Switching AP on Control Transfer
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From: Canada
Switching AP on Control Transfer
Does anyone know of any benefits of switching the Autopilot over to the side of pilot with control when control is handed over for short periods of time i.e. washroom breaks etc.? I'm talking here specifically about Airbus and switching between AP1 and AP2.
Are there any threats associated with flying the aircraft with the offside AP in control. Obviously it is recieving all it's data from the offside sensors and computers, and the threat here is that if there is a discrepancy between the two sides. But other than that any others? One would assume here that during cruise there are no major discrepancies, or that they've been sorted well before control is handed over.
Are there any threats associated with flying the aircraft with the offside AP in control. Obviously it is recieving all it's data from the offside sensors and computers, and the threat here is that if there is a discrepancy between the two sides. But other than that any others? One would assume here that during cruise there are no major discrepancies, or that they've been sorted well before control is handed over.
Joined: Mar 2001
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From: I wouldn't know.
Me neither. And in fact if the onside FMCG is inop (which is perfectly dispatchable according to the MEL) one has to use the offside AP anyway. Just annoying about the map range switching, still boggles my mind, on the boeing that didn't affect my map at all, one FMC was enough to drive two independent map displays with a lot more info than the bus manages.. Sorry about that rant.
Joined: Jun 2001
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From: FNQ ... It's Permanent!
Does anyone know of any benefits of switching the Autopilot over to the side of pilot with control when control is handed over for short periods of time
Let’s hope you are never faced with an emergency!
Last edited by Capt Fathom; 4th October 2018 at 21:35.
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From: United Kingdom
I assume you were born with a complete and comprehensive knowledge of the Airbus FCOM. For us mere mortals, sometimes we have to ask those more knowledgeable than ourselves (such as you), so that we can in time because such a sky god in turn.
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From: USA
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From: uk
Capt Fathom : I was one of the early crews to convert onto the A330 at Toulouse in 1994 and AP switching was in fact the SOP taught by the Airbus instructors at that time! That's probably where it came from.
Joined: Apr 2004
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From: United States of Europe
Good question!
I would advise against switching AP’s for temporary PF/PM switching on the A320/A330.
It can create quite an unexpected jerk beyond of what the AP would normally command.
The reason for this is the presence of a minor FD mismatch due to onside Air Data / IR data not being 100% synchronised.
This is noticeable in cruise when ADR 1 and ADR 2 altitude are slightly different. (But well within RVSM tolerances)
Also the FD mismatch occurs frequently in managed descent where the vertical profile differs between Capt and F/O side, this is directly caused by differing onside IR data (wind, GS etc).
For prolonged taskswitching it would be advisable to switch AP when possible because this allows you to monitor the AP performance. I.e. is the FD being followed or not.
hope this helps
I would advise against switching AP’s for temporary PF/PM switching on the A320/A330.
It can create quite an unexpected jerk beyond of what the AP would normally command.
The reason for this is the presence of a minor FD mismatch due to onside Air Data / IR data not being 100% synchronised.
This is noticeable in cruise when ADR 1 and ADR 2 altitude are slightly different. (But well within RVSM tolerances)
Also the FD mismatch occurs frequently in managed descent where the vertical profile differs between Capt and F/O side, this is directly caused by differing onside IR data (wind, GS etc).
For prolonged taskswitching it would be advisable to switch AP when possible because this allows you to monitor the AP performance. I.e. is the FD being followed or not.
hope this helps
Joined: Apr 2001
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From: overthere
think more along the lines of when the ablutie returns and is back in the seat .
Joined: Oct 2009
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From: UK
If you change the pressure setting on your side because the other guy is out of the room or whatever, it will fly according to the onside FD so even if you've got STD on your side and QNH on the other, the autopilot will do it's job with the associated AP. Technically, i'd imagine that TCAS should probably also be swapped over if you change control as the TCAS will fly according to the pressure setting selected on the associated FD, although perhaps it works in STD at all times to avoid altimetry errors, i don't know.
Joined: Oct 2009
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From: UK
On the A320 we can select between 1 and 2 and I have always assumed it is selecting between FD1 and FD2 (aka onside AP) although I've never bothered looking into the FCOM as to what that selection does, my knowledge is limited to our SOP which requires the sector PF to select the TCAS onto their side during cockpit prep.
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From: Somewhere over the rainbow
Playing with the baro setting has no effect on the TCAS. It always uses standard regardless of the pilots baro setting.
with AP1, AP holds altitude using ADR 1. So you want to transmit the most accurate altitude the AP is using so you will put ATC sys 1 and vice versa. If you pay attention when you are in alt or cruise, the altitude is always more precise on the side the AP is engaged.
with AP1, AP holds altitude using ADR 1. So you want to transmit the most accurate altitude the AP is using so you will put ATC sys 1 and vice versa. If you pay attention when you are in alt or cruise, the altitude is always more precise on the side the AP is engaged.
Joined: Apr 2004
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From: Planet Earth
Can you select a different autopilot on
an Airbus without disconnecting it ?
On all Boeing’s I’m familiar with it won’t
let you connect a different autopilot unless
you disengage and then reselect the desired AP
an Airbus without disconnecting it ?
On all Boeing’s I’m familiar with it won’t
let you connect a different autopilot unless
you disengage and then reselect the desired AP
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From: Off track, again
Joined: Apr 2004
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From: Planet Earth
Ok, not on our 75/ 67 fleet
if you attempt to select a different autopilot in
flight nothing happens, the MCP just doesn’t
accept the input
You have to disengage then reselect a different autopilot
if you attempt to select a different autopilot in
flight nothing happens, the MCP just doesn’t
accept the input
You have to disengage then reselect a different autopilot