Glide Slope Considerations to Provide Support for Aircraft Certification for Steep Angle Approaches International Flight International Flight Inspection Symposium Inspection Symposium Oklahoma City, OK USA June 2008 Oklahoma City, OK USA June 2008 David Quinet Aaron Wilson Avionics Engineering Center Ohio University
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Glide Slope Considerations to Provide Support for Aircraft Certification for Steep Angle Approaches International Flight Inspection Symposium Oklahoma.
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Glide Slope Considerations to
Provide Support for Aircraft Certification
for Steep Angle Approaches
International Flight Inspection International Flight Inspection SymposiumSymposium
Oklahoma City, OK USA June 2008Oklahoma City, OK USA June 2008
David QuinetAaron Wilson
Avionics Engineering CenterOhio University
Glide Slope Considerations to Provide Support for Aircraft Certification for
Steep Angle Approaches 2 of 27IFIS 2008, OKC
ILS Signal Requirements
• Localizer Signal:– Aligned with runway centerline– Meet Category I course roughness tolerances
• Glide Slope Signal– 5.5 to 8.65 degree path angle– Meet Category I path roughness down to an
altitude of 344 feet
Glide Slope Considerations to Provide Support for Aircraft Certification for
Steep Angle Approaches 3 of 27IFIS 2008, OKC
Location
• Previous Facility: Blythe removed when cooling tower built under approach– Aircraft decoupling due to updraft
• TMB: 09L– Known site performance– National FAA ILS test facility
• Equipment and infrastructure [power, foundations, buildings] already exists
• Established working relations with ATC
Glide Slope Considerations to Provide Support for Aircraft Certification for
Glide Slope Considerations to Provide Support for Aircraft Certification for
Steep Angle Approaches 21 of 27IFIS 2008, OKC
Null Reference
– Path Angle Change• Upper Antenna Height [0.01° per 1”]
– Verified height with tape measure
• Snow Accumulation
Glide Slope Considerations to Provide Support for Aircraft Certification for
Steep Angle Approaches 22 of 27IFIS 2008, OKC
Path Roughness
• Aircraft on Taxiways – No taxiways near mast
• Terrain Modification– Visual inspection
• SBO CSB Power Ratio– Test equipment
Glide Slope Considerations to Provide Support for Aircraft Certification for
Steep Angle Approaches 23 of 27IFIS 2008, OKC
8-Element Array
– Course Alignment Change• Phase change in antenna cable or DU
– Verified with ground checks
• Modulation Balance [0.001 DDM=> 2.3’ at threshold]– Verified using calibrated external equipment
– Structure Roughness• Constant
– No change to environment [buildings/parked aircraft] in front of array
» Visual inspection
– No change in CSB/SBO power ratio
» Verified using thru-line elements
Glide Slope Considerations to Provide Support for Aircraft Certification for
Steep Angle Approaches 24 of 27IFIS 2008, OKC
Signal Verification
• Based on ground measurements– Transmitter output power & modulation – In-line phase– GS antenna heights– Localizer ground checks (CL, width points)– Taken pre & post mission
Glide Slope Considerations to Provide Support for Aircraft Certification for
Steep Angle Approaches 25 of 27IFIS 2008, OKC
Path Angle Stability
Glide Slope StabilityBased on Ground Measurements
-0.6000
-0.4000
-0.2000
0.0000
0.2000
0.4000
0.6000
3/24/06 10/10/06 4/28/07 11/14/07 6/1/08
Date
Pat
h A
ngl
e C
han
ge (
Deg
rees
)
Transmitter (Change in Modulation Balance) Antenna (Change in Height) ICAO Tolerance
Glide Slope Considerations to Provide Support for Aircraft Certification for
Steep Angle Approaches 26 of 27IFIS 2008, OKC
Structure Roughness
Glide Slope StabilityTolerances come from a structure roughness margin of 33.5%
0.005
0.007
0.009
0.011
0.013
0.015
0.017
0.019
0.021
0.023
0.025
3/24/06 10/10/06 4/28/07 11/14/07 6/1/08
Date
CS
B-S
BO
Rat
io
CSB-SBO Ratio Values Tolerance
Glide Slope Considerations to Provide Support for Aircraft Certification for
Steep Angle Approaches 27 of 27IFIS 2008, OKC
Conclusions
• Localizer & Glide Slope remained within tolerances during all certification flights.
• Based on reference readings (antenna height); angle remained within 0.00015-degrees.