Question on AUTOLAND
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Question on AUTOLAND
Dear all,
I would like to clarify something on the AUTOLAND. I know this topic has already been discussed many times, but I haven't found a clear answer on this:
Is it possible, not legally but technically speaking, that an A320 can do a full AUTOLAND (FLARE and ROLLOUT), with the FMA showing CAT III SINGLE, or even CAT II or CAT I ?
Thank you for your answers,
Kind regards
I would like to clarify something on the AUTOLAND. I know this topic has already been discussed many times, but I haven't found a clear answer on this:
Is it possible, not legally but technically speaking, that an A320 can do a full AUTOLAND (FLARE and ROLLOUT), with the FMA showing CAT III SINGLE, or even CAT II or CAT I ?
Thank you for your answers,
Kind regards
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Thanks for the answer.
So technically, let's imagine the weather is NO DH, you don't see anything, LVP are in place at the airport, and our a320 is showing CAT II on the FMA; it can land automatically then. But legally, it's not allowed due to the fact that it would be fail passive, so no redundancy, so the law says don't do it because of that ?
So technically, let's imagine the weather is NO DH, you don't see anything, LVP are in place at the airport, and our a320 is showing CAT II on the FMA; it can land automatically then. But legally, it's not allowed due to the fact that it would be fail passive, so no redundancy, so the law says don't do it because of that ?
You can’t legally continue a CAT2 approach below DA/DH unless you have the required visual references. You are not permitted to start the approach (descend below 1000ft RA) unless you have the required RVR.
The aircraft will do it but it’s not legal or sensible due to the increased risk of an accident.
Assuming the RVR allows it you can fly down to the CAT2 DA/DH, if nothing seen fly a missed approach, or if you have the required visual references continue for an auto land.
If the RVR is less than the CAT2 limit (usually about 300/125/75) then you are not permitted to descend below 1000ft RA on the approach.
I hope that makes sense?
LD
The aircraft will do it but it’s not legal or sensible due to the increased risk of an accident.
Assuming the RVR allows it you can fly down to the CAT2 DA/DH, if nothing seen fly a missed approach, or if you have the required visual references continue for an auto land.
If the RVR is less than the CAT2 limit (usually about 300/125/75) then you are not permitted to descend below 1000ft RA on the approach.
I hope that makes sense?
LD
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Thanks for the answer.
So technically, let's imagine the weather is NO DH, you don't see anything, LVP are in place at the airport, and our a320 is showing CAT II on the FMA; it can land automatically then. But legally, it's not allowed due to the fact that it would be fail passive, so no redundancy, so the law says don't do it because of that ?
So technically, let's imagine the weather is NO DH, you don't see anything, LVP are in place at the airport, and our a320 is showing CAT II on the FMA; it can land automatically then. But legally, it's not allowed due to the fact that it would be fail passive, so no redundancy, so the law says don't do it because of that ?
for Low Vis Ops you need 3 things. Qualified crew, approved airport - LVPs in force & serviceable aircraft.
Btw fail-operational AP is one requirement for CAT3B. Auto thrust is another.
Last edited by InSoMnIaC; 1st Mar 2024 at 19:27.
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Ok thank you for your answers.
