otherwise, we see no more high-medium risk issues - Although others could develop as the concept matures

26-39



RMSS requirements

Reliability, maintainability, safety and support (RMSS) covers a range of operational and technical issues that must be considered from the beginning of a project

- See Lesson 12The key RMSS issues for our system concept are

(1) The level of redundancy required and (2) The training, maintenance and support concept

RMSS issues drive operations and support costs, the single largest element of Life Cycle Cost (LCC)

- Unfortunately, history is replete with programs that presumed that consideration of these key issues could be put off until later in the program

- This is a potentially fatal mistake that always increases downstream cost and risk and sometimes results in program cancellation

26-40



Redundancy

Two issues drive redundancy requirements- Flight and operational safety- Operations in manned airspace

Safety fundamentally drives operational utility and cost- No user wants to operate a UAV system if there is even a moderate risk of a crash in or around the operating area - Not only because they endanger personnel, crashes are

also very expensive If we plan to operate our UAV in or through civil airspace anytime during its operational life, flight critical systems probably need to be a minimum of “fail safe”- Backup systems allow the UAV to safely return to base after a failure (including engine systems, but not engines)

- “Fail operational” is a higher cost option allowing the UAV to continue a mission, albeit with degraded performance

- A redundant “See and avoid” sensor and communications capability will probably also be required

26-41



Training and support

Although other options should be considered later, we will assume that maintenance and support is “organic”- I.e., the using organization is responsible for maintenance

- We will use parametric data to estimate the number of maintenance personnel required

- Another option is contractor maintenance which probably requires a conceptual design trade study to evaluate

We also assume the user is responsible for proficiency training but that primary training and qualification is done by a separate organization- The number of training systems need to be included in the procurement estimates

- Similarly, primary and proficiency training hours need to be included in operations and support costs

These requirements will be documented and included in cost estimates to follow

26-42



Manpower requirements

Manpower estimates include- Operators (air vehicle, payload, communications and product analysis and dissemination)

- Maintainers (responsible for all system elements)- Headquarters staff (management, mission planners, etc.)- Indirect personnel (support personnel, etc)

We already identified a requirement for 7 operators- One WAS + one payload operator (for 4 air vehicles)- One ID air vehicle and payload operator - One payload product analyst and dissemination operator- One launch and recovery operator- One C3I operator (primarily focused on communications)- One back-up operator

For 24 hour, 7 day a week coverage by crews working 40 hours per week at a 125% staffing ratio we require 5.3 crews (which we round up to 6) - Or 42 full time UAV, payload, system, etc. operators

Parametric data based on historical manned aircraft experience is used to estimate maintenance manpower required • Note that Global Hawk fits the manned aircraft data• Predator does not which may reflect its Advanced Technology Demonstration (ATD) development history which did not emphasize the importance of maintainability

From this parametric we estimate the number of personnel required • 2.7 maintenance personnel

per baseline air vehicle plus payload or 33 maintainers per 12 air vehicle squadron

• On average, 6-7 maintainers per 8 hr. shift

Maintenance personnel parametric

0.00

1.00

2.00

3.00

4.00

5.00

6.00

0 250 500 750 1000 1250 1500

Maximum speed (kts)

FightersTransportsBombersEWRecceUAV

26-43



Predator

Global Hawk

Maintenance personnel

26-44



Other personnel

Headquarters personnel including…- Commanders (minimum of 1 per shift)- Mission planners (minimum of 1 per shift)- Supply and logistics (minimum of 2 per shift)- IT (minimum of 1 per shift)

..for a total of 51.25 = 7 additional personnel (minimum)

Indirect personnel including….- Guards, Medical personnel, Clerical staff, Etc.

… are typically estimated at an additional 25%Therefore, the total squadron manpower estimate is(42 operators + 33 maintainers + 7 staff)1.25 = 103 headsThis may be an optimistic estimate for the number of people required to keep 5 air vehicles on station 24 hours a day, 7 days a week, but unless we can identify the missing tasks, we should stick with this estimate

26-45



Life cycle cost

Development cost• The cost of developing a system• Considered a “non-recurring” cost

• Occurs only once (hopefully)Procurement cost

• The cost to buy a system once it is developed• Includes a lot of “recurring” cost

• Costs incurred every time a system is producedOperations and support cost (Q&S)

• The cost to maintain and operate a system after purchase

• Includes the cost of maintaining crew proficiency• Excludes the cost of combat operations

Development + procurement + O&S Life cycle costSee Course Review 5.2 (Life Cycle Cost)

26-46



Life cycle costCost methods - review

Airframe • Development - Equations 24.1 - 24.4• Procurement - Equations 24.5 - 24.10

Propulsion (procurement) - Eq 24.11

Ground Station + communications • Development - 70% air vehicle development• Procurement ≈ 1 air vehicle + sensor payload

Payload (procurement) - $5000/lb

Operations and support • Air vehicle & payload operators - estimate number• Maintenance personnel - chart 12-30• Other personnel - add 25%• Air vehicle operating costs (inc. engine) - chart 24-27• Ground station + communications - 8% procurement/yr• Payload - 8% procurement/yr

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Cost effectivenessc 2002 LM Corporation

• Development (assuming 3 test aircraft) = $138M - Airframe (from CERs) + $ 2M = $81M- Propulsion (off the shelf) - Control station + comms (@70% airframe) = $57M- RF and EO/IR payload (off the shelf)

