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

A320 CAT III B

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

A320 CAT III B

Old 1st Oct 2020, 11:53
  #1 (permalink)  
Thread Starter
 
Join Date: Aug 2001
Location: Above the Horizon
Posts: 118
A320 CAT III B

During an Autoland in CAT III B conditions, if the ROLL OUT mode does not engage what is the action to be taken?
Does one disconnect the AP and follow the Yaw Bar or carry out a Go Around?
Thanks
Boyington is offline  
Old 1st Oct 2020, 13:22
  #2 (permalink)  
 
Join Date: Mar 2012
Location: Having a margarita on the beach
Age: 48
Posts: 1,764
Originally Posted by Boyington View Post
During an Autoland in CAT III B conditions, if the ROLL OUT mode does not engage what is the action to be taken?
Does one disconnect the AP and follow the Yaw Bar or carry out a Go Around?
Thanks
Realistically speaking, by the time the CM2 realizes that ROLLOUT did not engage You would have already deployed the reverse, hence go around is not an option anyway.

FCOM says :

DIRECTIONAL CONTROL .................................................. MONITOR/ENSURE
– Monitor directional control, if the rollout is automatic. If rollout guidance is not
satisfactory, immediately disconnect AP and revert to manual directional
control.

With a few meters of RVR and a good back-up from the CM2 pointing out LOC deviations, you will be able to satisfactorily control the rollout on the ground.

Notwithstanding with the above, if You have not started reverse deployment at touch down, go around is always an option.
sonicbum is online now  
Old 5th Oct 2020, 23:21
  #3 (permalink)  
 
Join Date: Aug 2020
Location: Spain
Posts: 8
As sonicbum explains, by the time CM2 realises ROLLOUT has not engaged, CM1 would most probably have applied reverse thrust. So do not even think about a go around.

In the case CM1 has not applied reverse yet, I would not think of going around neither. If you are not capable of braking the aircraft following the yaw bar, it will be much more difficult to accelerate again the aircraft along the runway at high speed.
mantoga_srs is offline  
Old 11th Oct 2020, 21:53
  #4 (permalink)  
 
Join Date: Dec 2012
Location: N/A
Posts: 69
Originally Posted by mantoga_srs View Post
As sonicbum explains, by the time CM2 realises ROLLOUT has not engaged, CM1 would most probably have applied reverse thrust. So do not even think about a go around.

In the case CM1 has not applied reverse yet, I would not think of going around neither. If you are not capable of braking the aircraft following the yaw bar, it will be much more difficult to accelerate again the aircraft along the runway at high speed.
If reverse thrust is not yet deployed, the time for "re-acceleration" should not be too long . So, as long as reverser has not been selected I recommend to go around. Automatic roll out was, for an CAT IIIB approach, not planned just for fun.
LW20 is offline  
Old 11th Oct 2020, 21:57
  #5 (permalink)  
 
Join Date: Jun 2001
Location: Boldly going where no split infinitive has gone before..
Posts: 4,351
Originally Posted by LW20 View Post
If reverse thrust is not yet deployed, the time for "re-acceleration" should not be too long . So, as long as reverser has not been selected I recommend to go around. Automatic roll out was, for an CAT IIIB approach, not planned just for fun.
Yeah, but auto- take-off doesn't exist. If you can maintain center-line to do an aborted landing (which is what this would be, not a go-around), why not maintain it for a roll-out?
Wizofoz is offline  
Old 12th Oct 2020, 06:17
  #6 (permalink)  
 
Join Date: Mar 2006
Location: USA
Posts: 1,880
So now you've successfully gone around, and have a moment to breathe. Assuming you needed the rollout capability for the weather, now what? The plane's on the ground. Follow the yaw bar and taxi off the runway.

What's more interesting, is what exactly the AP will do in this scenario. Will it automatically disconnect? I couldn't find any information.
Check Airman is online now  
Old 12th Oct 2020, 07:58
  #7 (permalink)  
 
Join Date: Mar 2006
Location: England
Posts: 889
If you are landing in 3B conditions then the aircraft and autopilot system are fail operational.
Regulators can apply operating procedures in different ways, but essentially if the aircraft is below a specified height, alert - height, then the landing can be continued without crew intervention.

In the highest technical category the roll out system will also be fail-op; if a failure occurs then land, stay on the runway.
If the rollout sub system is not fail-op, then the lower integrity should require a higher visibility minima in the procedure to mitigate the possibility of failure; 'see to roll out'.

The technical specification and integrity of the auto-flight system should ensure that the system remains engaged until the same point when the pilot intervenes in normal operation.
However, this would depend largely on the level of system integration; e.g. if fully within the auto-flight computer, or a separate rollout system such as HUD (different minima for each type).
PEI_3721 is offline  
Old 12th Oct 2020, 23:16
  #8 (permalink)  
 
Join Date: Aug 2020
Location: Spain
Posts: 8
Originally Posted by LW20 View Post
If reverse thrust is not yet deployed, the time for "re-acceleration" should not be too long . So, as long as reverser has not been selected I recommend to go around. Automatic roll out was, for an CAT IIIB approach, not planned just for fun.
Once you have the wheels on the ground, if not a balked landing of course, the reason for going around must be major. Pilots are trained to abort a high speed take off in low visibility conditions. The chances of being capable to decelerate the aircraft on the runway are very high.
Think about going around. Of course first thing you check is the fuel you have left. If you are landing in a not very busy airport, probably you will have the chance of trying another approach. But imagine doing this in LHR, CDG, MAD...etc. The time it will take ATC being able to vector you for another approach can be quite long with a busy airspace and an airport operating in LVO. You can put yourself in a situation declaring emergency fuel, or diverting, when minutes earlier your aircraft was with the wheels on the ground, but automation was not able to do the rollout itself. Pilots are in the cockpit for a reason, and they are trained to take action when necessary.
mantoga_srs is offline  
Old 13th Oct 2020, 17:10
  #9 (permalink)  
 
