Spooky 2;
The Airbus A319/A320/A330/A340-300/500 series uses what is called "GroundSpeedMini". The intent is to maintain the energy level of the aircraft in strong headwinds and/or shear conditions. It will add more than 20kts but take it off quickly, as/when required. In my experience with all 3 types, the system is very responsive; it works extremely well. I can't recall a landing when it caused us to eat up more runway due to a higher than required speed over the fence.
The computation works in concert with the FMC-entered winds given by ATC. The added speed to Vapp was limited to 15kts, (Vapp is Vref + 5kts, so we're really adding 20kts to Vref), but the GSMini will, (and has, in my experience) added quite a bit more. Below 400ft, the software will maintain sufficent energy to land at Vapp.
What I have seen both from the flight deck and in flight data is the autothrust, still engaged, (thrust levers not closed to idle), increasing thrust to maintain the approach speed as the aircraft is in the flare and speed is bled off. This almost always results in a long flare and a long, (beyond the TDZ) landing.
DonLeslie;
Agree with your thoughts on adding 5 to the Vapp - BTDT and it works. Sometimes letting the airplane just hang on Vapp is a bit too small an energy reserve. That said, I much preferred manual thrust levers in manual flight and control my own energy level.
As an aside, on the A330/340 I always tried to derotate with enough rate to beat the forward bogies to the ground before they slammed down and was successful only part of the time. There wasn't the same problem with the 345.
PJ2
Last edited by PJ2; 12th August 2010 at 00:19.
Reason: drop extraneous comments, add more info re GSMini