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  1. Design of UAV Systems c 2004 LM Corporation • Lesson objective - to discuss • Requirements analysis • including … • Basing • Operational radius • Operational endurance • Maximum range • Speed • Turn around time • plus … • Example problem Requirements analysis 8-1

  2. Design of UAV Systems c 2004 LM Corporation Definition • Requirements analysis • Quantitative and qualitative engineering analysis to translate overall customer goals and objectives into a traceable set of “design-to” requirements • Provides the design team with a consistent set of numbers they can work to • Basically a form of “reverse engineering” • Working backwards to determine what combination of concepts, design and technology best meet customer expectations? • Usually a cost and risk-based analysis • What is the highest level of system performance achievable at the lowest cost and risk? • Air vehicle empty weight and payload weight are often used as cost surrogates Requirements analysis 8-2

  3. Design of UAV Systems c 2004 LM Corporation UAV system design drivers • Most top level UAV requirements focus on target area coverage, capability and time • Reconnaissance capabilitiesare typically defined in terms of types or numbers of targets and sensor resolution • Strike capabilitiestypically are defined in terms of types, numbers and distribution of targets • For the UAV air vehicle element this typically translates into derived requirements on • Basing • Operational radius • Operational endurance • Maximum range • Speed • Turn around time Requirements analysis 8-3

  4. Design of UAV Systems c 2004 LM Corporation Land Based Operations • The typical basing mode for aircraft • Other basing options impose penalties • Weight and complexity • …...and/or….. • Operational constraints • Land based operations are supported by over 45,000 airports world wide • Although most runways are short and unpaved • Very short fields penalize air vehicle design • Sophisticated high-lift systems are heavy and complex • Unpaved airfieldsincrease the penalty for takeoff, landing and ground operations • Landing gear, wheels and brakes comprise a significant percentage of air vehicle empty weight Requirements analysis 8-4

  5. (Total = 45,024) Design of UAV Systems What runway length do you design for? Data Source - c 2004 LM Corporation Worldwide airport data Requirements analysis 8-5

  6. Design of UAV Systems http://www.eden.com/~tomzap/b_apt.html c 2004 LM Corporation Typical unpaved field What runway type do you design for? Requirements analysis 8-6

  7. Design of UAV Systems c 2004 LM Corporation It depends on the mission • Example - A Korean venture capitalist sees a market for overnight aerial delivery of small, high value products between Korean and Chinese commercial and industrial airports. An automated UAV delivery vehicle could have cost benefits compared to a manned aircraft. • - He wants to operate out of a hub in Sachon • - He is familiar with the runways in Korea and is confident that they will support his delivery concept • - He is not familiar with the runways in China • - He asks for an initial study to assess UAV takeoff and landing requirements Requirements analysis 8-7

  8. Design of UAV Systems c 2004 LM Corporation Analysis approach • - We log on to the internet and access the “World Fact Book” at www.odci/cia/publications/factbook/indexfld.hmtl and collect runaway data for China and Korea • - A spreadsheet is created to correlate runway length and type vs. the number of runways per country • The results are plotted and compared Requirements analysis 8-8

  9. Airports - China Airports - ROK 100 100 90 90 Unpaved Unpaved Design of UAV Systems 80 80 Paved Paved 70 70 60 60 Number (%) 50 Number (%) 50 40 40 30 30 20 20 10 10 0 0 > 10Kft > 8Kft > 5Kft > 3Kft Total > 10Kft > 8Kft > 5Kft > 3Kft Total Runway Length (Kft) Runway Length (Kft) c 2004 LM Corporation Airport data Requirements analysis 8-9

  10. Design of UAV Systems c 2004 LM Corporation Assessment • Almost all ROK and Chinese airports with runways longer than 3000 feet are paved • - There is no real benefit to having a capability to operate from unpaved fields • 85% of the airports in China are 5000 feet or longer • - There is no real benefit to having a capability to operate from shorter fields in China • But only 33% of the airports in the ROK are 5000 feet or longer • Is this enough or should we serve shorter ones? • Answer: Korea is a small country with 54 airports with runways > 5000 feet Requirements analysis 8-10

