AIRPLANE
OPERATIONS
MANUAL
SUPPLEMENTARY
PROCEDURES
FLIGHT INSTRUMENTS
REVISION 28
1-02-82
Page
1
Code
01
ALTIMETER MISCOMPARE TOLERANCES
This Section provides information regarding maximum allowed
tolerances between PFD altitude indications and standby altimeter.
For the EMB-145, ERJ-140 and EMB-135 models, there are two pitot
probes, four static probes and one pitot static probe. Pitot probes 1 and
2 and the static ports send information to ADCs 1 and 2. The third
(auxiliary) pitot probe sends information directly to the standby
indicators.
The standby altimeter system is a back-up navigation source to be
used in the event of a total loss of the primary source (ADC).
The differences between the readings of ADC 1 and 2 altimeters and
between these and the standby system altimeter, with the airplane on
ground or in flight, can occur due to a number of reasons and may vary
with altitude, airspeed and airplane configuration. In addition, the static
port for the standby system and the static port for the primary system
are located in different positions.
This criterion considers additional parameters, as follows:
measurement errors, installation deviations, internal and skin waviness
distortions and airplane sideslip condition that bear an influence on
data variations when comparing the two systems. The new range of
values is applicable to both the Integrated Standby Instrument System
and the Conventional Standby System.
For all EMB-145, ERJ-140 and EMB-135 models, the maximum
acceptable difference between both ADC altimeter indications and
between the ADC altimeters and the Standby System are shown in the
table on the next page.
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