Join Date: Dec 2012
Location: N/A
Posts: 69
It seems you have not taken my point. If you touch down, reverser will usually be selected within approximately 1 or 2 seconds. Thereafter a go around is not possible and you have to maintain centerline with your own feet.
So if you are in a position to choose between GA or not, your nosewheel will be still in the air and at 0-75 the only thing you will see is white. To continue in this case only by looking at the yaw bar is unprofessional. If I remember correctly, also the Autoland Light flashes, so a GA is mandatory.
LW20 is offline  
Old 13th Oct 2020, 17:59
  #10 (permalink)  
 
Join Date: Mar 2006
Location: England
Posts: 889
Whilst pilots check the facts about AutoLand light illuminating or not - remember that the aircraft has landed, 'autoland' has happened, but the system has not engaged rollout submode.

Also consider the generic, world wide advice not to GA after reverse selection. Reverse might not have deployed, but if it has then the risk of asymmetric thrust could be greater than remaining on the runway. *

You cite the lowest possible visibility; these are statistically most unlikely (combine that probability with rollout failure) and even so, the pilot should see small segment of the runway.Operations are often limited by 50m RVR because of fire rescue limitations. Thus as the nose is lowered the effective visibility - visual segment increases and there is benefit from 'streaming' effect; in addition there is more reaction time as speed decreases. Actions would be to use max reverse and max manual braking.

* asymmetric thrust:- https://safetyfirst.airbus.com/app/t...df.php?p=25602


PEI_3721 is offline  
Old 14th Oct 2020, 12:48
  #11 (permalink)  
 
Join Date: Dec 2010
Location: MC80 Home One type Star Cruiser
Posts: 177
Originally Posted by LW20 View Post
It seems you have not taken my point. If you touch down, reverser will usually be selected within approximately 1 or 2 seconds. Thereafter a go around is not possible and you have to maintain centerline with your own feet.
So if you are in a position to choose between GA or not, your nosewheel will be still in the air and at 0-75 the only thing you will see is white. To continue in this case only by looking at the yaw bar is unprofessional. If I remember correctly, also the Autoland Light flashes, so a GA is mandatory.
PRO-NOR-SOP-19
AT TOUCHDOWN: The flight crew must select reverse thrust immediately after main landing gear touchdown.

By the time that CM2 noticed that roll-out hasn’t engaged, reverse should have already been selected. And in case of a rollout mode failure, the autoland light shouldn’t come on. The aircraft can still land the aircraft. I assume that includes lowering the nose to complete the landing. If the autoland light flashes, there’s something else going on.

AUTOLAND WARNING
With “LAND” or “FLARE” green on the FMA and at least one AP engaged, the AUTOLAND red light appears on the glareshield when the aircraft is below 200 ft RA and one of the following events occurs:
‐ The autopilots are lost, or
- The aircraft gets too far off the beam (LOC or G/S flash on PFD), or
- Loss of LOC signal above 15 ft, or loss of glide signal above 100 ft (transmitter or receivers), or
‐ The difference between both radio altimeter indications is greater than 15 ft, or
‐ The FMGS detects a long flare.
Bus Driver Man is offline  
Old 14th Oct 2020, 16:07
  #12 (permalink)  
 
Join Date: Aug 2020
Location: Spain
Posts: 8
Originally Posted by LW20 View Post
It seems you have not taken my point. If you touch down, reverser will usually be selected within approximately 1 or 2 seconds. Thereafter a go around is not possible and you have to maintain centerline with your own feet.
So if you are in a position to choose between GA or not, your nosewheel will be still in the air and at 0-75 the only thing you will see is white. To continue in this case only by looking at the yaw bar is unprofessional. If I remember correctly, also the Autoland Light flashes, so a GA is mandatory.
ROLL OUT mode will not engage when you are at 75ft. By the time you realise it has not been engaged, you will be rolling along the runway. Reverse thrust must be selected inmediately when your wheels are on the ground. So...
mantoga_srs is offline  
Old 14th Oct 2020, 16:19
  #13 (permalink)  
 
Join Date: Feb 2002
Location: location location
Posts: 89
He’s talking about 0-75m RVR not 75’ rad alt
charlies angel is offline  
Old 14th Oct 2020, 17:40
  #14 (permalink)  
 
Join Date: Mar 2006
Location: England
Posts: 889
Bus Driver, valuable info.
For interest (and some devilment), what action would be expected in the event of a red autoland warning.
PEI_3721 is offline  
Old 14th Oct 2020, 20:30
  #15 (permalink)  
 
Join Date: Aug 2020
Location: Spain
Posts: 8
Originally Posted by charlies angel View Post
He’s talking about 0-75m RVR not 75’ rad alt
Ah okey. Read it quickly and misunderstood it. Anyway, the rest would apply. In a real CAT 3 approach, believe me, by the time CM2 calls "no rollout" cm1 would already have applied reverse thrust.
mantoga_srs is offline  
Old 15th Oct 2020, 16:07
  #16 (permalink)  
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 2,687
Cat3b in 0/75mtr it should not be a problem maintaining a centre line with yaw bar and some visibility in front. Even in GA centre line needs to be maintained manually. In case of excursion it is safer to go off decelerating than during acceleration for a GA.
vilas 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.