1. Design of UAV Systems Putting it all together 24-1 Lesson objective - to show how to Put it all together With a focus on … The air vehicle Objectives Expectations - You will better understand how to approach air vehicle design  2002 LM Corporation

2. 24-2 Design of UAV Systems Putting it all together  2002 LM Corporation How do we start - review Analyze the problem -What does the air vehicle have to do? -Is any information missing? Look at some potential solutions -What are the overall design drivers? -Payload weight and volume -Range and endurance -Speed and propulsion type Pick a starting baseline Analyze starting baseline -Size and weight; range and endurance Analyze the other approaches -Compare results and select preferred baseline Define preferred overall system -Reasonable balance of cost, risk and effectiveness Document results Today

3. 24-3 Design of UAV Systems Putting it all together  2002 LM Corporation What kind of air vehicle - review Operates from 3000 ft paved runway (defined reqmn’t) Loiters over an area of interest (defined reqmn’t) -At h = 10-17Kft, 158nm-255 nm from base (derived) -Baseline loiter time = 12 hrs, do trade study on 6 and12 hr (system engineer, team decision) -Fly circular pattern, 2 minute turns (derived) -Maximum coverage area = 200nm x 200 nm (defined) -WAS for 10 sqm moving targets in 2 minutes (defined) Dashes 141 nm to target in 30 min. (derived reqm’nt) -Once per hour (follow-up customer response) -Based on WAS sensor or other information Images targets from 10 Kft (derived reqm’nt) Operates in “all weather” - 60% good weather, 30% bad but flyable, 10% terrible weather (unflyable) -This conflicts with our 100% availability assumption

4. 24-4 Design of UAV Systems Putting it all together  2002 LM Corporation Our first decision- review It is a very important one -What is the best propulsion cycle for the mission? -Internal combustion (IC), turboprop (TBProp) and turbo fan (TBFan) engines can all meet baseline speed (280 kt) and altitude (10-17Kft) requirements We bring our team together for the decision -Speed and altitude is at the upper end of IC capability, reliability required will be a challenge for an IC engine -TBProp is good cycle for low-medium altitude operations -TBFan is best at altitudes > 36 Kft but has best reliability We select the TBProp as our starting baseline and agree to evaluate a TBFan as the primary alternative -IC alternative decision will be based on size required Conventional wing-body-tail configuration(s) selected -Evaluate innovative concepts during conceptual design We document our decisions as “derived requirements”

5. 24-5 Design of UAV Systems Putting it all together  2002 LM Corporation Next decision- review How many engines? Generally determined by available engine size The smallest number of engines will always be the lightest and lowest drag How big will they be? Engine size is determined by thrust or horsepower-to- weight required to meet performance requirements One sizing consideration is takeoff; others are speed, acceleration and maneuver Initially we size for takeoff We design for balanced field length (BFL) = 3000 ft Approximate BFL = 1500 ft ground roll to lift off speed, 1500 ft to stop if engine fails at liftoff Later we will calculate performance over the entire mission and ensure that all requirements can be met This is what we will do today

6. 24-6 Design of UAV Systems Putting it all together  2002 LM Corporation Review – reqmn’t disconnect Initial system assessment assumed 100% air vehicle availability, weather now limits availability to 90% -This will affect SAR sizing (primarily) -We assumed SAR operation 100% of the time, therefore, the SAR only needed 80% area coverage -At 90% availability, the SAR needs to provide 89% area coverage (range increase to 102km) to achieve overall 80% (threshold) target coverage We decided to leave the baseline alone and finish the first design cycle before making the change? -During any design cycle, there will always be design and requirement disconnects -If we change baseline every time we find a disconnect, we would never complete even one analysis cycle Orderly changes occur at the end of an analysis cycle

7. -Our methodology sizes the fuselage as a cylindrical center section with elliptical fore and aft bodies -The fuselage is defined in absolute and relative terms -Fuselage equivalent diameter (Df-eq) is absolute but is iterated to assure volume required = available -Relative variables are length to equivalent diameter ratio (Lf/Df-eq), and forebody and aftbody length ratios -At a maximum speed of 282kts, a relatively low fineness ratio (Lf/Df-eq) can be used with minimum drag impact - We select a nominal value of 7.0 (cigar shape) to minimize wetted area (a weight and drag driver) -If we assume the fuselage forebody length = 1Df-eq and the aftbody = 2Df-eq, center section length (Lc) ratio will be 4/7 or Lc/Lf = 0.571 Review - fuselage considerations 24-7 Design of UAV Systems Putting it all together  2002 LM Corporation

8. To get started we put payload in the fuselage center section, close to the vehicle center of gravity - It accommodates a payload weight of 720 lbm and a volume of 26.55 cuft (density = 27.1 pcf) -It also carries some fuel (amount TBD, density = 50 pcf at “packing factor” PF = 0.8 or installed density = 40 pcf) -And it carries airframe structure and some systems (landing gear, etc., nominal installed density = 25 pcf*) -We assume other systems are in the fore & aftbodies We assume center section volume (Vc) is allocated entirely to payload at a packing factor (PF) = 0.7 -Therefore, Vc required = 26.55/0.7 = 37.9 cuft Later the spreadsheet will size for actual volume required Review - fuselage volume 24-8 Design of UAV Systems Putting it all together  2002 LM Corporation * 25 pcf is a reasonable estimate for installed electrical, mechanical systems including avionics, landing gear and engines

9. Review - fuselage geometry 24-9 Design of UAV Systems Putting it all together  2002 LM Corporation -From simple geometry, we express fuselage center section volume in terms of fuselage center section equivalent diameter (De) and Length (Lc) or Vc = (  /4)  Lc  De^2 = (  /4)  (Lc/Lf)  (Lf/Df)  De^3 Vc = 37.9, Lc/Lf = 0.571 and Lf/De = 7 De = 2.29 ft, Lf = 16 ft and Lc = 9.16 ft -Assuming forebody length = De and aftbody length = 2*De (k1 = 0.143, k2 = 0.286), L/D = 7 and w/h = 1 -Fuselage wetted area (SwetF) would be = 106.3 sqft -Knowing wetted area, we could calculate a fuselage drag coefficient = SwetF  Cfe/Sref (RayAD 12.5) and fuselage weight Wfuse) = SwetF*UWF -However, we will let the spreadsheet model do this for us later as part of an integrated analysis or where