  11. Design of UAV Systems c 2004 LM Corporation Vehicle Implications • A subsonic (low wing loading) jet powered UAV could operate from a 5000 foot runway in either country • A prop powered UAV could be able to operate from a 3000 foot runway in either country • - 3000 feet is possible for a jet it but requires a very low wing loading or a high thrust-to-weight (or both) • see Raymer, Figure 5.4 • Bottom line • A jet powered UAV could operate from 85% of the runways in China and 1/3 of the runways in Korea • A prop powered UAV could operate from >90% of the runways in China and >40% of the runways in Korea Requirements analysis 8-11

  12. Design of UAV Systems c 2004 LM Corporation Jet UAV example • Note that takeoff and landing requirements are based on distance over a 50 foot obstacle • See Raymer, 5.3 through page 103 for more information Requirements analysis 8-12

  13. Design of UAV Systems c 2004 LM Corporation Unpaved fields • Unpaved fields are not as bad as they may sound • They are designed for aircraft operations • Typically they are reasonably smooth • - They may not, however, be level • - Nor particularly straight • And they cannot be cleaned • - This is a problem for jet aircraft with engine inlets located near the ground • They also are generally unusable in wet weather • And aircraft with high gross weight/tire contact area ratios can sink into the ground, whether wet or dry • - Runways and taxi ways generally have a LCN (load contact number) rating to indicate how much load/tire contact area can be handled Requirements analysis 8-13

  14. Design of UAV Systems c 2004 LM Corporation Unprepared fields • Unprepared fields are different from unpaved fields • An unprepared field can be anything from a soccer field to a muddy pasture • - A requirement to operate from such fields can impose severe penalties on fixed wing aircraft • Low takeoff and landing speeds • Heavy duty landing gear • High flotation tires, etc. • The requirement can be met with a fixed wing aircraft but the result is usually a slow vehicle with a low wing loading (like a Piper Super Cub) or a faster vehicle with powered lift (e.g. Short Take Off Vertical Landing) • - According to Raymer, STOVL weight penalties are 10-20% for fighters and 30-60% for transports • Rotary wing aircraft are often a better option for operations from unprepared fields Requirements analysis 8-14

  15. Design of UAV Systems c 2004 LM Corporation Operations at sea • Operating an air vehicle from a ship is complicated • Manned fighters and fighter bombers have been operating from aircraft carriers for years • - But deck and air operations are complex • Very high level of pilot proficiency required • Crowded deck space • High potential for accidents and injuries • Helicopters also have been operating from smaller ships for years. Operations are less complicated but still demanding • - STOVL aircraft can also operate from smaller ships • - Fixed wing UAVs have operated from smaller ships with mixed success • Cruise missiles have operated from smaller ships and submarines but they do not recover back to the ship • - UAV/UCAV operations from subs are being studied Requirements analysis 8-15

  16. Design of UAV Systems c 2004 LM Corporation Benefits • Ship based air operations • 70% of the surface of the earth is covered with water • Operating from ships frees operators from requirements to build or establish land bases • Well equipped ships have housing and provisions for crew members and facilities and spare parts for maintenance and overhaul • Global mobility is enhanced But the cost is high and the ships involved are large and complex Requirements analysis 8-16

  17. Helicopters 8 SH-3 Sea King or.. 8 SH-60 Seahawk Fixed Wing Aircraft 14 F-14 Tomcat 4 EA-6 Prowler 36 F/A-18 Hornet 4 E-2 Hawkeye 6 S-3 Viking CVN-68 Nimitz-class Crew 5680 Design of UAV Systems 252 ft (77 m) 1092 ft (333 m) http://www.fas.org/man/dod-101/sys/ship/cvn-68.htm Aircraft designed for carrier operations typically pay a 10-15% weight penalty c 2004 LM Corporation Aircraft Carriers Requirements analysis 8-17

