why is there no CAT III plates?
Joined: Jul 2005
Posts: 292
Likes: 0
From: Europe
Issi Noho: My comment was in relation to your first post, which seemed to be..not correct. Sorry.
As for Sarah:
So, I have a problem with an SOP, namely to apply 50 RA minima for CATIIIa approaches. I am then honest enough to admit that I have a problem with that, because I thought it was wrong. This low vis stuff is a quite complex matter, and I am sure you have a couple of holes in your knowledge too. F.ex. can you continue a CATII if TDZ-lighting fails? What is required RVR for 2. and 3. segment of rwy? Distance between rwy edge lights CATIII? I could go on and on...you will eventually get some of these wrong..Got it?
As for Sarah:
So, I have a problem with an SOP, namely to apply 50 RA minima for CATIIIa approaches. I am then honest enough to admit that I have a problem with that, because I thought it was wrong. This low vis stuff is a quite complex matter, and I am sure you have a couple of holes in your knowledge too. F.ex. can you continue a CATII if TDZ-lighting fails? What is required RVR for 2. and 3. segment of rwy? Distance between rwy edge lights CATIII? I could go on and on...you will eventually get some of these wrong..Got it?
Joined: Dec 2003
Posts: 2,348
Likes: 839
From: Tring, UK
I've always wondered what the real differences were and indeed what the point was of many seemingly identical approach plates for the same runway. 
Granted, the minima are different but many operators publish these seperately and they are subject to revision due NOTAMs, unserviceabilities, etc. anyway.
What is going to help you fly a better approach when using a Cat III chart instead of just one with the ILS on it? (Of whatever category) Am I missing something? A LVP taxi chart with the appropriate holding points is useful but that's on another page...
Granted, the minima are different but many operators publish these seperately and they are subject to revision due NOTAMs, unserviceabilities, etc. anyway.What is going to help you fly a better approach when using a Cat III chart instead of just one with the ILS on it? (Of whatever category) Am I missing something? A LVP taxi chart with the appropriate holding points is useful but that's on another page...
Joined: Apr 2002
Posts: 734
Likes: 0
From: Nirvana South
AFAIK there are differences between CAT II & III ILS as well. CAT III requires near field monitoring of the ILS plus back-up Transmitters & generators. Beleive the lighting & hold points etc are the same - you need to check the ICAO Aerodrome requirements for the details. As mentioned elsewhere, the operator only gets certified to CAT IIIa for certain approaches which is a synthesis of aircraft & ground equipment, crew training & experience etc etc. It is quite possible to have an aircraft fully equipped for CAT III (or CAT II for that matter) but not be able to use it to those minima.
Surprizingly ILS beam accuracy is the least of your concerns, I took part in an evaluation for the JAA (as a back-seater) that looked at doing HGS CAT IIIa approaches for training on CAT I beams & there wasn't any difference - the box rejected the same inaccurate flying as it would have on a CAT III beam.
Joined: Apr 2005
Posts: 110
Likes: 0
From: somewhere around
I have an additional question about this topic.
An airport near our homebase has a CAT III ILS. A permanet notam report that the minumun RVR for app. are 100mt (so CAT IIIB). This notam is vaild untill the AIP will be changed. When the AIP will change how can a crew (let say from Livingston that car operate up 75m) know the minumun RVR for that app.??
p.s. I'm just a flight dispatcher.
An airport near our homebase has a CAT III ILS. A permanet notam report that the minumun RVR for app. are 100mt (so CAT IIIB). This notam is vaild untill the AIP will be changed. When the AIP will change how can a crew (let say from Livingston that car operate up 75m) know the minumun RVR for that app.??
p.s. I'm just a flight dispatcher.
Joined: Dec 2001
Posts: 413
Likes: 0
From: down-route
Issi noho,
You're fairly close to the truth. The reason you can't do a Cat2 approach followed by a manual landing is due to the size and the position of the valley on the approach to 06L at MAN.
