View Full Version : Autoland CAT 1

24th Nov 2009, 00:11
Hi, everybody I have a question that maybe sound silly but I wonder how to do it, lets asume you can accomplished with the requirements to do an ILS DME CATI approach auto land, ok What do you set on your app page DH or MDA?.. :bored:
thank you


24th Nov 2009, 02:20
CAT one minima.
DH (DA).

24th Nov 2009, 02:30
ok tka 411A but why? wh not mda :bored:

24th Nov 2009, 04:37
Toby I assume you are talking about A320.

If I can remember it correctly if you enter a value in the DH fild of the APP page this value is referenced to the radio altimeter and if you put it in the MDA field it is referenced to the barometric altitude readout.

As you want to fly a standard ILS CAT I approach the DA is a barometric altitude and to get the correct indications and voice callouts setting the DA in the MDA field would be just right.

Above might be wrong, as it is long ago that I flew an Airbus...

25th Nov 2009, 13:38
yes, I'm talking about A320, but I don't find info relate it to this case in normal cat I approach you use mda as reference but I want to know what diference does it make in a AUTO LAND CAT I use as refeence MDA or DH.
Any information I would really appreciate it.

tks, toby.

25th Nov 2009, 13:52
I think that at MDA - 50ft the Autopilot will disengage, because NPAs are suppose to use MDA as a setting, and to be sure that From MDA and below the Approach is flown manually, .....:ok:
In anycase try it in the Sim :}

Sir George Cayley
25th Nov 2009, 15:19
If one does an auto coupled ILS approach in say CAT 3a conditions then the ILS Localiser Sensitive Area (LSA) will be safeguarded, and hence the risk of disruption to the signal reduced.

If you do the same approach to a CAT 1 ILS the LSA will not be safeguarded, nor will ATC increase approach separation.

You may not be concerned about this, but I thought I'd mention it.

Sir George Cayley

25th Nov 2009, 17:50
There's fundamental difference between ICAO definitions of DH/MDA and DH/MDA as entered into A320 FMGS.

On A320s I've flown (s/Nos around 1200) entering DH would arm autocallouts ("HUNDRED ABOVE" and "MINIMUMS") and "DH" display on PFD - with reference to radio altimeter. Setting MDA would merely display it on PFD and make alt digital readout turn yellow below it. It would have no bearing on LVP, autopilot or autoland capability whatsoever.

CAT 1 ILS has barometric altitude referenced minimum, therefore DA is entered into MDA field. If you fly by reference to QFE, then DH is inserted as MDA.

However, I'm only too glad that I was never allowed to use autoland on CAT 1 ILSes or autothrust while flying manually.

26th Nov 2009, 03:12
tks for your replies, I will keep trying to find some reference about this scenario I understand what cat I approach require in order to stablish a minimum but in a 320 if I want to try an autoland there is where my doubt comes on and I wonder if there is some restriction or something :ugh:
may be I'm not clear enough but if there some A320 expertise I will really appreciate his opinion.

many tks, toby.

26th Nov 2009, 08:51
I know nothing of the dark and wondrous workings of the electric jet and what the autopilot will and won't let you do, but in my book (737) it is exactly as Captain Pugwash's mate says. Bug up for the Cat IIIx, advise ATC who, if you are lucky and they are not busy might give you a 'semi-protected' environment, and then allow the full automatics to proceed - with 'standard calls' - hovering like a fussy maitre-d' over the controls lest some infringement of the protected zone might cause an interesting diversion onto the grass. Common practice (not the grass) to get your mandatory 'minimum' landings to maintain qualification and for training. Normally works just fine.

26th Nov 2009, 08:54
Do you read the posts?:ugh:
I have written that at MDA minus 50ft the autopilot will disengage, because MDA is for NPAs

26th Nov 2009, 08:59
Greetings to you too, 'kijangnim' - was that addressed to anyone in particular?

26th Nov 2009, 09:12
You're not flying a non-precision approach though are you? It says 'ILS APP' on the ND.

With MDA in the box it will still fly a full autoland, the AP will NOT disconnect at MDA-50.

Right Way Up
26th Nov 2009, 09:20
Cat 1 minima is referenced to baro alt whilst Cat 3 is referenced to radalt. Therefore if you fly a practice autoland it is down to you which minima you set but you are still bound by the MDA. (obviously). Personally on a good weather day I would set DH, on a poor weather day, where I have planned an autoland in case of possible deterioration I will set MDA if the airfield has not declared low viz ops.

Despite the fact some people believe the autopilot will disconnect at
MDA -50, the aircraft will quite happily autoland.

charlies angel
26th Nov 2009, 10:02
Take yourself off to a dark room and repeat 100 times
" I do not understand how an airbus works, I am a danger to myself and anyone who plays with my flight simulator".
You clearly have no knowledge of mda,da,dh,mdh,lnav,vnav,lvp,rnp etc etc.
Please keep your incorrect opinions to yourself and watch and learn from the sidelines.
Now read the posts!!!:ugh:

26th Nov 2009, 10:30
Greetings and Apologies, no excuses, I should have reopened the books (been a while since I flew Airbus)
and indeed MDA - 50 feet is for NPA only so AP will not trip Sorry guys. :ouch:

26th Nov 2009, 10:43
As mentioned earlier, what you enter in the MCDU minima does not affect the landing capability of the aircraft at all. I have performed autoland many times in airfields with Cat 1 only and MDA set for the Cat 1 minima, purely for autoland currency. Obviously you have to have Cat 1 weather and be prepared to disconnect the AP at any stage if the aircraft is not doing as you would expect it to do.

