Effect of LVPs on autoland
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Joined: Jan 2007
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From: in the mist
Effect of LVPs on autoland
If carrying out a practice autoland in clear conditions with no LVPs in force, just how much worse can the landing be?
We had a clear runway from about 700' on finals, with a couple of a/c waiting to line up at the Cat 1 hold. This was at at a major airport with CAT3b (No DH) minima available. Our wee airbus flew what could be described as a poor approach from about 50' down. It flared too high, floated and then planted it when the speed ran out, went 3 meters or so downwind of the centerline, landed with drift on...
We had a clear runway from about 700' on finals, with a couple of a/c waiting to line up at the Cat 1 hold. This was at at a major airport with CAT3b (No DH) minima available. Our wee airbus flew what could be described as a poor approach from about 50' down. It flared too high, floated and then planted it when the speed ran out, went 3 meters or so downwind of the centerline, landed with drift on...
Joined: Mar 2003
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From: ? ? ?
Airbus FCOM 3.1.22, AUTOMATIC LANDING says :
"Automatic landing in CAT I, or better weather conditions, is possible on CAT I ground installations or on CAT II/III ground installations when ILS sensitive areas are not protected, if the following precautions are taken :
- omissis...
- The crew is aware that LOC or GS beam fluctuations, indipendent of the aircraft systems, may occur and the PF is prepared to immediately disconnect the autopilot and to take appropriate action, should unsatisfactory guidance occur.
- omissis...
- omissis..."
So, no LVPs in force >>> NO protections active... Take care !
"Automatic landing in CAT I, or better weather conditions, is possible on CAT I ground installations or on CAT II/III ground installations when ILS sensitive areas are not protected, if the following precautions are taken :
- omissis...
- The crew is aware that LOC or GS beam fluctuations, indipendent of the aircraft systems, may occur and the PF is prepared to immediately disconnect the autopilot and to take appropriate action, should unsatisfactory guidance occur.
- omissis...
- omissis..."
So, no LVPs in force >>> NO protections active... Take care !
Joined: Mar 2000
Posts: 1,337
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From: Sunrise Senior Living
Be very careful! I do quite a lot of these as a line trainer and often (I guess 40%) have to disconnect and land manually because I don't like what I see.
No protections - no guarantees! And always tell ATC what you are about to do - they might know something relevant!
Cheers,
mcdhu
No protections - no guarantees! And always tell ATC what you are about to do - they might know something relevant!
Cheers,
mcdhu
Thread Starter
Joined: Jan 2007
Posts: 565
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From: in the mist
Thanks guys,
I haven't done a practice one for a while... Certainly got my attention!... and it's making me think twice about doing it again. But, my company insists on a an autoland every 6 months (real or sim - std I think)
Now I'm a lacking in confidence for when I actually need this kit in anger. having seen a modern Boeing autoland in similar conditions with no problem, I'm a little less impressed by the airbus. I get the feeling "madam" is a bit too sensitive!
Any advice for when this kit is required "for real" guys?
I haven't done a practice one for a while... Certainly got my attention!... and it's making me think twice about doing it again. But, my company insists on a an autoland every 6 months (real or sim - std I think)
Now I'm a lacking in confidence for when I actually need this kit in anger. having seen a modern Boeing autoland in similar conditions with no problem, I'm a little less impressed by the airbus. I get the feeling "madam" is a bit too sensitive!
Any advice for when this kit is required "for real" guys?
Joined: Dec 2002
Posts: 2,775
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From: UK
Most autoland systems can be used without LVP, but the crew are expected to be extra vigilant because the performance might vary due to ILS interference.
IIRC there was a serious incident at LGW involving an MD-80 where departing traffic, over flying the LOC, caused large beam deviations which the autopilot translated into excessive roll angles at low altitude.
The performance as described could in part be related to radio altitude as the GS is usually phased out below 100ft. Also IIRC, flare is initiated by height or height-Gnd Spd relationship – depends on aircraft type; was the approach in a tailwind?
Alternatively some aircraft change autopilot gain as a function of altitude (or time/config), both pitch and roll can be affected; was there a late join, late config change?
In a similar manner to auto-landing without LVP, a good quality Cat 1 ILS can be used for auto-land practice providing that the ground profile of the undershoot is satisfactory – most UK ILSs meet the beam requirements, but not all airfields have a good ground profile.
So, as Henry states, “no LVPs in force >>> NO protections active... Take care.”
“And always tell ATC what you are about to do …” from personal experience, if auto-landing with ground-roll still engaged, be alert if a runway change is expected as a quick off–the-mark ATCO might change the ILS over which reverses the LOC beam sense; then you get a close view of the runway edge.
IIRC there was a serious incident at LGW involving an MD-80 where departing traffic, over flying the LOC, caused large beam deviations which the autopilot translated into excessive roll angles at low altitude.
The performance as described could in part be related to radio altitude as the GS is usually phased out below 100ft. Also IIRC, flare is initiated by height or height-Gnd Spd relationship – depends on aircraft type; was the approach in a tailwind?
Alternatively some aircraft change autopilot gain as a function of altitude (or time/config), both pitch and roll can be affected; was there a late join, late config change?
