A320 A/P disconnect

[MD83FO]

On a CAT I ILS approach, what is the lowest height the A/P can be disconnected with CAT 3 DUAL on FMA?

[sabenaboy]

I couldn’t find a definite answer in the FCOM.
Did find this:
- 160 ft AGL, but that’s without Cat II or III on the FMA
- “If the flight crew performs an automatic approach without autoland, the autopilot must be disengaged no later than at 80 ft AGL.” (For a Cat II approach)
So my answer would be: (unless company SOP's are more restrictive)
You can leave the A/P on and perform an auto land OR disconnect AP no later than 80 ft AGL if not performing an autoland.

[FlightDetent]

With CAT3 DUAL displayed, in normal case, there is no height AFM limitation for AP disconnect.

FD.

[juliet]

You're flying a cat 1 approach so 160' according to my books. It's always going to say cat 3 dual if the capability exists.

Obviously if you're doing a practice auto land that's different, but that's not the situation you specified.

[sabenaboy]

Originally Posted by juliet

You're flying a cat 1 approach so 160' according to my books

If you're using a standard Airbus FCOM you will find in FCOM-LIM-22-10:

ILS approach when CAT2 or CAT3 is not displayed on the FMA .................................. 160 ft AGL

To me that means that when doing a CAT I approach with 2 AP's and CAT 2 or 3 displayed on the FMA, there's nothing in the books stopping you from keeping the AP on until 80 ft AGL.

[FlightDetent]

To me that means that when doing a CAT I approach with 2 AP's and CAT 2 or 3 displayed on the FMA, there's nothing in the books stopping you from keeping the AP on, full stop.

Corrected for you.

[sabenaboy]

Originally Posted by FlightDetent

Corrected for you.

Yes, you're right. I would recommend to switch them off to leave the runway. ; -)

[FlightDetent]

I'd heed that call! Anyways, in case the pilots plans to disconnect, what would be the lowest height to do so? I like your 80 feet, though I do not recall any specific reference in the OEM books. Most likely because Airbus sees no need to teach airlines to fly.

Does any sort of FLARE MODE happen on the 330/340? If so, would it be the same 50 feet as on the thin-bus?

regards, FD.

[juliet]

Bit of common sense here people. You've said that you're flying a Cat 1 ILS. So you've briefed a Cat 1 and then been cleared for a Cat 1. Are people on here seriously suggesting that they will leave the autopilot in and allow the aircraft to autoland? Without a clearance for such and therefore without the sensitive areas protected, or a statement as such from tower and an acknowledgement from you?

As I read it that line in the FCOM gives an allowance for us to fly Cat 2/3 approaches. I agree it isn't particularly clear, perhaps read it as "ILS approach when not flying a Cat2 or Cat3 approach."

Juliet

[FlightDetent]

Juliet, I beg to differ, perceived common sense does not take over here.

That line in LIMITATIONS is very clear and reads exactly what is printed. Minimum height for autopilot use with CAT 1 displayed is 160 ft. Meaning, that if your FMA displays CAT 1 the autopilot is only certified to 160 feet.

With CAT 2 or better displayed there is no technical limitation for autopilot disengagement, as indeed the aircraft is autoland and rollout capable.

Noted though, there is a paragraph "Autoland in CAT 1 conditions" or similar. I would agree with what you suggest completely, but not within the scope of OP's question.

take care, FD.

[juliet]

I think it is within the scope of the question. OP is asking when to disconnect the AP on a Cat 1 approach. Leaving it in till landing is an autoland, not a Cat 1.

[seen_the_box]

Are people on here seriously suggesting that they will leave the autopilot in and allow the aircraft to autoland? Without a clearance for such and therefore without the sensitive areas protected, or a statement as such from tower and an acknowledgement from you?

We're permitted (indeed required) in my airline to fly practice autolands, when weather is CAT I or better. There's no requirement to tell ATC, or for the sensitive areas to be protected in such a case. The operating minima remains CAT I.

[FlightDetent]

s_t_b: seconded. In similar fashion, e.g. during LVP training, the minima is CAT I but it is autoland with all the bells and whistles.

yours, FD.

[juliet]

So when you are doing a practice autoland do you brief the appropriate contingencies? Failures below 1000', alert height, no autoland warning etc? I certainly hope you do.

An autoland is not a Cat 1 approach. A practice autoland as mentioned is a Cat 3b flown within the met parameters of Cat 1 (invariably).

[Amadis of Gaul]

Even if there's no requirement to advise ATC, I make a point of doing it. Just one more t crossed, I suppose...

