Descend management. Looking for advice (a320)

[WhySoTough]

Firstly, I'd like to apologize for making countless threads, asking so many questions, but I do feel as though a lot of people on here have been extremely useful, and ofcourse have much much more experience than me.

I find myself struggling to know basically for sure if I'm high or low on profile.
Some places in particular are worse than others.
I'm not sure if I should just increase speed a bit when ATC seems to be cutting me short, or maybe use speed brakes, maybe both?
Just something that's very new to me.
All the Captains have told me that it is quiet normal at this stage and that it takes some experience.

I'm looking for some opinions. Advice. Tips. Simple ideas, etc.

Feel free!!

Thanks guys!

[J.L.Seagull]

I'm new too! Been in your shoes just a few months ago!

Guidlines: (but not rules)

1. If you're above 10000ft, increase speed. (But common sense must prevail: if you're at 11000ft, and you need to reduce to 250kt at 10000, the no point in accelerating for 5-10 seconds!

2. Below 10000, use speed brakes.

3. If levelled off between 5000 and 10000, waiting for further descent clearance, slow down to green dot, and then descend (OP DES) and accelerate to 250kts.

4. Below 4000ft, if you really need to get down quick, first level off (V/S 0), then flaps 1, flaps 2, descend, and get the brakes out.

Of course, NONE of that will matter if you have to comply with ATC or a particular STAR; in which case, just manage the whole thing, and monitor.

If you feel you're unable, then advise ATC, or request for what you need.

Hope this helps!

[Hobo]

Use the 3x table. Profile is height in 1000 of feet x3nm + a bit to slow. Say ~5nm from 300 to 250 kts, ~5 to slow from 250 to 170 kts.

So eg:

If you are #1 to land at FL200 at 300kts you should be 20x3 +10(to slow)=70 track nms out from threshold.

If you need to be at a hold at FL60 210 kts, and are at 330 you need (33-6)x3 + ~7= 88nm, if you are closer than this you are high.

6000' at 170, you need 18 track miles to run.

Works a treat, speedbrakes or other 'let down aids' will not be required unless ATC step in with restrictions.

If you are high, and it's practicable, try winding the speed up to regain the profile. If not speedbrakes until profile regained.

[bubbers44]

The US is requiring 1500 hrs to fly an airliner. Maybe because you should know how to handle it before you get in it. Making 300 hr pilots airline pilots is a problem for some countries. Automation can not be guaranteed to work as demonstrated on AF 447. Passengers deserve a qualified crew when they buy their ticket.

[Hobo]

What a useful post bubbers.

WST is asking for help, which, if you can't give it, I suggest you start a new thread, and not criticise.

I take it you've contacted the FAA regarding your concerns.



.

[PJ2]

Originally Posted by bubbers44

The US is requiring 1500 hrs to fly an airliner. Maybe because you should know how to handle it before you get in it. Making 300 hr pilots airline pilots is a problem for some countries. Automation can not be guaranteed to work as demonstrated on AF 447. Passengers deserve a qualified crew when they buy their ticket.

bubbers, I think that was an unnecessary and uncharitable response to a good question from a fellow pilot wanting to learn. I think such a response discourages learning by new pilots. Isn't inexperience and lack of knowledge exactly what you're fighting against?

I had lots more than 1500hrs when I joined a major carrier in 1973 but when I transitioned to the DC9 I asked all kinds of questions of the skipper including how to calculate the descent properly. Most were kind enough to share their knowledge.

The x3 + 35nm out @ 10,000ft/250kts generally worked but I learned, (from asking more patient skippers than you have exhibited here) when to extend that distance or shorten it up.



WST[/B], the A320 has a wonderful set of tools to help you on the descent* but you are very wise to back that up with your own thinking and calculations. That kind of behaviour will keep you out of most trouble - keep it up.

* Going from memory here...Indications of the vertical descent profile for the A320 include:

1. On the FMC PROG > Descent Page, Line 2 right-side there is the VNAV PATH digital indication of deviation above/below path;

2. On the ND, there is the green Energy Symbol (an arc);

3. On the PFD, to the left of the Vertical Speed display there is the magenta Vertical Dev symbol, which provides a +/- 500' window of deviation from the theoretical descent path.

4. On the ND track display - the white (in non-Managed Mode) or magenta (Managed Mode descent) top-of-descent arrow & level-off arrow on the ND.

The best thing you can do is keep reading in your FCOM. Read about all these indications so you know them like the back of your hand - know what each symbol means. That kind of professional approach will keep you from becoming a "child of the magenta line" and will stand you on firm ground when it comes time someday to take your own command.

IMPORTANT:
At varying times and when you least desire or expect it, all these indications can and will let you down, just like all automation can and will. Know your own descent path and where you should be at all times. (A good habit to get into anyway is, each time you start a descent, always know the lowest safe-altitude you can descend to.) Sooner or later, ATC is going to change runways on you and you have to be ready to re-calculate, and use all the symbols to best advantage while comparing them to your own thinking and SA.