10. 24-10 Design of UAV Systems Putting it all together  2002 LM Corporation Review - engine installation Simple engine installations are always best unless there are over-riding considerations Such as high speed, stealth, thrust vectoring, etc. Otherwise, complexity reduces overall performance Nacelle geometry is driven by engine installation TBProp nacelles should be low drag, minimum length Our methodology models nacelles like mini-fuselages Cylindrical center section, elliptical fore and aft bodies Nacelle type is defined by an input wetted area fraction (vs. a typical podded nacelle) -1.0 = typical podded commercial jet transport nacelle -0.5 = nacelle attached to fuselage (e.g. Global Hawk) -0.0 = engine buried in the fuselage (e.g. DarkStar) We assume a single, attached, aft mounted engine L/Dnac = 4; k1 = 0.2; k2 = 0.4; Dnac/Deng = 1.25; nacelle Swet fraction = 0.5 Change from lesson 20

11. 24-11 Design of UAV Systems Putting it all together  2002 LM Corporation -Our design methodology sizes the wing separate from the fuselage -We have 4 primary decisions to make: size (planform area or Sref), shape (Aspect ratio or AR and taper ratio or ), sweep (  ) and thickness ratio (t/c) -Planform area will be determined by wing loading (W0/Sref), a primary design variable -A reasonable value for a turboprop is  30-60 psf (PredatorB & RayAD Table 5.5) -We pick a value of 30 and later will refine the estimate to ensure takeoff/cruise/loiter requirements are met -AR is a primary wing design variable determined by speed, maneuverability and lift-to-drag (L/D or LoD) ratio -High AR generally means high LoD (>20), low maneuverability (a few g’s) and low speed (<350 kts) -For long endurance we select a starting value of 20 Wing considerations (expanded)

12. 24-12 Design of UAV Systems Putting it all together  2002 LM Corporation -Taper ratio ( ) is a secondary wing design variable that drives wing drag due to lift achieved vs. a theoretical minimum (see RayAD Fig. 4-23) -A nominal value is 0.5 selected and needs no further pre-concept design trade -Wing sweep is driven by speed, at a maximum speed of 282 kts we have no need for wing sweep -Wing t/c has a major impact on wing weight, the higher the t/c, the lighter the wing weight -High t/c increases drag but trades favorably against wing weight at low speed -At 282 kts we select a nominal maximum value (t/c = 0.13), it needs no further pre-concept design trades -Of the wing design variables selected, only W0/Sref and AR need to be traded for our speed range Wing - continued

13. 24-13 Design of UAV Systems Putting it all together  2002 LM Corporation -Another concept design wing consideration is volume available for fuel -Wing fuel volume is defined in terms of percent wing chord and span available for tankage -Typically wing tanks start at the wing root or fuselage attachment and can extend to or near the wing tip -For our UAV application we assume the wing tank starts at 10% span and extends to 90% span (  1 = 0.1,  2 = 0.9). We estimate tank chord at 50% wing chord (Kc = 0.5) and fuel packing factor at 0.8 -These initial estimates are not upper limit values -The tanks could extend from fuselage centerline to wing tip if required (  1 = 0,  2 = 1) but it is unlikely that tank chord will exceed the assumed 50% -Fuel density again is estimated at 50 pcf at PF = 0.8 Review - wing volume Another change

14. 24-14 Design of UAV Systems Putting it all together  2002 LM Corporation During pre-concept design, our primary concern is tail type and size We use parametric (historical) data to estimate both horizontal and vertical tail size required For “V-tails” we size using projected areas During conceptual design we will resize to ensure adequate stability and control and handling qualities Our geometry model defines horizontal tail area (Sht) and vertical tail area (Svt) as fractions of Sref or… Sht = Kht  Srefand Svt = Kvt  Sref Where for an average air vehicle Kht ≈.25 and Kvt ≈.15 “Average” V-tail area would be 0.39Sref Our UAV will use an average V-tail area fraction Tail considerations Another change

15. Our aerodynamic model estimates lift and drag from geometry and input values of equivalent skin friction coefficient (Cfe) and “Oswald” wing efficiency (e) We will assume a state-of-the art Cfe value of 0.0035 to reflect our assumption of good surface smoothness (See RayAD Table 12.3) Wing efficiency (e) is estimated at a value of 0.8 using parametric data for an unswept wing at AR = 20 The model uses these inputs to calculate minimum and induced drag coefficients (Cd0 and Cdi) Lift coefficients are calculated from weight (W), Sref and flight dynamic pressure (q) where Cl = W/(q  Sref) Loiter and climb q are assumed to be at max L/D Review - aerodynamic model 24-15 Design of UAV Systems Putting it all together  2002 LM Corporation

16. “Bottoms-up” weight estimates are based on a combination of methods Airframe weight estimates use input unit weights and calculated wetted or planform areas Propulsion weight is based on T0/Weng or Bhp0/Weng Landing gear weight (Wlg) is based on an input gross weight (W0) fraction where Wlg = Kwlg  W0 “Other system” weights (Wsys) use another input weight fraction where Wsys = Ksys  W0 We will use nominal values from RayAD Table 15.2 adjusted for a typical turboprop UAV where Wing unit weight (Uww) = 3.25 psf Tail unit weight (Utw) = 2.6 psf Fuselage/nacelle unit weight (Ufpnw)= 1.8 psf Klg = 0.05 and Ksys (or “all-else empty” ) = 0.12 We also include an empty weight margin (5%) Review - weight model 24-16 Design of UAV Systems Putting it all together  2002 LM Corporation Another change