[Feather44]

- CAT 1 is an ILS Approach TYPE
- CAT 3 DUAL on FMA is an Auto Flight / Autoland CAPABILITY

Provided you did request (to practice autoland) and have been cleared by ATC, you can keep your AP up to taxi speed (20kt if not mistaking)

[FlightDetent]

Originally Posted by Amadis of Gaul

Even if there's no requirement to advise ATC, I make a point of doing it. Just one more t crossed, I suppose...

Same here.

[seen_the_box]

So when you are doing a practice autoland do you brief the appropriate contingencies? Failures below 1000', alert height, no autoland warning etc? I certainly hope you do.

An autoland is not a Cat 1 approach. A practice autoland as mentioned is a Cat 3b flown within the met parameters of Cat 1 (invariably).

Some CAT I approaches require an autoland in this outfit (CAT I LTS), and at some operators CAT II/III approaches don't necessarily end in an autoland (aircraft fitted with HUD guidance, for example). You're getting confused with the terminology. If the manufacturer and your company allows it and the aircraft is appropriately certified, you can do an autoland off any type of approach you choose (although of course in practice I can't think of an aircraft type which can autoland off anything other than an ILS/MLS).

As to your first question: the whole idea is that we brief and fly the approach as a CATIIIb approach and autoland. Therefore, we tend to run through the standard low vis briefing points (task sharing, standard calls etc.) However, clearly go around decision making is different in the practice case to the real one. We tend to brief that if we get a loss of CATIII/ auto land warning light etc. and we can safely revert to CAT I, we'll continue the approach manually to avoid an unncecessary go around.

Provided you did request (to practice autoland) and have been cleared by ATC, you can keep your AP up to taxi speed (20kt if not mistaking)

Certainly on our route network (Europe) there is no requirement to tell ATC. It doesn't change anything for them, and therefore they're not interested. We used to do it, and would invariably be met by silence, then a confused 'Roger' and occasionally a 'LVP protections are not in place.' It may be different in other parts of the world of course.

[safetypee]

TYPE includes weather, crew qualification, and ILS ground station and airport facilities.
CAPABILITY relates to the integrity of the auto-flight system.

Some Cat 1 ILS’s are suitable for practice autolands, but approval usually includes an understanding of the pre threshold terrain and the need for the crew to take responsibility for additional monitoring in case of deviation. Similarly for Cat2 /3, just because the ground station and airport facilities are suitable in poor weather this does not mean at all times, particularly if the protected zones are infringed or the ground station is operating single channel.

If a high accuracy, high integrity auto-flight system is flying with a poor quality input (Cat 1, or Cat2/3 unprotected beam) then a high accuracy output cannot be assured – review ILS beam, pre threshold and runway ground profile, and protected zones.

EURO Doc -013 via ICAO (now probably superseded by EASA docs)
6.8 Autoland operations when LVP are not in operation
6.8.1 ILS installations may be subject to signal interference by aircraft and other objects. In order to protect the ILS signal during operations in Low Visibility Conditions the sensitive area is protected during LVP. This ensures that the accuracy of the ILS signal is maintained.
6.8.2 There are a number of occasions when pilots wish to perform autoland operations when LVP are not in operation. These may be for pilot qualification and recency, for operational demonstration and in-service proving flights and for system verification following maintenance. In particular, some aircraft operators recommend that their pilots perform autoland operations routinely in order to reduce pilot work load during marginal MET conditions and after long haul flights.
6.8.3 When LVP are not in operation, it is possible that aircraft and vehicles may cause disturbance to the ILS signal. This may result in sudden and unexpected flight control movements at a very low altitude or during the landing and rollout when the autopilot attempts to follow the beam bends. As a result pilots are advised to exercise caution during these operations according to the instructions provided in their Operations Manual.
6.8.4 Pilots should inform ATC if they wish to conduct an autoland with protection of the LSA. In this case, ATC must inform the pilot if protection of the ILS/MLS sensitive area will or will not be provided. In some States, the hours where practice autolands are permitted are published in the AIP.

Examples from national authorities:-
http://www.caa.gov.qa/sites/default/...uto%20land.pdf
AIP for SWITZERLAND (section AD-1.1) valid from 17 SEP 2015 (para4.5.2)

http://www.pprune.org/tech-log/27905...ml#post3337711

[juliet]

STB - Im not getting confused at all. The OP asked about AP disconnect on a Cat1, no mention of autoland practice or otherwise. Cat3B, as you say, is a capability that will always show up providing conditions are met.

Obviously ATC requirements for a practice autoland vary around the globe. I do find it surprising that ATC aren't covering themselves by declaring the sensitive areas not protected.