A320 descent and ils approach

[I-WEBA]

Hi everybody . two questions. what do you think about manage descent of a320 ? do you use it or you prefer open des or vertical speed ? if you use v/s how many miles do you add in order to decelerate ?

the standard rule for ils app is flap 1 then 2000 ft flap2 gear down , f3 and full. someone told me that sometimes usually landing weight above 60 tons is better intercepting at flap 2 . when you intercept at flap 2 do you leave speed decelerating to Sspeed or you use a higher selected speed?

bye and happy Easter

[Young Paul]

Managed descent works fine, if you set up the right constraints. However, the fact is that you are rarely left to fly speeds and tracks that you programmed in the FMGC, so you need a feel for the alternatives.

The most useful metric I have in my arsenal is that a three degree glideslope uses 320 feet per mile, or near enough three miles per thousand feet. So if I'm told I have 25 miles to run, a three degree slope to the threshold should have me at around 8000' AGL. At 250 kts/8000 ft, I'm a little hot at that stage. At 6000/250 I'm looking good. At 250 kts and 10000', I'm definitely high and need to do something now to sort it out. And so on.

Oh yes, and don't think about the threshold - that way lies unstable approaches. Instead, think about 1500/160. Or 2000/180. Give yourself an earlier gate that you know if you make, then the last part of the approach will be okay.

[PantLoad]

Why are you asking PPrune? You should be asking your training department, and they should answer your questions in two ways.

First, they should directly answer your questions.

Second, they should 'direct' you to the written SOP that answers your
specific questions.

It is essential that you get BOTH answers! Any training department
guru worth his salt can and does reference his/her answer to an SOP.

The Airbus SOP is very explicit, both in the FCOM and the FCTM. They even publish diagrams that illustrate the descent and approach profiles.

THESE PROFILES WORK!!!!! PROVEN!!!!

Your company's SOPs may differ from Airbus. U.S. airlines typically do vary from manufacturers' SOPs. I understand that airlines in the rest of the world, many times, use the manufacturer's SOPs.

Either way....

If your company's SOPs do not seem to work, they should be changed. Again, a friendly contact with your training department representative can notify them of a problem.

Airlines, today, that are worth a damn, will be open to SOP changes...to ensure the SOPs are relevant, that they work, that they work all the time, and that they protect the crew from Chief-Pilot-Office carpet dances...or worse. (e.g. violations, accidents, death and destruction)

My former airline (I'm retired) required that, under normal circumstances, we do idle descents. We had the option of 'Managed' or 'Open Descents'. The caveats were (1). the last 1000 feet of descent, we limit the vertical speed to between 500 FPM and 1500 FPM, and (2) for small altitude changes, we should use 'Vertical Speed'... (e.g. 1000 feet or 2000 feet altitude change...it's OK and even better to use vertical speed.)

Airbus even explicitly and illustratively (diagrams) dictates 'gates' as Young Paul suggests. They do this, again, in the FCTM and the FCOM, but also in other Airbus pubs, such as Flight Operations Briefing Notes.....

My suggestion: Find authoritative documents and stick your nose in them. Learn the SOPs inside and out. Know them and routinely practice them. Other pilots will be amazed with your flying skills. The training department people will smile everytime they see you. You'll earn the respect and admiration of everyone.


Fly safe,


PantLoad

[Microburst2002]

You know your altitude, but not your distance to fly. So I suggest an altitude based rule.

Then, the problem is an energy problem. Your energy depends on your altitude and your speed. For a given weight and speed, you will have a gradient. Flying fast and light, you may be descending at 400 or more fpnm. Flying slow and heavy, at less than 300 fpm. typically the gradient is around 330 fpnm (3nm per each 1,000 ft).

I calculate flight levels to go times 3 plus minus gradient correction (due to weigth/speed) plus minus wind correction (10% per each 20 kt component) and plus deceleration (between 6 and 10 miles depending on weight and speed).

It also varies between models (older have more gradient) and engines (IAE have less gradient).

