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Airbus approach phase activation

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Airbus approach phase activation

Old 13th Feb 2015, 01:18
  #41 (permalink)  
 
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WBF
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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Old 13th Feb 2015, 10:34
  #42 (permalink)  
 
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Qwsa on page 1 provided the reference which I hadn't previously seen reading this thread - FCTM SI 90. I was taught it by an instructor early on in my career 5 years ago and the FMGC has had software updates since. I agree it updates based upon current gross weight and can hang my hat on it now I've seen it in writing rather than assuming or believing anonymitys on PPRuNe. That and I have never seen a need or had a need to activate the approach that early that it updates. 1 tonne is 1 knot and it rounds up! How early are you lot seeing this on an A320 activating it?! Personally I do it when given an ATC speed on approach, when I need to select speed on approach because of my profile or at 20 miles, whichever the sooner - none of which burn a tonne or even half a tonne in the process.
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Old 13th Feb 2015, 10:59
  #43 (permalink)  
 
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"Early on in my career 5 years ago..." QED.
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Old 13th Feb 2015, 11:20
  #44 (permalink)  
 
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Meaning what Peter? I understand QED but can't derive your meaning......

I'm very sure this site is full of miserable commuters, lonely people down route. I was one too. Make a change. I'm off.
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Old 13th Feb 2015, 15:00
  #45 (permalink)  
 
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I saw in the latest manual the bulletin is repeat of what WBF quoted from an earlier one. It is very clear that VLS(all speeds) are recomputed to the weight at activation but does it update further if approach is delayed is not clear.
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Old 13th Feb 2015, 16:02
  #46 (permalink)  
 
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Thank you Vilas, I'm glad you read it the same way.

The FCTM reference however , within the realms of a BA verbal reasoning test, is quite clear that VAPP prior to activation is on the basis of 'estimated landing weight' and after activation it's on the basis of 'current gross weight' - there is no 'at the time of application' there.

Reference is FCTM SI 90 'VAPP determination without failure' - last 6 sentences before the equation. It's all the point scorers needed to provide rather than providing assumed opinion, pearls of wisdom and vitriol.
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Old 13th Feb 2015, 16:24
  #47 (permalink)  
swh

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Activating the approach phase updates the GW with the actual fuel used, the weight is not being memorised. The reference should be under GW/CG error input after engines started.
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Old 13th Feb 2015, 16:49
  #48 (permalink)  
 
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WBF
That is what I also meant. This is from actual bulletin
GW and CG values are computed from entered ZFW and ZFWCG corrected for the predicted FOB and CG variation. When the Approach phase is activated, the characteristic speeds are recomputed using the actual weight and CG.
The performance model used to compute the characteristic speeds, is accurate enough to provide speed errors of less than 2 kt from the certified speeds.
Off course few knots practically makes no difference
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Old 13th Feb 2015, 19:39
  #49 (permalink)  
 
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Guys if it didn't update it would not change. Don't need to think so hard about this its pretty obvious.
Revision 1A had no effect on this in our fleet.
Don't understand why you are so hung up on this but if you believe your fleet does not update I would suggest you set a cruise altitude in PROG and re activate after any significant holds or delays you encounter. Your doing it for nothing and will appear foolish because it won't change the data more than 1 kt but it might make you feel better.
Good Luck guys
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Old 13th Feb 2015, 21:57
  #50 (permalink)  
 
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Some of these guys would argue about the proper way to enter the line at Starbucks, right to left or left to right....
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Old 27th Feb 2015, 22:31
  #51 (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.
True. Not only 1, but whatever altitude is below your crz altitude. Whatever number between 1 and current FL. Concept is, 1 is understood as FL001.
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Old 7th Mar 2015, 16:54
  #52 (permalink)  
 
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Any time after take off if you check the VLS on approach page it is calculated from estimated landing weight which is equal to ZFW+EFOB at destination. It remains constant as long as EFOB remains same.The actual aircraft gross weight is not taken in consideration, but if you activate approach now the VLS immediately changes to VLS for present aircraft weight. It is not frozen at that weight but will vary with the aircraft weight but is not noticeable as it changes only1KT/Ton.
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Old 16th Mar 2015, 05:22
  #53 (permalink)  
 
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Airbus approach phase activation

Vilas,

Regarding your query with respect to approach phase activation, you may refer to OEB 819 page 5/6 under the para 'CHARACTERISTICS SPEED COMPUTED BY FMGC'. There it is mentioned that when the approach phase is activated, the characteristic speeds are recomputed using the actual weight and speed.
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Old 16th Mar 2015, 07:31
  #54 (permalink)  
 
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CMpilot1
I know the OEB. That is what I am also saying. In my post 52 I explained it a bit further.
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