FIGHTER AGILITY METRICS, RESEARCH, AND TEST PHASE I REPORT KU-FRL-831-2 by: Randall K. Liefer, John Valasek and David P. Eggold Supervised by: Dr. David R. Downing THE UNIVERSITY OF KANSAS CENTER FOR RESEARCH, INC. Flight Research Laboratory Lawrence, Kansas ABSTRACT Proposed new metrics to assess fighter aircraft agility are collected and analyzed. A framework for classification of these new agility metrics is developed and applied. A complete set of transient agility metrics is evaluated with a high fidelity, nonlinear F-18 simulation provided by the NASA Dryden Flight Research Center. Test techniques and data reduction methods are proposed. A method of providing cuing information to the pilot during flight test is discussed. The sensitivity of longitudinal and lateral agility metrics to deviations from the pilot cues is studied in detail. The metrics are shown to be largely insensitive to reasonable deviations from the nominal test pilot commands. Instrumentation required to quantify agility via flight test is also considered. With one exception, each of the proposed new metrics may be measured with instrumentation currendy available. Simulation documentation and user instructions are provided in an appendix. Table of Contents Abstract ............................................. i Table of Contents ...................................... ii List of Figures ......................................... vi List of Tables ......................................... ix List of Abbreviations .................................... x 1. Introduction ........................................ 1 1.1 Background of Agility ........................... 1 1.2 Current State of Agility .......................... 3 1.3 Objectives of this Project ......................... 5 2. Problem Definition ................................... 8 2.1 Summary of Traditional Metrics .................... 8 2.2 Published Agility Metrics ......................... 18 Transient, Functional, Potential ............... 20 Lateral, Pitch, Axial ....................... 22 ii 2.3 Vehicle Description (F-18 HARV) and Simulation Overview .......................... 25 2.4 Simulation Plan ................................ 31 3. Simulation Study .................................... 33 3.1 Axial Agility .................................. 33 3.1.1 Introduction ............................ 33 3.1.2 Axial Agility Metrics ...................... 33 3.1.3 Power Onset and Power Loss Parameters ........ 34 3.1.4 Axial Agility Test Case Description ............ 36 3.1.5 Axial Agility Data Reduction Methods .......... 41 3.2 Pitch Agility .................................. 45 3.2.1 Introduction ............................ 45 3.2.2 Published Pitch Agility Metrics ............... 47 3.2.3 Pitch Rate versus Angle of Attack Metric ........ 58 3.3 Lateral Agility ................................. 62 3.3.1 Introduction ............................ 62 3.3.2 Time-to-90 Metric ........................ 66 3.3.3 Test Method ............................ 69 3.3.4 Data Reduction and Analysis ................ 71 ooo ILl 3.3.5 Simulation Results ........................ 72 4. Flight Test Issues .................................... 76 4.1 Background .................................. 76 4.2 Analysis of Cuing Method ........................ 79 4.3 Sensitivity to Cue Following Errors .................. 81 4.3.1 Sensitivity of Pitch Agility Metrics ............. 81 4.3.2 Sensitivity of Lateral Agility Metrics ........... 92 4.4 Instrumentation for Agility Flight Testing .............. IX 5. Summary .......................................... 10l 5.1 Conclusions .................................. 105 5.2 Recommendations for Further Research ............... l(I) 6. References ......................................... 111 Appendices A. Specific Excess Power (P_) ........................ 116 B. Published Agility Metrics ......................... III C. Simulation Documentation ......................... 142 C.1 Introduction ............................. 142 C.2 Capabilities and Models ..................... 144 C.2.1 Aerodynamics ...................... 144 C.2.2 Flight Control System ................ 145 iv C.2.3 Actuators ......................... 145 C.2.4 Equations of Motion ................. 146 C.2.5 Integration Method .................. 146 C.2.6 Multi-Rate Calculations ............... 146 C.2.7 Autopilot Modes .................... 147 C.3 Program Organization ...................... 147 C.4 User Instructions .......................... 170 C.5 Check Case Comparisons .................... 172 ¥ List of Figures 2.1 T-38 V-n Diagram .................................. 12 2.2 Typical Ps Diagram for a Single Aircraft ................... 14 2.3 Differential Ps Plot .................................. 