For instance, in one of the older CFM engined 320s of my airline, flying at the typical 280 kt descent with full house (63 tons) I will have a nearly 300 fpnm descent gradient. With an average 25 kt tailwind, My number is FL times 3 plus a 10% plus another 10% plus 8 miles. I do it very quickly because of so much practice and I am proud to say that it works really really well.

Then you need to "bet" on how many miles you are really going to fly.

I also don't pull to open des at high altitude and plunge. i select V/S and maintain an approximately 3º slope (in still air) till i can pull to open without sinking. It is kind of a manual repressurization segment.

Most of the times, if the miles to be flown are the same as i have planned, I do better than the donut. It comes up and below me all the way and I just add thrust once in the glide.

[FlightDetent]

the standard rule for ils app is flap 1 then 2000 ft flap2 gear down , f3 and full. someone told me that sometimes usually landing weight above 60 tons is better intercepting at flap 2 . when you intercept at flap 2 do you leave speed decelerating to Sspeed or you use a higher selected speed? My experience is limited but never I had problems sticking to Airbus suggested procedure, S speed at G/S intercept and getting dirty at 2000 AAL. Stable at 1000. ATC requests permitting, of course. Inbetween 42t and 75t, even with some tail-wind it works like a charm. (studying FCOM for FAPs below 2000 AAL needed).

Descending along GP with F2 and selected 180/160 never made any sense so far.

Ready to be educated,
FD (the un-real)

[Microburst2002]

as long as you have S speed when you capture G/S, everything is OK (above 2000 ft) At 2000 and below, it is better to select conf 2 one dot below.

then, continue configuring depending on the situation (GW, tailwind, traffics ahead and behind and IMC or VMC conditions). If you can, low drag low noise is desirable and is good to delay the landing gear and landing configuration. It is also good for the airplane to decelerate before selecting the next configuration.

If not, just continue with everithing step by step to be stabilised in time.

[jtr]

FlightDetent 42t and 75t, even with some tail-wind it works like a charm

You are talking about weights ranging from pretty much BEW or a green A/C with no pax and min fuel all the way through to 10t over MLW depending on which variant... quite the range. In both the 319 and the 320 any tailwind and a LW of more than about 60t will see you not sliding down at S speed on the G/S but rather creeping away from the speed.

As someone mentioned, use the FCTM/FCOM as your reference point, then refine it as you get comfortable.

[FlightDetent]

JTR: Correct, truly empty 319 to "full house" charter A321 on a tankering sector, the manufacurer's procedure never failed me. Yes, there are times when things do not go as smoothly as my FDM manager likes, but these were always due to outstanding external factors.

Some of the usual suspects:
- A/THR adding power at S speed +10
- baloon effect of F2 and IAS increase as the AP dives down to re-capture G/S
- intercepting G/S at 190 kts while S speed is 170
- 160 to 4NM at CF1, gear up (S speed -15) on an A319

The book guidance is just about perfect. Whenever I stick to it :8 it works. Indeed, for approaches from 1700, 1500, 1200 ft a modified version is required yet still this is in the book.

Common day pilots (us) are no smarter than the standards team in Toulouse. And do not have the 25 yr experience/feedback from across the world.

Stable at 1000,
FD (the un-real)

[Microburst2002]

Then, why are they changing everything so often?

I don't think they are stupid, but I don't think they are aeronautical gods, either.

The recommended method is OK. But adapting to circumstances, optimizing or being more conservative, as required, shows good airmanship. And refusing to depart from the recommended technique no matter what because that is what it is in the book, that is poor airmanship, and I am sure none of us do it.

Don't forget thaf we have now a stall recovery procedure. 20 years after the advent of the 320.

[I-WEBA]

hi microburst, i am very interested in the way you calculate . just to know if i understood , for instance we are flyng FL350 , old A320 cfm, des speed 290 and expected tailwind 45 kts . how do you calculate ?

[Springer1]

At MY computed TOD, my first choice is to use V/S for its smoothness in the initial pitch and descent vs Open Decent or Managed. I select the current speed then SLOWLY crank the V/S towards 3000" fpm. Takes more work but the results are a much smoother decent over the other modes.