Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Airbus FBW Autothrust Question

Wikiposts
Search

Notices
Tech Log The very best in practical technical discussion on the web

Airbus FBW Autothrust Question

Thread Tools
 
Search this Thread
 
Old 18th January 2017 | 15:18
  #1 (permalink)  
Thread Starter
20 Anniversary
 
Joined: Aug 2004
Posts: 17
Likes: 0
From: UK
Airbus FBW Autothrust Question

You are in a steady state normal cruise at (say) FL350 with AP and ATHR engaged and in managed speed. You encounter a wind shift that causes the speed to start reducing. The ATHR tries to compensate for this by increasing thrust. Eventually the thrust is up to the current limit, but the speed is still decreasing and approaching VLS. If you now push the thrust levers up to the TOGA gate:
(A) Do you get any further increase in thrust?
(B) What would the FMA now be reading?
Raymond Dome is offline  
Reply
Old 18th January 2017 | 15:40
  #2 (permalink)  
15 Anniversary
 
Joined: May 2006
Posts: 911
Likes: 9
From: FL510
At altitude TOGA thrust isn't much higher than climb, the difference is almost negligible.
The FMA will show TOGA as thrust, but wouldn't change otherwise - go around mode is armed only with the flap lever out of zero.
safelife is offline  
Reply
Old 18th January 2017 | 16:27
  #3 (permalink)  
10 Anniversary
 
Joined: Jun 2014
Posts: 1,052
Likes: 72
From: Village of Santo Poco
I've "goosed" it by putting it in MCT for a few seconds. Seems to help when ATHR gets a little lazy.
Amadis of Gaul is offline  
Reply
Old 18th January 2017 | 18:13
  #4 (permalink)  
 
Joined: Mar 2000
Posts: 1,337
Likes: 1
From: Sunrise Senior Living
Top Right corner of the E/WD is the Thrust Rating Mode and Thrust Limit Value.
Watch the Thrust Limit Value as you select MCT from CLB - it may increase a little.
As you select TOGA from MCT, the value - and the thrust - will remain the same. The Mode will change from MCT to TOGA but MCT is as good as it gets at altitude.

mcdhu
mcdhu is offline  
Reply
Old 18th January 2017 | 19:23
  #5 (permalink)  
 
Joined: Dec 2015
Posts: 507
Likes: 1
From: France
Originally Posted by safelife
At altitude TOGA thrust isn't much higher than climb, the difference is almost negligible.
The FMA will show TOGA as thrust, but wouldn't change otherwise - go around mode is armed only with the flap lever out of zero.
ATHR state would switch from engaged and active to just engaged. And would re-activate when THR CLB is re-set.

Raymond : If headwind is increasing, there is a very high chance that it will decrease all the more just after.
In high altitude cruise, wind can make you go from Valpha prot to MMO and the contrary in only a few seconds !
There is nothing ATHR can do about that.
Maybe a solution would be to maintain a speed as high as possible and protect yourself from overspeed with spoilers.

Or be ready to apply altitude corrections to help speed vary.
(In normal law, the flight control computers WILL apply altitude corrections if it comes to that)
KayPam is offline  
Reply

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



Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.