Go Back  PPRuNe Forums > Ground & Other Ops Forums > Questions
Reload this Page >

Following Flight Director after takeoff in A320

Questions If you are a professional pilot or your work involves professional aviation please use this forum for questions. Enthusiasts, please use the 'Spectators Balcony' forum.

Following Flight Director after takeoff in A320

Old 4th May 2020, 11:51
  #1 (permalink)  
Thread Starter
 
Join Date: Mar 2020
Location: Krefeld
Posts: 11
Following Flight Director after takeoff in A320

Hi,

I have read that one should not follow the flight director (around 20) after takeoff during SRS phase. Instead a pitch of approximately 12,5 is recommend until the acceleration height is reached.
Is this correct?

If yes, I'm noticing in the simulator that the speed is not staying at V2+10 knots (SRS speed) but is instead increasing very fast in direction to managed climb speed = e.g. green dot speed.
Due to that when the switch from SRS to climb mode occurs I have usually already reached very high speeds by then. Above slat retraction speed!

When staying with the flight director during SRS phase (pitch around 20) the speed stays roughly at V2+10knots and the plane starts to accelerate to managed climb speed only after surpassing acceleration height, which I assume is correct.

Can someone please clarify this!

Thank you!

Best regards Andi

Last edited by 737Andi; 4th May 2020 at 12:11.
737Andi is offline  
Old 4th May 2020, 12:40
  #2 (permalink)  
 
Join Date: Sep 2007
Location: Windsor, UK
Age: 31
Posts: 252
Hi Andi,

I think you’re mistaken. With both engines operating, you rotate normally at about 3 degrees/sec towards 15 degrees and wait for the SRS/FD to display and follow them. It should keep the speed somewhere between V2+10/20.

Maybe what you’re confusing is the engine failure at or just after v1 (the ones we practice a lot in the sim). In this case, apply appropriate rudder and smoothly rotate (2.5 deg/sec) TOWARDS 12.5 degrees. From experience, you usually aim just below that (maybe 11 or so) and let the SRS work out the ideal pitch to keep the speed not less than V2, then pitch to the FD. If you pitch straight to 12.5 degrees, sometimes it can lead to the speed reducing by a few knots initially which could cause you to go below V2 (especially if you pitch over 12.5 accidentally).

Champ
champair79 is offline  
Old 4th May 2020, 22:14
  #3 (permalink)  
 
Join Date: Dec 1999
Location: In my own little world
Posts: 1,448
As champ says on one engine pitch towards 12.5 and wait for SRS to do its magic and calculate the pitch it thinks is appropriate. However, if you rotate a bit slowly and speed gets a bit fast the FD in SRS can command some high pitch attitudes which if you follow them will lead to speed dipping below V2 with a subsequent low commanded pitch and vertical speed below 0 to regain V2. The trick is to get to about 12.5, pause, and after a few seconds the FD will come to you. Makes it a lot easier and more stable to fly.

Last edited by lurkio; 4th May 2020 at 22:15. Reason: Clarified talking about engine out
lurkio is offline  
Old 4th May 2020, 22:34
  #4 (permalink)  

Only half a speed-brake
 
Join Date: Apr 2003
Location: Commuting home
Age: 42
Posts: 2,838
The airplane has a pitch limit for FDs after take-off at 17,5. So after establishing in the climb with a standard pitch, we do follow the FDs. The autopilot would as well from above 100' RA, and it works perfectly ok.

Are you using full TOGA thrust for the take-off or a reduced setting? What is your payload? Is your acceleration altitude the same as thrust reduction?
FlightDetent is offline  
Old 5th May 2020, 08:30
  #5 (permalink)  
 
Join Date: Nov 1999
Location: UK
Posts: 1,339
Yes, a bit of confusion between rotate pitch, SRS, and engine failure pitch.

The point about SRS is not to follow it immediately after leaving the ground. Pitch to +15 (+12.5 if OEI), give it a couple of seconds to settle, then follow the SRS - which modulates the horizontal FD bar.

As some have said, the +12.5 during OEI is a maximum pitch really; any more than that, or an overshoot, could drop your speed too low - a previous airline used to specify +10 pitch for engine failure, (then follow SRS), before they adopted Airbus SOPs.
Uplinker is offline  
Old 5th May 2020, 08:46
  #6 (permalink)  
Thread Starter
 
Join Date: Mar 2020
Location: Krefeld
Posts: 11
Thank you for all answers!

Makes sense now...I will try it in the sim next time.
737Andi is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.