As we all know, when an aircraft descends on the ILS the corrections required (in order for the aircraft to stay on the glide-slope) are also reduced. The Flight Guidance System (FGS) is programmed to take this into account. The input for the increased sensitivity of the ILS is from the Radio Altimeter.
Unfortunately for 06L, the valley occurs at a very inconvenient place, ie. when the aircraft is 100feet above the touchdown point - which would be the normal Cat2 DH. There's a chance the FGS could be making a large correction at this stage as the input from the Rad Alt leads the system to believe that it is higher than it actually is. At the Cat2 DH the aircraft should be stable. The concern is that when the autopilot is disconnected, the aircraft could be chasing the glideslope which could lead to a destabilised approach as the aircraft subsequently deviates from the required profile.
On the Cat3 approach for 06L, the valley isn't an issue as the FGS will continue flying the flying down to the touchdown point.
To summarise then. A Cat2 approach followed by a manual landing can't be done on 06L due to the fact that the pilot could be taking control at a stage when the aircraft could be slightly destabilised.
You're fairly close to the truth. The reason you can't do a Cat2 approach followed by a manual landing is due to the size and the position of the valley on the approach to 06L at MAN.
As we all know, when an aircraft descends on the ILS the corrections required (in order for the aircraft to stay on the glide-slope) are also reduced. The Flight Guidance System (FGS) is programmed to take this into account. The input for the increased sensitivity of the ILS is from the Radio Altimeter.
Unfortunately for 06L, the valley occurs at a very inconvenient place, ie. when the aircraft is 100feet above the touchdown point - which would be the normal Cat2 DH. There's a chance the FGS could be making a large correction at this stage as the input from the Rad Alt leads the system to believe that it is higher than it actually is. At the Cat2 DH the aircraft should be stable. The concern is that when the autopilot is disconnected, the aircraft could be chasing the glideslope which could lead to a destabilised approach as the aircraft subsequently deviates from the required profile.
On the Cat3 approach for 06L, the valley isn't an issue as the FGS will continue flying the flying down to the touchdown point.
To summarise then. A Cat2 approach followed by a manual landing can't be done on 06L due to the fact that the pilot could be taking control at a stage when the aircraft could be slightly destabilised.
Joined: Feb 2006
Posts: 980
Likes: 11
From: On the dark side of the moon
False Capture:
I am not doubting your information, but here in Toronto, we fly CAT II approaches to an autoland on RWY 06L with a DH that is 100 ft above the threshold height. As there is a valley short of the threshold (where two large aircraft have ended up over the years), the actual DH used in the FMS is 108 ft. The valley is actually deeper than that (probably 30 ft below threshold height), but is rising back up at the DH point. Is the valley at MAN deeper than that at the DH point?
Jeff
I am not doubting your information, but here in Toronto, we fly CAT II approaches to an autoland on RWY 06L with a DH that is 100 ft above the threshold height. As there is a valley short of the threshold (where two large aircraft have ended up over the years), the actual DH used in the FMS is 108 ft. The valley is actually deeper than that (probably 30 ft below threshold height), but is rising back up at the DH point. Is the valley at MAN deeper than that at the DH point?
Jeff
Joined: Dec 2006
Posts: 16
Likes: 0
From: europe
Cat 2 plates used as CAT 3,a,b,c if airport runway used is approved and in force at time of approach,and if crew and aircraft are qualified.
Ie : Cat 2 shows 105RA,and you and your shiny aircraft are approved cat3a, 50 RA is set and 200RVR required.
Notams will tell you for preflight brief whether a cat3 is allowed.
If your a/c doesnt autoland on the centerline,always nice to advise ground about it and confirm it was your machine which
up rather than their system..
Safe Flights,
Ie : Cat 2 shows 105RA,and you and your shiny aircraft are approved cat3a, 50 RA is set and 200RVR required.
Notams will tell you for preflight brief whether a cat3 is allowed.
If your a/c doesnt autoland on the centerline,always nice to advise ground about it and confirm it was your machine which
up rather than their system.. Safe Flights,
Joined: Jan 2008
Posts: 67
Likes: 0
From: london
737 jockey
“As in my example of a CATII minima of 105 RA, I presume the CATIIIa would be higher than 50, perhaps 55...”
