Honeywell SPZ-8000 - Radio Altitude Comparator

A miscompare condition occurs when one of the above parameters
deviate greater than the allowed threshold. When a miscompare
is detected, the FGC reversion will be dependent upon whether
the
IRS monitor resident in the AHRS or IRS 3 is valid. With
the
IRS monitor invalid, all FD modes will be dropped, the AP
and YD will disengage, and the
IRS miscompare will be
annunciated.
A heading miscompare with the
IRS monitor invalid
will cause the aircraft to revert to wings level from
HDG hold
and annunciate the IRS
miscompare.
With the
IRS monitor valid, a miscompare in the FGC will cause
the FGC to look at the miscompare discretes from the
IRS
monitor.
The
IRS monitor compares the parameters listed below
between
IRS 1 and IRS 2.
Parameter Allowed Error Threshold
Pitch/Roll 3°
Pitch Rate
Yaw Rate
0.3°/sec +Avg Rate /32
Roll Rate
Normal Accel
Lateral Accel 0.05 g + Avg Delta Accel /32
Fore-Aft Accel
Heading N/A
A miscompare condition in the
IRS monitor occurs whenever the
above parameters deviate greater than the allowed threshold
between the
IRS monitor and IRS 1 or the IRS monitor and IRS 2.
The IRS
monitor will set the appropriate discrete to the FGC
(either
IRS 1 miscompare or IRS 2 miscompare).
The FGC does not use the miscompare discretes from the IRS
monitor until the FGC has detected a miscompare. At that point
the FGC uses the
IRS monitor as a voter by looking at the
miscompare discretes.
The FGC will stop using data from the
IRS with which the IRS monitor has miscompared and EICAS will
annunciate “FGC NOT
USING IRS (X)”.
3. B.
(6) (c)
Radio Altitude Comparator
The parameter compared by the
FGC is shown below.
Parameter
Allowed Error Threshold
Radio Alt
5 ft + ALT Avg /8
22-14-00
Page 298.86
Apr 15/93
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