  18. Helicopters Up to 42 CH-46 Sea Knight Crew 1100 Sailors 1900 Marines LHD-1 Wasp-class Fixed Wing Aircraft Up to 20 AV-8B Harriers Design of UAV Systems 200 ft (61m) 252 ft (77 m) http://www.fas.org/man/dod-101/sys/ship/cvn-68.htm • Only Short Takeoff Vertical Landing (STOVL) aircraft and helicopters currently operate from assault ships • - A fixed wing UAV designed to operate from this class ship would probably use powered lift (10-20% weight penalty) 844 ft (253 m) c 2004 LM Corporation Assault Ships Requirements analysis 8-18

  19. Design of UAV Systems http://sun00781.dn.net/man/dod-101/sys/ship/LHD12.JPG Decks are crowded and space is limited c 2004 LM Corporation Typical assault ship Requirements analysis 8-19

  20. Other surface ships • Fixed wing aircraft have been launched from other types of ships • - Handling is complex and this is not widely used Design of UAV Systems www.wa3key.com/growler.html http://www.fas.org/irp/program/collect/pioneer.htm Regulus - 1950s Pioneer - 1990s c 2004 LM Corporation Requirements analysis 8-20

  21. The big problem is landing • - Current interest focuses on rotary wing UAVs but other concepts are being studied Design of UAV Systems http://www.fas.org/irp/program/collect/pioneer.htm US Navy VTUAV Replaces Pioneer http://www.lmaeronautics.com/image_gallery/index.html http://www.fas.org/irp/program/sources.htm c 2004 LM Corporation UAV ship operations Requirements analysis 8-21

  22. Design of UAV Systems www.wa3key.com/growler.html • Cruise missiles have been launched from the decks of submarines • - Current concepts are torpedo tube launched http://www.fas.org/man/dod-101/sys/smart/bgm-109.htm c 2004 LM Corporation Submarines Requirements analysis 8-22

  23. Design of UAV Systems http://www.fas.org/irp/agency/daro/uav96/page32.html http://www.lmaeronautics.com/image_gallery/index.html Launching UAVs from subs is being studied - Size and weight penalties are significant Operating UAVs from subs has been demonstrated c 2004 LM Corporation UAV operations Requirements analysis 8-23

  24. Design of UAV Systems c 2004 LM Corporation Air launch • Launching UAVs from aircraft is straight forward • The UAV benefits are reduced size and weight • Carrier aircraft adds to operational range • Engine can be sized for cruise • Landing gear can be sized for landing weight • But there are limitations on size and weight • Under wing mounted (NB-52 with X-15A-2) • - Length = 52.5 ft, span = 22.5 ft, height = 14 ft • - Weight = 56.1 Klb • Upper fuselage mounted (B747 with Shuttle) • - Length = 122 ft, span = 57 ft, height = 57 ft • - Weight = 180 Klb • Under fuselage mounted (L1011 with Pegasus) • - Length = 55 ft, span = 22 ft, diam. = 4.2 ft • - Weight = 51 Klb Requirements analysis 8-24

  25. http://www.dfrc.nasa.gov/gallery/photo/index.html Design of UAV Systems Under wing carriage of large vehicles requires something like a B-52 http://www.dfrc.nasa.gov/gallery/photo/index.html Upper fuselage loading and unloading is very complex Unless your customer has such resources, carriage will be constrained to smaller aircraft c 2004 LM Corporation Practical constraints Requirements analysis 8-25

