ADIRS Flashcards
IR mode selector functions?
OFF: turns off both IR and ADR
NAV: normal mode - both operational
ATT: able to restore heading and attitude if IR FAULT is flashing. (MCDU heading must be updated every 10 min. (precession)
IR and ADIRS can be turned off separately via their pbs
What does a flashing IR FAULT PB vs solid FAULT mean?
Solid means the IR has failed completely.
Flashing means that ATT should be selected.
ATT: able to restore heading and attitude if IR FAULT is flashing. (MCDU heading must be updated every 10 min. (precession)
When must a complete IRS alignment be preformed?
Basically every flight for the 330.
ie FFOD (any flight departing prior to 12pm - aircraft on ground more than 3 hours)
or
GPS not available and nav coverage poor on expected route
or
GPS not available and expected flight time more than 3 hours
or
if residual ground speed exceeds 5 knts after a flight
Proc
Crew change
Departure airport located between latitudes 2 north and 2 south
If you flew inter-island, on a quick turn would a IRS alignment be necessary?
Yes, a fast IRS alignment must be performed anytime a complete IRS alignment is not necessary.
How do you complete the 2 types of IRS alignments? Under what conditions is it not allowed?
Complete alignment: turn ADIRS selector off for more than 5 sec, then back to NAV. (ON BAT light comes on temporarily)
Fast alignment: turn off for less than 5 seconds. (resets groundspeed only)
Aircraft movement will restart alignment.
Do not align during engine start, or while engines are running.
(during fueling is ok)
How long is fast IRS Alignment? What does it reset?
30 secs
resets groundspeed only
required if full alignment not required
How long does a full IRS alignment last? What does it reset?
7-10 minutes
Resets groundspeed / drift / captures present position
Why is the ADIRS left on when we leave the aircraft?
Provides the fuel system with temp info etc. in order to calculate fuel density during fueling.
What limitations exist regarding operation in RNP airspace when no GPS is available?
IRS only in RNP airspace:
Flight time outside of NAV coverage must be less than:
6.2 hours from the time of IRS alignment or
5.7 hours from the last FM update
Why does the ADIRS panel show ON BAT when the ADIRS is powered up?
During power up the system does an internal power check using batteries only.
When will a horn be heard in the nose wheel well?
When the ADIRS is on battery power only.
This could also be the APU Fire horn.
What is the basic nav mode for Each FMGEC? Regarding aircraft position?
GPS/INERTIAL
MIX IRS position continuously corrected for the GPIRS position.
What is the MIX IRS position?
The FMGECs compute a mean-weighted average between the three IRS positions it receives. If one IRSs drifts abnormally, the MIX IRS position uses an algorithm that decreases the influence of the drifting IRS.
What is the GPIRS
The GPIRS is a mixture between the Mix IRS and the Mix GPS position. Weighted more heavily to GPS.
How does each FM position use the Bias?
FM position equals the IRS MIX position plus the BIAS. The Bias is the vector (distance and direction) that the Mix IRS position is away from the radio or GPIRS position. The system constantly memorizes the BIAS when radio or GPS is available. If radio or GPS signal is lost, the Bias remains the same until reception is regained.
