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					Trade Study Methods




                      9-1
                  Types of Trade Studies



• Controlled Convergence - Preliminary Method Used by
Engineering. Quick Method to Compare “Primitive” Design
Variables
• Cost Effectiveness - Links Force Structure Implications to Top
Level Requirements Analysis
• Comprehensive - Considers all Applicable Decision Criteria




                                                                   9-2
                          Time Frames For
                        Trade Study Methods


                         --Comprehensive--

              ------Cost-Effectiveness-------

          -Controlled Convergence-
                                                Production &
Pre Concept                                     Deployment
& Tech Dev         A        B               C



           Concept &           System
                                                   Operations &
          Technology        Development &
                                                     Support
          Development       Demonstration
                                                                  9-3
Controlled Convergence
      Trade Study




                         9-4
              Steps in Applying Controlled
                  Convergence Method


1. Design Alternatives to Same Level of Detail
2. Choose Comparison Criteria
3. Choose a Baseline for Comparison Purposes
4. Compare the Alternatives to the Baseline
5. Sum Pluses and Minuses
6. Can New Alternative Be Created by Changing Negative(s) of a
   Strong Alternative?
7. Can Weak Alternative Be Eliminated?
8. Return to Step 4 or Document Findings and Proceed



                                                                 9-5
               Controlled Convergence Method For
                    Preliminary Trade Studies

                     Design
                     Alternatives
Comparison                               1       2   3   4   5
Criteria                            (Baseline)
(Design Primatives)
Thrust/Weight (T/W)                      S       –   S   –   +
Weight/Wing Ref. Area (W/S)              S       –   –   +   +
Coef. of Lift (C )
                L                        S       –   +   –   –
Cruise Performance (Specific fuel        S       S   +   S   +
  consumption, range, speed)
Observables (Shaping, materials,         S       S   +   S   –
  propulsion, etc.)
Payload Capacity                         S       –   +   –   S
Agility (maneuverability &               S       +   +   –   +
  controllability)
               ...
 TOTAL +'s                               0       1   5   2   4
 TOTAL S's                               7       2   1   1   1
 TOTAL –'s                               0       4   1   4   2

                      + Significantly Better
         Legend       S About the Same
                      – Significantly Worse


                                                                 9-6
  Strengths and Weaknesses of Controlled Convergence
            Preliminary Trade Study Method


• Difficult for Strong-Willed Person to Dominate Decision Making

• Encourages Development of Additional Design Alternatives

• Time to Converge Can Be Controlled



       Repeated Applications of This Method Will Result in
          “Fuzzy” Comparisons of Leading Alternatives




                                                                   9-7
Cost-Effectiveness
   Trade Study




                     9-8
Alternative Configuration Scoring Methods




                                            9-9
9-10
9-11
           Life Cycle Cost Composition




                                    PLUS                PLUS          PLUS             PLUS
•   Management                •   Tech Data            • Initial   • RDT&E        • Operations &
•   Hardware                  •   Publication          Spares      • Facility
•   Software                                                                        Support
                              •   Contractor Service                 Construction   (Includes
•   Nonrecurring "Start-up"   •   Support Equipment
•   Allowance for Changes                                                           Post-Produc-
                              •   Training Equipment                                tion Support)
     FLYAWAY COST             •   Factory Training
                                                                                  • Disposal
             WEAPON SYSTEM COST

                   PROCUREMENT COST

                       PROGRAM ACQUISITION COST

                                  LIFE CYCLE COST




                                                                                               BV41861
                                                                                                         9-12
                    Cost Estimating Methods Used
                     During Acquisition Phases

P = Primary     Pre Concept Concept &    Early in      Early in
                                                                     Prod. &
S = Secondary   & Tech.     Tech. Dev.   System Dev. & System Dev. &
                                                                     Dep.
                Dev.                     Demonstration Demonstration

 Parametric         P            S            S           N/A        N/A




                    S            P             S         N/A         N/A
 Analogy



 Bottom-            N/A          S             P          P          P
 Up Eng.