17. Volume requirements are calculated while iterating bottoms-up weight and geometry Fuel, payload, system and landing gear weights are used to estimate fuselage and pod (if any) volume required Fuel volume = fuel weight/( fuel density  PF ) Payload volume = 26.55 cuft (chart 11-61) Landing gear volume = gear weight/25 pcf Other systems volume = other systems weight/25 pcf Volume available is calculated by the geometry model using input estimates of useable volume per component Nominal value = 0.7 for fuselage and pods (if any) Nominal value for nacelles is a configuration variable In our baseline, we assume the nacelle is unavailable for anything except the engine, inlet and nozzle Df-eq is adjusted to equate volume available and volume required plus 30% margin (or PF = 0.7/1.3 = 0.54) Review - volume model 24-17 Design of UAV Systems Putting it all together  2002 LM Corporation Final change

18. Our propulsion model is a simplified “cycle deck” used to represent both turboprops (TBP) and turbofans (TBF) Engines are sized at sea level static conditions (h=0, V=0) based on input values of thrust or power to gross weight required (T0/W0 or Bhp0/W0) The models predict performance at other values of altitude and speed by assuming that power or thrust vary primarily with airflow (WdotA) Differences between TBFs and TBPs are determined by input values of bypass ratio (BPR), fan specific thrust (T0-fan/W0dotA-fan) and a reference speed (V0) Our UAV studies will use the TBP and TBF values in Lesson 18, chart 18.33 Review - propulsion model 24-18 Design of UAV Systems Putting it all together  2002 LM Corporation

19. Air vehicle performance is estimated using calculated values of gross weight (W0), empty weight (We or EW) and fuel weight (Wf) The mission is calculated forward and backward Forward calculations use simplified performance models to estimate fuel required for engine start-taxi- takeoff, climb and cruise out to initial loiter location Another calculation works backward from empty weight and calculates fuel required for landing reserves and loiter, cruise back, dash from target, combat over the target (including payload drop) and dash to target The sum of the two subtracted from the starting fuel weight is the amount of fuel available for loiter A Breguet endurance calculation using the pre and post loiter weights then predicts operational endurance Review - air vehicle performance 24-19 Design of UAV Systems Putting it all together  2002 LM Corporation

20. We will define our mission to meet maximum distance requirements for each of the two mission types WAS cruise out = 255nm at 27.4Kft Baseline operational endurance is 12 hr, with trade study options for 6 hr and 24 hr endurance Positive ID mission cruise out = 200 nm @ TBD Kft We will size for 12 hrs over the surveillance area, including loiter and ingress/egress The positive ID mission requires a 282 kt dash (out and back) Based on requirement for 1 target ID per hour 3000ft balanced field length takeoff and landing requirements are assumed - Clto = 1.49, Bhp0/W0 = 0.092 Review - mission description 24-20 Design of UAV Systems Putting it all together  2002 LM Corporation 100 nm 158 nm 200 nm x 200 nm 255 nm

21. WAS mission definition 24-21 Design of UAV Systems Putting it all together  2002 LM Corporation 0Engine start 1Start taxi 2Start takeoff 3Initial climb 4Initial cruise 5Start pre-strike refuel 6End pre-strike refuel Start cruise 7End cruise, start loiter 8End loiter 9Start ingress 10End egress,combat 11 Weapon release 12 Turn 13Start egress 14End egress, start cruise 15Start post-strike refuel 16End post-strike refuel 17End cruise 18Start hold 19End hold Notation WAS MISSION Engine start + taxi time = 30 min Start + taxi thrust level = 10% Takeoff (max thrust time) = 1 min Climb + cruise out distance = 255nm Cruise altitude = 27.4Kft Cruise speed = TBD Ingress/egress altitude = n/a Ingress/egress speed = n/a Ingress/egress dist. = 0 Cruise back distance = 255 nm Landing loiter time = 1 hr Landing fuel reserves = 5% See Lesson 21 – performance 0 2 3 4 5678 10 11 12 13 151617 18 19 1 14 9

22. ID mission definition 24-23 Design of UAV Systems Putting it all together  2002 LM Corporation 0Engine start 1Start taxi 2Start takeoff 3Initial climb 4Initial cruise 5Start pre-strike refuel 6End pre-strike refuel Start cruise 7End cruise, start loiter 8End loiter 9Start ingress 10End egress,combat 11Weapon release 12 Turn 13Start egress 14End egress, start cruise 15Start post-strike refuel 16End post-strike refuel 17End cruise 18Start hold 19End hold Notation 0 2 3 4 5678 10 11 12 13 151617 18 19 1 14 9 POSITIVE ID MISSION Engine start + taxi time = 30 min Start + taxi thrust level = 10% Takeoff (max thrust time) = 1 min Climb + cruise out distance = 200nm Cruise altitude =  10Kft Cruise speed = TBD Ingress/egress altitude = 10Kft Ingress/egress speed = 282 kts Ingress/egress dist. = N  282 nm where N = number of searches Cruise back distance = 200 nm Landing loiter time = 1 hr Landing fuel reserves = 5%

23. Review - spreadsheet model 24-24 Design of UAV Systems Putting it all together  2002 LM Corporation Configurations are defined in absolute and relative terms -Payload weight, volume and number of engines are described in absolute terms (forebody, aftbody and length are relative to diameter) -Fuselage diameter can be input as an absolute value or as a variable to meet volume requirements - Aero and propulsion parameters (Cfe, e, Fsp0, f/a, etc.) are defined as absolute values - Everything else (wing, tails area, engines, nacelles,etc.) is defined in relative terms (AR, W0/Sref, BHp0/W0, Sht/Sref, BHp0/Weng, Waf/Sref, UWW, etc.) Missions are described in absolute terms -Takeoff times, operating radius, speed, altitude, etc Most variables are input via worksheet Overall, some are input via worksheet Mperf - Mperf inputs are used to converge the overall solution

