Here I’m performing an approach with a 10kt Headwind component in the DEFAULT a320NEO with a gross weight of ~70,000KG.
According to the Airbus A320 Quick Reference Handbook (QRH) the Vls speed for an aircraft on CONF FULL with a GW of 70tns is 140 kts, which corresponds to the Vls on the speed tape above.
Vᴬᴾᴾ, the final approach speed is VLS+APPROACH CORRECTION (COR). COR is 1/3 headwind component, with a minimum of 5kts and a max of 15kts. With a 10kt headwind the COR should be 5kts because 1/3 of 10kts < 5 kts.
Therefore the final approach speed should be 145kts. Yet the MCDU calculates
a approach speed of 155 kts, the magenta indicator on the speed tape corresponds to ~152kts.
I have submitted a ticket to Zendesk so hopefully this will eventually be rectified. My question for the meantime is simple:
Should I give the ‘speed’ over to the aircraft (Managed speed) on approach and have a speed in excess what I calculate the approach speed to be OR should I select my own approach speed using the calculation from the QRH?
Zendesk: 132958
correct me if I’m wrong but it looks like you set landing conf3 which refers to a VLS of 145 kts + 5 kts COR would be 150 kts for VAPP?
Yep, it sure does appear so. It’s impossible to change the conf in the default A320N. Vls on the PFD seems to correspond with Conf full, however
Looks to me like you are using the chart from a CEO.
For NEO VLS conf full at 70T, CG < 25% is 135 and VLS conf 3 is 146 (134 and 145 respectively if greater than 25%).
The approach speeds are definitely a bit buggy in the stock model from what limited examples I’ve seen of it, but two points to mention:
-
Ground speed mini means that target speed displayed on the PFD will not necessarily match the Vapp in the MCDU (but will never be less than it as here…), although I haven’t flown the stock model at all really to know if GS mini is actually modelled.
-
70T is above max landing weight, so an overweight landing, just in case you weren’t aware… so you’d only be landing at that weight in an emergency.
Out of interest I put your numbers (70 tonnes, 10kt headwind) into the LPC and Vapp Conf full is 140kt, Vapp Conf 3 is 151kts which lines up with what you would expect once given the correct VLS figures for a NEO.
So if the aircraft thinks it is doing a conf 3 approach, the PFD target speed is actually pretty close.
VLS and Vapp on the MCDU are both incorrect but somehow the programming seems to get it about right (for conf 3) on the PFD… go figure.
VLS on the PFD is aircraft state sensitive and nothing to do with any flap configuration selections in the MCDU. If you have physically selected conf full (and have no other issues to account for) you would expect the PFD to display VLS conf full regardless of any other selections.
1 Like
It’s a contrived situation of course, in the real aircraft you wouldn’t have this problem.
So… If you want to do a flap full landing, and the stock aircraft doesn’t let you set up for anything other than a conf 3, then sure just select the correct Vapp speed manually after selecting flap full. If it’s even modelled in the first place you would lose GS mini protection in doing so, but no biggy - especially in lighter winds.
There is the issue though that just like with conf 3 it doesn’t seem able to get the VLS quite right for conf full either (the actual correct Vapp of 140 would put you only ~2kts above VLS in your screenshot) so to be on the safe side you could just fly VLS+5 instead if you wish.
