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captainpaddy
7th Apr 2006, 23:47
Hi there!

Can anyone give me any techniques or rules they use for descent planning to the FAF on the A320? Details I'm after are modes used, points at which you reduce speed, when you intend to get flap 1 out, etc.

I realise that each descent profile is different, so general tips and comments will do fine!! The managed descent all the way to ILS capture is obviously the easiest case, but I'm after ways to cover most dynamic situations.

Cheers!

CP

Hand Solo
8th Apr 2006, 00:26
Forget managed descent, it'll leave you high when they give you a shortcut. First thing to do is to work out track miles to the field and direct miles then decide what figure between you think you really have. You need 3xheight (in 1000s) to descend on a 3 degree slope plus a mile per 20kts to reduce speed. If you aim to be at 2000ft agl on the glide at just under 7 miles at 180 kts you can calculate back to decide whether you're high or low. In most instances V/S is the best mode to use to ensure continous descent. 5 x groundspeed as a V/S will give you a three degree slope, adjust accordingly. OP DES will work if you're very high but is best avoided close to the ground if your company stipulates RoD restrictions close to MSA as it can lead to some very high RoDs.
Personally I think all you need is flap 1 prior to LOC intercept, then flap 2 gear down at 2000ft with subsequent selections according to speed requirement. In speed terms if you have anything over 180 kts when you hit the glide the aircraft will not slow down, especially with A. ICE on. Landing gear will be necessary to reduce speed. If you are level on the LOC you can maintain 250 kts until about 3 miles prior to the G/S as long as your prepared to take the gear at G/S*.
My personal favourite 'Get Out Of Jail' card is to select V/S -2900 with full speedbrake which will see the aircraft stabilise at the V/S with an airspeed of 260-270kts, which gives you a guaranteed RoD and a speed you can predict. If you're still to high then reduce the V/S to -500, get below 250kts and lower the gear then resume the V/S -2900. Speed will stabilise around the 220kt mark, which may require Flap 1 depending on weight but is within placard speeds. These figures generally work across the range, adjusted up or down by 10kts if its a 321 or 319.
Forgot to mention that you should always have Flap 1 out when you capture the glide slope. If you don't then the go around mode won't be armed. Selecting TOGA then leads to the very unpleasant FMA of TOGA / GS / LOC !!!!

captainpaddy
8th Apr 2006, 00:49
Many thanks HS!!!

Exactly what I was after!

Any other suggestions or comments will be greatly from anyone!!

Regards,

CP

Dream Land
8th Apr 2006, 03:43
Also I would add that descent planning is ultimately affected by the cost index your company uses.

Dani
8th Apr 2006, 05:34
Excellent post from Hand Solo!

Altough he is right Airbus Training recommends to use managed descent all times! Most airlines that follow the AI procedures closely do so. They start descent in DES at the descent marker on the ND, reduce the Speed when the FMGS tells you to (where it has been programmed) and reduce to VGD (green dot speed) when they overfly the decel point.

When you get a short cut you get the warning "MORE DRAG", which is the moment they use speed brakes.

My favorite is open descent, where I have complete control over the descent myself. At around FL 100 I use speed and V/S selected and have full influence on my flight path.

I still use the information given from FMGS as a cross check of course. If I'm 2000 ft above the calculated descent path, I'm there where I want to be economically, since in nowadays ATC environment you tend to make more track miles than less.

hth,
Dani

Airbus_a321
8th Apr 2006, 08:05
hand solo which a/c was you flying before, a BOEING ? Don't take this question too serious. :O
---------------------------

Basicly, to use all the benefits of this highly sophisticated, excellent AIRBUS you final aime should be, trying to fly managed as long as possible and as long as practicable, means if traffic situation permits. This is the way this aircraft is designed for !

Of course deviating from the managed profile, due to short-cuts etc and you find youself high on profile you have to use basic skills, means use rawdata informations to check altitude against remaining track miles, as mentioned in previous posts and act accordingly. BUT there is not only one way to fly.

The DECEL information is a very conservative helpful information. You can trust on it, or if you don't for whatsoever reason, I don't know, it's in any case a useful information you should not just disregard.

All the stuff concerning CONFIG changes is "basicly" a matter of your landing weight, which results in different dynamic energies.