24. Overall worksheet inputs 24-25 Design of UAV Systems Putting it all together  2002 LM Corporation RowDescriptionValue 08Volume margin1.3 09Headwind (kt)0 10Climb V/Vstall1.25 11Loiter V/Vstall1.1 13Idle time (min)30 14Idle power (%)10 15Takeoff time (min)1 16Takeoff param220 17Takeoff CL1.5 18Takeoff altitude0 31Landing loiter (min)60 32Landing reserve.05 34# of fuselages1 35Fuse. offset/(b/2)0 36Df (starting value)2.29 37Lf/Df-equiv 7 38Fuselage k1.143 39Fuselage k2.286 40Fuselage w/h1 41Forebody PF0.7 42Centerbody PF0.7 43Aftbody PF0.7 46Ln/Dn-eq5 47Dn-eq/Dengine1.25 48Nacelle k10.2 49Nacelle k20.4 50Nacelle w/h1.0 51Nacelle Swet fract.0.5 52Nac. Non-prop PF0.0 54Number of pods0 55Pod offset/(b/2)n/a 56Pod D-eq/Df-eqn/a 57Pod L/D-eqn/a 58Pod k1n/a 59Pod k2n/a 60Pod w/hn/a 61Pod PF0.0 65Taper ratio0.5 66Thickness ratio0.13 67Tank chord ratio0.5 68Tank span ratio 10.1 69Tank span ratio 20.9 72Horiz tail area0.39 73Vert tail area0 75Skin frict coef.0035 76Oswold efficiency0.8 77Fuse drag factor1.0 78Wing drag factor1.0 81# of engines1 82Model Bhp0default 83Eng Fsp90 84Fan (prop) Fsp5 85Ref speed (kts)50 86Bypass ratio133 87Prop efficiency0.8 88Fuel/air ratiodefault 89Engine L/D-eq2.5 92Starting W0default 93Engine Hp0/Weng2.25 94Eng. inst. wt. factor1.3 95Land gear fraction.05 96System + wt.fract.0.12 97Fuse+nac unit wt.1.8 98Wing unit wt.3.25 99Horiz tail unit wt.2.6 100Vert. Tail unit wt.2.6 101Empty wt. margin.05 102Misc. wt. Fraction.02 104Fuel density50 105Fuel PF0.8 106Engine rho (unst’l)22 107LG rho (instal)25 108System + rho (inst’l)25 109Payload rho (inst’l)27.12

25. Mperf worksheet inputs - WAS 24-26 Design of UAV Systems Putting it all together  2002 LM Corporation Row DescriptionValue 4h4 (kft)27.4 5h7-cruise (kft)27.4 6h7-loiter (kft)27.4 7h8-loiter (kft)27.4 8h9-10,13-14 (kft)27.4 9h11-12 (kft)27.4 10h14 (kft)27.4 11h17 (kft)27.4 13.V-cruise180 14V-ingress (& egress)282 15Op dist (nm)255 16Ingress/egress (nm)0 17Combat (min)0 19Max climb M0.48 20T factor (cruise&clmb)1 21T factor (op loiter)1 22T factor (ingress/combat)1 23SFC factor (cruise&clmb)1 24SFC factor (op loiter)1 25SFC factor (ingress/cmbt)1 26Drag factor1 27Airframe weight factor1 28Fus+nac Swet factor1 Row DescriptionValue 52Df-equiv0 – to iterate 2.29 – fixed Df 56W0/Sref30 57Fuel fractionTBD 58Additional fuel0 61Bhp0/W0TBD 64Payload retained (lbm)720 65Payload dropped (lbm)0 75Aspect ratio20 76Wing efficiency (e)0.8 Design mission definition

26. Mperf worksheet inputs - ID 24-27 Design of UAV Systems Putting it all together  2002 LM Corporation Row DescriptionValue 4h4 (kft)10 5h7-cruise (kft)10 6h7-loiter (kft)10 7h8-loiter (kft)10 8h9-10,13-14 (kft)10 9h11-12 (kft)10 10h14 (kft)10 11h17 (kft)10 13.V-cruise180 14.V-ingress (& egress)282 15.Op dist (nm)200 16.Ingress dist.(nm)141 17.Combat (min)0 Row DescriptionVa 58Additional fuel0.0 64Payload retained (lbm)720 65Payload dropped (lbm)0 75Aspect ratio20 76Wing efficiency (e)0.8 77Lamda0.5 Secondary mission definition

27. 24-28 Design of UAV Systems Putting it all together  2002 LM Corporation The spreadsheet iterates the air vehicle to meet input weight, geometry,volume and propulsion requirements Bottoms-up weights must be iterated by definition Geometry is adjusted with each weight iteration to maintain proper fuselage-wing-tail relationships Engine and nacelle size is adjusted as required Waf/Sref and volume required/available are the variables used to converge weight and geometry during iteration Waf/Sref is used as an input to the weight model and an output from the geometry model Fuselage diameter is adjusted to meet volume required When the values converge, mission model performance estimates will be valid, even though… - Mission range may be short (or long) - Climb rate may be inadequate (even negative) -Cl may be too high (exceeding stall margins) Initial sizing

28. 24-28a Design of UAV Systems Putting it all together  2002 LM Corporation Civil/military certification requirements and good operating practice specify that certain speed and performance be mainatined. Typical values Takeoff (V/Vstall  1.1) Climb (V/Vstall  1.20) Cruise (V/Vstall  not defined) Landing approach (V/Vstall  1.2-1.3) Service ceiling = 100 fpm UAVs have not yet established criteria but safety and good practice will dictate something similar One difference will be operational loiter speed margin, to get high LoD we need to operate at V/Stall  1.1 For design project purposes, we will apply the above margins except we require enough thrust margin for 300 fpm (Ps = 5 fps) Speed and performance margins

29. 24-29 Design of UAV Systems Putting it all together  2002 LM Corporation Performance convergence Worksheet Mperf accepts new inputs to improve or adjust performance -Fuel fraction (FF) is adjusted to meet range and/or endurance requirements -Bhp0/W0 or T0/W0 is adjusted to meet takeoff or rate of climb requirements or achieve consistency (see below) -W0/Sref is adjusted to improve LoD or takeoff distance -AR and wing efficiency (e) can also be traded to improve overall performance The values are adjusted by hand until a satisfactory solution is achieved This includes ensuring adequate (and consistent, if configurations are being compared) margins such as residual ROC, T-D and stall margin -Bhp0/W0 or T0/W0 is further iterated to achieve the desired level of consistency

