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A320 CDFA LNAV NAV/FPA

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A320 CDFA LNAV NAV/FPA

Old 24th Feb 2019, 08:53
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A320 CDFA LNAV NAV/FPA

Good day fellow A320 pilots,

I have my type rating only for a short while, during training we did early stabilized approaches for NPAs. Hence I would be level at the FDP altitude configure then at 1NM from FDP Id set the FPA required and at 0.3NM from the FDP Id pull FPA.

My airline recommends we do CDFA and decelerated approaches. So I usually descend in vertical speed to the FAP then for an ILS or fully managed NPA with FINAL APPROACH Id arm the approach mode when cleared. However with a NAV FPA approach descending with vertical speed to FDP at what distance would I turn FPV on and select the FPA for the approach.

Regards

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Old 24th Feb 2019, 13:18
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Laterally managed and vertically selected requires TRK-FPA ON only after FAF. Before that you may use v/s at your convenience.
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Old 24th Feb 2019, 13:25
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Originally Posted by iggy View Post
Laterally managed and vertically selected requires TRK-FPA ON only after FAF. Before that you may use v/s at your convenience.
So lets say the FAF is at 11NM from threshold, could I only select TRK-FPA ON at 10.5NM or by 11NM I need TRK-FPA ON. Thanks for the thread reply!
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Old 24th Feb 2019, 14:58
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Originally Posted by migueloliv View Post
Good day fellow A320 pilots,

I have my type rating only for a short while, during training we did early stabilized approaches for NPAs. Hence I would be level at the FDP altitude configure then at 1NM from FDP Id set the FPA required and at 0.3NM from the FDP Id pull FPA.

My airline recommends we do CDFA and decelerated approaches. So I usually descend in vertical speed to the FAP then for an ILS or fully managed NPA with FINAL APPROACH Id arm the approach mode when cleared. However with a NAV FPA approach descending with vertical speed to FDP at what distance would I turn FPV on and select the FPA for the approach.

Regards

Hi,

do not confuse a CDFA with a constant descent with no intermediate level offs. A CDFA stands for Continuous Descent Final Approach and, as the name suggests, it starts at the FAF and it means that You will fly down to the minima with a constant angle and no level offs in between (that is the opposite, for example, of flying the so called "dive and drive" where You plunge to the minima straight from the FAF and wait for the MAPt), which is basically what You always do in both managed and selected approaches. If You are making Your way down to the FAF in V/S just switch to TRK/FPA 1 NM before it so that You will be fine to pull Your FPA 0.3 NM before. Consider also that in those circumstances leading You to fly a NPA in NAV/FPA, You may well allow Yourself to fly levelled a couple of miles before the FAF in order to grant the early stabilisation (that is SOPs for example for several operators).
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Old 24th Feb 2019, 15:50
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Originally Posted by migueloliv View Post
Good day fellow A320 pilots,

I have my type rating only for a short while, during training we did early stabilized approaches for NPAs. Hence I would be level at the FDP altitude configure then at 1NM from FDP Id set the FPA required and at 0.3NM from the FDP Id pull FPA.

My airline recommends we do CDFA and decelerated approaches. So I usually descend in vertical speed to the FAP then for an ILS or fully managed NPA with FINAL APPROACH Id arm the approach mode when cleared. However with a NAV FPA approach descending with vertical speed to FDP at what distance would I turn FPV on and select the FPA for the approach.

Regards

If youre planning doing a fully managed approach, you would not need to set from v/s to fpa, there is no need, just arm the approach.
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Old 24th Feb 2019, 15:58
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Originally Posted by sonicbum View Post
Hi,

do not confuse a CDFA with a constant descent with no intermediate level offs. A CDFA stands for Continuous Descent Final Approach and, as the name suggests, it starts at the FAF and it means that You will fly down to the minima with a constant angle and no level offs in between (that is the opposite, for example, of flying the so called "dive and drive" where You plunge to the minima straight from the FAF and wait for the MAPt), which is basically what You always do in both managed and selected approaches. If You are making Your way down to the FAF in V/S just switch to TRK/FPA 1 NM before it so that You will be fine to pull Your FPA 0.3 NM before. Consider also that in those circumstances leading You to fly a NPA in NAV/FPA, You may well allow Yourself to fly levelled a couple of miles before the FAF in order to grant the early stabilisation (that is SOPs for example for several operators).
From what I understand what my airline wants is that we fly a constant descend to FAF from TOC using V/S to control our descent rate and never leveling off. Then a decelerated approach (so no level flight a couple of miles before). If Im descending in V/S and press the FPV wont the aircraft revert to a equivalent FPA of my current V/S? In that case would I still turn on the FPV 1 mile before then at 0.3 id just turn the FPA knob?
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Old 24th Feb 2019, 16:27
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Originally Posted by Black Pudding View Post


