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Airbus approach phase activation

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Airbus approach phase activation

Old 6th Feb 2015, 01:12
  #21 (permalink)  
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I didn't know it did that in heading mode. But 250 kts on LOC capture, That's a bit sporty isn't it? How do you avoid overshooting and get configured and stable with that intercept speed?
There is a chart in the FCOM which shows distance, intercept angle and speed combinations within which LOC capture is possible. It could be a useful referance for making up your own rules of thumb.
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Old 6th Feb 2015, 01:32
  #22 (permalink)  
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you can use NAV to intercept the final approach course and lead the turn, it is legal to the final approach fix.
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Old 6th Feb 2015, 04:09
  #23 (permalink)  
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if Decel pseudo waypoint is sequenced in heading mode, it will activate at localizer capture or upon NAV capture in approach.
i would never push speed without knowing my managed target on PERF page.
I just want to make sure I understand this correctly. Slow guy here. What do you mean by the decel pseudo waypoint is sequenced in heading mode?
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Old 6th Feb 2015, 10:07
  #24 (permalink)  
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A lot of people saying things without reference - if you can't back it up, don't say it.

Cough, as for why that happened - well, there's a reason why the word 'coincidence' is in the dictionary. Are you SURE it's because of that? Or is it because your colleague changed the wind in the box? Is it because GS mini was having a play? Vapp changes all the time, Vls doesn't - Vls is determined by weight. Vapp is on the basis of Vls, 1/3 wind, athr, ice accretion etc.

Peter, not necessarily. Having an extra knot isn't unsafe. 1 tonne is 1 knot. Being a pilot and flying is all about being around about right. Pilot maths: 2+2 is about 5. There's 3% error in Vls calculation and we are instructed to increase the gap between Vls and Vapp to 5 knots as it often shows as less on the PFD.
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Old 6th Feb 2015, 14:25
  #25 (permalink)  
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From IAF to IF>FAF segment if the intercept angle is sharp then on the chart there is a lead in radial or bearing drawn from the nav aid only after crossing that radial it is permitted to change the intercept heading to more suitable one but when radar vectored if you are given a heading to intercept then you must intercept the LOC on that heading. Also when in HDG mode if you did not activate approach and intercepted LOC (obviously in select speed)unless the decel point is ahead of you it will not auto activate and when you go managed speed will increase to 250KTS.
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Old 6th Feb 2015, 14:56
  #26 (permalink)  
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correct villas, DECEL pseudo waypoint will sit at aprox 13 track miles, if you are inside this distance and intercept localizer or NAV, approach phase will activate automatically, in leu of flying over DECEL point.
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Old 6th Feb 2015, 22:27
  #27 (permalink)  
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Exactly as written. We were checking Vls in FMGC was similar to Vls on speedtape (which it was) We then watched Vapp reduce to speedtape Vls +4 so I checked what was on the Perf page. The old Vapp was 124, the new one was 123 and it was written in small font, so definitely not overwritten.

We both commented on it at the time. I had seen it before, my colleague had not...

Edit to add.

Today, my colleague activated approach in a 321 quite early. Perf page Vls was 135 (Vapp 140) and then we entered unexpected holding. Exceedingly long approach followed, we landed with the numbers saying 133 and 138, no other modifications and no I'm not dreaming it.

Now there are FMGC's by different manufacturers. Maybe this is a type difference between the one we use (that does simply use GW after app activation) and yours which may not?

Last edited by Cough; 7th Feb 2015 at 20:08.
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Old 9th Feb 2015, 10:27
  #28 (permalink)  
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Tried it today in a 333. Activated the approach over an hour before landing: approach page VLS jumped from 127 to 136 and steadily reduced back to 127 for landing. Uncanny: it was as though the aircraft knew how heavy it was and knew that we were getting lighter as the fuel burned down. (As expected, screwed all the predictions though...) As was said earlier, don't read too many nuances into FCOM English, it's a foreign/second language to most of the authors after all.
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Old 10th Feb 2015, 06:04
  #29 (permalink)  
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So if one "accidentally" activates the approach, is there anyway to "un-activate" it?
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Old 10th Feb 2015, 06:38
  #30 (permalink)  
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VLS is real time speed(shown on PFD). It is always correct even with flap/slat jam. As all airbus guys know just put present altitude on progress page to get back to cruise phase.

Last edited by vilas; 13th Feb 2015 at 01:59.
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Old 10th Feb 2015, 07:35
  #31 (permalink)  
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So if one "accidentally" activates the approach, is there anyway to "un-activate" it?
Yes... Re-enter a cruise level.

The box does not memorise weight and freeze the speeds. Also the airbusses in the largest airbus operator of europe change speeds in the box as the weight reduces, for example due to extended downwind vector in.

