Can You Do A Late Runway Change On An Airbus Without Disconnecting The Autopilot ?

[used2flyboeing]

Dear friends, Can you do a late runway change on the AIRBUS on final ? - IE or do you have to disconnect the autopilot do dial in a new heading etc..

Thanks !

[NigelOnDraft]

Not quite sure what you're after here? And how "late on finals"? And whether you're talking "possible", or the best way of doing it?

Having just come off the 757/767, and now on A320, the Airbus is a little quicker (button presses) to change runways in the box, and if such a change was anticipated, the "secondary Flt Pln" I find easier to use than whatever the Boeing box equivalent was...

However, if you're discussing less than, say 2000', and visual, can't see why anyone would even think of doing this on the box, and not disconnecting everything and look out of the window!

NoD

[LEM]

Maybe what used2 means is that on Boeing you can't change mode once it has captured both LOC&Glide, unless you press TOGA (or using some tricks...).

Is it possible on the Bus to select Heading mode after APP light extinguished?

[SLT]

You can change the runway down to a late stage of the approach - ie. 700 feet. At 700ft RA with APPR mode engaged, the ILS course and frequency are locked into the receiver. Nothing you do will change them. At 400ft RA - LAND mode engages and the only way you can get out of it is either to go around, or disconnect the AP/FD.

I'd agree with Nigel though - do you really want to be having your head down and fiddling about that late on? Just take the AP/FD off and fly the aeroplane! Assuming you are sidestepping to a parallel runway - you'll even get GS mini. If you're IMC - get the other guy to hard tune the new ILS and follow that if you have time - if you're too low for all that and IMC - go around.

Hope this helps! :ok:

[LEM]

A bit confused: just as a curiosity, you confirm before 400 ft RA on the Bus you engage Heading mode if you were tracking LOC and GLIDE?
On Boeings you can't.
:confused:

[RadarContact]

Yes, you can disengage GS and LOC mode by switching to HDG. You'll automatically go to V/S mode as well.
But does this make sense once you're on final?

Theoretically you could maintain heading and vertical speed until the other runway is inserted and then re-intercept with LOC/GS armed... (definately easier on parallel runways)

[used2flyboeing]

I agree with you all about being heads down on late final ! I know that some boeing autopilot flight director systems allow the flight crew to make a late runway change without disengaging the autopilot. You can transition to a new runway assignment if radio altitude is greater than 1500 feet. The system logic determines whether or not localizer and/or glideslope have been captured and enters predetermined modes as a result - therefore one can transition to the new approach while enabling instrument landing system retuning while maintaining autopilot engagement. I believe the modes are:

A) in the event localizer but not glideslope of the initial ILS has been captured,
i) maintain the aircraft's current pitch mode,
ii) disarm glideslope capture,
iii) transition aircraft roll to a predetermined roll mode, and
iv) enable ILS tuning to the desired runway,

B) in the event glideslope but not localizer of the initial ILS has been captured,
i) retain the current roll mode,
ii) disarm localizer capture,
iii) transition aircraft pitch to a predetermined pitch mode, and
iv) enable ILS tuning to the desired runway,

C) in the event both localizer and glideslope have been captured,
i) transition aircraft roll to a predetermined roll mode,
ii) transition aircraft pitch to a predetermined pitch mode and
iii) enable ILS tuning to the desired runway.

It will NOT work below 1500 - I really agree with your comment though " Just take the AP/FD off and fly the aeroplane! Assuming you are sidestepping to a parallel runway - you'll even get GS mini" Too expensive to go around .."- if you're too low for all that and IMC - go around "


Thanks ! Im familiarizing myself with the training philosophies between birds - Thanks !

[earnest]

The answer is yes, and it is a well laid down and practised procedure on circling approaches when you know you are going to be discontinuing the approach to the RW set up in the primary flight plan. You will also be discontinuing the approach quite late on, at least you always will be in the sim where you frequently have to practise this manoeuvre, because Capt TRE IRE sets the weather to minima which is usually below 1,500 ft AAL.

At 100 ft above the MDA (H) you select V/S to zero and pull the knob (or just push the V/S mode knob on newer spec FMGCs) and it levels out almost perfectly on your circling MDA. Then use heading mode to steer the aircraft onto the landing runway’s downwind (which as other contributors have said will take it out of whatever approach mode it’s in). Activate the secondary flight plan (2 button pushes) and the other RW’s data is instantly ready for use, as is the Mini GS.

If it’s a late RW change (for example that still wind turns out to be too much tailwind for comfort), then the same technique will get you on the D/W of the other RW. It’ll take a few seconds to put the landing RW into the primary or secondary flt plan (whichever you decide is quickest to use), and to put the landing RW’s data into the performance page (but you don’t have to put this data in, the aircraft doesn’t sulk and stop you from landing despite what some people will tell you).

I think there is a big distinction between hand flying and being “heads in”. Breaking off an approach to a RW is often high workload and if the automatics are used correctly both guys can be eyes out and "ears out" as much as possible. Some would argue if you’re changing your mind about the landing RW below 500 ft then a go around may be the safer option.

It’s all described in fluent Airbus-speak in the manuals.