D.I.Y. GS-mini?
So what about you, Olendirk, trying to stay within SOPs in your Boeing 737; next to a captain like BOAC, wielding his rolled-up newspaper – ready to flagellate?
I presume you are flying an approach speed which has been calculated by yourself – or by the FMS, based on the reported surface wind; and that you are using an IAS knob manually to alter the target? If that surface wind is small, you will have added little to VREF, and are at the most vulnerable to the inevitable wind-sheer. With luck, the sheer will be gradual – but it may be sudden, as in my example (see my previous posts).
To deal with serious cases, my suggested technique starts with calculating an estimated threshold GS. This involves correcting threshold IAS to TAS, if necessary; then subtracting the headwind component. This is "GS-mini". Once established in landing config at the selected approach IAS, look at the indicated GS. If it is below GS-mini, wind up the selected IAS to try and correct it, but do not exceed the stabilised-approach IAS criterion for this approach. Do not exceed GS-mini. As the headwind falls, GS rises, so you must reduce the selected IAS. Once it has reached the original approach speed, leave it alone.
Ensure you NEVER select an IAS below the SOP approach speed. If the tower reports a big revision to the reported surface wind, revert to the normal SOP (and, just as normal, consider the possibility of a go-around). In any case, ensure that the calculated approach speed is selected by 100ft. [Once the AP has been disconnected, these selections have to be made by the PNF.]
If the above technique is unacceptable to your fleet managers and trainers, or to the captains you fly with, there may be very good reasons; the possibility of mis-selecting too low an IAS being one, depending on your FCU and FMS. BOAC's opposition may seem to be pure Luddism, but it could also be that he is in the honourable business of enforcing SOPs. In less-regulated times, it has been done on other aircraft. You, however, may have to wait for an Airbus...