View Full Version : Standby Instruments ADIRS A320

6th Dec 2018, 07:09

after reading all the stuff im totally confused. Cann somebody explain me in easy words, how the ADIRS System (ADR, IR, STBY) works in the A320? I always thought that we have 3 ADRs and 3 IRs. One Fails, we can Switch them to the side where it is lost. Do the ADR3 or IR3 give Inputs to the STBY ISIS? I thought it is a stand alone platform but the Manual obviously says that it gets Input from ADIRS 1 and 3?

Some easy Explanation would help and thanks so much!


6th Dec 2018, 08:56
Hi SW,
Some easy Explanation would help

The ISIS is stand alone Artificial horizon, Speed and Altitude (from own gyro, standby probe and static vents).
The input from ADIRS 1 and 3 are for heading information and something called "Accelerometer Gyrometer" (whatever that means).
https://www.livescience.com/40103-accelerometer-vs-gyroscope.html explains why it is better to have a mixture of gyroscope (from ISIS) and acceleration information (from ADIR) to give a better attitude reference.

It was discussed at length here: https://www.pprune.org/tech-log/406443-a320-isis-what-adiru-inputs.html

6th Dec 2018, 20:53
Do the ADR3 or IR3 give Inputs to the STBY ISIS?

No, the ISIS is fed by Stby probes only.
However, ADR3 receives input from stby probes.

In a nutshell, ADR3 readings on PFD's & ND's are visible only when switching AIR DATA to CAP/FO 3

7th Dec 2018, 10:07
As goldenrivet pointed, ISIS is fed by STBY ports and probes. There are air data modules in STBY ports/probes to provide anemometric data to the 3rd ADR.

The confusion usually exists because in case of blockage in 1+2 the ISIS still works. The air data switching in position 3 recovers the problem and people associate the ISIS with ADR3, but in reality those 2 use the same tubes.

8th Dec 2018, 12:02
From the A350. Standby Pitot (ISIS)

https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/960x720/a350probes_zps123a792c_ccc5cfb5252a85fca5dc47ccf1af864c9dfb0 2f6.jpg

Capt Fathom
9th Dec 2018, 03:02
I hope they remember to pull all those stickers off before they go flying! :E

10th Dec 2018, 14:23
OT, but SSA measurement is interesting

10th Dec 2018, 17:35
The IESS on the Embraer, is the only part of the aircraft which uses 'classified' technology.