  26. Design of UAV Systems http://www.spectrumwd.com/c130/dc130p1.htm http://209.207.236.112/irp/program/collect/aqm-34n.htm Orbital Sciences Pegasus Span: 22 ft. Diameter: 4.2 ft. Length: 55 ft. Weight: 51 Klb Ryan AQM-34N Span: 32 ft. Weight: 3,830 lbs. Length: 30 ft. Speed: 420 mph Height: 6.75 ft. Range: > 2000 NM c 2004 LM Corporation More reasonable sizes Requirements analysis 8-26

  27. Design of UAV Systems c 2004 LM Corporation Aerial recovery • AQM-34 reconnaissance drones were recovered in mid air during the Vietnam war • 65% of the drones were successfully recovered, many using a Mid Air Retrieval System (MARS) equipped helicopter which performed an aerial “snatch” • Despite past success, aerial recovery is complex and dangerous (for the helicopter) • I can find no pictures of the recovery system but take my word for it, aerial recovery of UAVs is very difficult Requirements analysis 8-27

  28. Design of UAV Systems c 2004 LM Corporation Next subject(s) • Lesson objective - to discuss • Requirements analysis • including … • Basing • Operational radius • Operational endurance • Maximum range • Speed • Turn around time Requirements analysis 8-28

  29. Design of UAV Systems c 2004 LM Corporation Operational radius and endurance • Why are they important? • Operating radius defines how far the UAV operates from base • - Typically sizes the system architecture (comms, etc.) • Endurance (time on station) and operating radius typically size the air vehicle • Example - Global Hawk (RQ-4A) early program goals Requirements analysis 8-29

  30. Design of UAV Systems c 2004 LM Corporation RQ-4A question Where did 24 hours and 3000 nm come from? • They were driven by customer and crew considerations • - UAV products are generally needed around the clock (24 hours a day, 7 days a week) • - Air operations are planned in 24 hour cycles • - Crews operate on 8 or 12 hour cycles* • Original Global Hawk endurance would allow 2 air vehicles to provide 24/7 coverage at 3200 nm with fixed takeoff and recovery times. • 3200 nm would allow operations from secure bases far from a combat zone (Diego Garcia - Kuwait = 2640 nm) * Civilian air crews operate on 8 to 14 hour cycles Requirements analysis 8-30

  31. Design of UAV Systems c 2004 LM Corporation Expanded explanation • Preflight checks and maintenance • - Nominal 1.5 hours (est.) • Time to taxi and takeoff • - 30 minutes (from NGC) • Time to climb • - 200 nm @ 225 kts (135 KEAS* average) = 1 hr • Time enroute • - 3000nm/350 kts = 8.6 hrs • Time on station • - 24 hours for single vehicle coverage • Enroute return = 8.6 hrs • Time to descend • - Nominal 1 hour (est.) • Landing loiter time • - 1 hour (from NGC) • Time to land and taxi • - Estimate 15 minutes • Post flight checks - Nominal 1.5 hours (est.) Single vehicle nominal flight + ground time = 48 hours; i.e. one vehicle can launch every 24 hours * See Chapter 17 for definition Requirements analysis 8-31

  32. Design of UAV Systems c 2004 LM Corporation Maximum range • Why is it important? • Defines how far the UAV can deploy from base • Establishes the support assets required to support deployment • Global Hawk 12500-13500 nm range permits self deployment anywhere in the world without aerial refueling Requirements analysis 8-32

  33. Design of UAV Systems LOS h c 2004 LM Corporation Range and endurance impact • Range and endurance drive system size, complexity and cost • Range - Communication architecture goes from simple to complicated when range exceeds line of sight (LOS) • LOS (nm) ≈ 0.87sqrt [2h(ft)] (see Chapter 9)  • LOS @ 10Kft = 123 nm • LOS @ 65Kft = 315 nm • - Beyond line of sight (BLOS) coverage requires comm relay (surface or airborne) or satellite* • Endurance (time on station) - 12 hour endurance (at 3200 nm) Global Hawk type air vehicle would be about 60% the empty weight at the same payload • - Range and endurance would also drop by 40%** • - Number of air vehicles for 24/7 would increase 50%h Examples * More about this in Chapter 9 (week 14) ** Explanation to come - Chapter 24 Requirements analysis 8-33

