Alternative Obstacle Clearance Criteria for RNP RNAV Instrument Approaches

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© 2004 The MITRE Corporation. All Rights Reserved. Alternative Obstacle Clearance Criteria for RNP RNAV Instrument Approaches S.V. ※Vince§ Massimini, DSc Frederick A. Niles April 2004 2 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Obstacle Clearance Surfaces (OCSs) Instrument Landing System (ILS) 3 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. OCSs for ILS 4 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Vertical OCSs Not to Scale 200' Touchdown Elevation - 954' 2,379' 1,237' 7,983' 3 Glide slope o 185' HAT 250' HAT 668' HAT 954' 1,154' 3,533' 4,770' 12,753' 34:1 ILS/GLS 5 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Determining Visibility Minima HAT = 326 ft Glide Slope = 3º Threshold Crossing Height = 50 ft 954 ft 5280 ft = 1 sm 3960 ft=3/4 sm HAT = 257 ft 1. Determine Height Above Touchdown (HAT) from OCS 2. Determine visibility from distance of HAT point to runway threshold 3. Approach lights can affect visibility Not to Scale 6 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Wide Area Augmentation System (WAAS) GPS Satellites Communication Satellite (with WAAS transponder) Ground Earth Stations Wide Area Master Station Wide Area Reference Station GPS WAAS Correction Terms, Integrity Data GPS-Like Signals 7 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Local Area Augmentation System (LAAS) Global Positioning System VHF Data Broadcast LAAS Differential Receiver Stations Correction Terms, Integrity Data LAAS Differential Transmitter Station GPS Satellites GPS Satellites Surveyed Antenna All elements sited on airport property Local Area Augmentation System GPS/LAAS User Equipment 8 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. GPS/WAAS/LAAS Approaches Area Navigation (RNAV) Approaches • WAAS intent has been to provide several levels of service for instrument approaches 每 Lateral Navigation (LNAV) • No vertical guidance (Non-precision Approach) 每 Lateral/Vertical Navigation (LNAV-VNAV) and Barometric/Vertical Navigation (BARO-VNAV) • Comparable performance to NPA lateral guidance and vertical guidance using barometric altimeter • Requires WAAS or GPS-BARO/VNAV (no DME/DME in USA) • Best theoretical HAT is 250 ft (rarely attained) 每 LPV • ※Near CAT I service§ • Best LPV minima: 250 ft HAT 9 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. GPS/WAAS/LAAS Approaches (Concluded) • LAAS (and future WAAS with dual frequency) 每 GNSS Landing System (GLS) • Equivalent of ILS CAT I • Best GLS/ILS Cat. I minima: 200 ft HAT LNAV/BARO-VNAV 350＊ LPV-1 250＊ GLS/ILS 200＊ 3o 10 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Display Sensitivity of GLS/LPV Approaches MAWP Not to scale Reference: DO 229C (WAAS MOPS) 11 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. RNAV OCSs • Although the navigation error is generally constant throughout the approach for RNAV systems, the increase in display sensitivity results in progressively smaller total errors as the aircraft approaches the runway/NAVAID • Resultant RNAV OCSs are 每 GLS: Identical to ILS 每 LPV (APV I): • Horizontal is identical to ILS • Vertical is more conservative (closer to ground) to account for reduced vertical integrity 12 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. RNP RNAV • RNP RNAV has potential benefits in the oceanic, en route, terminal, and approach domain 每 RNP-10 implemented in oceanic airspace • Reduced route separation 每 RNP approaches developed at some airports in Alaska • Significant airport access benefits attained • Focus of this discussion will be the final approach segment 13 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. RNP RNAV Approaches • RNP RNAV assumes constant display sensitivity and constant navigational errors 每 Nearly constant total flight errors approaching the runway • Currently use BARO-VNAV vertical profile 每 Other profiles are under investigation • RNP-.3 can be flown with GPS, WAAS, or LAAS avionics 每 RNP-.3 using DME/DME currently not authorized in USA • RNP RNAV below .3 will require Special Aircraft and Aircrew Authorization Required (SAAAR) 每 Additional certification, equipment, and training 14 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. 