A320 and ILS: Q&A
Following the article on the ILS and the A320, here is some additional information from the PFD and ND screens of the A320 (mod A32NX) of FS2020.
How to read the information on these screens?
When the two APs are engaged and the FMA displays the possible approach capability (up to 5000 ft / ground, it will be CAT 1, then below 5000 ft, CAT 2, then CAT3 Single and CAT 3 Dual) . Warning, this display does not give the category of the approach in progress but the ability of the airplane to carry out it (which means that if during the entire approach you have CAT 2 displayed instead of CAT 3 Dual, you cannot fly a CAT III approach).
The FMA (Flight Mode Annunciator)
In the above case, we are doing a CAT I, but the plane would be able to do a CAT III (and if we could engage the two APs, we would have CAT 3 Dual indicated).
NB: the simultaneous 2 AP function is not yet available with A32NX.
In the APPR page, can we have a value in MDA and a value in DH?
No. If we put a value in MDA then a value in DH, normally the value of MDA will be erased. And if we put a value again in MDA, DH will be erased. The last value entered "wins".
The plane cannot have two minimum values.
Note that the new FMS standards, the FMA line is called BARO and the DH line is called RADIO, which is quite logical, BARO referring to a barometric altitude given by the altimeter and RADIO referring to a height given by the radio-probe.
How is CAT decided?
Cat I, Cat II, Cat III A / B / C it depends on the weather
Cat A, B, C, D (it depends on the stall speed of the aircraft with the gear and flaps extended)
Cat 1, 2, 3 single or 3 Dual, on 320 it says which approach the plane is capable of making.
(There are still the aircraft categories for wake turbulence J, H, M, L).
How to choose between MDA and DH?
MDA is for a Cat I approach which must finish "by hand", DH is for a Cat II, III A / B or C approach (and therefore an automatic landing).
If the terrain is in LVP, it's an automatic landing, if it isn't, it's Cat I.
Can we do a manual approach below the minima?
To continue a Cat I approach below the minima (200 ft / ground), see:
A part of the approach lighting, or the threshold, or the threshold marks, or the threshold lights, or the threshold identification lights, or the approach angle light or the area of touchdown or touchdown area markings or touchdown area lights or runway edge lights.
With 550m of view, it's not at all gained ... even if it's easier at night.
As we "pierce" under 3 ° (almost standard value of an ILS), that means we lose 300ft per NM. So at 1NM from the threshold we are at 300 ft / ground. As we have the right to descend in Cat I only up to 200 ft / ground, we will be there at 2 thirds of 1 NM or 1852 x 2/3 = 1235 m. If we only have 550 m of view, even with a 900 m approach ramp, the go-around is almost inevitable.