Transcript Slide 1

International Flight Inspection Symposium
Oklahoma City, OK USA June 2008
Qualifying DME
for RNAV Use
Gerhard Berz, EUROCONTROL
Jochen Bredemeyer, FCS
Overview
• RNAV Infrastructure
Assessment Guidance
– Infra Requirements
– Assessment Process
– Special Eval’s
• Multi-channel DME
Assessment
– Feasibility
• DME First Installed
Prior to 1989
– Interoperability
• Many more…
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ICAO PBN Context
• ICAO RNAV-1
• Infrastructure needs to support
Navigation Application
– U.S. (FAA): AC90-100
– Europe: JAA TGL-10
(Becoming EASA AMC20-16)
– Performance & Functional
Rqmts for Aircraft
• P-RNAVEUROPE ≤ RNAV-1ICAO
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– for airspace users that have
been certified to RNAV-1
Specification
– Supported by GNSS or
DME/DME or D/D/Inertial
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P-RNAV Infrastructure Guidance
•
Deals with infrastructure
only, NOT with procedure
– GNSS  Ref ICAO Doc
9849, GNSS Manual
– Primary focus on DME
TOC:
1. Intro: Actors & Tools
2. Requirements
3. Process
4. Technical Topics
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Infra Assessment Actors & Process
Flight Inspection
Organization
Airspace
Planning
Procedure Design
RNAV
PROCEDURE
Designated
Engineering
Authority
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Use of Software Tools
• Use of tools is recommended
– Line-of-sight prediction based on terrain model
– To incorporate requirements from Guidance Material
• Assessment without Flight Inspection is possible
provided experience
–
–
–
–
Existing Flight Inspection reports (individual DME)
Current use of airspace and DME aids
Procedure altitude (TMA SID/STAR vs. B-RNAV)
Engineering judgement
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Requirements (Extracts)
• ICAO NSP decided to rely on DOC
– Aircraft uses non-standard FOM
– Use outside of DOC is avionics responsibility
• Accuracy Error Budget, TSO C66C
– PBN Manual, Annex 10 and PANS-OPS aligned
• FMS Criteria
– Subtended angle criteria etc. documented such that
ANSP does not need to undertake avionics study
• SID and STAR
– Establish limits of DME/DME Coverage (30 sec)
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Assessment Objectives
1. Prove procedure is supported by usable
DME within DOC range
•
Confirm PANS-OPS Assumptions about SIS
2. Identify DME that could degrade RNAV
solution
•
•
•
•
Critical DME
Receivable DME far outside of DOC
TACAN or DME Installed Pre-1989
Co-Channel DME
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Technical Topics
• Negative Elevation Angles
• DME not under ANSP control
(cross-border)
• Critical DME
• Gaps in DME/DME RNAV Service
SOME TESTS
(UK, Japan)
Flight
Inspection
Challenge !
– DR, INS, Resiting
• Offsets and Direct-To
• DME First Installed Prior to 1989
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3rd Part of this
Presentation
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Part II
• Infrastructure Assessment Guidance
Material Summary
• Multi-channel DME Inspection
Capability
• DME First Installed Prior to 1989
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Multi-Channel DME Inspection
• Aircaft and FIS time expensive
• FI airspace access becoming more limited
– Especially in busy TMA’s
• It is clearly recognized that conventional scanning DME
are not suitable for measurement purposes
• Receiver requirements
– Reliably measure received signal strength
– Detect multipath distortion
– Complement typical FI receivers
• Specifically developed receiver (SISMOS / DME)
– Presenting test results of multi-channel capability
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Signal-In-Space Monitoring System
Receiver and processor for DME/SSR channels
L-band antenna (aircraft: bottom TACAN antenna)
when airborne
Logarithmic L-Band receiver
(962-1213MHz)
-90dBm ... -20dBm
Baseband signal
Signal processing
(Correlator)
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Conventional Flight
Inspection System
Position vector
Real time display and
recording
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Six Channel Reception
GPS tow: 477223s Altitude: 22904ft
-60
Level / dBm
-65
Ch #3 Helgoland DME (former TACAN)
Ch #5 Skrydstrup TACAN
Ch #1 Elbe DME
-70
-75
Ch #0 Hamburg TACAN
-80
Ch #4 Vesta DME
Ch #2 Schleswig TACAN
-85
1330
1332
1334
one pass
1336
1338
1340
Process time / sec
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Signal Level Reception
• Sufficient sampling to detect
relevant multipath fading ~ 1Hz
– More channels possible, could be
adapted to environment
– Figure shows Skrydstrup with
135Hz fine and 15Hz coarse
modulation
-51
-52
-53
Level / dBm
• TACAN signal levels are
modulated by bearing
component ~10dB
Channel 5:SKR GPS: 476189s Alt: 15245ft
-50
-54
-55
-56
-57
-58
-59
304.72
• Trial revealed Helgoland TACAN
with partial modulation
304.73
304.74
304.75
304.76
304.77
304.78
304.79
Process time / sec
– Incomplete change to DME
operation
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304.8
Six Channel Pulse Video
Channel 4:VES t0=1332.9s GPS: 477216s Alt: 22902ft
Level / dBm
-50
• Multipath
distortions
clearly visible
-60
-70
-80
-90
-100
-110
t1=0.59ms
t2=0.84ms
t3=0.91ms
t4=1.04ms
t5=2.04ms
Non-continuous time scale
Channel 1:LBE t0=1332.3s GPS: 477216s Alt: 22902ft
-60
-70
-80
-90
-100
-110
t1=0.10ms
t2=0.74ms
t3=0.84ms
t4=1.48ms
t5=1.58ms
Non-continuous time scale
Channel 5:SKR t0=1333.2s GPS: 477216s Alt: 22902ft
-50
Level / dBm
• Correlation
Algorithm to
detect
abnormal
pairs for
closer
engineering
inspection
Level / dBm
-50
-60
-70
-80
-90
-100
-110
t1=0.08ms
t2=0.45ms
t3=0.52ms
t4=1.09ms
t5=1.90ms
Non-continuous time scale
etc . . . . . .