Be well, and enjoy the A320 - it, and the A330/A340 are dreams to fly, but they're nothing more than just airplanes. Practice...practice, practice,... disconnecting the autothrust and practice hand flying all your skipper and company will permit. If either don't permit hand-flying, use all means at your disposal to push hard to have an automation-hand flying policy written into your OpsSpec and FCOM documents which will permit such practice in suitable conditions.

[3bars]

So bubbers, with 1500 hours in a Cessna 152 you are fully qualified to fly the Dreamliner?! I would suggest if you're planning a descent from FL420 at 350 knots in your light aircraft, somethings gone seriously wrong! Two completely different beasts

[Bengerman]

All sensible stuff from PJ2, I would just add that whilst using the tools available in front of you the most important thing to do with those tools is to ensure that the data you entered in the first place is sensible and does what you want it to do.

The old maxim, garbage in garbage out remains valid.

[Dream Land]

Excellent advise from Capt. Seagull.

Happy flying!

[Sciolistes]

I'm not sure if I should just increase speed a bit when ATC seems to be cutting me short, or maybe use speed brakes, maybe both?
Just something that's very new to me.

Boeing guy here, but the principle remains the same. If you're not sure if increasing speed (perhaps with drag) then I suspect you are not fully relating the aircraft's drag profile to technique.

First of all, the aircraft has a min drag speed, above and below which drag increases. You generally can't go below it without adding flap as it is usually roughly coincident with clean speed. Because the drag curve above min drag speed is very flat on modern jet airliners, you will have to increase speed significantly, or else you will actually end up shallowing your net descent gradient. Once you increase speed significantly (like 300kts), drag increases to such a degree, that even taking into account deceleration, your net gradient is steeper so long as you can hold the speed for long enough.

If you are at around 5-4000' AAL and being cut short, IMHO, simply increasing speed is unlikely to be a wise choice as you will just increase the track miles required as you probably only have a 20-30 knot window. However, when you add drag (any drag), the drag curve moves up and left, meaning total drag increases and the min drag speed reduces. Some pilots like to use this to add drag with flaps but stay at clean speed, using the flaps as speedbrakes, which is not recommended on the Boeing.

Basically, the best option is to hold your current speed (I'm assuming between 240kts and clean speed) with speedbrake and/or gear extended (depending how high you are), allowing you to significantly increase your gradient and decelerate later, extending flaps on schedule and ensuring you are still going to be intercepting with flap and an appropriate speed so you don't get suckered into a potentially unstable approach.

[BOAC]

Originally Posted by WST

All the Captains have told me that it is quiet normal at this stage and that it takes some experience.

I'm sure I have asked you this before, but are NONE of these 'Captains' offering any help or are they all just saying 'it's normal'?? Looking at all your posts it would appear that either you are flying in a very odd airline where no-one wants to help you or you are not asking the right questions/people. I suggested before that you should talk at least to a Training Captain - far better than taking pot luck here.

[WhySoTough]

Thank you all very much for the responses!!

Bubbers,

I have nothing to say to you, 3bars summed it up nicely.

BOAC,

No, the TRIs and TREs are very very helpful. It's just that everyone has his own technique and opinion.
Again, lots of guys here are very very experienced too, and as you see above, have different advice to offer.
I dont get why you keep asking me that. I am looking for different opinions, to see what other 320 experienced pilots do, how they adapted to it, etc.

[Microburst2002]

Hi WST

First, you have to be aware that it is your altitude what determines how many track miles you need. If you have more miles, you are low. If you have less, you are high.

Then, you can only know if you are high or low if you know your distance to go, which not always happens.

In the 320, this rule of thumb works very nicely: FLx3 plus 10 (when you are above 10,000 ft at ECON speed, typically about 290 kt) and only plus 6 when below 10,000 ft at 250 kt. If at green dot when being vectored in approach, FLx3 plus 3 miles. After S speed, FLx3 plus zero.

In your next descents, when using DES and on profile, check if I am right or not (note: if you activate approach before the Decel point, the VDEV is no longer valid because it "thinks" you still have 250 kt. I can tell you are high when you are not. A few miles after the Decel point it will become valid again)

Wind effect is about a 5% of the distance per each 20 kt of wind component.

In descents I regularly check my gradient, both in the air and relative to the ground, with V/S and TAS or GS. Sometimes air gradient on which I base the rule of thumb is steeper or shallower, then I know that I will have to correct.

In latest models THR IDLE is not a real idle, it is increased, so in DES the path is shallower than in OP DES.

During descent you can calculate if you are high or low relative to the FPLN miles and also direct distance to the runway. If the difference is significant and you don't know if you will be given a short cut, you have to bet for one option but be prepared for the other.

