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NASA CONTRACTOR REPORT 166274 NASA-CR-166274 19830001759 Investigation of Advanced Navigation and Guidance System Concepts for All-Weather Rotorcraft Operations H. W. Upton G. E. Boen J. Moore CONTRACT NAS2-1 0743 August 1982 (~ .:.;... ! i-.1 ?-..: ' j 19B? .. ~... \. ~ LANGLEY R;::SEARr:H CENTER L!2RP.RY. NASA NJ\S/\ HN.:?TON, VIRGINIA ~(IIIIIIIIIIII 1111 11111 11111111111111111111111 NF02336 NASA CONTRACTOR REPORT 166274 Investigation of Advanced Navigation and Guidance System Concepts for All-Weather Rotorcraft Operations H. W. Upton G. E. Boen J. Moore Bell Helicopter Textron Fort Worth, Texas Prepared for Ames Research Center under Contract NAS2-l0743 NI\S/\ National Aeronautics and Space Administration Ames Research Center Moffett Field. California 94035 This Page Intentionally Left Blank PREFACE This investigation of Advanced Navigation and Guidance System Concepts for All-Weather Rotorcraft Operations has been con ducted. under National Aeronautics and Space Administration Contract No. NAS2-10743. Gratitude is expressed for the guidance and assistance of Messrs. William Snyder, John Foster, and John Bull, NASA-Ames, and also to the· BHT employees who aided in the investigation and preparation of this report. 1 I J iii This Page Intentionally Left Blank TABLE OF CONTENTS PREFACE. iii LIST OF FIGURES. viii LIST OF TABLES . xi SUMMARY. 1 1. INTRODUCTION. 3· 2. SURVEY ..... 5 2.1 MAJOR FINDINGS . 5 2.2 IFR QUESTIONNAIRE ANALYSIS . 7 2.2.1 Company Related . 7 2.2.2 Aircraft and Equipment Related. 7 2.2.3 Mission Related . 9 2.2.4 Agency .... 11 2.2.5 Facilities .. 11 2.3 INTERVIEW COMMENTS 12 3. MISSION MODEL . 14 3.1 VISIBILITY MINIMUMS. 14 3.2 MODEL ..... 15 3.2.1 Landing and Takeoff sites . 15 3.2.2 Mission Segments. .. 16 3.2.3 Mission Segment Description . 16 . 4. SYSTEM DEFINITION . 20 4.1 BASELINE AIRCRAFT .. 20 4.2 SYSTEM REQUIREMENTS .. 20 4.2.1 Guidance and Control. 20 4.2.2 Area Navigation . 30 4.2.3 Terminal Area Navigation and Heliport Requirements . 35 4.2.4 Display Requirements ...... 39 4.2.5 Air Traffic Control Requirements .. 42 v TABLE OF CONTENTS (Continued) Page 4.2.6 System State of the Art . 43 4.2.7 Advanced Technology Considerations. 44 4.2.8 Regulatory Agency Considerations .... 44 4.2.9 Cost. .. .... 45 4.3 CANDIDATE SYSTEMS ... 45 4.3.1 Controls. 45 4.3.2 Area Navigation Systems . 49 4.3.3 Comparison of Area Navigation Systems 66 4.4 TERMINAL NAVIGATION AND APPROACH SYSTEMS . 70 4.4.1 Radar . 70 4.4.2 Television and FLIR . 105 4.4.3 Microwave Landing Systems (MLS) 108 4.4.4 Lighting ........ 112 4.4.5 Microwave Passive Reflectors .. 113 4.4.6 Obstacle Detection and Avoidance ... 115 4.4.7 Image Enhancement and Map Matching. 117 4.4.8 Comparison of Terminal Navigation and Approach Systems .... 120 5. FEASIBILITY ANALYSIS ......... 123 5.1 ALLOWABLE ERROR ...... 123 5.2 APPROACH SYSTEM FEASIBILITY. 128 5.2.1 GPS Terminal Navigation and Approach Feasibility.. ... 128 5.2.2 Radar Terminal Navigation and Approach Feasibility. 130 5.3 SAFETY CONSIDERATIONS ... 138 5.4 RECOMMENDED SYSTEMS .... 141 5.4.1 Category III Zero-Visibility System 141 5.4.2 Category II 30.4m (100-foot) Minimum Ceiling System. 142 5.5 OPERATIONAL LIMITATIONS ...... 146 vi TABLE OF CONTENTS (Concluded) Page 5.6 REQUIRED TECHNICAL DEVELOPMENTS. 147 5.6.1 System Developments . 147 5.6.2 Radar Development . 148 5.6.3 GPS Development . 149 5.6.4 Simulation of Approach using Radar and GPS Displays ........... 149 5.7 SYSTEM COSTS . · · · · · · · · 151 I 1 5.7.1 Light Helicopters . · · 152 5.7.2 Medium Helicopters. · · · · · · 152 5.7.3 Large Helicopters . · · · · 152 1 5.7.4 Radar Costs . · · · 152 I · · · .. , 5.7.5 Cost Summary. · · · · · 154 6. CONCLUSIONS . 156 APPENDIX A.. 158 REFERENCES .. 188 ABBREVIATIONS AND ACRONYMS .. 194 \ t APPENDIX B.. 196 j .. vii LIST OF FIGURES Figure 1 Envelope of autorotation characteristics (IFR certificated helicopters, sea level, standard day) . 22 2 Typical height velocity curve 23 3 Relationship between control display sophistication. ... 28 4 Optical attenuation due to fog and clouds . 33 5 Radio frequency attenuation due to clouds, fog, and rain . .. ..... 34 6 Boston Aerospace utilization at 500 feet MSL. 36 7 Obstacle clearance approach angles. 36 8 Effect of flight path control on noise footprint.. 37 9 Imaginary surface for heliports 38 10 Control system block diagram. 47 11 Near-term Loran-C coverage. 51 12 Resolution elements required for landing site detection. 71 13 Helicopter airborne radar approach plate. 74 14 Oil rig targets on weather radar display on final approach . 75 15 Maximum radar range vs rain rate. 78 16 Attenuation vs frequency 25 mm/hr precipitation 79 17 . Range vs frequency with/without precipitation 79 18 Rotor radar typical antenna pattern . 