30. 24-30 Design of UAV Systems Putting it all together  2002 LM Corporation Spreadsheet demonstration Df-equiv3.04 Waf/Sref - geom13.25 Waf/Sref13.25 b40.6 W03304 W0/Sref40.00 FF0.19890.199 Wfuel (total)657 Wing fuel @ 50 ppcf185 Remaining fuel volume req'd (cuft)9 Fuselage center section vol (cuft)88 Pod volume (cuft)0 Wpay707 Wpay (dropped)00 WE19121913 Bhp0/W00.121 TOP Bhp0/W0 req'd0.121 Bhp0400 Sref83 Swetfpppn210 Swet422 AR20.00 Neng11 Bhp0 req'd (ea)400 TBP model Bhp0 (ea)2111 ESF req'd0.189 Vol-eng(ea)8.1 D-eng1.60 D-nac 2.00 Column B Column C Notional values

31. 24-31 Design of UAV Systems Putting it all together  2002 LM Corporation Spreadsheet results Engine size mismatch for WAS and ID mission -Negative Ps at 10 Kft, 282 Kt - requires Bhp0/W0 increase to 0.10 Cruise speeds near LoDmax yielded best performance -161 kts for WAS @ 17 Kft, 144 kts for ID at 10Kft Positive ID was the driving mission -Baseline 12 hour operational endurance WAS air vehicle sized to W0 = 3304 lbm, EW = 1912 lbm -For 12 IDs in 12 hrs, W0 = 16534 lbm, EW = 7996lbm -Also required increased diameter fuselage (to 4.5 ft) to accommodate additional fuel required Changing wing loading (W0/Sref) yielded little benefit -Higher: loiter and cruise speeds offset smaller wing -Lower: increased wing size offset smaller engine Changing aspect ratio (AR) was of little benefit -Increased AR (25) yielded small weight improvement Earlier example problem

32. 24-32 Design of UAV Systems Putting it all together  2002 LM Corporation WAS concept W0 = 3080 lbm EW = 1744 lbm AR = 20 Sref = 77sqft Swet = 381 sqft Payload = 707 lbm Fuel = 603 lbm Power = 373 Bhp TBProp Max endurance = 15.3 hrs Max speed = 350+ kts 39.2’ D Side 19.7’ D Side 2.82’ This air vehicle can stay on station at 17Kft for 12 hours at an operating radius of 255 nm Note – not to scale Earlier example problem

33. 24-33 Design of UAV Systems Putting it all together  2002 LM Corporation ID concept W0 = 16534 lbm EW = 7996 lbm AR = 20 Sref = 413 sqft Swet = 366 sqft Payload = 707 lbm Fuel = 7660 lbm Power = 2000 Bhp TBProp Max endurance = 57.3 hrs Max speed = 350+ kts 90.9’ D Side 33.5’ D Side 4.78’ This air vehicle can perform 12 IDs in 12 hours at 10Kft at an operating radius of 200 nm Note – not to scale Earlier example problem

34. 24-34 Design of UAV Systems Putting it all together  2002 LM Corporation Parametric comparisons During every step of the PCD process, we always test our performance estimates vs. data on known aircraft -This is essential to ensure our results make sense Critical comparisons for our concept are defined by Breguet range and endurance equation variables -LoD, SFC and weights (airframe, propulsion and EW) LoD comparison -We would compare our estimates to RayAD Fig 3.5 but our vehicle is beyond Raymer’s parametric range -For AR=20, Sref = 77, Swet = 381 and Sref = 413, Swet = 1614 our “wetted ARs” (A/[Swet/Sref]) = 4.0 and 5.1 vs. Raymer’s maximum value of 2.4 -But from the trend of the data our assessed values of LoDmax = 27-30 look slightly optimistic -We can also compare to Global Hawk with a reported LoDmax of 33-34 at an estimated “wetted AR”  7

35. 24-35 Design of UAV Systems Putting it all together  2002 LM Corporation LoD comparison This data shows that our model LoDmax estimate may be optimistic by about 5% -We will put a 10% multiplier on our Cdmin estimate to correct for it (Cell B25 = 1.1) -Why do you suppose we corrected a 5% high LoD estimate by increasing minimum drag by 10%? - Could we have done it another way? Manned aircraft data source : LM Aero data handbook Model estimate Corrected value

36. 24-36 Design of UAV Systems Putting it all together  2002 LM Corporation SFC comparisons Data source : Roskam A&P * Note – turboprop SFC is defined in terms of horsepower. Our turboprop model converts horsepower to thrust and uses TSFC for performance calculations This data shows that our model SFC estimates are within performance bounds for 2 typical turboprops* -Although 250 kts at 10Kft looks a little optimistic

37. This data shows that our calculated weights are low compared to regional turboprops but high compared to U-2 and Global Hawk - But the results are close enough for now Another weight related issue is operating a high AR wing at 280 kts at low altitude (flutter and gust potential) 24-37 Design of UAV Systems Putting it all together  2002 LM Corporation Weight comparisons TR-1 Global Hawk TR-1

38. 24-38 Design of UAV Systems Putting it all together  2002 LM Corporation Final comparison GA Altair (Predator B variant) W0 = 7000 lbm EW = ? Sref = 315 sqft AR = 23.5 Payload = 750 lbm Fuel = 3000 lbm Power = 700Hp TPE-331-10T Endurance = 32 hrs Max speed = 210 kts With these inputs our concept would have a 49 hour endurance at 50 Kft but require a 45% airframe weight reduction

39. Data comparison shows that our model estimates are reasonable, although some are probably optimistic We have already decided to put a factor on our drag estimates to reduce LoDmax to the data trend line We will also should put a 10% multiplier on ingress- egress SFC to put it in the middle of the parametric range But we will have to wait for conceptual design to see if our weights are optimistic or pessimistic Some people, however, will put on additional margins to ensure early estimates will be achievable Typically 5-10% on SFC and drag and 10-20% on weight Putting additional margins on our estimates, however, should not be necessary since our parametric data already shows they should be generally achievable -Adding more margin would be overly conservative and negate otherwise valid design solutions 24-39 Design of UAV Systems Putting it all together  2002 LM Corporation Overall conclusions