There is no BASIC RULE how to DECEL, like on old aircrafts maybe (e.g. at 20nm dot this, at 10nm do this and so on) - AIRBUS flying is something very dynamic and good AIRBUS pilots are flexibel and open minded to cope with different situations and use ALL the build-in features provided to the pilots.

There is NOT only ONE way to fly the AIRBUS.

Flying, I should better say to configer e.g. an A321 close to MLW for landing is completely different, then an A320 with almoust zero load.
In the first case it is not bad so select FLAPS 1 in an early stage of approach, in the 2nd case it might be well sufficient to start the configuration changes while intercepting the G/S for example or even later.

But, to be honest, I am "managed-minded", and I like and try to fly in MANAGED mode as long as possible using this excellent FMGS, it's sometimes a kind of challenge to fly MANAGED and to use the FMGC as the only interface to the aircraft systems, although sometimes it would be easier to to call just for HDG PULL or SPEED PULL etc. like on the old a/c like a B... or so :D

So if you have the chance to fly the entire approach down to the landing fully MANAGED, you may observe that it works perfect. A great aircraft.

pakeha-boy
8th Apr 2006, 11:50
A321...would agree with you totally....Hand solo that was an amazing piece of crap you wrote..I have been flying the A320 for 12yrs now,and if you flew it the way you say,you would bust a line check every time.....do you actually fly the A320,????and if so what position?

captainpaddy
8th Apr 2006, 12:16
Pakeha-boy,

I get so disappointed when people display their ignorance publicly. The way you may operate the airbus may not actually be the only way it should, can or will be done. And I'm not saying you're wrong in using whatever technique you do, but surely you realise there are oodles of different ways that every machine is operated. If I wanted one way to do it I would have read the bloody FCOM and been done with the whole thing. I'm looking for opinions from different viewpoints so I can create my own.

Quote "do you actually fly the A320,????and if so what position?"

Yes, yes, calm down. I'm sure Hand Solo is actually just a FS2004 jock who only ever saw an airbus through a chain link fence once. Proves that you are correct. Fair enough. I just hope the attitude doesn't make it onto the flight deck.

CP:ugh:

Hand Solo
8th Apr 2006, 14:16
Basicly, to use all the benefits of this highly sophisticated, excellent AIRBUS you final aime should be, trying to fly managed as long as possible and as long as practicable, means if traffic situation permits. This is the way this aircraft is designed for !

Well if you're flying into a sleepy little Greek airfield at night with no other traffic and procedural approaches then by all means use managed descent because there's nothing to disrupt the plan. If you're flying into major European hubs where the approach procedures are merely a guide and you can expect frequent radar vectors, speed control and direct routings from multiple ATC sectors then forget about it because the FMGC won't handle it. And if you try to reduce to green dot speed when the FMGC tells you at FRA you'll get an almighty bo**ocking from ATC too!

One other point is that if you let managed descent fly the profile it can level off at the platform altitude, put a fistful of power on as the speed target is 250kts then take it all off when it overflies the decel point and the target jumps to green dot. Thats a rather poor performance in noise abatement terms and also screws up any attempts at a continuous descent approach which is requested at airports like LHR.

Pakeha-boy: It's not your fault, I guess you're just not used to busy airspace down in NZ. By the way I flew the 319, 320 and the 321 on sector lengths between 150nm and 1600nm in both European and Russian (metric) airspace.

Dani
8th Apr 2006, 14:19
Don't worry, Paddy, there are people who fly the airbus like it would be no aircraft anymore but a game boy ;-)

I've seen quite some operators now and can confirm that there are two different schools of procedures: One that flies the Airbus exactly like AI teaches them, and the others who have their own procedures, checklists, call outs and of course also their own way of flying it. The later are mainly "classical" airlines with a long history like LH, SR, LX, US operators. They also run their own training department and own sims.

You can't say one way is better than the other, as you suggest. But I have the feeling that Airbus procedures are ment to be fool proof, while they also tend to produce pilots who loose basic flying skills.

Dani

captainpaddy
8th Apr 2006, 14:38
Good point Dani.

I'm inclined to agree with Hand Solo's point that managed descent isn't available at a busy european hub where you spend most of your time on headings. What I'm after is rules of thumb or hints and tips for descent planning when the expected routing is not followed for whatever reason. HS's first post seemed to be heading that way before we all got diverted!!

CP

FlapsOne
8th Apr 2006, 16:03
The best operators will use either managed or selected profiles to best match the situation at the time and stay alert to changing circumstances.

