.
Category II systems.
.
Category I systems, which the operator wishes to use for autoland in good visibility.
5.2 For inspection of the above systems the aircraft shall be fitted with equipment which will provide repeatable following of the required path (1549). Systems considered suitable to this purpose include telemetry of the ground based tracking system’s output to a separate instrument in the aircraft, or an autopilot. If an autopilot is used the CAA shall be satisfied that it is capable of safe operation down to 50 feet above the threshold elevation (1550).
6 Equipment
6.1 Measurement and Recording Equipment
6.1.1 A normal ILS/DME inspection system shall be capable of measuring and recording the following parameters (1551): a) Localiser Field strength. b) Localiser Modulation Sum (SDM). c) Localiser Difference in Depth of Modulation (DDM). d) Glidepath Field strength. e) Glidepath Modulation Sum (SDM). f) Glidepath Difference in Depth of Modulation (DDM). g) Marker Beacon Field strength. h) Marker Beacon Fly-through Time.
i) DME Field strength.
j) DME Distance.
6.1.2 The recording equipment shall be capable of recording any of the ILS parameters listed in paragraph 6.1.1 (1552). The equipment shall measure and record beam structure by comparison of tracking data and the ILS signal, from a distance of at least 4 NM from the runway threshold (1553).
6.1.3 It shall be possible to annotate the recordings with comments and any other necessary information at the time of making the recording (1554).
6.1.4 For beam bend measurements, the total time constant of the measuring and recording equipment shall be 92.6/V seconds where V is the aircraft velocity in kilometres per hour (1555).
6.1.5 If digital sampling/storage is used, the sampling rate shall be compatible with this time constant but never less than 4 samples per second for all parameters which are continuously measured (1556).
6.1.6 The equipment shall be capable of recording a minimum of 4 parameters simultaneously (1557).
NOTE: Post inspection processing may be necessary to achieve the required accuracy for certain parameters.
7 Measurement Uncertainty
7.1 Maximum permitted measurement uncertainty at 95% confidence level (1558).
NOTE: Throughout the following tables, the figure of 2dB for field strength is the permitted uncertainty for repeatability of measurement. It is not a requirement for absolute field strength measurement.
7.1.1 Localiser
Cat I Cat II Cat III
Alignment (average) (related to threshold) 2.0m (2078) 1.0m (2079) 0.7m (2080)
Displacement sensitivity (of the actual figure) 4% (2081) 4.0% (2082) 2.5% (2083)
Field strength (relative) 2dB (2084) 2dB (2085) 2dB (2086)
Off course clearance 3% (2087) 3% (2088) 3% (2089)
Course structure Outer limits of coverage to ILS Point A 6μA (2093) 6μA (2094) 6μA (2095)
Course structure ILS Point A to threshold 3μA (2096) 1μA (2097) 1μA (2098)
Modulation sum (absolute mod depth) 1.6% (2099) 1.6% (2100) 1.6% (2101)
Polarisation 1.5μA (2012) 1.0μA (2013) 1.0μA (2104)
7.1.2 Glidepath
Cat I Cat II Cat III
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