40. 24-40 Design of UAV Systems Putting it all together  2002 LM Corporation Adjusted baseline 39.9’ D Side 19.95’ 2.0’ D Side 7.9’ 2.85’’ W0 = 3178 lbm EW = 1792 lbm AR = 20 Sref = 79 sqft Swet = 391 sqft Payload = 707 lbm Fuel = 651 lbm Power = 384 Bhp TBProp Max endurance = 15.3 hrs Max speed = 350+ kts This air vehicle has 10% drag and 280 Kt SFC multipliers and can stay on station for 12 hours at 17Kft or perform 2.8 ID missions at 10Kft in 2.8 hours Note – not to scale Earlier example problem

41. 24-41 Design of UAV Systems Putting it all together  2002 LM Corporation Balancing mission requirements Since size requirements for vehicles to do the WAS and ID missions are so different, we will do a study to determine which size vehicle can do both missions at the lowest cost using the following approach: Size WAS concepts for 6, 12, 24 and 48 hours of loiter ID mission performance will be a fallout We will then calculate the number of aircraft required for 24/7 surveillance for 30 days for both missions We will do simple weight based cost estimates Air frame and systems less installed propulsion: $ 200/lbm EW-Weng for ICProp (Lesson 8-45), $400 for TBProp, $800/lb for TBFan Payload: $5000 per pound Engine : $150/lbm for ICProp, $700/lbm for TBProp, $1000/lb for TBFan Finally we will do a simple cost effectives comparison to select our preferred size concept

42. 24-42 Design of UAV Systems Putting it all together  2002 LM Corporation WAS sortie rate elements In order to estimate number of aircraft required we have to perform a preliminary sortie rate analysis See Lesson 7 (Sortie Rate) chart 10, We will use the maintenance and planning times in chart SRR-10 as representative values The nominal mission ground times required are: Maintenance and flight preparations – 180 minutes Preflight checks - 6 minutes Post landing checks and taxi - 25 minutes The remaining elements of the sortie are Engine start-taxi-takeoff - 31 minutes Time to climb to 17 Kft – 6.7 minutes Outbound and return cruise time - 184 minutes WAS - 6, 12, 24 or 48 hours Landing loiter – 60 minutes Land – 3 minutes Use RAND data and adjust for UCAV vs. UAV Include maintenance time = f(flight hrs)

43. 24-42a Design of UAV Systems Putting it all together  2002 LM Corporation Sortie rate elements * http://www.rand.org/publications/MR/MR1028/ Therefore: SR(UAV)  24hours/[1.68  FT + 4.9] SR(UCAV)  24hours/[1.68  FT + 5.9] TAT  3 hrs UCAV unique Include in flight time

44. 24-43 Design of UAV Systems Putting it all together  2002 LM Corporation ID sortie rate elements The ID mission sortie is identical to the WAS mission except for the flight times where the spreadsheet values are: Time to climb to 10 Kft – 3.5 minutes Outbound and return cruise time - 163 minutes ID’s = 1 hour each Earlier example problem Still valid

45. Time required to fly a WAS sortie are: 6 hr loiter - 496 min. + 6 hrs = 14.26 hrs 12 hr loiter - 20.26 hrs 24 hr loiter - 32.26 hrs 48 hr loiter - 56.26 hrs The number of missions an air vehicle can fly in 30 days vs. the number required, therefore, are: 6 hr loiter - able to fly 50.5 missions vs. 480 required 12 hr loiter - can fly 35.5 missions vs. 240 required 24 hr loiter - can fly 22.3 missions vs. 120 required 48 hr loiter - can fly 12.8 missions vs. 60 required The number of flight vehicles required, therefore, are: 6 hr loiter - 480/50.5 = 9.5  10 12 hr loiter - 240/35.5 = 6.8  7 24 hr loiter - 120/22.3 = 5.4  6 48 hr loiter - 60/12.8 = 4.7  5 24-44 Design of UAV Systems Putting it all together  2002 LM Corporation WAS coverage requirements Earlier example problem

46. 24-45 Design of UAV Systems Putting it all together  2002 LM Corporation WAS air vehicles required The total number of air vehicles required are greater than the number required to meet flight requirements We assume one air vehicle is always on standby in case one of the flight vehicles has a problem And we assume all vehicles vehicle under go maintenance at rate of 3.4hrs + 0.68*Flight Time The total number of air vehicles required for continuous WAS mission coverage, therefore, are: 6 hr loiter - 10 + 1 = 11 12 hr loiter - 7 + 1 = 8 24 hr loiter - 6 + 1 = 7 48 hr loiter - 5 + 1 = 6 Earlier example problem

47. 24-46 Design of UAV Systems Putting it all together  2002 LM Corporation WAS air vehicle cost At a nominal air vehicle cost of $400 per pound of empty weight and a nominal payload cost of $5000 per pound, we can calculate WAS costs as follows: 6 hr loiter - 12 air vehicles = $6.6M, Payloads = $38.9M Total cost = $45.4M 12 hr loiter - 9 air vehicles = $5.7M, Payloads = $28.3M Total cost = $34.0M 24 hr loiter - 8 air vehicles = $7.3M, Payloads = $24.7M Total cost = $32.1M 48 hr loiter - 7 air vehicles = $16.9M, Payloads = $21.2M Total cost = $38.1M Earlier example problem You should include engines as separate cost element

48. 24-47 Design of UAV Systems Putting it all together  2002 LM Corporation ID mission requirements Assuming one target identification per hour, the times required to fly an ID sortie are: 1 ID – 471.5 minutes + 1 hrs = 8.86 hrs 2 IDs - 9.86 hrs 4 IDs - 11.86 hrs and 8 IDs - 15.86 hrs The number of missions an air vehicle can fly in 30 days vs. the number of IDs required are: 1 ID – able to fly 81.3 missions vs. 720 required 2 IDs - can fly 73.0 missions vs. 360 required 4 IDs - can fly 60.7 missions vs. 180 required 8 IDs - can fly 45.4 missions vs. 90 required The number of flight vehicles required, therefore, are: 1 ID - 720/81.3 = 8.85  9 2 IDs - 360/73.0 = 4.93  5 4 IDs - 180/60.7 = 2.96  3 8 IDs - 90/45.4 = 1.98  2 Earlier example problem