15 2.4 Turn Rate, Turn Radius Relationships ..................... 16 2.5 F-5E Turn Performance ............................... 17 2.6 Proposed Classification Framework ....................... 24 2.7 F- 18 Physical Characteristics ........................... 26 2.8 Simulation Flow Diagram ............................. 30 3.1 Axial Acceleration Example, Mach .6, Sea level .............. 37 3.2 Axial Acceleration, Mach .4 - .9, Sea level ................. 38 3.3 Axial Deceleration Example, Mach .6, Sea Level ............. 39 3.4 Axial Deceleration, Mach .4 - .9, Sea Level ................. 40 3.5 Power Onset Parameter ............................... 43 3.6 Power Loss Parameter ................................ 44 3.7 Maximum Pitch Up Time History ........................ 48 3.8 Time to Pitch to Maximum Load Factor ................... 50 3.9 Time to Pitch From Maximum to Zero Load Factor ........... 51 3.10 Maximum Load Factor Rate ........................... 52 3.11 Minimum Load Factor Rate ........................... 53 vi 3.12 Maximum Pitch Rate from Steady Level Flight ............. 55 3.13 Max Neg. Pitch Rate During Unload ..................... 56 3.14 Maximum Pitch Rate Capability at 15,000 ft ............... 59 3.15 Minimum Pitch Rate Capability at 15,000 ft ................ 60 3.16 Kinematics of a Loaded Roll .......................... 63 3.17 Body Axis Rates for Stability Axis Roils .................. 67 3.18 Control Time History for a Typical TgoManeuver ............ 70 3.19 Time to Capture • = 90* at 15,000 ft .................... 73 3.20 Time to Capture • = 90* at 30,000 ft .................... 74 4.1 Time to Max Load Factor Error Sensitivity, 15,000 ft .......... 84 4.2 Pitch Up Load Factor Rate Error Sensitivity, 15,000 ft ......... 86 4.3 Nose Up Pitch Rate Error Sensitivity, 15,000 ft .............. 87 4.4 Time to Zero Load Factor Error Sensitivity, 15,000 ft .......... 89 4.5 Pitch Down Load Factor Rate Sensitivity, 15,000 ft ........... 90 4.6 Nose Down Pitch Rate Error Sensitivity, 15,000 ft ............ 91 4.7 Stick Deflections for Typical TgoManeuver ................. 92 4.8 TgoError Sensitivity, Mach .4, 15,000 ft .................... 95 4.9 TgoError Sensitivity, Mach .5, 15,000 ft .................... 96 4.10 Tg0Error Sensitivity, Mach .6, 15,000 ft .................. 97 4.11 TgoError Sensitivity, Mach .7, 15,000 ft ................... 98 vii 4.12 T9oError Sensitivity, Mach .8, 15,000 ft .................. 99 A.1 Flight Path Geometry for Accelerated Climb ................ 118 B.1 Relative Energy State ................................ 129 B.2 Concept of Combat Cycle Time ......................... 132 B.3 Def'mition of Pointing Margin .......................... 133 B.4 Dynamic Speed Turn Plots ............................ 135 C.1 Generalized Simulation Flow Diagram .................... 148 C.2 Detailed Simulation Wiring Diagram ..................... lff_ C.3 Sample Input File for SIM 2 ........................... 171 C.4 Longitudinal Check Case, Mach .6, 10,000 ft ................ 173 C.5 Longitudinal Check Case, Mach .8, 35,000 ft ................ 175 C.6 Longitudinal Check Case, Mach .9, Sea Level ............... 177 C.7 Lateral Check Case, Mach .4, 20,000 ft .................... 179 C.8 Lateral Check Case, Mach .6, 10,000 ft .................... 181 C.9 Lateral Check Case, Mach .8, 35,000 ft .................... 183 C.10 Lateral Check Case, Mach .9, Sea Level .................. 185 ,oo Vlll List of Tables 2.1 Typical Wing Loading and Thrust to Weight Ratios ........... 10 4.1 Deviations for Pitch Sensitivity Tests ..................... 83 4.2 Deviations for Lateral Sensitivity Tests .................... 94 C.1 SIM 2 Initialization Sequence .......................... 163 C.2 Dynamic Loop Sequence for One Frame ................... 164 C.3 Common Simulation Variables .......................... 1(:5 ix List of Abbreviations Nondimensional variation of rolling moment with control surface El 8 deflection Nondimensional variation of pitching moment with control surface Cm 8 deflection CAS Control Augmentation System E Total mechanical energy E, Specific mechanical energy D Drag FCS Flight Control System HARV High Angle of Attack Research Vehicle HQDT Handling Qualities During Tracking Moment of inerfias about X, Y and Z axes Ixz XZ product of inertia Ls Dimensional variation of rolling moment with control surface deflection MBB Messershcmitt-BSlkow-Blohm Ms Dimensional variation of pitching moment with control surface deflection Ps Specific Excess Power R Turn Radius X S Reference wing area Time to capture 90 ° bank angle change T/W Thrust to weight ratio TR Turn rate V Velocity V/Vc Relative Energy State W Weight WVR Within Visual Range W/S Wing Loading b Wing span Mean aerodynamic chord g Acceleration due