2 x RNP Primary Area each side of centerline 1 x RNP Secondary Area 1 x RNP Secondary Area 1 x RNP 1 x RNP 2 x RNP 2 x RNP Required Navigation Performance (RNP RNAV) Not to Scale © 2004 The MITRE Corporation. All Rights Reserved. The GPS Approach Minima Estimator (GAME) Model 16 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. GAME Objectives • Computer model developed to provide objective estimates of benefits of IAPs • Digital airport, terrain and obstacle data • Simplified approach design criteria 每 Straight-in approach with five mile final • No intermediate segment • Variable glide-slope possible, but only 3 degrees slope presented 每 Missed approach only for GLS/ILS • Simplified missed approach 17 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. GPS Approach Minima Estimator (GAME) Model Minima Estimation Software Repeat for Thousands of Runway Ends Approach Design Criteria Generate Statistics 0 500 1000 1500 2000 2500 -0.5 -0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75 LNAV/VNAV Visibility - LNAV Visibility (sm) Terrain Data Base Obstacle Data Base Airports Data Base 18 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. GAME Airports: 1534 airports and 5073 runway ends CONUS: 1429 Alaska: 104 Hawaii: 1 19 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Instrument Approach HATs 0 500 1000 1500 2000 2500 3000 200 (.75) 250-257(.75) 258-327 (1.0) 328-395 (1.25) 396-465 (1.5) 466-534 (1.75) 535-603 (2.0) 604-740 (2.25) More Obs tacle s Prevent HAT (ft) (No-light Visibility (sm)) Number of Runways GLS/ILS LPV LNAV/VNAV RNP .3 RNP .1 20 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Observations • ILS, GLS, and LPV dominate the lowest visibility minima • Even RNP RNAV with SAAAR has increased approach minima at most runways relative to ILS/GLS/LPV 每 Some runways will exhibit improved minima • E.g., Runways in Alaska noted previously 每 Despite additional certification, equipment and training requirements • Why do the RNP RNAV approaches show reduced benefits? 每 Investigate effect of removing secondary areas from OCSs 每 Investigate effect of curved approaches (short finals) • 3 nm length of final 21 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. RNP-.3 and LNAV/VNAV-BARO/VNAV With Secondary Areas + .6 nmi wide .3 nmi wide LNAV/VNAV Primary and Secondary Areas RNP-.3 Primary and Secondary Areas 22 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. RNP-.3 and LNAV/VNAV-BARO/VNAV No Secondary Areas + .6 nmi wide LNAV/VNAV Primary and Secondary Areas RNP-.3 Primary Area 23 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Effect of Secondary Areas 0 500 1000 1500 2000 2500 200 (.75) 250-257(.75) 258-327 (1.0) 328-395 (1.25) 396-465 (1.5) 466-534 (1.75) 535-603 (2.0) 604-740 (2.25) More Obstacles Prevent HAT (ft) (No-light Visibility (sm)) Number of Runways RNP .3 RNP .3 No Secondary RNP .1 RNP .1 No Secondary 24 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Effect of Short Finals (Curved Approaches) 0 500 1000 1500 2000 2500 200 (.75) 250-257(.75) 258-327 (1.0) 328-395 (1.25) 396-465 (1.5) 466-534 (1.75) 535-603 (2.0) 604-740 (2.25) More Obstacles Prevent HAT (ft) (No-light Visibility (sm)) Number of Runways RNP-.3 Short Final RNP-.3 Normal Final RNP-.1 Short Final RNP-.1 Normal Final 25 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Observations • Removal of secondary areas and use of short finals has some effect at some runways, but RNP RNAV performance is still not comparable to ILS, GLS or LPV • Why? 26 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. ILS/GLS/LPV ----- RNP-.1 ----- -5000 -3000 -1000 1000 3000 5000 0 6000 12000 18000 Distance from RWT (ft) Distance from C/L (ft) Distribution of Controlling Obstacles 5000+ LNAV/VNAV Approaches 27 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Narrow RNP RNAV OCSs • Suppose we narrow the RNP RNAV OCS significantly • Example: 每 ILS/GLS/LPV OCS is + 400 ft wide near the runway threshold 每 Let 2 x RNP = 400 ft 􀃎 RNP = 200 ft/6076 ft/nm = .033 nm • No secondary areas 2 x RNP Not to Scale 28 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Effect of RNP-.033 0 500 1000 1500 2000 2500 3000 200 (.75) 250-257(.75) 258-327 (1.0) 328-395 (1.25) 396-465 (1.5) 466-534 (1.75) 535-603 (2.0) 604-740 (2.25) More Obstacles Prevent HAT (ft) (No-light