In a similar manner to auto-landing without LVP, a good quality Cat 1 ILS can be used for auto-land practice providing that the ground profile of the undershoot is satisfactory – most UK ILSs meet the beam requirements, but not all airfields have a good ground profile.
So, as Henry states, “no LVPs in force >>> NO protections active... Take care.”
“And always tell ATC what you are about to do …” from personal experience, if auto-landing with ground-roll still engaged, be alert if a runway change is expected as a quick off–the-mark ATCO might change the ILS over which reverses the LOC beam sense; then you get a close view of the runway edge.
Thread Starter
Joined: Jan 2007
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From: in the mist
Wind was 210/7 onto 26L at LGW. No oscilation observed on the glide or loc. Everything steady passing through 100' with the a/c configured fully before 1500 agl and stable way before all sop criteria.
I was close to disconnecting and recovering the thing myself. Instead.. Took the standard banter from the cabin crew and asked my fo "huh?". Thought afterwards it's better we discover any problems in cavok than our coleagues do in 200m.
Can't understand how a solid, stable approach could be messed up so much by lack of LVPs (only conclusion I've come to).
I was close to disconnecting and recovering the thing myself. Instead.. Took the standard banter from the cabin crew and asked my fo "huh?". Thought afterwards it's better we discover any problems in cavok than our coleagues do in 200m.
Can't understand how a solid, stable approach could be messed up so much by lack of LVPs (only conclusion I've come to).
Joined: Nov 1999
Posts: 647
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From: East side of OZ
I have had two autoland attempts go nuts in the flare over the last couple of years in VMC conditions. One was due to a wind shift, from 10kts crosswind to a head wind in the last 100' and the other NFI, no traffic and no wind. I've also seen a great autoland in the max crosswind allowable for the type, B767-300, of 25kts. The actual LVP limit is 10kts. Why the performance is so variable I have no idea but it makes me ultra cautious when doing an autoland either for practice or for real.
Regards,
BH.
Regards,
BH.
Joined: Dec 2002
Posts: 2,775
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From: UK
May be of interest, but air/surface temperature can affect auto-land performance near the runway, thus due to the late disturbance the performance can suffer.
A light wind, hot day, sun on runway creates thermals. So too for changes with type of surface – blacktop to concrete often found at the undershoot to runway transition.
Occasionally a vertical temperature variation – early morning / late evening can can also cause a disturbace.
A light wind, hot day, sun on runway creates thermals. So too for changes with type of surface – blacktop to concrete often found at the undershoot to runway transition.
Occasionally a vertical temperature variation – early morning / late evening can can also cause a disturbace.
Joined: Jan 2008
Aviation Qualifications: Non-Aircrew
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From: UK
It's not just the Cat 1 hold that may affect you.
For example at EGCC during LVP safeguards sections of the permiter road are also closed off to prevent vehicles straying into an area which may affect things.
It's not that uncommon for practice auto-lands to be carried out but you really should let ATC know what you're doing.
They will then let you know the status ... i.e. OK but protection is not in place.
For example at EGCC during LVP safeguards sections of the permiter road are also closed off to prevent vehicles straying into an area which may affect things.
It's not that uncommon for practice auto-lands to be carried out but you really should let ATC know what you're doing.
They will then let you know the status ... i.e. OK but protection is not in place.
Joined: Mar 2003
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From: ? ? ?
So what the most important thing you want to know when asking ATC whether LVP are in progress
To simulate autoland each company estabilish own procedure, to be added by airmanship, be always ready to react quicly. Again...
no LVPs in force >>> NO protections active... Take care !
Joined: Jan 2004
Posts: 794
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From: England
LVP safeguarding doesn't necessarily mean that LVP's are actually in force. All the physical safeguarding needs to be in place before ATC can operate LVPs, so if conditions are Cat I or above then ATC can still operate to Cat I holds. This also keeps delays to a minimum as LVPs significantly reduce the movement rates which causes delays to build up very quickly at busy airports.
Joined: May 2004
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From: Moscow
'LVP are in force or not. No half way.'
Of course. I didn't mean 'half-way'. LVP is an established and approved (not by me) complex procedure. What's the critical point for pilots in this complex? Some ask about LVP while others don't.
Of course. I didn't mean 'half-way'. LVP is an established and approved (not by me) complex procedure. What's the critical point for pilots in this complex? Some ask about LVP while others don't.
Joined: Oct 2004
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From: Nova Prospekt
We (atc) have to know about your autoland,because the opposite ils on the same runway might be on.This could be for technical or calibration purposes.
Many years ago an A320 almost bit the dust, when the captain did an autoland without telling anyone.The airbus barely made it to the runway in one piece.
It was later found out that the upset was caused by the aircraft crossing the active LLZ of the opposite direction.
So always inform ATC when intending to do a practice autoland.
WWW
Many years ago an A320 almost bit the dust, when the captain did an autoland without telling anyone.The airbus barely made it to the runway in one piece.
It was later found out that the upset was caused by the aircraft crossing the active LLZ of the opposite direction.
So always inform ATC when intending to do a practice autoland.
WWW