• Procurement (assuming 20 aircraft, 12 WAS payloads and 8 ID payloads) = $65.3M - Airframe (from CERs) = $1.0M each- Propulsion ($1000/lbm) = $200K each- ID payload ($5K/lb)= $665K each- WAS payload ($5K/lb) = $3M each- 3 Control stations + comms ≈ 3*(1 airframe + 1 payload) = $14M

• Average air vehicle + payload cost = $3.3M

Program cost

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• One UAV squadron consists of 12 air vehicles and 2 ground control stations (1 as back up) - 10 aircraft assigned to operational missions, 1 in

reserve, undergoing maintenance• 6 flight crews are required (rounded up from 5.5)

- At 2000 hours per person per year• We assume the squadron performs two (2) 30 day

surveillance missions per year- Each 30 day mission requires 5459 flight hours

- 160 WAS missions of 25.8 hrs each- 121 ID missions of 14 hrs each

- During the other 10 months per year, the squadron trains primarily on simulators, each UAVs flies 1 hr per week for an average of 208 hours per month

- Total annual squadron flight hours = 12998

O&S summary

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• Annual personnel costs are $5.15M • 103 @ $50K/yr (est.)

• Annual air vehicle direct operating costs are $2.46M- See LCC Review Chart 20 @ EW = 2101lb and Direct operating

cost per flight hour (DOCFH) = 0.09$*EW $189/FH @ 12998 FH/yr

• Annual ground station + communications operating costs are $528K - 2 stations0.08[$3.3M]

• Annual average payload operating costs are $2.2M - 0.0812 [$2.3M]]

• Annual O&S costs = $10.34M

O&S and LCC

20 year Life cycle costs = $410M

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Final derived requirements

Derived requirements (from our assumptions or studies)• System element

• Maintain continuous WAS/GMTI coverage at all times• One target ID assignment per hour• Uniform area distribution of targets• Communications LOS range to airborne relay = 158 nm• LOS range from relay to surveillance UAV = 212 nm

• Air vehicle element• Day/night/all weather operations, 90% availability• Turboprop power• Takeoff and land from 3000 ft paved runway• ID/WAS altitudes = 7 – 30Kft• Operational loiter location = 158 nm (min) – 255 nm (max)• Operational loiter endurance = 18 hrs• Loiter pattern – 2 minute turn• Dash speed = 280 kts• Dash distance 860 nm• Dash altitude 7 Kft

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• Air vehicle element (cont’d)• Accommodate 603 lbm, 20 cuft modular payload • Provide fuel interface for auxiliary payload fuel tank• Provide 4000 W power for payloads• Cruise L/D 24.6 at 30 Kft and 191 KTAS • Loiter L/D 24.7 at 7 kft at 141 KTAS at• Cruise TSFC 0.34• Loiter TSFC 0.34• Bhp0 457• W0/Sref = 40 psf• Weng 208 lbm• Clto 1.5• Wlg 189 lbm• Removable wing panel to reduce ID mission aircraft aspect

ratio to 12• Etc.• Etc.

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Payload element• Modular WAS and ID payloads

• Common weight/volume/power 603 lbm/26.9 cuft/4000W• WAS Payload module• SAR/GMTI

• Range/FOR /resolution/speed = 102 km/45/1 m/2 mps• Uninstalled weight/volume/power 370 lbm/9.25 cuft/3400W

• Communications • Range/type = 212nm/air vehicle and payload C2I

• Uninstalled weight/volume/power 57 lbm/5.9 cuft/300W• Range/type = 158nm/communication relay

• Uninstalled weight/volume/power 57 lbm/5.9 cuft/300W• Communications antennae (2 each)

• Uninstalled weight/volume/power 25 lbm/2 cuft/TBD W• ID Payload module

• EO/IR • Type/range/resolution = Turret/3 km/0.5 m• Uninstalled weight/volume/power 40 lbm/1 cuft/450W

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Payload element (continued)• ID Payload module (continued)

• Communications (including antennae)• Range/type = 212nm/air vehicle and payload C2I

• Uninstalled weight/volume/power 77 lbm/7.9 cuft/300+W• Auxiliary fuel

• Fuel weight/installed volume 490 lbm/ 14 cuft • Control Station element

• Provide waypoint/flight path control• 6 control consoles [air vehicle/EO/IR (2), SAR (1), C3I (1),

product process/dissemination(1), launch and recovery(1)] • Provision for back-up/jump seat (1)• Back-up power for X hours operation off grid• Etc.

• Support element• Provide organic maintenance for 12 air vehicles operating 24/7

for 30 days• Provide proficiency training for crew members• Provide …..• Etc.

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Pre-concept design - remarks

Lessons 14, 24 and 25 are examples of the design considerations and thought processes used in pre-concept design- Use them as a process guide, not a cook book- Make sure that you review the spreadsheet calculations

and ensure that lift coefficients are always below stall (use Clmax = 1.2 and a stall speed margin of 25%)

- Also make sure that you have sufficient thrust at all points in the mission (and enough volume for fuel, etc)- Inadequate thrust shows up as a negative rate of

climb and thrust-drag- Finally, make sure you do cost effectiveness trades to

select your preferred concepts

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Questions?

design of uav systems uav system design 26-1 lesson objective - to complete the example uav system...

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