Airbus approach phase activation
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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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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.
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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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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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.
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.
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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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
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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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
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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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.
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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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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.
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.