                                                                           9-13
                      Relative Values of LCC Elements
                           (based on 100 aircraft)

                               Life Cycle Cost


   RTD&E (4.3%)               Procurement (49.6%)          Operations & Support
                                                                 (46.1%)
0.30   Demo/Validation      0.59   Tooling & Engineering 1.74 Replenish Sppt Eqpt
2.12   Air Vehicle        31.52    Airframe              10.72 Fuel
0.13   Engine               8.83   Engine                 0.92 Base Level Maint.
0.22   Offensive Avionics 2.31     Offensive Avionics    11.55 Depot Maint.
0.70   Launcher             2.18   Launcher               3.70 Updating/Mods
0.02   Training             0.17   Training               0.78 Replenish Spares
0.06   Special Support Eqpt 1.94   Special Support Eqpt   0.06 Vehicular Eqpt
0.47   Test & Evaluation    0.36   Test & Evaluation     12.61 Military Personnel
0.15   Project Management 0.07     Project Management     0.46 Civilian Personnel
0.13   Data                 0.15   Data                   1.29 Support Personnel
                            1.52   Initial Spares         2.23 Pipeline Costs
                                                                              9-14
Comprehensive Trade Study




                            9-15
          Principal Steps in Comprehensive
                     Trade Study



1. Identify Decision Criteria within Broad Decision Categories
2. Quantify Decision Criteria for Each Configuration
3. Analyze Customer Preferences for Each Decision Criterion
4. Assign Weights to Decision Criteria
5. Score Each Configuration (Sum Weights x Preferences)
6. Perform Sensitivity Analysis on Weights If Configuration
   Scoring Is Close




                                                                 9-16
9-17
9-18
9-19
                Sample Configuration Decision Categories

                               Air Vehicle

Effectiveness                     Cost                Risk

Threat Acquisition              Flyaway              Technical
   Avoidance
  Hit Avoidable              Weapon System             Cost
Given Acquisition
                               Procurement           Schedule
 Sortie Survival
   Given Hit
                           Program Acquisition     Producibility
Target Acquisition
                               Life Cycle          Supportability
   Target Kill
Given Acquisition
                                                   Management
 Kills per Sortie
  Targets Killed
   Over Time                                                        9-20
                Utility Functions - Preference Indicators

    • Utility Functions Provide a Good Technique for Translating Diverse
    Criteria Into a Common Scale. (i.e., Range in NMi, MTBF in Hours, etc.)
    • Utility Scores Range From 0 to 1 With 0 Being Least Preferred and 1
    Being Most Preferred.


     Examples

         Utility for Range                       Utility for MTBF
1                                       1




Threshold       Objective                   Threshold       Objective
    Range in MNi                                MTBF in hours

                                                                              9-21
                        Hints for Determining
                    the Shape of Utility Functions

                                     1
1   After Establishing the                      Critical,
    Minimum Requirements                       Risk Prone
    and Goal, Draw Neutral
                                                                 Non-Critical,
    Preference Position as
                                                                 Risk Average
    Shown                Neutral
                        Preference
                                         Req           Decision Factor      Goal

                                     1
2   Divide Decision Factor
    into Quartiles and
    Assess 25%, 50%, and
    75% Points Relative to
    Neutral Preference
                                         Req           Decision Factor      Goal
                                                                                 9-22
                 Sensitivity Analysis of
                Configuration Preferences


• Select Factor of Interest Such as Performance Range

• Increase Weight for Factor of Interest Until the Preferred
Alternative / Configuration Changes

• Incrementally Lower the Weight for Factor of Interest Until
the Preferred Alternative / Configuration Changes




                                                                9-23
                                    Exercise

Background: As system requirements are identified and flowed down form the
SDR, design options for the Group A hardware must be identified and trade
studies performed to determine the best design. Five design options have been
developed for Group A and have been evaluated by the AFS design team.
Documentation of this first pass design review by the team is presented below
and must now be used to select the best design in support of entrance criteria for
the program PDR.

Exercise: In order to limit the scope of this Exercise, the design trade study
will be restricted to the Aft Antenna and Radome assembly. Referring to the
Introductory Briefing material presented on the four subsequent charts, the
Statement of Customer Requirements Part 2, and the Aft Antenna/Radome
Functional Requirements Baseline, evaluate the designs provided and perform
a comprehensive trade study to select the best design.