In Europe, at busy airports, there is little option other than to use selected guidance because that's what is needed in a heavily radar controlled environment.

Using V/S and a selected speed profile to give something like 210kts at 12nm, LOC intercept at F1, 180 (ish)kts til 8-10nm, 160kts til 4nm and stable by 1000' will fit the bill on most occasions.

The rest is airmanship!

javelin
8th Apr 2006, 20:55
As with all techniques, there will be many ways to achieve the same effect.

I have about 8,000 hours on 320/321 and 330and still use managed descent whenever I possibly can. You have to enter the most accurate estimate of what you think the descent and approach will be, i.e. make height constraints conditional where terrain permits, get rid of holds from the primary route if you think you won' do one.

Managed descent will then use the speed window to keep you on the path, if the speed drops, go direct to the next point, it is usually a change in wind/temp from forecast.

I operate this way into busy European airports as well as sleepy foreign ones and busy US/Canadian airports and it always works.

When I see pilots play the FCU boogie, it nearly always ends in an untidy descent and a gob of speedbrake - something that should be very rarely used on a 320 :ok:

captainpaddy
8th Apr 2006, 21:54
Thanks Javelin!

Am I correct in saying that managed descent will always plan for an idle descent? I realise that constraints may require a constant FPA between waypoints, but it should at least start with an idle segment?

CP

Shuttleworth
8th Apr 2006, 22:57
Actually Hand Solo's post is very accurate.
I can't beleive any airbus pilot wouldn't recognise immediately all the points he made.
Just be aware that much of the paragraph is taken up with the question of how to handle an approach where ATC hav eleft you high 30 to 50 miles out.
In my experience ( isn't it a pity we no longer get to sit on the jumpseats of other airlines) VS is a far better mode than Managed Descent when operating into busy TMA's. Certainly it's common at my employer (319,320,321) and I also watched Virgin pilots use it a great deal on their A340's.

cornwallis
9th Apr 2006, 00:03
I use vs to do a cda.Managed is just not workable in the tma of many airfields .I usually have thrown managed away as I pass through 10k .It is rare to overfly the decel point when you are on a radar heading so i usually activate approach at the same time to avoid any embarassment later!

Check Airman
9th Apr 2006, 05:53
I think the only positive thing we can say here is that there are different ways to accomplish the same task. Some ppl obviously prefer Mnaaged modes, and others prefer selected modes. I think we all need to remember to be respectful of the other's opinions. We must be open to using ALL modes available, and not be too biased towards one, as they all have their uses in different situations. It doesn't seem to make sense to always aim to use one particular mode. Just use the easiest and most efficient mode.

High Wing Drifter
9th Apr 2006, 07:50
Excuse my ignorance, but is a managed descent the same as VNAV mode?

kellykelpie
9th Apr 2006, 12:52
For what it's worth I use two different methods. I always want to be 250kts at 5000' with 20nm to run. Outside this distance I want to be intercepting 4times my altitude. As an example at 60nm 15000ft is my reference. Normally I am a little higher than this but as long as I'm intercepting the 4x (eg 10000 at 40) I feel comfortable.

If I feel I need a more accurate picture (chance of getting cut in by ATC) I use distance x 3 - 4000 if at 300ish knots, -2000 if at 250 and a straight 3x if at greendot.

For an ILS (IAE 2500) take flap 2 no later than 2000. If heavy or tailwind allow more (2200 - 2500). Once flap 2 continue configuring - don't delay as you may not have above idle at 1000/500 for stable approach.

captainpaddy
9th Apr 2006, 13:16
Thanks Kellykelpie!

Very useful!

Does anyone else use Alt X 4? I'm used to Alt X 3 on my previous machine but I realise that some extra distance will be necessary for speed reductions. I have heard that about 1 mile for a 20 knot reduction is a reasonable figure???

Check Airman
9th Apr 2006, 20:14
Excuse my ignorance, but is a managed descent the same as VNAV mode?

Yes it is.

CLB = VNAV SPD
ALT CRZ = VNAV PTH
DES = VNAV PTH

High Wing Drifter
10th Apr 2006, 08:33
Thanks Check Airmen.

javelin
10th Apr 2006, 13:55
320 - 3 x height
330 - 4 x height

320 340kts to 15 miles, level, no brakes, slow configure and land :E

330 try the same and it's a fly by :(