I am about to study the so called IRS Display Unit of the PMDG-737 ( FCom2,page 817,see attached printscreen )

but as I am rather confused by it I hope somebody can explain more then the manual.

 

In particular :

 

- Whatever keyboard entry I make,nothing happens.Why ?

- What is the purpose of the IRS Display anyway ?

 

I greatly appreciate your help.

 

HubertWerni

 

 

Wait keyboard entry? Are pressing the L and R keys on your keyboard? This is not what it means.If you read the page before this one, 11.10.17, it shows the unit it is talking about and you will see a dial to select L or R . This display unit is at the very top of the overhead panel, above the IRS selectors

The IRS display is kinda useless, actually. I use it during setup to view time-to-align and that's about it. Everything else on the display can be viewed via the FMC. 

 

If for some reason you want to align the IRSs via the overhead, simply turn them on (Selectors both to NAV), Display Selector to PPOS, then type the coordinates in, using the format DDMM.DM. I just checked and it does work. 

Useless... until you lose the FMCs on an ETOPS / Class II nav leg. ;-)

Useless... until you lose the FMCs on an ETOPS / Class II nav leg. ;-)

 

True - though in that case would you be down to navigating with the chart and a plotter? I didn't think the NG had any dedicated IRS navigation equipment. 

Pretty much. The IRS display just feeds you position and course information. Assuming you were on course when the fmc failure happened, you'd just need to continue steering the course on your flight plan between fixes, plotting positions regularly to ensure you're still on course and making small corrections as necessary. You have to plot positions anyway on a class II leg so it's just a matter of doing it a bit more frequently.