Jump to content

[PROCEDURE] What is the best mode for a quick descent ?


Flow Bloisi

Recommended Posts

Hi guys,

 

Im doing a lot of training offline ivao or vatsim network with the bubus to be full prepared when i will go into ATC condition, i keep only active sky weather.To day i simulated a too high altitude:

Destination airport was LEBL with PUMAK star

Runway 07 ILSLZ, fuel on board at landing about 3.2 3.5

 

What i dot is the following, i descent to FL290 from FL350 then i wait like 2 or 3 minutes at FL290 (for simulate approach on busy airports with a lot of plane like ivao network where the ATC can't respond quickly) after this time i pushed OP DES with middle spoilers out, descent rating was between 27000ft/mn and 3500ft/mn.The problem is i never coma back on vnav path, i was 1600ft higher when 250kt restriction come so i deployed full spoiler to slow down at 250kt but my next point was at about 7000ft and i was finishing to decelerate at 10 000ft... so finaly i was 3000ft higher, i use V/S and middle spoiler out to keep 240kt and on the Next waypoint i was about 1800ft too high.

 

So in this case what mode use ? stay VNAV give an uncorfatble descent rate for passenger and EXPED too, V/S and OP DES are they the good way to go down quickly ?

 

I noticed OP DES is very good below 10000ft on VOR approach, it can be very hepful to control a good speed and descent rate to the FAF.On boeing plane i was using LVL/CHG when i was to high with spoilers but in this case what i saw today is little bit different on airbus plane.Maybe i miss something ? 

Thanks

Link to comment
Ju_li_en Ke_ml_er

OP DES is the fastest way to decent but bare in mind that the TOD computed by the FMGC is for a continuous descent. If you're going to level of at some point in the descent you need to take that into account and start your descent earlier. 

On Ivao if there is a radar controller  he will tell you when to start the descent taking into account the level off he'll ask you to do. You also have the option of asking him earlier to descend if you see the TOD approaching on the ND and don't hear about him. Let him know what you need before it's too late and then can't comply with what he asks you to do.

Link to comment
Simon Kelsey

Pull OP DES and get some drag (ie spoilers) out. This will give you idle thrust and pitch to maintain the selected speed (ie equivalent to FLCH).

You can also pull selected speed and wind the speed up towards the barber pole. With the boards out this will give you quite an impressive rate of descent.

If you're really, really high the gear is an option too (but once it's down it's down, unless you fly a missed approach of course -- best not to go mucking around bringing the gear up and down constantly). Bear in mind the speed limit for extension though.

Sent from my GT-I9505 using Tapatalk

Link to comment
Riccardo_Parachini

OP DES is the fastest way to decent but bare in mind that the TOD computed by the FMGC is for a continuous descent. If you're going to level of at some point in the descent you need to take that into account and start your descent earlier. 

Inviato dal mio iPhone utilizzando Tapatalk

Correct about OP DES, increasing speed up to the top can give quite interesting rate, however be careful on the distance to the airport. As on the example increasing speed is the best way to get back on the path, if you are close it's better reducing about 180 flap 2 and maybe the gear, this can give a great rate of descent.

FMGC computed Tod doesn't give a continuos descent, it plans a level flight segment to decelerate, at the D point. Generally 1nm each 10knots to lose. For example: if the FAF is at 12nm you'll level off at 17/18nm at 4000ft to decel from 250 to green dot (except some particular airport with high minima were deceleration is far from the FAF)... Anyway, In the next few months Airbus should release a software update to implement continuos descent deceleration.

Inviato dal mio iPhone utilizzando Tapatalk

Link to comment
Riccardo_Parachini
Hi guys,
 
Im doing a lot of training offline ivao or vatsim network with the bubus to be full prepared when i will go into ATC condition, i keep only active sky weather.To day i simulated a too high altitude:
Destination airport was LEBL with PUMAK star
Runway 07 ILSLZ, fuel on board at landing about 3.2 3.5
 
What i dot is the following, i descent to FL290 from FL350 then i wait like 2 or 3 minutes at FL290 (for simulate approach on busy airports with a lot of plane like ivao network where the ATC can't respond quickly) after this time i pushed OP DES with middle spoilers out, descent rating was between 27000ft/mn and 3500ft/mn.The problem is i never coma back on vnav path, i was 1600ft higher when 250kt restriction come so i deployed full spoiler to slow down at 250kt but my next point was at about 7000ft and i was finishing to decelerate at 10 000ft... so finaly i was 3000ft higher, i use V/S and middle spoiler out to keep 240kt and on the Next waypoint i was about 1800ft too high.
 
