Cat IIIB in A320

[Boyington]

While doing a Cat III B approach in A 320 it is required to give a callout at 1000ft. Does this have to be on the Pressure Altimeter or on RA? Can someone please clarify and also give the reason. Thanks.

[Consol]

It's rad alt.

[I-2021]

While doing a Cat III B approach in A 320 it is required to give a callout at 1000ft. Does this have to be on the Pressure Altimeter or on RA? Can someone please clarify and also give the reason. Thanks.
Radio Altimeter. The reference is 1000 ft AAL, if you're landing at an airport with an elevation of, let's say, 2000 ft You will never (hopefully) see 1000 ft indicated on your baro PFD.

[wiggy]

I know nothing about the 'bus so can't give a techie answer but just a thought that for low vis Ops 1000 feet AAL is the approach ban point (e.g "do we have the RVRs to go any further", and associated questions).

[Goldenrivett]

Does this have to be on the Pressure Altimeter or on RA?

It should be done from the Pressure Alt (Runway Elevation + 1,000 ft).
Unless the terrain is flat, the radio ALT will indicate the approach ban point at the wrong point. (e.g. Geneva RW05 over lumpy terrain, RW23 over a flat lake)

[Right Way Up]

It will depend on your company SOPs ......however it should be 1000 ft above elevation based on the baro readout. i.e. LGW airfield elevation approx 200 ft, Call "1000" when passing 1200 on the baro.

[wiggy]

It will depend on your company SOPs

As on all types that makes sense - Out of interest now the issue has been raised is just to emphasise the approach ban issue or something more techie?..

[Metro man]

The decision to downgrade to CAT1/2 because of a system failure has to be made above 1000'.

[wiggy]

Makes sense to me, now hopefully the OP got at least one answer to the "why"!!!!

[Denti]

Now if airbus just would copy boeing a little bit more, display the 1000ft and 500ft gates on the altitude band and on the vertical situation display please...

[FlightDetent]

@Boyington: I believe all the FCOM references for LVP say RA, this is however not entirely correct. The author, probably for simplicity, omits the possible terrain characteristics.

Normally all 1000 ft references (approach ban, stabilized policy, ECAM quarantine) should be based on AAL, or above THR ELEV. SOP between companies may vary.

@Denti: how cool is that!

[dixi188]

On the A300 the "1000ft Radio" Altitude call was to alert you to look for the AFCS going from "Land Arm Amber" to "Land Arm Green" at 700ft.
We were only Cat3A but I wonder if it is the same logic.

[Amadis of Gaul]

It's RA for us with a caveat that at some airports "this may not be accurate". SJO comes to mind.