Originally Posted by
Chris Scott
On Boeings and MD, IIRC, the equivalent to VAT is VREF, but the latter only has one value: that for full flap with full L/E devices. Every combination of L/E devices and flaps has its own increment above VREF. VREF is always bugged on your ASI. You then add any config-required increment for the landing, and bug that as well. During the intermediate approach, as you you extend whatever devices are available, you fly the appropriate increments above VREF - like you do on a normal approach.
Not so - the performance manual for (for example) a B737-400 will give you a VREF for each configuration - so you would have speeds such as VREF30 and VREF40 where the number in the title indicates the flap setting . Then, using the BA SOP as an example, there will then be (typically) an increment added to that for wind and gust factor - usually something like "half headwind plus all the gust factor up to a maximum of VREF+15". Therefore with a steady 14kt headwind the approach speed would be VREF30+7kt.
VREF30 would be bugged with a fixed bug on the ASI, the moveable "command bug" set to the approach speed, and another fixed bug set to VREF30+15kt which would be the speed to be flown during the initial stages of the go-around (prior to acceleration and flap retraction)