hi all,upon landing, i have to press the Vref button on the FMC, what is this Vref exactly for?

Vref is your landing reference speed, that is calculated by the FMC according to your current weight.The APPROACH REF page will propose you 3 flap configurations. When clicking next to any, it will select that Vref (see the PFD speed cue) and will add the winds correction factor on same page as target speed for landing (see LEGS page). You should set the MCP SPD dial to that speed (including wind correction) to set the AT target.So the idea is to give you a correct landing speed depending on your chosen landing config. If you fly slower, chances are high the anti stall system will kick in and you'll miss your approach.anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Thanks Anthony,so Vref is basically your landing speed? When you say dial down to the Vref speed on the MCP, when do i actually do this? at the OM? or where?And when i do dial down do i have the SPD button lit on the AP?Wont this make the plane slow to that speed, thereby kicking in the N1 so as not to stall?

>Thanks Anthony,>>so Vref is basically your landing speed? >>When you say dial down to the Vref speed on the MCP, when do i>actually do this? at the OM? or where?>>And when i do dial down do i have the SPD button lit on the>AP?>Wont this make the plane slow to that speed, thereby kicking>in the N1 so as not to stall?>I'd recommend you have the airplane configured for the approach (flaps and gear set, speed at Vref or decreasing to Vref) as you intercept the glideslope on an ILS or crossing the FAF inbound on a non-precision approach. That way you are stable, with no configuration changes to worry about as you make the approach.If you have the flaps set first, the airplane will not stall at Vref, as Vref is usually 1.3 times the stall speed for that flap setting.If you're in good visual conditions and are tracking the ILS just for reference, than you can hold the gear and flaps and speed reduction until later, and make a faster approach to the airport. But when you're making the approach "for real" - in the soup, it's customary (because it's safest) to get the airplane configured and slowed before you start the final descent.