9-1 Trade Study Methods. 9-2 Types of Trade Studies Controlled Convergence - Preliminary Method Used by Engineering. Quick Method to Compare “Primitive”

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Trade Study MethodsTrade Study Methods

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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

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Time Frames For Trade Study Methods

Concept & Technology

Development

System Development & Demonstration

Production & Deployment

Operations & Support

APre Concept & Tech Dev B C

-Controlled Convergence-

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

--Comprehensive--

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Controlled Convergence Trade Study

Controlled Convergence Trade Study

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Steps in Applying ControlledConvergence 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

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Controlled Convergence Method ForPreliminary Trade Studies

Design Alternatives

ComparisonCriteria(Design Primatives)

Thrust/Weight (T/W)Weight/Wing Ref. Area (W/S)Coef. of Lift (C )Cruise Performance (Specific fuel consumption, range, speed)Observables (Shaping, materials, propulsion, etc.) Payload CapacityAgility (maneuverability & controllability)

SSSS

S

SS

–––S

S

–+

S–++

+

++

–+–S

S

––

++–+

–

S+

TOTAL +'sTOTAL S'sTOTAL –'s

070

124

511

214

412

Legend+ Significantly BetterS About the Same– Significantly Worse

1 2 3 4 5(Baseline)

L

...

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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

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Cost-Effectiveness Trade Study

Cost-Effectiveness Trade Study

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Alternative Configuration Scoring Methods

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Life Cycle Cost Composition

BV41861

WEAPON SYSTEM COST

• Tech Data• Publication• Contractor Service• Support Equipment• Training Equipment• Factory Training

• Management• Hardware• Software• Nonrecurring "Start-up"• Allowance for Changes

FLYAWAY COST

PLUS PLUSPLUSPLUS• Initial

Spares• RDT&E• Facility Construction

• Operations & Support (Includes Post-Produc- tion Support)

• Disposal

PROCUREMENT COST

PROGRAM ACQUISITION COST

LIFE CYCLE COST

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Cost Estimating Methods UsedDuring Acquisition Phases

Parametric

Analogy

Bottom-Up Eng.

Pre Concept & Tech. Dev.

Early in System Dev. & Demonstration

Prod. & Dep.

P

S

N/A

S

P

S

S

S

P

N/A

N/A

P

N/A

N/A

P

P = PrimaryS = Secondary

Early in System Dev. & Demonstration

Concept & Tech. Dev.

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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/Validation2.12 Air Vehicle0.13 Engine0.22 Offensive Avionics0.70 Launcher0.02 Training0.06 Special Support Eqpt0.47 Test & Evaluation0.15 Project Management0.13 Data

0.59 Tooling & Engineering 31.52 Airframe 8.83 Engine 2.31 Offensive Avionics 2.18 Launcher 0.17 Training 1.94 Special Support Eqpt 0.36 Test & Evaluation 0.07 Project Management 0.15 Data 1.52 Initial Spares

1.74 Replenish Sppt Eqpt10.72 Fuel 0.92 Base Level Maint.11.55 Depot Maint. 3.70 Updating/Mods 0.78 Replenish Spares 0.06 Vehicular Eqpt12.61 Military Personnel 0.46 Civilian Personnel 1.29 Support Personnel 2.23 Pipeline Costs

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Comprehensive Trade Study

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Principal Steps in ComprehensiveTrade 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

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Sample Configuration Decision Categories

Air Vehicle

Effectiveness Cost Risk

Threat AcquisitionAvoidance

Hit AvoidableGiven Acquisition

Sortie Survival Given Hit

Target Acquisition

Target KillGiven Acquisition

Kills per Sortie

Targets KilledOver Time

Flyaway

Weapon System

Procurement

Program Acquisition

Life Cycle

Technical

Cost

Schedule

Producibility

Supportability

Management

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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.

Range in MNi MTBF in hoursThreshold Objective

1 1

Examples

Utility for Range Utility for MTBF

Threshold Objective

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Hints for Determiningthe Shape of Utility Functions

After Establishing theMinimum Requirementsand Goal, Draw NeutralPreference Position asShown Neutral

Preference

1

2 Divide Decision Factorinto Quartiles and Assess 25%, 50%, and 75% Points Relative toNeutral Preference

Req Decision Factor Goal

Req Decision Factor Goal

1

1

Critical,Risk Prone

Non-Critical,Risk Average

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Sensitivity Analysis ofConfiguration 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

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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.

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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.

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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 Antenna5. Aft Transmit Antenna and Raydome6. WRD-650D24 Waveguide7. Coaxial Cable

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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.

AJS Statement of Customer Requirements(Cont.)

Customer Priorities:1. Power Transmitted.2. Weight3. First production delivery.4. Cost not to exceed $125,000/unit (for 20 units).

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Types of Radomes

Types of Construction Uses and Advantages

• Solid-Wall Construction Laminated Glass Cloth/Resin or Filament Wound

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

• Narrow Frequency Band• High Strength• Optimized Electrical Performance

• Broad Frequency Bandwith• Lightweight

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Extensive Testing of Antennas ConfirmsThat 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

9-32

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.

9-33

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.

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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.

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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.

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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.

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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.

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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%.

9-55

Option 1

Decision Criteria Weighting Factor Grade Score Comments

Antenna Gain High 0Antenna Gain Low 0VSWR High 0VSWR Low 0Axial Ratio 0Power Handling 0Operating Envelope 0Flight Loads 0Vibration 0Acoustic Loads 0Weight 0Volume 0RMSS 0Predicted Cost 0Performance Risk 0Schedule Risk 0Cost Risk 0

Total 0

Option 2



Total 0

Option 3



Total 0

9-56

See Trade Study Example (Excel)

Documents

9-1 Trade Study Methods. 9-2 Types of Trade Studies Controlled Convergence - Preliminary Method Used by Engineering. Quick Method to Compare “Primitive”