If youre planning doing a fully managed approach, you would not need to set from v/s to fpa, there is no need, just arm the approach.
The question I made was based on flying an LNAV in NAV/FPA. For example in case of temperature corrections I wouldnt be able to arm approach mode and fly a VNAV below the chart compensated temperature.
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Old 24th Feb 2019, 16:58
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migueloliv There are no guidelines for your case, you just need to try.

My suggestion
- Tweak the V/S so that you are happy with the vertical path. Once you have a final setting that will take you to FAF: switch the bird on immediately.

Personally, I never learned to use 0,8 deg FPA, 2,1 or 1,3. Even seeing the arrow does not help focus the brain, I just seem to need -1000 / -700 / -500 / -300 fpm.

Enjoy the aeroplane. Judging by the choice of the question the Borg's got you.
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Old 24th Feb 2019, 18:12
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Originally Posted by migueloliv View Post


From what I understand what my airline wants is that we fly a constant descend to FAF from TOC using V/S to control our descent rate and never leveling off. Then a decelerated approach (so no level flight a couple of miles before). If Im descending in V/S and press the FPV wont the aircraft revert to a equivalent FPA of my current V/S? In that case would I still turn on the FPV 1 mile before then at 0.3 id just turn the FPA knob?
Hi miguel,

it is perfectly normal that Your operator wants You to fly a constant descent to Your FAF and the procedure thereafter. In the vast majority of circumstances You will fly NPAs "ILS alike", meaning with FINAL APP guidance. In those other situations where NAV-FPA or TRK-FPA is required, You will also need to fly an early stabilised approach, meaning that You will need to be fully configured by the FAF. The combination of selected vertical guidance and the aircraft configuration "usually" suggests to have a small level segment, but of course it is not mandatory as per Your Operator policies. In that case, as mentioned by another poster, it is basically up to you on when You will switch to TRK/FPA guidance as long as You're ready to "pull" by the .3 NM.
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Old 24th Feb 2019, 22:00
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Originally Posted by sonicbum View Post
Hi miguel,

it is perfectly normal that Your operator wants You to fly a constant descent to Your FAF and the procedure thereafter. In the vast majority of circumstances You will fly NPAs "ILS alike", meaning with FINAL APP guidance. In those other situations where NAV-FPA or TRK-FPA is required, You will also need to fly an early stabilised approach, meaning that You will need to be fully configured by the FAF. The combination of selected vertical guidance and the aircraft configuration "usually" suggests to have a small level segment, but of course it is not mandatory as per Your Operator policies. In that case, as mentioned by another poster, it is basically up to you on when You will switch to TRK/FPA guidance as long as You're ready to "pull" by the .3 NM.
There is absolutely no requirement from Airbus to fly an early stabilized approach for those approaches. It's only recommendation
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Old 25th Feb 2019, 03:07
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Originally Posted by sonicbum View Post
You're ready to "pull" by the .3 NM.
The advance pull is required to exit ALT mode to FPA or V/S timely enough so that through inertia and automation lag the aircraft wouldn't start descending late - the actual trajectory.


Because in Miguel's scenario he's already in an active vertical mode, the advice above does not apply.
You can change the reference to FPA any time, even at 10000 or higher. My personal technique for the profile they demand is in the previous message. What is also perfectly doable, is to keep V/S even a little longer, past the FAF. No benefit at all in doing so but no harm done either.

@migueloliv:
As long as you know which trajectory you want and where the aircraft is, you will be fine. Take any reference you need to keep the task as easy as possible - that is correct use of automation and cockpit resources (evaluation item). Inevitably, at one point you want FPA instead of V/S.


The guidance to do 1 / 0.3 NM, from your type rating course
- assumes you are closing to FAF in ALT mode
- has a technical reasons behind each of the values.
Neither of which applies for your question.



