Hi GuysIf you fly an approach in VNAV, does the aircraft automatially decelerate towards VREF or do you need to set it manually in the speed window?Also can someone explain at what point you would reduce to VREF and if the speed is reduced in steps?Kindest Regards

VNAV takes its command from the FMC. You would change from VNAV to LEVEL CHANGE (LVLCHG) or VERTICAL SPEED (VS) and reduce speed according to the flaps schedule and or when instructed to do so by ATC.You can reduce speed after each flap change and this is indicated on the Primary Flight Display (PFD) I select flaps 1 at about 21nm from touch down at about 220 kts and then flaps 5 at about 180kts flaps 10 at 170kts flaps 15 at 160kts flaps 25 at 150kts and flaps 30 for landing at around 140 kts depending on the weight of aircraft and approach speed set in the FMC.You will get different opinions even from real world pilots and I know a few who have all told me differing methods but all lead to the same thing--A SAFE LANDING!!!Hope that helps.Alan

Most planes, including 737, I use the following:250kias below FL100220kias on downwind or at 15dme.180kias on basereducing 160 when intercepting the glidereducing Vref at 4nm/outer marker.Dion Mollert

Hi GuysIf you fly an approach in VNAV, does the aircraft automatially decelerate towards VREF or do you need to set it manually in the speed window?Also can someone explain at what point you would reduce to VREF and if the speed is reduced in steps?Kindest Regards

Hi,Are you sure the current PMDG 737 supports VNAV approaches correctly?A Ryanair captain I knew tried it and said the ACFT went goo goo :)Bert Van Bulck

VNAV takes its command from the FMC. You would change from VNAV to LEVEL CHANGE (LVLCHG) or VERTICAL SPEED (VS) and reduce speed according to the flaps schedule and or when instructed to do so by ATC.

If you're doing a VNAV approach, why are you going from VNAV to LVL CHG or VS?

Yes, the FMC steps the airspeed bug to Vref landing speed. An important point to remember is when Vnav is engaged, the airspeed window on the MCP will be blank, always (unless you engage speed intervention). It's blank because the FMC is controlling airspeed and altitude restraints that are programmed into it's LEG's page. When flying a Vnav approach, the FMC will reset the airspeed bug as you manually select higher flap settings. If you look on the LEG's page, you will generally see the final Vref speed + 5 knots already calculated. During the Vnav approach, the FMC will automatically set the airspeed bug to this speed when the flap handle is moved to 30 flaps.You'll want to be at Vref + 5 (or what ever the wind correction value for a hand flown approach) at the FAF or by GS capture. Going from clean configuration airspeed to landing configuration Vref is always done in increments. First you need to learn the max flap airspeed limits. Typically in the 737NG series, we use flaps 1, 5,15,25,30 and 40. As you extend the flaps, you can see this limit displayed on the PDF airspeed tape. A yellow bar is permissible and red dashed squares are not. You need to study the 737NG profiles for aircraft configuration during the approach phase. Typically, flaps 5 is a good airplane configuration for maneuvering before prior to the FAF or GS capture point. John Floyd