                                                                                     9-24
              AJS Statement of Customer Requirements



Customer: Kurdish Fighter Program (Peace Whey)

Operational Need: Fighter aircraft operating in a hostile environment require
extensive electronic countermeasures (ECM) to defeat air-launched and ground-
launched threats to the survivability of the aircraft. These ECM systems must be
capable of generating and broadcasting radio frequency (RF) energy at sufficient
power levels and in appropriate patterns to defeat any threat encountered by the
aircraft.




                                                                               9-25
                AJS Statement of Customer Requirements
                                (Cont.)

Description: The AJS shall be capable of installation on a lightweight, high-speed,
multi-role fighter and shall be supportable in primitive forward operating bases. The
system shall be capable of transmitting radio frequency signal in the microwave
frequency range at sufficient power levels and in patterns capable of successfully
jamming all identified threats at the required operational range. The AJS system
shall consist of the following major components:

    1. Core Avionics: Shall consist of the jammer, the radar warning receiver, and
    the OFP software. Shall be capable of generating the required RF signal in the
    microwave band at required power levels and of detecting radar emissions from
    the threat set at the required ranges.
    2. RF Switch H/I/J Band: Shall control selection of broadcast frequency
    bands as required.
    3. Fire Control Radar Notch Filter: Shall prevent interference of the Fire
    Control Radar (FCR) by the AJS system.
    4. Forward Transmit Antenna
    5. Aft Transmit Antenna and Raydome
    6. WRD-650D24 Waveguide
    7. Coaxial Cable
                                                                                   9-26
              AJS Statement of Customer Requirements
                              (Cont.)

Schedule:

   1. Flight Test: The Safety of Flight(SOF) unit for flight test shall be
   available for installation 26 months after program go-ahead.
   2. First Production Delivery: The first production assembly shall be
   delivered 36 months after program go-ahead.
   3. Delivery Rate: Delivery of AJS units shall be at the rate of 2 units per
   month.
   4. Total Quantity: The total quantity of AJS units shall be 20.


Customer Priorities:
    1. Power Transmitted.
    2. Weight
    3. First production delivery.
    4. Cost not to exceed $125,000/unit (for 20 units).

                                                                                 9-27
9-28
9-29
                         Types of Radomes

    Types of Construction                   Uses and Advantages

• Solid-Wall Construction            • Narrow Frequency Band
  Laminated Glass Cloth/Resin        • High Strength
  or Filament Wound                  • Optimized Electrical
                                       Performance


• Sandwich-Wall Construction         • Broad Frequency Bandwith
  Laminated Glass Cloth/Resin        • Lightweight
  Impregnated Skin with Various
  Dielectric Cores




                                                                  9-30
            Extensive Testing of Antennas Confirms
             That Performance Will Be Achieved

Parameters Tested:

       - Electrical Requirements: Antenna Range
         1. Radiation Patterns and Gain
         2. Voltage Standing Wave Ratio (VSWR)
         3. RF Power Handling
         4. Antenna-to-Antenna Isolation

       - Environmental Requirements: Engineering Test Labs
         1. Vibration
         2. Temperature - Altitude
         3. Humidity
         4. Acoustical Noise
         5. Mechanical Shock



                                                             9-31
                 Airborne Jamming System (AJS)
               Statement of Customer Reqt.’s: Part 2

Performance:

  1. Frequency: The AJS shall provide performance over the frequency ranges
and angular pattern as represented in Table 1. The low-band transmission line
shall be coaxial cable. The high-band transmission line shall be double-ridge,
pressurized Waveguide of type WRD-650D24.
  2. RF Power Handling: The AJS, while operating in any combination of
temperature and pressure consistent with the aircraft operating envelope (as
shown in Figure 1), shall be capable of handling 1500 watts peak power in a
continuous transmit mode.
  3. Antenna Polarization: The transmit antennas shall be left-hand circularly
polarized.
  4. Antenna Gain: The gain for each antenna shall be as specified in Table 1
and Figure 2. The gain is defined as gain measured at the minimum level of the
axial ratio and is referenced to isotropic linear polarization.


                                                                             9-32
                 Airborne Jamming System (AJS)
               Statement of Customer Reqt.’s: Part 2

Environmental:

  1. The AJS total system shall be capable of operation at all points in the
aircraft flight envelope as specified in Figure 1.

