ADIRS (Air Data Internal Reference System)
- Supplies flight data:
- Speed
- altitude and attitude
ADIRS (Air Data Internal Reference System)
- Supplies flight data:
- Speed
- altitude and attitude
ADIRU (Air Data Internal Reference Unit)
- There are 2x ADIRU
- Each ADIRU contains Internal reference and Air Data parts
IRS supplement
- L/R IRS supply altitude, heading, vertical speed, and other data for the flight instruments
- L/R IRS supply pos, wind and other data to the FMC
- L/R IRS also supply data for the A/T, flight control computers and other systems
IRS Pre-flight alignment
- IRSs sense altitude, true north and position
- They use gravity to calculate initial attitude
- The earth’s rotation to calculate true north and position
- Make sure there earth’s rotation is the only movement sensed by the IRS the airplane must not be moving
- 5-10 minutes alignment. 5 minutes at the Equator and 10 minutes at 70 degrees latitude. High latitudes (70 degrees to 78) 17 minutes
ADIRU (Air Data Internal Reference Unit)
- There are 2x ADIRU
- Each ADIRU contains Internal reference and Air Data parts
IRS (Internal Reference System)
-IRS contains:
-Electronic sensors
-non-mechanical laser gyroscopes
(which measure the airplanes movement on all 3 axis)
Signals form sensors calculate:
- True and magnetic heading
- Acceleration
- Vertical speed
- Ground speed
- Track
- Wind
- Latitude/Longitude
- The 737’s IRSs replace:
- Mechanical gyros
- Internal navigation
IRS supplement
- L/R IRS supply altitude, heading, vertical speed, and other data for the flight instruments
- L/R IRS supply pos, wind and other data to the FMC
- L/R IRS also supp
IRS Mode Selector Unit (MSU)
- DC lights indicate IRSs are doing DC power test
- Must put airplane’s position during alignment
- The IRS compare sensed position with one put in the FMC and last position IRSs were shut down
- If flash it on align occurs if the IRS sensed position is too far away from CDU pos or from last pos
IRSs during flight
- Each IRS calculates its pos
- There are no updates form other sensors
- Although IRSs are very accurate, errors accumulate
- The FMC also uses navigation radio data to calculate and show its pos
High altitude IRS ops
-Near magnetic poles, IRSs cannot provide magnetic heading in some areas. The IRSs continue to supply true heading
IRS recommendations
-During a turn-around, IRS shutdown and realignment recommended (waits 30 seconds after shutdown)
IRS fast realignment
- Not sufficient time for a fill realignment
- No movement
1. Turn mode selectors to align
2. Turn mode selectors to nav
3. Alignment completes in 30 seconds or less
ISD/ISDU (Inertial System Display )
- ISDU shows IRS data
- Display selector shows IRS data
- ISDU to PPOS to enter Latitude and Longitude in case needed to enter