Visibility (sm)) Number of Runways GLS/ILS LPV LNAV/VNAV RNP .033 No Secondary 29 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Observations • Even with significantly reduced RNP values, the RNP minima are still not comparable to ILS. GLS, or LPV • ※Culprit§ must be the vertical OCS • As an example, suppose we use the GLS vertical OCS 200' Touchdown Elevation 34:1 ILS/GLS 27:1 LPV 23:1 RNP/BARO-LNAV/VNAV 954' 2,379' 1,237' 7,983' 3 Glideslope o 185' HAT 250' HAT 668' HAT 954' 1,154' 3,533' 4,770' 12,753' Not to Scale 30 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Effect of GLS Vertical OCS on RNP RNAV Note: Normally RNP is restricted to 250 ft HAT minimum. For GLS vertical, a minimum of 200 ft HAT is assumed. 0 500 1000 1500 2000 2500 3000 3500 200 (.75) 250-257(.75) 258-327 (1.0) 328-395 (1.25) 396-465 (1.5) 466-534 (1.75) 535-603 (2.0) 604-740 (2.25) More Obstacle s Prevent HAT (ft) (No-light Visibility (sm)) Number of Runways GLS/ILS LPV LNAV/VNAV RNP-.033 No Secondary RNP-.1 No Secondary RNP-.3 With Secondary 31 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Observations • The use of the improved vertical OCS produced lower minima for RNP RNAV approaches 每 ILS/GLS OCS only proposed as an example • Complexity of certification for small RNP values (such as RNP-.033) is unknown 每 RNP-.1 will still require SAAAR • Increased certification, equipment, and training costs • RNP RNAV and SAAAR will certainly be beneficial at some airports, but it is clear that there will be no substantial benefit over ILS, GLS or even LPV at most airports • Is there a less costly/easier way to attain good minima at most airports? 32 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Hybrid Approaches • It may be possible to combine RNP, GLS, and/or LPV into a single hybrid approach, where RNP RNAV criteria are used far from the runway, and the aircraft transitions to a GLS or LPV approach near to the runway 每 Possible application using ILS also • Such approaches should avoid the extra certification, equipment, and training of SAAAR • What would the benefits be of such approaches? 33 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. RNP-.1 and ILS/GLS/LPV Hybrid Horizontal Depiction -5000 -3000 -1000 1000 3000 5000 6000 12000 18000 Distance from RWT (ft) Distance from C/L (ft) 34 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Hybrid RNP/GLS and RNP/LPV Approaches 0 500 1000 1500 2000 2500 3000 200 (.75) 250-257(.75) 258-327 (1.0) 328-395 (1.25) 396-465 (1.5) 466-534 (1.75) 535-603 (2.0) 604-740 (2.25) More Obstacles Prevent HAT (ft) (No-light Visibility (sm)) Number of Runways RNP-.3 w/Secondary GLS/ILS RNP-.3/GLS/ILS Hybrid LPV RNP-.3/LPV Hybrid 35 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Observations • Application of current RNP RNAV approach criteria will result in higher minima at most airports in comparison to ILS, LAAS or WAAS-based approaches 每 Some airports will benefit, but most will have higher minima • Improvement of the vertical profile of RNP RNAV offers significant benefit with respect to approach minima 每 GLS vertical OCS investigated in this paper • Hybrid RNP RNAV and LAAS/WAAS approaches appear to have excellent capability to achieve the benefits of RNP and low approach minima while avoiding the costs of SAAAR 每 RNP to GLS and LPV investigated in this paper © 2004 The MITRE Corporation. All Rights Reserved. Backup Slides 37 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. Instrument Approaches to Juneau, Alaska, USA 38 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. -1000 -800 -600 -400 -200 0 200 400 600 800 1000 0 100 200 300 400 500 600 700 800 900 1000 Difference (feet) Number of Approaches HAT ft) ---GAME HAT (no Missed Approach) 每 Actual ILS HAT ---GAME HAT (with Missed Approach) 每 Actual ILS HAT Effect of the Missed Approach GAME Validation 39 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. GLS/LPV Missed Approach Splay FAA Order 8260.50 40 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. GLS/LPV Missed Approach Splay FAA Order 8260.44A 41 April 2004 © 2004 The MITRE Corporation. All Rights Reserved. RNP Missed Approach Splay FAA Order 8260.51

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Alternative Obstacle Clearance Criteria for RNP RNAV Instrument Approaches