Q

1

• Q
• Flight Inspection Division

2
Flight inspection of ground aviation facilities
Q experience with GPS

• Karel Kucera, Flight Checking Engineer
• Marek Dobrozemský, Flight Checking Engineer

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FID - Supervision of

• ILS, VOR, DME, NDB, VDF, COM
• RADAR SYSTEMS
• PAPI, VASIS
• ALS, RLS
• Flight Procedures
• FM interference

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FID - Fleet

• Let 410 UVP
• Commuter aircraft equipped with latest avionics,
  autopilot and GPS
• 80 to 200 KTS IAS, unpressurised, 3hrs duration,
  unpaved runways operation (600m)

• Beechjet 400
• Business Category jet with an advanced dual
  Flight management and autopilot systems
• 150 to 320 KTS IAS, GND to FL 450, 3hrs duration

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Method
Comparing position indicated to reference one.
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RS Evolution

• Ground reference points
• Optical instruments
• Standard Theodolite
• Radio Telemetry Theodolite (RTT)
• Digital Radio Telemetry Theodolite (DRTT)

• GPS (DGPS, RTK)

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Steps utilising GPS

• 1992 new equipment NM 3625B on BE40
• 1993 - 1995 Testing period
• since 1994(1995) Operational use
• 1995 backup aeroplane L4T equipped NM 3625 B
• 1998 NM 3625 B - CR2 modified to RTK method
• 1999 NM 3625 B - CR3 modified to RTK method
• 2002 Omnistar corrections included

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ILS cat. III - critical application
ILS points configuration
Runway
Approach direction
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Critical requirements

• ILS parameters

at point B

• Positioning system accuracy

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Testing

• Gradual, following technology implemented
• APRS (DGPS solution)
• Static tests
• Dynamic tests
• RTK
• Static tests
• Dynamic comparisions
• Theorethical evaluation

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APRS (history)

• DGPS, INS, LRF
• declared accuracy 1m horizontal, 1.5m vertical
• required
• PDOP lt 2.4,
• HDOP lt 1.5,
• gt6 SATs in view,
• lt100 km from reference station
• LRF post processing made possible vertical
  accuracy 0.14m

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APRS Testing

• First comparing flight test results of both DRTT
  and APRS (same datalink used)
• Second frequency added to data link -gt REFERENCE
  CHECK procedure
• 91 approaches in horizontal plane
• 80 approaches in vertical plane
• Declared accuracy confirmed
• Scenarios static and dynamic both in horizontal
  and vertical plane

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APRS Testing scenarios (1)

• Static test in horizontal plane

WPT 1
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APRS Testing scenarios (2)

• Static test in vertical plane

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APRS Testing scenarios (3)

• Dynamic tests
• approaches to two points (vertical, horizontal)
• Reference check (APRS, DRTT)
• DRTT placed to standard points for LLZ respective
  GP flight testing.
• Horizontal until E point
• Vertical until B point

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Sensor positions
antenna vectors
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Test Results

• Static tests

• Dynamic tests

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RTK

• Static tests performed - very optimistic results
• Flight tests (RTK-DRTT comparison) confirms high
  degree of accuracy
• High accuracy ensured only if RTK fixed.
• Problem to find the ruler to verify dynamic
  measurements
• Theoretical error assessment put in place

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RTK accuracy considerations
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Technology Today

• Calibration Position Reference GPS, DGPS, RTK
• up to dm accuracy in position
• up to ILS cat III flight checking
• DRTT as a backup
• long experience

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Measuring Accuracy

• Standard deviation typically lt 5 cm (on GPS
  antenna)
• 32 cm horizontal transformed to aircraft
  measuring antenna position
• 16 cm vertical transformed to aircraft measuring
  antenna position

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Ground support

• Mobile DGPS reference station
• DGPS reference station network
• Major aerodromes (LKPR, LKTB, LKMT, LKKV)
• Providing coverage over all CR
• Database of coordinates (WGS-84)
• Surveyed by Czech Army Topographical Institute
• Verified by independent agency
• Special WPT database
• Computed points
• GPS surveyor
• Geodetic (D)GPS, OMNISTAR corrections, 0.8m ,
  0.02m relative

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Conclusions

• RTK successfully used for Flight test up to ILS
  cat III
• Independence of ground assistance - effectivity
• Human factor influence reduction.
• Visibility independence - better serviceability
• Experience with these technologies in ACFT
  guidance.
• Knowledge for future coming satellite
  technologies
• EGNOS
• GALILEO