Flying faster because of decreasing winds

[Chris Scott]

Wizofoz,
I see that you are a purist, like me. As you say, no velocity is absolute; it has to be relative to something. However, astronauts excepted, pilots and humans usually measure it in relation to the local surface of mother earth. Although the latter is revolving at up to 900kt about the Earth's axis, and the Earth is making its rapid journey around our sun, and our sun is travelling around the Milky Way galaxy, etc.; this reference is steady enough – and therefore useful – for the purpose of defining the "V" in the kinetic-energy equation.
The same cannot be said for the atmosphere, I can assure you, particularly when you are descending through divers layers of same.

Port Strobe,
If it's "Horlicks" to state that, for a given mass, inertia (kinetic energy) is a function of GS, perhaps you can tell us what else? IAS?
Although I was trying to avoid formulae, it is actually proportional to the GS (velocity) squared, which makes a shortage of it even more difficult to correct.
You also suggest: "...when you get a bus job then let autothrust faff with your speed until you're content."
A/Thr is not required, unless demanded by an airline's SOP. During 14 years on the A320, 90% of my manual approaches were flown with manual thrust from 1000ft, and 99% with "managed" IAS indicated as the target speed on the ASI. "Managed" IAS always provides GS-mini protection on Airbuses since the A320.
The great thing is: you don't need so many thrust changes – see (4), below.

BOAC,

(1) We agree on one point: adherence to SOPs. That was the only post-posting misgiving I had yesterday evening. See (5), below.

(2) But you are still choosing to misinterpret the concept of avoiding an unsustainably low ground speed on the approach. Perhaps you should read my post again – more carefully. And electricdeathjet's.
Given the chance, of course, Airbuses would stall in exactly the same way: at an IAS. The trick on the approach is to avoid a predictable, critical loss of IAS by anticipating the loss of headwind.
Let's look at the common example in my post above. Using your traditional technique: if the surface wind is known to be calm, you will have added nothing to your approach IAS. Assuming sea-level/ISA, an approach speed (VAPP) of 125kts, and a steady headwind of 25kts above (say) 100ft; you will be soldiering on in your B737 quite happily at a GS of 100kts. Fine so far... But what is the point, when you know that your GS is going to need to increase by 25kt in the last 100ft (10-12 seconds) of the approach; involving a big handful of thrust, and (not being an A320) a lot of pushing/re-trimming?
If the SOP is to fly a stabilised approach, why allow it to be predictably de-stabilised close to the ground?

(3) You imply that we are ignoring the all-importance of IAS. On the contrary: IAS is precisely what we are trying to conserve.

(4) The "GS-mini" concept protects IAS by constantly offering the pilot an IAS target ("managed speed") which results from:
the higher of VAPP and the IAS required to achieve the minimum GS.
If the headwind component on the approach is higher than reported on the ground (and entered into the PERF page of the FMGS), the IAS target will be above VAPP. It will also rise and fall with the current headwind component. Despite (in fact, because of) this changing IAS target, the thrust requirement remains roughly the same, because the aircraft's kinetic energy remains constant at the constant GS.

(5) This changing, managed IAS produces two issues that have to be addressed.
> (a) SOP stabilised-approach IAS criteria have to be relaxed slightly. In the above example, the managed IAS target at 500ft would be VAPP+25 (150kt).
> (b) If the difference between headwinds aloft and on the ground is very great – say, 45kt at 1500ft – the resulting IAS target of VAPP+45 may exceed the flap limit for the next flap extension. So a suitable selected IAS has to be maintained, which will often be dictated by ATC anyway. As the headwind declines, the GS rises, and managed IAS can be introduced, subject to ATC.