So it seems that legally, the aircraft capability on FMA [CAT III DUAL/SINGLE / CAT II / CAT I] is linked to the type of ILS approach flown:
FMA CAT III DUAL --> you can perform AUTOLAND with no DH (meaning automatic approach + FLARE + ROLL OUT)
FMA CAT III SINGLE --> you can perform automatic approach until DH=50ft, then LEGALLY you have to disconnect to fly the last 50ft manually, but TECHNICALLY the aircraft can still land by itself without intervening manually, it is just fail passive, so if another failure occurs, the aircraft may deviate from its path, so this is why we take it manually for safety
FMA CAT II --> you can perform automatic approach until DH=100ft, then LEGALLY you have to disconnect to fly the last 100ft manually, but TECHNICALLY the aircraft can still land by itself without intervening manually, it is just fail passive, so if another failure occurs, the aircraft may deviate from its path, so this is why we take it manually for safety
But for FMA CAT I, it means there is no autopilot engaged, so the approach can't be flown automatically right ? So it is not linked to a CAT I ILS approach with a DH of 200 ft, it has no link to that (whereas for CAT II and CAT III it is linked to the CAT II and CAT III ILS approach with their respective DH)
I hope I can make myself understood, I want to fully understand the philosophy behind, tell me if something is not correct in what I said above, thank you for your help
So it seems that legally, the aircraft capability on FMA [CAT III DUAL/SINGLE / CAT II / CAT I] is linked to the type of ILS approach flown:
FMA CAT III DUAL --> you can perform AUTOLAND with no DH (meaning automatic approach + FLARE + ROLL OUT)
FMA CAT III SINGLE --> you can perform automatic approach until DH=50ft, then LEGALLY you have to disconnect to fly the last 50ft manually, but TECHNICALLY the aircraft can still land by itself without intervening manually, it is just fail passive, so if another failure occurs, the aircraft may deviate from its path, so this is why we take it manually for safety
FMA CAT II --> you can perform automatic approach until DH=100ft, then LEGALLY you have to disconnect to fly the last 100ft manually, but TECHNICALLY the aircraft can still land by itself without intervening manually, it is just fail passive, so if another failure occurs, the aircraft may deviate from its path, so this is why we take it manually for safety
But for FMA CAT I, it means there is no autopilot engaged, so the approach can't be flown automatically right ? So it is not linked to a CAT I ILS approach with a DH of 200 ft, it has no link to that (whereas for CAT II and CAT III it is linked to the CAT II and CAT III ILS approach with their respective DH)
I hope I can make myself understood, I want to fully understand the philosophy behind, tell me if something is not correct in what I said above, thank you for your help
Last edited by Aperture; 1st Mar 2024 at 20:08.
Not quite.
Ref FMA’s
CAT3 Dual= Autoland + Auto rollout
CAT3 Single = Autoland + manual rollout (or auto rollout but be prepared to intervene)
CAT2 = Some airlines mandate an autoland as per CAT3A, some allow a manual landing but you must respect the minimum autopilot disconnect height as per FCOM
CAT1 = Man land
For autoland + manual rollout the autopilot is disconnected after nose gear touchdown. You must NEVER disconnect the autopilot while airborne on a CAT3 approach.
Remember this is the aircraft telling you what it CAN do, not what you must do. The aircraft can autoland and auto rollout with either CAT3 or CAT2 on the FMA, but it may not be legal. Once you know what the aircraft can do, then you need to look at what’s available for the runway in question. Some runways are no autoland, some are CAT2 at best or CAT3 single at best. Some CAT3 Dual with a DH and some CAT3 Dual no DH. It all depends on the standard of ILS transmitter installed. Remember LVP’s must be in force for you to proceed below the CAT1 DA without visual reference regardless of what the FMA says. Some airfields, EG Munich, may only offer you a CAT2 approach even though there is CAT3B NO DH minima published and your FMA says CAT 3 DUAL.
For example you can fly a CAT2 approach with CAT3 Dual on the FMA if CAT2 is lowest minima for that runway.
You CAN’T fly a CAT3 approach with CAT2 on the FMA.
You CAN fly a CAT1 autoland with CAT2 or CAT3 on the FMA as long as minima is published for that runway that is lower than CAT1, no LVP’s required as it’s a CAT1 approach.
It’s a minefield out there!
LD
Ref FMA’s
CAT3 Dual= Autoland + Auto rollout
CAT3 Single = Autoland + manual rollout (or auto rollout but be prepared to intervene)
CAT2 = Some airlines mandate an autoland as per CAT3A, some allow a manual landing but you must respect the minimum autopilot disconnect height as per FCOM
CAT1 = Man land
For autoland + manual rollout the autopilot is disconnected after nose gear touchdown. You must NEVER disconnect the autopilot while airborne on a CAT3 approach.
