Thales 421, Эксплуатация и обслуживание, Страница: 252 / 256

LLZ 421
Alignment Procedure LLZ−2F (LPD) Operation and Maintenance
ILS 420
8−22
Ed. 07.08 SOAC
8.7.6 Width Alarm
a) Open dialog ’Monitor 1 − Current Executive Data’ (for MCS: dialog ’Monitor 1 − Measurements/
Limits: Current Executive Data’). Select indication ’Exec. CRS Width DDM’.
b) Open dialog ’Transmitter 1 − Waveform Data #1’. Change ’CRS SBO Amplitude’ to reach the pre-
set alarm limits. If necessary, restrict further as specified by the flight check crew.
c) Open dialog ’Monitor 1 − Executive Alarm Limits’ (for MCS: dialog ’Monitor 1 − Measurements/
Limits: Current Executive Data’). Enter displayed ’Exec. CRS Width DDM’ value as the alarm limit.
8.7.7 Miscellaneous
Some other parameters must also be checked, e.g. the range. No further settings must be made with
the transmitter or monitor however.
NOTE: During flight check the ident signal of the localizer is also checked by the flight check crew.
For this check, the system has to be set to normal operation, i.e. monitor bypass is re-
moved to enable the transmission of the ident signal. If monitor bypass is set, transmitting
of the ident signal is disabled.
Finally, the system has to be set to normal operation, i.e. monitor bypass is removed, TX1 is aerial
and the key−lock switch at the LCP is set to "Remote".
8.7.7.1 "Out of Phase"−Clearance
If there are any clearance induced measured DDM distortions on center−line caused by reflections
of the clearance signal by large hangars etc. the phasing of the 30 Hz clearance modulation signal
relatively to the 30 Hz course modulation signal can be adjusted to suppress these distortions. The
following typical selections are recommended (the general setting range is 1 to 359 degrees) and can
be made by software adjustment regarding additional information on the measurement strip:
− No noticeable distortion (basic setting, no critical DDM−deviation)
0°
− Main distortion source at the 150 Hz side
18°
(right hand side as seen from a landing aircraft;
critical DDM−deviation to 150 Hz)
− Main distortion source at the 90 Hz side
150°
(left hand side as seen from a landing aircraft;
critical DDM−deviation to 90 Hz)
− Strong distortion sources at both sides of the runway
89°
(critical DDM−deviation to both 90 and 150 Hz)
REMARK:
If necessary, appropriate settings for ’Out of Phase Clearance’ are performed via the PC user program
(ADRACS resp. MCS) software depending on flight check results. The settings must be used corre-
sponding to the installed type of antenna system (angle values for dipole reflector system and LPD
system may vary).
Open dialog ’Transmitter1−Waveform Data #1’ and open dialog ’Transmitter2−Waveform Data #1.
Click on value of parameter ’Out of phase clearance’. Select value ’Enabled’. Click on value of param-
eter ’Phase’. Enter the appropriate angle value in
deg (typical assignation see above).