On a CAT2 approach the minima may be different because of the terrain on the approach, for CAT3a the minima is always going to be 50 RA because you will always be over the runway, therefore if this minima is set in stone, why produce a meaningless CAT3 plate.
“As in my example of a CATII minima of 105 RA, I presume the CATIIIa would be higher than 50, perhaps 55...”
On a CAT2 approach the minima may be different because of the terrain on the approach, for CAT3a the minima is always going to be 50 RA because you will always be over the runway, therefore if this minima is set in stone, why produce a meaningless CAT3 plate.
Joined: Nov 2001
Posts: 119
Likes: 0
From: Between EGGP and EGCC
Using Cat 2/3 plates instead of cat 1 ILS
Fullwings said:
What is going to help you fly a better approach when using a Cat III chart instead of just one with the ILS on it? (Of whatever category) Am I missing something? A LVP taxi chart with the appropriate holding points is useful but that's on another page...
Hiya Fullwings....
One good reason for the extra plates (which has not been touched on yet in this thread) is the fact that lower minima might result in performance issues on the go-around to clear all obstacles, esp single engine. The go-around track might be totally different in Cat 2/3 cases to satisfy this requirement.
Cheers
WM
What is going to help you fly a better approach when using a Cat III chart instead of just one with the ILS on it? (Of whatever category) Am I missing something? A LVP taxi chart with the appropriate holding points is useful but that's on another page...
Hiya Fullwings....
One good reason for the extra plates (which has not been touched on yet in this thread) is the fact that lower minima might result in performance issues on the go-around to clear all obstacles, esp single engine. The go-around track might be totally different in Cat 2/3 cases to satisfy this requirement.
Cheers
WM
Joined: Mar 2000
Posts: 1,337
Likes: 1
From: Sunrise Senior Living
WaterMeths is onto it!
For a normal approach with a DH down to 200', the approach climb gradient required is 2.1% for a twin and 2.7% for a quad - JAR 25.121 Subpart B/FAR25.121 Subpart B refer.
However, for instrument approaches with a DH below 200', a OEI gradient of 2.5% is mandated. JAR 1.510 Subpart B and AWO 236 refer.
Thus, a different MAP may be required for Cat 2 and better so we use the cat 2 plate to brief from.
Cheers,
mcdhu
For a normal approach with a DH down to 200', the approach climb gradient required is 2.1% for a twin and 2.7% for a quad - JAR 25.121 Subpart B/FAR25.121 Subpart B refer.
However, for instrument approaches with a DH below 200', a OEI gradient of 2.5% is mandated. JAR 1.510 Subpart B and AWO 236 refer.
Thus, a different MAP may be required for Cat 2 and better so we use the cat 2 plate to brief from.
Cheers,
mcdhu
Only half a speed-brake
Joined: Apr 2003
Posts: 4,459
Likes: 136
From: Commuting not home
Only half a speed-brake
Joined: Apr 2003
Posts: 4,459
Likes: 136
From: Commuting not home
PANS OPS (ICAO Doc 8168) Vol I:
3.6.1.7 Normally procedures are based on a nominal missed approach climb gradient of 2.5 per cent. A gradient of 2 per cent may be used in the procedure construction if the necessary survey and safeguarding can be provided; with the approval of appropriate authority, gradients of 3,4
or 5 per cent may be used for aircraft whose climb performance permits an operational advantage to be thus obtained. When other than a 2.5 per cent gradient is used, this will be indicated on the instrument approach chart and, in addition to the OCA/H for the specific gradient used, the OCA/H applicable to the nominal gradient will also be shown.
Joined: Dec 1999
Posts: 402
Likes: 0
From: Wilmslow and North Yorks
Guys, neither i nor the aircraft I fly are cleared for Cat III ILS's approaches in poor weather. I do however calibrate them.