So in this case what mode use ? stay VNAV give an uncorfatble descent rate for passenger and EXPED too, V/S and OP DES are they the good way to go down quickly ?
 
I noticed OP DES is very good below 10000ft on VOR approach, it can be very hepful to control a good speed and descent rate to the FAF.On boeing plane i was using LVL/CHG when i was to high with spoilers but in this case what i saw today is little bit different on airbus plane.Maybe i miss something ? 
Thanks

Another small tip, when you are levelled off due to ATC, as in the example, reduce your speed up to green dot. When you are cleared to descend again, gradually increase your speed with open des. You'll get back on profile sooner


Inviato dal mio iPhone utilizzando Tapatalk
  • Like 2
Link to comment
Simon Kelsey

Another point worth mentioning -- you only get half speedbrake with the autopilot engaged (moving the lever beyond the halfway position has no effect). However, in manual flight you can get full speedbrake extension.

  • Like 2
Link to comment
21 minutes ago, Simon Kelsey said:

Another point worth mentioning -- you only get half speedbrake with the autopilot engaged (moving the lever beyond the halfway position has no effect). However, in manual flight you can get full speedbrake extension.

Oh good point, thank you... Already wondered sometimes... So even in selected mode the spoilers don't fully extend?

Link to comment
Simon Kelsey
6 minutes ago, GameMichi said:

So even in selected mode the spoilers don't fully extend?

Not if the autopilot is engaged, no: half speedbrake only. Only when you disconnect the autopilot and hand-fly can you access full speedbrake.

  • Like 1
Link to comment
Quote

Another small tip, when you are levelled off due to ATC, as in the example, reduce your speed up to green dot. When you are cleared to descend again, gradually increase your speed with open des. You'll get back on profile sooner

Thanks, have to try that.

Quote

Not if the autopilot is engaged, no: half speedbrake only. Only when you disconnect the autopilot and hand-fly can you access full speedbrake.

Really ? it's a pretty goood thing to know.

Link to comment
4 hours ago, Simon Kelsey said:

Not if the autopilot is engaged, no: half speedbrake only. Only when you disconnect the autopilot and hand-fly can you access full speedbrake.

Whats the policy / SOP with pilots with speedbrake and autopilot use? Should speedbrake lever only be extended to the half position with the autopilot on and not the full position (although only half will extend)? 

When autopilot disconnects and the speedbrake is in the full position -- does the speedbrake automatically extend to full? 

Is it bad practice to position the speedbrake lever in full position in autopilot mode?

Thank you,

Ben

Soarbywire.com

Link to comment
Alfredo Terrero
4 hours ago, Rikypara said:


Another small tip, when you are levelled off due to ATC, as in the example, reduce your speed up to green dot. When you are cleared to descend again, gradually increase your speed with open des. You'll get back on profile sooner


Inviato dal mio iPhone utilizzando Tapatalk

This is a nice technique I often use. Play with your speed, it helps a lot. Also, we don't feel vertical speed, just acceleration. So, a constant -500 fpm will feel the same as -3000 fpm theoretically. What can be uncomfortable is how quickly the plane pitches up/down to reach those vertical speeds, and also the pitch attitude. I've been on some real life flights where the pitch attitude was a bit too low, and it felt a bit uncomfortable. 

Link to comment
Simon Kelsey







Whats the policy / SOP with pilots with speedbrake and autopilot use? Should speedbrake lever only be extended to the half position with the autopilot on and not the full position (although only half will extend)? 







When autopilot disconnects and the speedbrake is in the full position -- does the speedbrake automatically extend to full? 







Is it bad practice to position the speedbrake lever in full position in autopilot mode?


The FCOM says to select half speedbrake on on the lever.

I would agree that placing the lever to full with the AP engaged would be poor practice for exactly the reason you mention - I am sure that the spoilers would instantly go to full as soon as the autopilot clicked off for any reason though I don't think the FCOM is explicit about this.

Sent from my GT-I9505 using Tapatalk

  • Like 1
Link to comment
Klearchos Terpos

I personally use the technique below  when flying to airports without rnav arrivals and constraints. I use open des with 320 knots indicated. I plan to level off at the altitude at which I capture the localizer and/or glidepath according to the chart to decelerate and that's it. Of course I need to request high speed from atc first. This is a technique frequently used by Aegean airlines pilots. it is really efficient and gets you down really quickly. It demands however a lot of practice.

  • Like 1
Link to comment
Norman S Bowman

Hi,

The way Clark manages his descent is fine but only if ATC will allow it

.In most parts of Europe airspace constraints and aircraft spacing by ATC will generally not allow that sort of descent other than in an emergency.

Link to comment
×
×
  • Create New...