80 viii LIST OF FIGURES (Continued) Figure Page 19 HELMS rotor radar antenna 82 20 HELMS approach to airport · · · · 83 21 HELMS approach mode concept . · · · · 84 22 Ground intercept range circle HELMS display · 84 23 HELMS approach with expanding scale display 85 24 HELMS hooded approach results · · · · · · · · 86 25 HELMS approach to open field. 87 26 HELMS hooded navigation test results .. 89 27 British rotor blade trailing edge blade antenna 91 28 Flight 23 24 4 78 Southampton water fawlly jetties . 92 29 Flight 39 28 November 78 over Charing Cross 93. 30 Radar and dish antenna on rotor hub . 93 31 Linear array antenna on rotor hub . 95 32 Antenna blade mount concepts ... 96 33 Linear array in blade root. 100 34 Transmissivity vs range 8-14 micron spectral region . 107 35 Passive reflector glide slope indicator · 114 36 Microwave and laser rain attenuation. · 117 37 Sketch of final approach path · · · · 126 38 Sketch of final approach segment with calculated allowable error and sensor errors · · · · · · . 127 ix LIST OF FIGURES (Concluded) Figures 39 Z-Set field test results - position errors. 129 40 Advanced Navigation and Guidance System B (high resolution radar primary) . 143 41 Advanced Navigation and Guidance System A (GPS primary) . ~ 144 x LIST OF TABLES Table 1. Quantitative Navigation Requirements Summary . .. 24 2 System Failure Effects. 48 3 LORAN-C Error Compared with AC 90-45A Requirements ............ 52 4 LORAN-C Navigation Accuracy in Northeast Corridor. 53 5 Navigation Sensor Error Performance . 53 6 Calculated GPS Performance Summary. 59 7 FAA Navigation System Accuracy Standards .. 59 8 Composite Performance Comparison of Modern Ra~io Navigation Systems . 67 9 Ratings for Area Navigation Systems for On-Board System . 69 10 HELMS High Resolution Radar Characteristics . 81 11 Rotor Blade Radar . 90 12 Comparison of MM and X Band Rotor Blade Radar . 103 13 MPSBLS Equipment Specifications . 110 14 Ratings of Terminal Navigation and Approach System for On-Board System. 122 15 Terminal Area Navigation and Approach Requirements. 125 16 Levels of Redundancy ........ 139 17 Failure Effects - Category III System 140 18 Category III Major System Components. 141 19 Category II Major System Components . 142 xi SUMMARY This study of Advanced Navigation and Guidance Systems for Rotary Wing Aircraft investigates the requirement for all weather operations for rotary wing aircraft and the technical and cost feasibility of several advanced systems. A survey of commercial operators was conducted in which it was found that there is strong interest in improved Instrument Flight Rule (IFR) operations with the average desiring 30.Sm (100 foot) minimum ceiling and 0.4 Km (1/4 mile) visibility. Both IFR and non-IFR operators indicated that present regu latory weather minimums for sites which they operate into . average 9lm (300 foot) ceilings and 0.8 km (1/2 mile) visi bility. 1 i It was also indicated that the operators would pay an average of 7 percent of aircraft cost to achieve lower IFR limits. An analysis of the problems of operating in 30.Sm (100 foot) ceiling and 0.4km (1/4 mile) visibility was made. The ina bility of obtaining accurate data on very low visibility conditions, especially at remote sites, led to a recommendation for designing a system for zero-visibility operation. A mission model was then constructed to represent the modes of flight normally encountered in a mission representative of operation in these visibility limits. Candidate systems were then examined for capability to meet the requirements of the mission model. It was then determined that in addition to the requirement for area navigation, terminal area navigation, and approach that it was critical to the mission to have good low-speed handling qualities on approach. The most promising terminal navigation systems were found to be LORAN-C and Differential CIA code GPS with neither system having capability of precision approach in zero-visibility. The most promising terminal navigation system and the only system that shows good promise for precision approach to a remote, restricted site in zero-visibility is high resolution X-band radar, probably using a rotor-mounted antenna. Two principal systems are recommended. The first is for approaches to a hover in zero-visibility based on LORAN-C, high-resolution radar and a dual-redundant fail-safe control system with good low-speed handling qualities. The system also contains advanced pictorial-type displays. 1 The second recommended system for 30.Sm (100 feet) minimum ceiling operation is based on using the"Differential CIA Code GPS with a navigation computer, advanced displays, and a dual redundant fail-safe control system. A third system, recommended for 30.Sm (100 feet) minimum ceiling and 0.4 km (1/4 mile) visibility, uses a monopulse beam-sharpening technique to improve tracking accuracy of the weather radar. The system would be aided by strong lights on the landing site .. Recommendations are made for development of the high resolu tion radar, simulation of the control display system for steep approach and landing, and for development of an obstacle .