  34. Design of UAV Systems c 2004 LM Corporation Fleet size • Number of air vehicles required driven by: • Time on station, operating radius and cruise speed, turn around and other times. Global Hawk example: • - Total ground time = 3.75 hrs, time to climb/descend/land = 3 hrs, time enroute = 2*[op’n radius]/speed =17.5 hrs • If time on station=24 hrs, 2 vehicles req’d, one launch every 24 hours • If time on station=12 hrs, 3 vehicles req’d, one launch every 12 hours • If time on station = 6 hrs, 5 vehicles req’d, one launch every 6 hours 24 hour coverage Requirements analysis 8-34

  35. If time on station = 2 hrs, 13 vehicles req’d, one launch every 2 hours 24 hour coverage Design of UAV Systems * Air vehicle cost excludes payload (which should be included) - more about this later c 2004 LM Corporation Time on station – cont’d Notional example Requirements analysis 8-35

  36. Range analysis • Straight forward assessment of required or desired target area (commercial or military) coverage • Commercial and military considerations functionally similar • Military assessments driven by targets and “threat lay down” • Drive routing considerations (which impacts range req’d) • Commercial assessments driven by target markets and routing • Common considerations • Launch base(s) • Target(s) • Recovery base(s) • Deviations from most efficient routes (great circle) • Both types require geographic area analysis • Typically a problem for individual students Design of UAV Systems c 2004 LM Corporation Requirements analysis 8-36

  37. Geographic area analysis • Efficient assessment of geographic area coverage requires digital mapping software and data bases that are not typically available to students. • Example - A UAV operating out of Korea has an operating mission radius of 1200 nm • - How much of the Chinese land mass could it survey? • - How would coverage compare to a UAV with a 600nm operating radius? • - Assume that you do not have time to grid a map and manually count squares Design of UAV Systems c 2004 LM Corporation Requirements analysis 8-37

  38. Design of UAV Systems 600 nm 1200 nm c 2004 LM Corporation Geographic area coverage? Requirements analysis 8-38

  39. Simple solution Internet databases are available on airports (numbers, types, and locations). You can use airports as surrogates for geographic area. • Example - A Korean venture capitalist sees a market for overnight aerial delivery of small, high value products between Korea and Chinese commercial and industrial airports. He believes an automated UAV delivery vehicle could have cost benefits compared to a manned aircraft. • - He wants to operate out of a hub in Sachon • - How would we do a requirements study to determine what UAV operating ranges, types and speeds would be required? Design of UAV Systems c 2004 LM Corporation Requirements analysis 8-39

  40. Design of UAV Systems c 2004 LM Corporation Analysis approach • We randomly select 25 Chinese ICAO airports with long runways • ICAO designations indicate the airports are used for commercial operations • Long runways identify major airports with significant airline operations • We log onto Worldwide Airport Path Finder and start to develop a database. Requirements analysis 8-40

  41. Unfortunately fallingrain.com no longer maintains this site Design of UAV Systems c 2004 LM Corporation Example • This is the output from WAPF at http://www2.fallingrain.com.air/ • WAPF has a database of all known airports and allows a user to plan a flight between any airports with ICAO designators. This example is a 52 nm flight from Sachon (RKPS) to Pusan (RKPP). • A data set is created by calculating the distances between Sachon and each of the 25 Chinese airports • The data set is listed in order of distance, from shortest to longest and plotted Requirements analysis 8-41

  42. ICAO ID Distance(nm) zsqd 381.00 zytl 390.00 zsss 411.00 zshc 488.00 zsnj 499.00 zycc 545.00 zbtj 567.00 zsof 574.00 Design of UAV Systems zsfz 700.00 zhcc 701.00 zhhh 743.00 zbyn 762.00 zsam 817.00 zbhh 841.00 zgha 863.00 zggg 1052.00 zgkl 1104.00 zuck 1130.00 zppp 1142.00 zuuu 1243.00 zgnn 1281.00 zghk 1302.00 zwww 1931.00 zwtn 2315.00 zwsh 2463.00 c 2004 LM Corporation The data set Requirements analysis 8-42