Remember this is the aircraft telling you what it CAN do, not what you must do. The aircraft can autoland and auto rollout with either CAT3 or CAT2 on the FMA, but it may not be legal. Once you know what the aircraft can do, then you need to look at what’s available for the runway in question. Some runways are no autoland, some are CAT2 at best or CAT3 single at best. Some CAT3 Dual with a DH and some CAT3 Dual no DH. It all depends on the standard of ILS transmitter installed. Remember LVP’s must be in force for you to proceed below the CAT1 DA without visual reference regardless of what the FMA says. Some airfields, EG Munich, may only offer you a CAT2 approach even though there is CAT3B NO DH minima published and your FMA says CAT 3 DUAL.
For example you can fly a CAT2 approach with CAT3 Dual on the FMA if CAT2 is lowest minima for that runway.
You CAN’T fly a CAT3 approach with CAT2 on the FMA.
You CAN fly a CAT1 autoland with CAT2 or CAT3 on the FMA as long as minima is published for that runway that is lower than CAT1, no LVP’s required as it’s a CAT1 approach.
It’s a minefield out there!
LD
Last edited by Locked door; 1st Mar 2024 at 21:11.
Just be aware that, if the GS and LOC are not protected, you can have a wild ride. I was an engineering observer for hundreds of flight test autolands and, since all were done in VMC, there was no protection. Things got quite exciting low on one approach when a grass mower passed in front of the LOC antenna.
On another flight test program a Douglas trijet nearly took out runway signage because the crew didn't understand the implication of an unprotected ILS. A very late GA saved the sign (and perhaps the aircraft).
On another flight test program a Douglas trijet nearly took out runway signage because the crew didn't understand the implication of an unprotected ILS. A very late GA saved the sign (and perhaps the aircraft).
But for FMA CAT I, it means there is no autopilot engaged, so the approach can't be flown automatically right ? So it is not linked to a CAT I ILS approach with a DH of 200 ft, it has no link to that (whereas for CAT II and CAT III it is linked to the CAT II and CAT III ILS approach with their respective DH)
The minimum height to disconnect the autopilot on an ILS with CAT1 showing on the FMA is 160ft AGL, if you don't disconnect the autopilot FLARE mode will engage and the aircraft will perform an autoland followed by an auto roll out. It won't be legal but the aircraft will go ahead and do it. If you disconnect the autopilot CAT1 stays on the FMA, the flight directors stay engaged and will also enter FLARE and ROLL-OUT mode during the landing.
Basically it is quite possible, but not legal, to autoland with CAT1 on the FMA.
Just because something is possible does not mean it is without additional risk.
Minimum use heights for lesser autoflight categories might be because of reliance on an assumed level of human action to recover from failure; the system might fail 'hard' due to a lowered levels of redundancy, internal monitoring, etc.
The height limits are established during flight test, they are often judgements of expected human performance. If they are abused - 'it's ok because we are visual' doesn't guard against the nature of surprise or having a nasty bump.
Similarly for human limitations in lower visibilities; operational limits must be respected as they are designed to cover a wide range of expected scenarios and different pilots' ability. You don't know where your rating stands on a particular day or in the local conditions.
Minimum use heights for lesser autoflight categories might be because of reliance on an assumed level of human action to recover from failure; the system might fail 'hard' due to a lowered levels of redundancy, internal monitoring, etc.
The height limits are established during flight test, they are often judgements of expected human performance. If they are abused - 'it's ok because we are visual' doesn't guard against the nature of surprise or having a nasty bump.
Similarly for human limitations in lower visibilities; operational limits must be respected as they are designed to cover a wide range of expected scenarios and different pilots' ability. You don't know where your rating stands on a particular day or in the local conditions.