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Multi-Channel DME Inspection
• Receive ONLY
– Not possible to measure ranging accuracy
• But unprecedented clarity of signal effects
– Classical DME still needed for this
• But low field strength / multipath / low accuracy is well
correlated..
• Advantage of Passive Device
– Continuous DME network monitoring possible
– Take advantage of ALL other FI and ferry flights
– Receiver concept and feasibility demonstrated
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Part III
• Infrastructure Assessment Guidance
Material Summary
• Multi-channel DME Inspection Capability
• DME First Installed Prior to 1989
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DME First Installed Pre 1989
• 1989 ICAO Annex 10 Change
– Requires transponder to use first pulse timing
– All TSO-C66 interrogators use first pulse timing today
• Eurocontrol Navigation Subgroup
– Can these 20+ year old DME support P-RNAV?
• Potential for “deleterious effects to NAV solution”…
• Accuracy error budget SIS allocation: 0.1NM (95%)
– PANS-OPS Tolerances
– Cross-border issue (difficult to identify)
• Europe-wide forced upgrade was considered
• Thales / Face FSD-15
– Anticipated standards change and made time reference
configurable
– Enables tests using either pulse reference in identical
environments
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Vesta DME near Esbjerg, DK
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Vesta DME
• Flight Calibration Services
(FCS)
– Beech B300 Super King Air
D-CFMD
– 2 Honeywell DME Error
Budget
– 2 Collins TACAN
MP Impact
– SISMOS
• Reciprocity
on 2nd Pulse
• Test Program
– 10NM Orbit 3000 ft
– Inbound and Outbound
Radials 3000 ft
– Once in 1st Pulse and once
in 2nd Pulse Mode
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ESBJERG
VESTA DME
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Test Results - Multipath
• NO nominal SiS performance difference between 1st and 2nd Pulse
– Possible to meet P-RNAV Accuracy Error Budget on 2nd Pulse TXPDR
– Requires “clean” environment: IF multipath issues exist, they will be
greater
• Even clean environment creates hard-to-predict multipath fades
– In addition to characteristic scalloping & oscillations
– Effect would not be obvious from modeling
• Vertical dipole over conducting ground plane
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Test Results - Interoperability
• While obvious from theory, bias is observable in flight test data & lab
• If aircraft uses 1st pulse reference and ground 2nd pulse, then aircraft
pulse spacing becomes relevant for error budget
• Interrogator OEM’s take full advantage of the ±0.5µs (±0.04NM)
tolerance
– Resulting “interoperability error” has been allocated to transponder
– VESTA FSD-15 total range error remains around 0.03NM regardless of
pulse reference (Root-Sum-Square Effect)
Interrogator
Transmit
Transponder Transponder
Receive
Transmit
Interrogator
Receive
2nd Pulse
1st Pulse
t
Propagation + PAIR
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Transponder
Delay
Propagation - PGROUND
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Pre-1989 DME Conclusions
• 2nd Pulse Timing
– Key vulnerability is reflection delay of 1st pulse around 12µs (X-channel)
– Such delays are actually “difficult to create”
• Reflector needs large conducting surface coincident with suitable reflection
angles and
• To be located on ellipse of pulse spacing path delay (hangars or lakes /
snow covered plains with DME on hill)
• Multipath fading and scalloping can be observed independent of
time reference
– Impossible to predict with modeling, but normally of limited magnitude
• Infrastructure Assessment Guidance Updated
– Pulse spacing tolerance error acceptable for such few DME
• Most such DME will be replaced in the coming years
– P-RNAV support is possible – but needs to be verified as for 1st pulse
DME’s
• “Interoperability Error” needs to be taken into account
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Conclusions
• P-RNAV Infrastructure Assessment Guidance
Material is available
– Summarizes about 3 years of effort (Standards
harmonization, establishment of process and
technical topics)
• RNAV / DME Inspection requires Innovation
from Flight Inspection
– New receiver concepts for concurrent measurements
– Integration with Pre- and Post-Flight Analysis
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Qualifying DME for RNAV Use
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Questions?
• Thank You for Your Attention !
• Feedback of RNAV / DME Flight
Inspection Experience is WELCOME
– [email protected]
• Free Copies of “P-RNAV Infrastructure
Assessment Guidance Material”
Document are available on request
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