  43. Design of UAV Systems c 2004 LM Corporation The plot A UAV with an operating radius an 1300 nm can cover 90% of the airports studied. The radius has to double to cover the remaining 10%. Is this the result of the small data base used or does it indicates that a study is needed to determine if covering the last 10% is cost effective? Requirements analysis 8-43

  44. Does this help you answer? Design of UAV Systems c 2004 LM Corporation • China is a big country • Not many people live in the western half Requirements analysis 8-44

  45. Why is it important? • It has a major impact on the cost and complexity of the air vehicle - Speed costs! Design of UAV Systems Jet Turboprop Piston Engine Data source - http://cessna.com/aircraft/ c 2004 LM Corporation Speed Requirements analysis 8-45

  46. Design of UAV Systems c 2004 LM Corporation Block time • Why it is important? • It is what an aircraft gets paid for • Passenger or freight customers pay by the trip • Once an aircraft is loaded with freight or passengers, it doesn’t earn any more money until it is loaded again • But from a revenue standpoint, if an aircraft has to sit on the ground for long periods of time between flights, it almost doesn’t matter if it flies fast or slow. • Time on the ground (ground turn around time) is a key mission consideration Block time = Mission distance/block speed Requirements analysis 8-46

  47. Block speed • What is it ? • The average speed for an entire mission including takeoff, climb, cruise, descent and landing • Why it is important? • It is the only speed that matters from a revenue stand point Design of UAV Systems c 2004 LM Corporation Requirements analysis 8-47

  48. ICAO ID Distance(nm) zsqd 381.00 zytl 390.00 zsss 411.00 zshc 488.00 zsnj 499.00 zycc 545.00 zbtj 567.00 zsof 574.00 Design of UAV Systems zsfz 700.00 zhcc 701.00 zhhh 743.00 zbyn 762.00 zsam 817.00 zbhh 841.00 zgha 863.00 zggg 1052.00 zgkl 1104.00 zuck 1130.00 zppp 1142.00 zuuu 1243.00 zgnn 1281.00 zghk 1302.00 zwww 1931.00 zwtn 2315.00 zwsh 2463.00 c 2004 LM Corporation Sortie length analysis • Sortie length • = time to service, taxi, load & unload + distance/(block speed) • Assumptions • - 1 hour to load and takeoff • - 1 hour to land and unload • - 40 knot headwind • Block speeds • 60,120 kts (piston engine) • 240 kts (turboprop) • 480 kts (subsonic jet) • 960 kts (supersonic jet) Min. coverage 50% coverage 90% coverage Requirements analysis 8-48

  49. Design of UAV Systems c 2004 LM Corporation Analysis results • 60 & 120 kt UAVs cannot provide overnight service • A 240 kt UAV can make one (1) flight per night (90% coverage) • A 480 kt UAV can fly two (2) 90% coverage missions (one round trip) per night • Or 1 max. distance mission • A 960 kt UAV can fly 3 times per night (90% coverage) Total time (hr) Block speed (kts) Questions - Which speed is most cost effective? - What are the sensitivities of the results to the assumption of a 2 hour turn-around time (international flight)? Requirements analysis 8-49

  50. Design of UAV Systems c 2004 LM Corporation Cost effectiveness • Best option = 240 kts • Lowest cost to meet requirements • Relative cost (assumption) • - 60 kt UAV = 1.00 • - 120 kt UAV = 2.00 • - 240 kt UAV = 4.00 • - 480 kt UAV = 8.00 • - 960 kt UAV = 16.00 • Relative income • = 12hrsBlock time Requirements analysis 8-50