26th Nov 2009, 10:47
Hi toby320, here is your answer,

You set the applicable CAT I minima on the MDA field.
You are allowed to perform an autoland (yes autopilots remain engaged in LOC GS modes even below MDA-50) in CAT I conditions or better and at least CAT II landing capability displayed in the FMA. If autoland light on take over manually (in CAT I conditions you most probably wil have visual references) or go around.
Take into acount LSA might not be protected and remember your CAT I minima is your decision altitude which means you have to go around if no visual references by this altitude.
By the way you are allowed to perform autoland under these conditions even in CAT I only installations.


Edit: Wizzaird was a bit faster than me.

26th Nov 2009, 11:05
Fair bit of confusion here. Even Boeing Obi Wan Kenobi BOAC felt he had to say something (nice to see you on an Airbus thread - yes I have gone to the dark side...).

Just to clarify it for toby 320:

1) LAND/FLARE/ROLLOUT will be displayed as long as you have selected an ILS approach and have ONE autopilot engaged

2) As long as the above is displayed the aircraft will autoland, REGARDLESS of whether you selected a DH or DA/MDA but you MUST have at least Cat II displayed on the FMA (based on systems availability)

3) Auto callouts will be armed regardless of selecting DH or DA/MDA. They will just be based on either baro alt or rad alt depending on which one you picked. There are additional callout modifications specific to each type of approach e.g. ONE HUNDRED as opposed to HUNDRED ABOVE if you picked NO DH (Cat IIIb).

So to go back to your original question, you can select a Cat I minimum in the MDA field of the MCDU and do an Autoland. Airbus recommends you select both autopilots if they are available. But it will work with one as long as no failures occur to downgrade the landing capability below Cat II (again, as displayed on FMA).

Beware of the ILS-sensitive area being not protected (see BOAC post)


Edit: both Wizaird and aristoclis were faster than me :ok:

26th Nov 2009, 11:39
And don't forget to Keep in mind the Autoland limitation: airport elevation-glide-X-wind....

26th Nov 2009, 11:47
Hi Toby,

If you are still looking for referance, I take it you have the FCOM?

If so, you might find plenty of info in..

FCOM 4.5.70

In particular,

TASK SHARING FOR CAT I APPROACH (or better) (javascript:top.displayRef() and


There are a few notes at the bottom that might help.


26th Nov 2009, 12:07
Guys, IAW "my concierge can fly it " policy, Airbus industry allows autoland wherever and whenever operator deems it safe. I've came across two examples:

Airline X allows autoland only on CAT2 (or better) certified ILSes with LVP in force. Practice autolands can be performed in VMC only and again strictly on CAT II ILSes.

Airline Y allows autoland on any ole ILS, as long as rollout is not used on CAT1. AP has to be disengaged after the mainwheels touch down but before nosewheel is down.

I'm all X. It's very tempting to just sit back and let 320 guide you, but if you succumb, you'll turn into flying imbecile very rapidly.

26th Nov 2009, 12:28
I'm all X. It's very tempting to just sit back and let 320 guide you, but if you succumb, you'll turn into flying imbecile very rapidly.

Is it?
In my company (Z) everybody tries to avoid autoland (scheduled every 1st and 15th for fleet monitoring), manual landings are much more fun. I thought it would be the case for most pilots...

26th Nov 2009, 12:32
You're right, it is more fun for pilots. ATPL wielding sysops may disagree.

26th Nov 2009, 12:45
Agreed, I am always reluctant to give away my landing to a computer but it does two things:
1. Fulfil a mandatory company requirement of 2 autolands per month
2. Keeps you in practice for when the RVR is 75m!:ooh:

27th Nov 2009, 21:03
well, I really appreciate for all your replies guys, many tks.:ok:


Sir George Cayley
27th Nov 2009, 21:10
And the SGC post who mentioned it first:ok:


Aztec Kid
28th Nov 2009, 04:36
It is my understanding that the ILS beam quality may not be suitable for automatic landings on all CAT I installations. Deficient beam quality combined with an unusual terrain profile could lead to less than optimal autoflight performance that could occur at an altitude that may make timely corrective action problematic.

Below is an excerpt from the FCOM Autoflight Limitations section, which I have seen for a variety of current models of Airbus aircraft. I know of one operator that only permits automatic landings on CAT II/III ground installations. This is because they do not want to take the time to evaluate CAT I ILS beam quality at each airport. I would be interested in learning how other operators are dealing with this issue.

The Kid


The automatic landing system’s performance has been demonstrated on runways equipped with CAT II or CAT III approaches. However, automatic landing in CAT I or better weather conditions is possible on CAT I ground installations or on CAT II/III ground installations when ILS sensitive areas are not protected, if the following precautions are taken:

• The airline has checked that the ILS beam quality, and the effect of the terrain profile before the runway have no adverse effect on AP/FD guidance. In particular, the effect of terrain discontinuities within 300 meters before the runway threshold must be evaluated.

1st Dec 2009, 12:41
If not for practice CAT III approach, what's the benefit of making autoland on CAT I beam anyway?