49. 24-48 Design of UAV Systems Putting it all together  2002 LM Corporation Equivalent WAS coverage WAS sortie equivalent IDs are: 6 hr loiter = 1.5 IDs 12 hr loiter = 2.8 IDs 24 hr loiter = 5.1 IDs 48 hr loiter = 9.5 IDs The number of ID missions a WAS air vehicle can fly in 30 days vs. the number required, therefore, are: 1.5 IDs - can fly 76.8 missions vs. 478.9 required 2.8 IDs - can fly 67.7 missions vs. 261 required 5.1 IDs - can fly 55.4 missions vs. 141.2 required 9.5 IDs - can fly 41.4 missions vs. 75.9 required Total number of ID vehicles required, therefore, are: 6 hr loiter or 1.5 IDs - 478.9/76.8 = 6.2  8* 12 hr loiter or 2.8 IDs - 261/67.7 = 3.9  5* 24 hr loiter or 5.1 IDs - 141.2/55.4 = 2.5  4* 48 hr loiter or 9.5 IDs – 75.9/41.4 = 1.8  3* * If WAS and ID vehicles are identical, a 2nd back up is not required Earlier example problem

50. 24-49 Design of UAV Systems Putting it all together  2002 LM Corporation ID air vehicle cost At a nominal air vehicle cost of $400 per pound of empty weight and a nominal payload cost of $5000 per pound, ID costs are: 1.5 IDs – 8 air vehicles = $4.2M, Payloads = $24.7M Total cost = $29.0M 2.8 IDs - 5 air vehicles = $2.9M, Payloads = $14.1M Total cost = $17.0M 5.1 IDs – 4 air vehicles = $3.1M, Payloads = $10.6M Total cost = $13.7M 9.5 IDs – 3 air vehicles = $5.6M, Payloads = $7.1M Total cost = $12.7M Earlier example problem

51. 24-50 Design of UAV Systems Putting it all together  2002 LM Corporation Total cost The most cost effective single vehicle solution for both missions is an 18 hour WAS vehicle that can also perform 4 IDS Therefore ID air vehicles launch once every 4 hours while WAS air vehicles launch once every 18 hours for an average of 7.3 missions per day

52. 24-51 Design of UAV Systems Putting it all together  2002 LM Corporation Resulting configuration W0 = 3911 lbm EW = 2153 lbm AR = 20 Sref = 98 sqft Swet = 464 sqft Payload = 707 lbm Fuel = 1016 lbm Power = 473 Bhp TBProp Max endurance = 21.4 hrs Max speed = 350+ kts 44.2’ D Side 21.2’ 2.1’ D Side 8.5’ 3.0’ This air vehicle can stay on station for 18 hours at 17Kft or perform 4 ID missions at 10Kft in 4 hours Note – not to scale Earlier example problem

53. 24-52 Design of UAV Systems Putting it all together  2002 LM Corporation What it really looks like W0 = 3911 lbm EW = 2153 lbm AR = 20 Sref = 98 sqft Swet = 464 sqft Payload = 707 lbm Fuel = 1016 lbm Power = 473 Bhp TBProp Max endurance = 21.4 hrs Max speed = 350+ kts This air vehicle can stay on station for 18 hours at 17Kft or perform 4 ID missions at 10Kft in 4 hours Approximately to scale 44.2’ 2.1’ 8.5’ 21.2’ 3.0’ Looks like a ½ scale TBProp Global Hawk Earlier example problem

54. 24-52 Design of UAV Systems Putting it all together  2002 LM Corporation TBProp status We have completed our first pre-concept “design cycle” We have explored the basic concept and found that one 4000 lbm class vehicle can meet both WAS and ID mission requirements at minimum cost The vehicle size is reasonable and the internal volume available should accommodate the required payloads, propulsion, systems and fuel We have shown that the required weight, aerodynamic and propulsion performance levels are consistent with the state-of the art and should be achievable However, we have not completed pre-concept design We still have a requirement problem resulting from the assumption of 100% availability vs. 90% flyable days We also need to conduct goal vs. threshold and and explore alternative TBProp architectures (Charts 8-59/63) And we need to evaluate alternate propulsion concepts

55. 24-53 Design of UAV Systems Putting it all together  2002 LM Corporation Alternative propulsion concepts One of our early decisions was to compare TBFan and IC engine concepts against our TBProp baseline But only if an IC engine of appropriate size is available However, the minimum size TBProp required to perform the ID mission is 420 Hp This minimum power required exceeds the size of the largest available IC engine Therefore, we can drop IC the engine from our study on the basis of size incompatibility TBFan concept evaluation will be straight-forward with few decisions required At the relatively low speeds and altitudes associated with our mission, there is only one viable option A fuel efficient high bypass ratio (BPR) engine We select a nominal BPR=5 as being representative of high efficiency engines of this type

56. 24-4 Design of UAV Systems Putting it all together  2002 LM Corporation TBF alternative We develop a spreadsheet model nearly identical to a TBProp, the major differences being engine definition From PCD Review Part 1.5, PRR-14, nominal T0/Weng = 5.5; installed thrust loss  10% (for good installation) From PRR-26 TBFan parametric data we select a fan specific thrust value of 25 sec for BPR = 5 From PRR-22 we select the remaining model inputs Geometrically, the only difference will be the nacelle TBFan nacelles are modeled as open-ended cylinders where by definition k1n = k2n = 0 We assume nominal values of Lnac/Dnac = 4 and Dnac/Deng = 1.25 Takeoff performance will also be different, a 3000 ft balanced field length for a jet (ground roll of 1500 ft) requires a thrust based takeoff parameter of 100

