PPOS on the IRMP
 

Taking the IRS as fitted to the 737-800 as a reference, if you set PPOS on aligment on the IRS Mode Panel,then go to NAV, does PPOS then freeze or does it continue to record the IRS calculated Lat and Long as you fly?

Dick

Not sure I understand, Dick? PPOS selects 'Present Position' for display so, yes, it is 'frozen' during (10 minute) alignment but moves with you in nav. Is that what you are asking?

As BOAC says, we set PPOS into the FMC from GPS L, which transfers it to the IRSs for alignment: after the 10 minute alignment it switches to NAV ( we just switch them both straight to NAV on start up) it starts to compute position.

Perhaps I should have said "remains frozen", but the question looked clear enough. This comes from a question and answer which implied that the PPOS readout did in fact remain frozen. I don't have the direct experience to arbitrate so I ask real operators - who have confirmed my understanding -thank you

Dick