Far from the runway, use speed increase to correct a high on profile situation. Closer to the runway use speedbrakes and when close to the approach, reduce speed, maybe using speedbrakes, and get some flaps.

[TypeIV]

What methods do you use for your headwind/tailwind corrections?

I use the cruise-FL wind and divide it by three and add/subt. it from my track miles for the top of descent determination and also in mid-descent I interpolate it mentally between crzFL-MSL and it works great, but takes a couple of seconds and is not as easy to do by heart as the rest of the calculations. Leaves me less time of coffee drinkin' and talkin' to the girls

[I-2021]

Hi WST,

lots of valuable inputs here ! Always remember that in any case communication plays a major and vital role. If you don't feel comfortable with the situation and you feel like you're not able to manage it then speak up. ATC will help you most of the time giving you extra track miles and your Captain will help you suggesting actions based on his experience. Always use all your available resources. With time and experience you will be more confident and you will be able to anticipate more and therefore be more comfortable in a different variety of scenarios. Communication will save your day till the end of your career and it's free of charge. If you plan to reduce your speed to green dot for energy management in a busy radar airspace with lots of traffic around you (especially behind you) then a call to ATC stating your intentions will be very helpful to them and to all the other traffics for effective separation. This is just a simple example of the variety of scenarios where an open communication with all the agents involved will reduce your workload and provide useful elements.

Cheers !

[bubbers44]

Sorry to change the direction of this post. I didn't mean to. I was remembering when I was a new captain on a 737 being handed a brand new FO that obviously had never flown in the Flight Levels before because he told ATC we were climbing to 23,000 ft instead of FL230. He couldn't copy the clearance so I had to. To make matters worse the autopilot was inop when we were dispatched. Returning to LAS at FL350 we had a PD to 240 clearance and at 100 miles seemed to have no interest in starting a descent so asked him when he was going to start down. He said his buddy, the check airman neighbor that got him hired told him how to do it. I said OK, just don't embarass ourselves by having to do a 360. It was 10:00 PM so figured we would have light traffic. On a 10 mile final at 10,000 ft and 340 knots I asked him which way he would like to do his 360?

I think airliners have two pilot seats because it takes two competent seasoned pilots to do the job right. Also we don't hire 1500 hr C152 pilots to fly our airliners. The above example slid through the cracks with the help of his buddy.

[jtr]

40nm, 10,000', 250kt

20nm, 5,000', activate approach, managed speed, V/S - 700'/min

Hard to go wrong, not withstanding ATC having their way with you.

[bubbers44]

That is pretty much the way I do it. consider weight and winds and plan a 1000 ft spool up. Of course we knew this on the first day of our airline job. Why is it different now? Did we have to meet higher standards than now?

[EIU_EEC]

please refer to this airbus flight ops briefing note: http://www.airbus.com/fileadmin/medi...DESC-SEQ02.pdf
and this Airbus Descent Monitoring

[J.L.Seagull]

Thanks Dream Land! Much appreciated. However, I'm still just an F/O, that too with just 600hrs TT.

To PJ2: Awesome advice... only thing is, you've got it HORRIBLY WRONG and BRILLIANTLY CORRECT, all at the same time! :-D i.e. all that you're describing is probably Boeing. I used to be a type-rated engineer on both Airbus and Boeing, so I remember those colors and indications from the 777. On the Scarebus, you said.....

1. On the FMC PROG > Descent Page, Line 2 right-side there is the VNAV PATH digital indication of deviation above/below path;

*** Actually, its called V/DEV (vertical deviation), not VNAV PATH.

2. On the ND, there is the green Energy Symbol (an arc);

*** Only in HDG mode, not in NAV mode.

3. On the PFD, to the left of the Vertical Speed display there is the magenta Vertical Dev symbol, which provides a +/- 500' window of deviation from the theoretical descent path.

*** er.. no! The "yo-yo" (official Airbus terminology) is on the Altimeter scale on the right side. The digital readout in the center of the Altimeter scale has 500' above it to the top of the scale, and 500' below it. So, you have a +/-500' deviation indication. On some airplanes, it will be a magenta hollow circle, and on others (newer FMS's) it's a solid green circle.

4. On the ND track display - the white (in non-Managed Mode) or magenta (Managed Mode descent) top-of-descent arrow & level-off arrow on the ND.

*** No such colors on the Airbus. You have Magenta if there are constraints built into the FMS, like on a SID or STAR, otherwise its Blue or White. For details refer to FCOM DSC-31-45 P 11/54.

PJ2, I'm not trying to be anal, or critical of your advice. Everything that you've described is correct, and brilliant. It's just for Boeings. WST seems new to the whole thing, and he may end up more confused than ever looking for stuff in the books or on the airplane that just isn't there.

Fly safe!