Why is this even a discussion? You activate approach phase when you start final deceleration for the approach. In other words when you or the controller thinks that it is time for deceleration to minimum clean (in controller jargon 220kts).

The biggest problem with activating approach too early is that your fmgs descent prediction no longer works properly. In open des mode the blue arrow is no longer based on your actual selected speed.

Last edited by 737Jock; 10th Feb 2015 at 07:54.
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Old 10th Feb 2015, 08:07
  #32 (permalink)  
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Also, a quick shorthand method in the 330 (works on the McBoeing MD11 / B717 box, too) is to just type the number "1" in the scratchpad and drop it in LSK L1 on the PROG page (the altitude field). Makes the current FCU selected altitude your cruise altitude.

Incidentally, lots of similarities between the FMS's of the Airbus and the McDonnell Douglas boxes (LAT REV / VERT REV, "snowflake" instead of an execute key, McD's FMS speed basically the same as approach-phase managed speed etc). Anyone know why? Always wondered. Sure made the transition easier between the two.
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Old 11th Feb 2015, 02:36
  #33 (permalink)  
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So if one "accidentally" activates the approach, is there anyway to "un-activate" it?
Yes there is.

Reminds me of the time the MCDU temporarily seized up in CRZ at FL390 as I was making a position report. I was new and hadn't seen it do that before. I randomly pressed a few buttons and nothing. Reaching for the books, it suddenly sprang back to life - and remembered the sequence of each button I had pressed...
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Old 11th Feb 2015, 03:35
  #34 (permalink)  
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if you activate the app by accident you can go to the progress page and enter any crz altitude and you will un activate.

and i was reading on the post someone did mention that the speeds will be wrong because the a/c will capture the weight at that moment....that is wrong....the a/c will assume it will land soon so the speed representation on the approach page will assume that you will be landing at your current weight now....however its not frozen.....AIRBUS is smart

so long story short you can activate approach when ever you like brother.
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Old 11th Feb 2015, 19:35
  #35 (permalink)  
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You couldn't be more wrong about the airbus using static data in a dynamic environment. An apology to Peter and recognition of your own arrogance will go a long way on this forum here. The best info will come without ego!

I'm sure your instructors at your large airline will love to know what you have discovered but perhaps they already know it and your misinterpreted them just as you mis interpreted the bulletin you referenced.

Slow down and keep reading/asking questions, you have a whole career to figure this thing out and it starts with understanding that you know very little and once you do figure something out, software changes may render that knowledge obsolete as well.

I'm new here, enjoyed this thread y'all.
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Old 12th Feb 2015, 02:28
  #36 (permalink)  
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Welcome to the forum, my friend. I agree with you wholeheartedly on the whole lifelong learning thing, but, as you're new 'round these parts, let me just tell you not to put too much stock into things you read here. You'll thank me later. Or maybe you won't, I dunno, hell, I fully admit to not knowing much of anything.
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Old 12th Feb 2015, 11:53
  #37 (permalink)  
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Show me the reference. We are discussing the A320 here not the 330, 380 or Boeing 787. The reference is clear. I appreciate it probably does rectify the whole time but for the final time, seeing the wood and not the trees, on an A320 1 tonne is 1 knot. Get a grip.
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Old 12th Feb 2015, 12:05
  #38 (permalink)  
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WBF. One tonne being one knot is not the issue. Please clarify that you are of the belief that if the approach phase is activated, say one hour into a five hour trip, the speeds calculated then will be frozen and unchanged at the end of the flight?
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Old 12th Feb 2015, 16:29
  #39 (permalink)  
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WBF, you keep asking for reference that speeds are being recalculated continuously when APP phase is active, yet you didn`t provide any reference that the contrary is true. In FCOM it`s only written that when app phase is activated, speeds are recalculated using current GW, not that they are memorized/freezed/whatever. As anyone actually flying A320 can check him/herself, speeds are being continuously updated after app phase activation as the GW reduces.
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Old 13th Feb 2015, 01:18
  #40 (permalink)  
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Its great that you demand documentation but all you really need to do, if you do in fact fly 320s, is watch the box. Clearly your instructors never provided a reference to support your current position because they're wrong and the bulletin you linked above clearly does not suggest what you believe to be the case.
I would suggest you consider the possibility that your bulletin means what it says, that "current" weight is used for the calculation and not the weight recorded at the time of approach phase activation. I have no idea what your instructors really told you but that's dead wrong.
Here in the states we usually hold 250kts until within 8 or 10 miles of FAF so we usually activate the app phase at transition altitude. Its becoming more and more common to fly RNAV arrivals with speed constraints and allowing the phase to self activate is a nice feature that I wish more US pilots used on such approaches but they are pretty rare.
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