A320 - when does ac activate app mode ?
 

Hi there

does anybody know exactly when the 320 activates the app mode ?
From what i have read it says 15 NM out of destination…but are these track miles ?

It is activated in 2 ways.

If the aircraft is in NAV mode and it flies over the DECEL point, it will activate the approach phase automatically, or the pilot can activate the approach phase manually using the FMGC PERF page.

Hope that helps.

Doesn't need to be in NAV, just overfly the DECEL point.

Must be NAV or APPR - otherwiese it won't activate automatcally

Yes it's track miles.

Many STARs bring your ac closer than 15Nm from the airport.
Auto activation of the app when you have 40 track miles or more to go would not make sense.

As far as I know, the "Decel waypoint" is only here to assure a continuous deceleration so that you reach:

- 1000ft AGL at Vapp in landing conf (for precision Approaches)
- the FAF/FAP at Vapp in landing conf (for NPAs) Provided you inserted Vapp on it
- a speed constraint which is below green dot somewhere in the STAR

No exact point
 

There is no exact point. It depends on many variables.

To prove it, put in an approach in the box. Note the decel point. Then assume that you're doing a stabilized approach (Vapp at the FAF) and enter the Vapp speed restriction at the FAF.

Note what happens to the decel point - it moves so that you hit it sooner.

Denti - the decel point will be on your screen in HDG, but flying over it won't activate.

Just make sure it has activated, keep the PERF page displayed until it does. It's very embarrassing when you manage the speed on final, the engines power up to accelerated you to 250kts and the master warning goes off as you have a flap over speed.

The good news is that this is something you will only ever do once.;)

Yup, my mistake, it won't activate in HDG, but it will in APP.

Yes you would hope so wouldn't you? - I've managed to do it twice in 11 years..........:ugh:

Yes, flying over the decel point in NAV will automatically activate the approach. The decel point of course takes into account any speed and height constraints that are in the database or that you have programmed in.

Also note that as the approach phase activates, speed reduces which can easily put you high especially if ATC give you track shortening. This problem is more noticeable when you are light and the approach speed is low, there is a big speed reduction from the typical 220kt range you are normally doing when approach phase activates to come back to green dot.

Selected speed may be needed to ensure you stay on profile. 220kts is a good speed in the A320 as you will usually be able to take half speed brakes and not infringe on VLS. Flaps 1 can be selected and the speed reduced to 190kts, stow the boards, take Flaps 2 and you are well set up for the approach.

Wake up everyone!
The approach MODE is activated by the pilot pressing the APP pb on the FCU.
OP.... you mean the approach PHASE.

Thanks TP, nice lesson on confirmation bias.:D
In return, I feel this could make you actually smile a little: The approach MODE is armed by the pilot pressing the APP pb on the FCU. Holiday cheers, FD!:ooh:

Guys,

FCOM 22 20 40 30 "Predictions Displayed on the ND" tells us that the 'D' indicates:

- The point at which the ac is predicted to decelerate for the approach (and thus switch to the approach phase)
- Magenta, if in managed speed and NAV or approach mode is engaged
- White if in selected speed or HDG/TRK mode
- Automatic deceleration only occurs when displayed in magenta

mcdhu

Thanks FD..... doh!

So the next question is why do some airlines put in speed control gates prior to the decel point?

Instead of (ATC aside) lettig the ac barrel down at 250kts, level out at THR IDLE then hit the decel point and start slowing down towards the IAF?

Probably to ensure stabilised approaches, if you meet the gates at the specified speeds you are unlikely to be high and fast on final. Unstabalised approaches usually start much earlier than 1000' with ATC track shortening combined with an inability to judge a descent profile being a common cause.

Flying the full STAR or RNAV approach will usually have you well positioned for landing, being taken off the arrival and given headings resulting in reducing track miles and losing the speed constraints requires skilled judgement to arrive at the correct speed and configuration on final.

Whenever I tell the PM to "activate and confirm, please".

Which rather begs the question, why would one ever activate but not confirm? :E

Tyro P,

Relax we are only trying to help the guy, the wording wasnt clear, besides you dont activate the approach, you ARM it.

How do you get an overspeed? When you push for managed speed, does it not respect the Vfe limit?