AIU FAIL—The AIU FAIL is an amber cap-
tion that illuminates to advise that the analog
interface unit (AIU) is no longer outputting
valid data.
Static Port Switch—The static port L and R an-
nunciators illuminate (amber) to advise when
the air data static sources are isolated to the
pilot Rosemount probe (L illuminated) or to
the copilot probe (R illuminated). In normal
operations, the switch is centered on BOTH,
and neither static port annunciator is illumi-
nated. This indicates that the air data sources
are cross coupled.
For the following, refer to Figure 16-15:
A—Is on the ADDU LCD. This annunciator in-
dicates that the ADDU is selected as the ac-
tive master ADDU. An absence of this symbol
indicates that the ADDU is operating as the
slave ADDU.
COM—Is on the ADDU LCD. This annunci-
ation indicates that the ADDU is no longer
receiving RS-422 data from the other ADDU.
Altitude preselect is disabled on the slave
ADDU when this occurs.
OFF—Is on the ADDU LCD. When this cap-
tion is in view, all other indications will be
blank. This indicates an internal ADDU fault.
STBY—Is on the ADDU LCD. This annunci-
ator indicates that the ADDU is no longer ap-
plying a static source error correction and
altitude reporting information is no longer
available on this ADDU.
Refer to Figure 16-13 for the following:
VIB OFF—Is on the standby altimeter. The an-
nunciation indicates that the standby altime-
ter internal vibrator is off.
NOTE
The COM, OFF, and STBY annun-
ciations can possibly be cleared by
cycling the appropriate circuit break-
ers for the affected ADDU.
OPERATING PROCEDURES
ADDU
The ADDU is capable of displaying altitude
in feet or meters and barometric scale in
inches of mercury (in. Hg) or hectopascals
(Hpa). At initial power-up, the ADDU de-
faults to the setting that was effective at the
last power interruption.
16-14
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
Figure 16-14. Air Data Panel Indications
Figure 16-15. Air Data Display Unit (ADDU)