With two operating IRSs’ I can on the IRS Display Unit (ISDU) select WIND and it will display the present inflight TRUE wind direction and wind speed in Knots (I am aware that the selection may differ to aircraft type).
For EFIS/Glass cockpit aircraft do you require an FMC to be able to have that wind info to display correctly on your Map/ND display?
My understanding is that there is an inbuilt Mag converter in the IRS in order to be able to display the Wind info in relation to Magnetic North.
But I have also heard that the FMC averages out the wind information that it receives from the IRS.
What would be the case if you have Dual FMCs, would each FMC average out the wind info it gets. I always wondered if that was the reason on a Dual FMC setup that the wind info displayed on the NDs was very slightly different for a quick moment.
If the FMCs fail, would that wind info on the ND be accurate or would you need to refer to the direct readout from the ISDU?