Hi vilas,
Am surprised that, as time approaches the 32nd anniversary of my first go in an A320 sim (an early, highly-unreliable Thomson-CSF model at Blagnac), yours is incapable of simulating the conditions of an everyday, windy approach!
Hi FlightDetent,
Thanks for providing that PDF of the FCOM Bulletin 820/1, dated June 2004. Is it still current, I wonder? it could have been better written, I think, some of it even liable to cause confusion.
It seems the expression "MAX" has been used when "the greater of" would have been more appropriate.
For example, in the table near the bottom of Page 3 dealing with VAPP computation for "A320 with Mod 25225 / A319 / A321" the text should - I think - continue more like this:
"VAPP = VLS + the greater of [5] and [1/3 of the Tower headwind-component]"
And the statement in the middle of Page 4 should read more like this:
"IAS target = the greater of [VAPP] and [GS-mini + current wind-component]"
The biggest change to the speed computations since my days, as previously mentioned, is the reduction of GS-mini to VAPP -10 when the headwind component of the W/V pre-inserted in the PERF page is 10 kt or less, or there's a tailwind. It does seem a bit arbitrary, considering that a VAPP of 130, for example, will translate to a GS-mini of 120 whether the pre-inserted W/V amounts to a 10 kt headwind-component or none at all. Taking the classic nocturnal windsheer case, a headwind of 10 kt at, say, 50 ft agl would produce a speed target of 130: equal to VAPP, or VLS +5. If the wind on the runway is a slight tailwind, the IAS could drop below VLS as the flare is initiated.
This slight change of policy on GS-mini may in part have been in response to something i saw all-too-often on windy days. As the target IAS rapidly reduced in the latter stages of the approach, the A/THR seemed unable to keep up, resulting in the IAS at 50 ft agl being significantly above target. This could be potentially compromising on a short runway when the surface wind was calm.