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Old 25th Feb 2019, 07:18
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Originally Posted by FlightDetent View Post
The advance pull is required to exit ALT mode to FPA or V/S timely enough so that through inertia and automation lag the aircraft wouldn't start descending late - the actual trajectory.
That is why I have written "pull" in inverted commas.
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Old 25th Feb 2019, 07:22
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Originally Posted by Cak View Post


There is absolutely no requirement from Airbus to fly an early stabilized approach for those approaches. It's only recommendation
Sure it is a recommendation. Do You teach / have been taught to fly decelerated selected NPAs ?
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Old 25th Feb 2019, 13:29
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Originally Posted by sonicbum View Post
That is why I have written "pull" in inverted commas.
You got me confused either way then - the gentleman already has a active selected vertical mode, he does not need to pull anything?

For your second question on decellerated 2D approaches: within strict and limited RoE: absolutely yes.

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Old 25th Feb 2019, 15:08
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Originally Posted by FlightDetent View Post
You got me confused either way then - the gentleman already has a active selected vertical mode, he does not need to pull anything?
No, as he is already in V/S.

Originally Posted by FlightDetent View Post

For your second question on decellerated 2D approaches: within strict and limited RoE: absolutely yes.
Wonderful then, enjoy it ! A few weeks back I was shooting an NDB approach in NAV-FPA in Eastern Europe with OAT -20 at 2 AM and a 250 hours cadet on the RHS doing his final line check. As per our SOPs those kind of approaches must be flown early stabilized, but if I had Your skills I would definitely get the gear down at 1000 ft AGL while smoking a cigarette ;-)
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Old 25th Feb 2019, 15:42
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I am glad you asked what those rules of engagement are.

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Old 25th Feb 2019, 16:54
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I should know better than to argue about this one on the internet, but here goes:

You want to fly a temperature corrected NPA in NAV-FPA. The FDP is at 2000’ (2100’ temp corrected) at 4.7NM from threshold. Elevation 900’ . You are at 15NM at 5760’ descending -400fpm.

Please explain to me how you can intercept and maintain the 3.1 deg path without ever leveling off,while decelerating and configuring at the same time.
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Old 25th Feb 2019, 17:43
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Originally Posted by migueloliv View Post


The question I made was based on flying an LNAV in NAV/FPA. For example in case of temperature corrections I wouldnt be able to arm approach mode and fly a VNAV below the chart compensated temperature.
you said Fully Managed Approach
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Old 25th Feb 2019, 23:10
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Originally Posted by Radu Poenaru View Post
Please explain to me how you can intercept and maintain the 3.1 deg path without ever leveling off,while decelerating and configuring at the same time.
Exactly, in this case you dont have a correct V/DEV to guide you since you are doing temperature corrections and I find it impossible to intercept the path perfectly while descending, decelerating and configuring at the same time.

second in the FCOM it talked about the 75ft on the V/DEV if you are below you have to go around. For LNAV I cant find any vertical limits. So is it again 75ft(3/4 dot) or something else?
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Old 26th Feb 2019, 08:28
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Originally Posted by migueloliv View Post

[…]I find it impossible to intercept the path perfectly while descending, decelerating and configuring at the same time.

It is! It’s quasi-impossible. The only time this might work is if you have ridiculous long final, (imagine +7000’ platform) and comming in high above the glidepath. Come in V/S all the way to the FDP aiming to get there way above platform. Switch FPA and keep going at 4-5 deg with your PM reading intermediate alts, until you are getting closer. Meanwhile configure and decelerate, though the 4deg will not help there, so you are probably speed brakes out by this point, maybe you even disconected A/P to get full speebrakes. When 200’ above select 3.2 etc (or ask PM to keep setting FPA as you disconnected AP) until you intercept. If you ever intercept. Could it be done? Well, maybe. But should this be the SOP? It looks sloppy, unprofessional and it’s unsafe. Better not do this with me unless you buy me a large drink after the flight.

How much more elegant would it be to level off 1 NM before the FDP, calmly call “ALT” ask for flaps 3 and select TRK/FPA and -3.1deg. Then when PM says “descent point” pull the FPA and ask for full flaps(or slightly before). Already on profile.

Which pilot would you like to fly with?

Last edited by Radu Poenaru; 26th Feb 2019 at 08:38.
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