57. 24-55 Design of UAV Systems Putting it all together  2002 LM Corporation Overall TBFan inputs ColDescriptionValue 03R-start (nm)default 17Headwind (kt)0 18Clmax1.2 19V/Vstall1.25 25LoD startdefault 26SFC startdefault 27EWF startdefault 28Kttoc startdefault 31Idle time (min)30 32Idle power (%)10 33Takeoff time (min)1 34Takeoff param100 35Takeoff CL1.5 40Takeoff altitude0 43Landing loiter (min)60 44Landing reserve.05 47# of fuselages1 48Fuse. offset/(b/2)0 50Lf/Df-equiv 7 51Fuselage k1.143 52Fuselage k2.286 53Fuselage w/h1 55Nacelle De startdefault 56Ln/Dn-eq4 ColDescriptionValue 57Dn-eq/Dengine1.25 58Nacelle k10 59Nacelle k20 60Nacelle Swet fract.0.5 61Nacelle w/h1.0 63Number of pods0 64Pod offset/(b/2)n/a 65Pod D-eq/Df-eqn/a 66Pod L/D-eqn/a 67Pod k1n/a 68Pod k2n/a 69Pod w/hn/a 73Taper ratio0.3 74Thickness ratio0.13 75Tank chord ratio0.5 76Tank span ratio 10.1 77Tank span ratio 20.9 78Tank pack factor0.8 78Horiz tail area0.39 79Vert tail area0 84Skin frict coef.0035 85Oswold efficiency0.8 86Fuse drag factor1.0 87Wing drag factor1.0 ColDescriptionValue 90# of engines1 91Model Bhp0default 92Eng Fsp90 93Fan Fsp25 94Ref speed (kts)100 95Bypass ratio5 96Installed T00.9 97Fuel/air ratiodefault 98Engine L/D-eqn/a 99Engine densityn/a 101Starting W0default 103Engine T0/Weng5.5 104Eng. inst. wt. factor1.3 105Land gear fraction.05 106System wt.fraction0.1 107Fuse+nac unit wt.3 108Wing unit wt.5 109Horiz tail unit wt.3 110Vert. Tail unit wt.3 111Empty wt. margin.05 113Misc. wt. Fraction.02 Changes from TBProp shown in red Earlier Spreadsheet

58. 24-56 Design of UAV Systems Putting it all together  2002 LM Corporation Mperf TBFan inputs ColDescriptionValue 3h4 (kft)17 4h7-cruise (kft)17 5h7-loiter (kft)17 6h8-loiter (kft)17 7h9-10,13-14 (kft)10 8h11-12 (kft)10 9h14 (kft)17 10h17 (kft)17 13Vcruise200 14V-ingress/egress280 15WAS op dist (nm)255 15ID op dist (nm)200 16WAS dash (nm)0 16ID dash (nm)141 17Combat (min)0 19Max climb M0.48 20T factor (cruise)1 21T factor (loiter)1 22T factor (combat)1 23TSFC factor (cruise)1 24TSFC factor (loiter)1 25TSFC factor (combat)1 26Drag factor1 ColDescriptionValue 27Airframe weight factor1 28Fuse+nac Swet factor1 59Df-equiv3.04 63Waf/Sref (input)TBD 67W0/Sref40 68Fuel fractionTBD 74Payload retained (lbm)707 75Payload dropped (lbm)0 77T0/W0TBD 78Aspect ratio20 Changes from TBProp shown in red Earlier spreadsheet

59. 24-57 Design of UAV Systems Putting it all together  2002 LM Corporation TBFan WAS concept W0 = 4865 lbm EW = 2454 lbm AR = 20 Sref = 122 sqft Swet = 517 sqft Payload = 707 lbm Fuel = 1656 lbm Engine = 1299 Lbf TBFan Max endurance = 15.4 hrs Max speed = 280 kts This air vehicle can stay on station at 17Kft for 12 hours at an operating radius of 255 nm It is 41% heavier than a TBProp with the same performance 49.4’ D Side 21.3’ D Side 3.04’ 1.8’’ 7.2’ Note – not to scale Earlier example problem

60. 24-58 Design of UAV Systems Putting it all together  2002 LM Corporation TBFan ID concept W0 = 5660 lbm EW = 2761 lbm AR = 20 Sref = 141 sqft Swet = 573 sqft Payload = 707 lbm Fuel = 2133 lbm Engine = 1511 Lbf TBFan Max endurance = 18.8 hrs Max speed = 280 kts 49.4’ D Side 21.3’ D Side 3.04’ 1.8’’ 7.2’ This air vehicle can perform one ID at 10Kft at an operating radius of 200 nm It is 39% heavier than a TBProp with the same performance Note – not to scale Earlier example problem

61. 24-59 Design of UAV Systems Putting it all together  2002 LM Corporation TBFan conclusions The TBFan alternative is bigger and about 40% heavier than the TBProp baseline for both design missions The relatively low-speeds and altitudes required really are optimum for TBProp operations TBFan cycles are better suited for higher speeds and altitudes We can now confidently drop the TBFan concept from further consideration And document the results of our alternative concept study as rationale for our future exclusive focus on TBProp engines We will also document the rationale for selecting an 18 hour WAS capability for our preferred baseline to meet both WAS and ID mission requirements

62. 24-60 Design of UAV Systems Putting it all together  2002 LM Corporation TBProp continued Even though we have concluded that the TBProp is the best overall solution to meet mission requirements, we still need to address some unresolved issues The impact of 10% of the weather being unflyable vs. our assumption of a 100% flight rate vs. the threshold requirement for 80% target coverage The cost effectiveness of designing for threshold vs. goal performance The effectiveness of alternative See Lesson 3, charts 13-15 The support concept required Overall system life cycle cost

63. 24-61 Design of UAV Systems Putting it all together  2002 LM Corporation Homework 1.Using spreadsheet TBProp.AE261Example.xls and total mission procurement cost as the figure of merit, for the TBProp example, do the following trades (one trade for each team member, individual grades): Aspect ratios (AR) of 10-20-25-30 at W0/Sref = 30 W0/Sref of 15-30-45-60 at AR = 10 Aspect ratios (AR) of 10-20-25-30 at W0/Sref = 60 W0/Sref of 15-30-45-60 at AR = 30 2. Select best combination of W0/Sref and AR and use TBProp.AE261Example.xls to trade 12-24-48 hr WAS loiter times (team grade). Select the best loiter time and explain why it turned out that way 3. Use TBProp.AE261Example.xls to determine best WAS and ID cruise speeds. Explain why (team grade) 4. Discuss ABET issues #5 and #6 and document your conclusions (one paragraph each – team grade)

64. 24-61 Design of UAV Systems Putting it all together  2002 LM Corporation Intermission