 2. The antenna/radome assembly shall have a mean time between failures
(MTBF) of greater than 50,000 hours.




                                                                               9-33
9-34
9-35
9-36
9-37
9-38
9-39
9-40
9-41
                          Exercise # 4
                       Option 1 Risk Issues


Risk Issues:   Very good chance additional heat sink capacity will be
               needed to sustain power rating. This creates .4 pound of
               weight risk. Schedule risk is assessed as low.




                                                                          9-42
9-43
9-44
                             Exercise # 4
                          Option 2 Risk Issues


Risk Issues:       Low system weight achieved through use of spiral antenna
impacts power handling capability and gain. Design of antenna mounting
hardware results in predicted failure of vibration and acoustic loading spec
due to resonant response within frequency envelope. Structural design
changes required to meet vibration and acoustic specs result in a highly
likely probability that the total assembly weight will add 1 pound of weight,
exceeding spec. There is also a better than even chance that two additional
calendar months design/development time will impact delivery of SOF
hardware.




                                                                                9-45
9-46
9-47
                             Exercise # 4
                          Option 3 Risk Issues


Risk Issues:       Slightly higher-than-spec gain in the high band is due to
an improved dielectric currently under development. The risk of additional
development and testing costs resulting in a assessment of a probable AJS
system cost increase per unit of +3%. There is an unlikely probability the
qual test requirements could impact the SOF hardware delivery schedule,
but this is assessed as low risk.




                                                                               9-48
9-49
9-50
                            Exercise # 4
                         Option 4 Risk Issues


Risk Issues:      Design Option 4 includes a solid-wall radome, normally
used with narrow-bandwidth systems. Potential severe internal heat loads
could result from RF energy reflection from the radome. Performance risk is
assessed as highly likely to reduce power handling capability by .5 watt.




                                                                              9-51
9-52
9-53
                             Exercise # 4
                          Option 5 Risk Issues


Volume:               Design consistent with available installation volume
Predicted Unit Cost: $19,460
Risk Issues:       Option 5 includes a pressurized radome to achieve an
operational altitude greater than required by the specs. However, this design
has a history of pressure leak problems. Loss of pressure could result in
arcing and system damage impacting performance and reliability. Upgrade
to seals and increased leak testing would require additional cost and test
time. Assessment indicates probable additional costs would increase AJS
unit cost by 10%.




                                                                                9-54
Option 1

Decision Criteria    W eighting Factor Grade   Score       Comments

Antenna Gain High                                      0
Antenna Gain Low                                       0
VSW R High                                             0
VSW R Low                                              0
Axial Ratio                                            0
Power Handling                                         0
Operating Envelope                                     0
Flight Loads                                           0
Vibration                                              0
Acoustic Loads                                         0
W eight                                                0
Volume                                                 0
RMSS                                                   0
Predicted Cost                                         0
Performance Risk                                       0
Schedule Risk                                          0
Cost Risk                                              0

Total                                                  0

Option 2

Decision Criteria    W eighting Factor Grade   Score       Comments

Antenna Gain High                                      0
Antenna Gain Low                                       0
VSW R High                                             0
VSW R Low                                              0
Axial Ratio                                            0
Power Handling                                         0
Operating Envelope                                     0
Flight Loads                                           0
Vibration                                              0
Acoustic Loads                                         0
W eight                                                0
Volume                                                 0
RMSS                                                   0
Predicted Cost                                         0
Performance Risk                                       0
Schedule Risk                                          0
Cost Risk                                              0

Total                                                  0

Option 3

Decision Criteria    W eighting Factor Grade   Score       Comments

Antenna Gain High                                      0
Antenna Gain Low                                       0
VSW R High                                             0
VSW R Low                                              0
Axial Ratio                                            0
Power Handling                                         0
Operating Envelope                                     0
Flight Loads                                           0
Vibration                                              0
Acoustic Loads                                         0
W eight                                                0
Volume                                                 0
RMSS                                                   0
Predicted Cost                                         0
Performance Risk                                       0
Schedule Risk                                          0
Cost Risk                                              0

Total                                                  0


                                                                      9-55
See Trade Study Example
        (Excel)




                          9-56

				
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