There is really not a lot of difference between a CAT I ILS and a CAT III in terms of equipment or how it works. The Localiser for a CAT III will generally have more elements, making it more accurate, the Glideslope antenna will be of a more accurate type and, crucially, they will calibrated to a much more accurate standard and will have a much higher level of protection on the ground. Also, it's not always possible to install a CAT 2/3 depending on surrounding terrain and a huge number of physical airfield issues.
My understanding of the difference between a CAT II approach and a CAT III is simply the inputs that are used to determine your minima. On a CAT II you will use a Radar Altimeter input (75 feet or whatever) as the minima, on an a CAT III it may be 50' (which WILL be your Threshold Crossing Height) or it may be RVR related or both. The Bollin valley at MAN causes the RA to over-read close in to the Runway therefore denying a CAT II approach. A CAT III is available because it doesn't utilise the RA, the ILS Localiser is flight checked down the length of the runway to provide rollout guidance, with the GS being checked to the 50' TCH position.
As for separate CAT III plates, unless the go-around is different for performance reasons, there is really no need for a separate plate as the ILS procedure should be the same regardless of whether you are flying a CAT I or CAT III, all the plate really needs is the Minima to use for each type of available approach......feel free to flame me if i'm wrong
Cheers
There is really not a lot of difference between a CAT I ILS and a CAT III in terms of equipment or how it works. The Localiser for a CAT III will generally have more elements, making it more accurate, the Glideslope antenna will be of a more accurate type and, crucially, they will calibrated to a much more accurate standard and will have a much higher level of protection on the ground. Also, it's not always possible to install a CAT 2/3 depending on surrounding terrain and a huge number of physical airfield issues.
My understanding of the difference between a CAT II approach and a CAT III is simply the inputs that are used to determine your minima. On a CAT II you will use a Radar Altimeter input (75 feet or whatever) as the minima, on an a CAT III it may be 50' (which WILL be your Threshold Crossing Height) or it may be RVR related or both. The Bollin valley at MAN causes the RA to over-read close in to the Runway therefore denying a CAT II approach. A CAT III is available because it doesn't utilise the RA, the ILS Localiser is flight checked down the length of the runway to provide rollout guidance, with the GS being checked to the 50' TCH position.
As for separate CAT III plates, unless the go-around is different for performance reasons, there is really no need for a separate plate as the ILS procedure should be the same regardless of whether you are flying a CAT I or CAT III, all the plate really needs is the Minima to use for each type of available approach......feel free to flame me if i'm wrong
Cheers
Joined: Dec 2000
Posts: 523
Likes: 0
From: very close to STN!!
specially trained!!!
that's how they find out whether or not you have received the "Special High Intensity Training"!!!
if they made CAT 3 charts, everyone would be flying CAT 3 approaches willy nilly.
this way, they make sure only the "initiated" make it in----
if they made CAT 3 charts, everyone would be flying CAT 3 approaches willy nilly.
this way, they make sure only the "initiated" make it in----
Joined: Dec 2006
Posts: 2,486
Likes: 8
From: The No Transgression Zone
Stator vane, here in the US they'll publish them in the TERPs--- but I've never thought of going willy nilly on a ILS cat 3 with a Mooney/ or C182
Special AIRCRAFT and aircrew required!
http://www.myairplane.com/databases/...00610I4RC3.PDF
http://www.myairplane.com/databases/...0610I22LC3.PDF
http://www.myairplane.com/databases/...6039I17CC3.PDF
http://www.myairplane.com/databases/...6039I17LC3.PDF
Special AIRCRAFT and aircrew required!
http://www.myairplane.com/databases/...00610I4RC3.PDF
http://www.myairplane.com/databases/...0610I22LC3.PDF
http://www.myairplane.com/databases/...6039I17CC3.PDF
http://www.myairplane.com/databases/...6039I17LC3.PDF
Joined: Mar 2000
Posts: 1,337
Likes: 1
From: Sunrise Senior Living
Mmmmmm......thanks FD, you've just exposed a misunderstanding I have been harbouring for years!! I'll have to give this further thought - as to why we brief from the Cat 2 plate when we use mins from inserts in our Jepp Txt Manual.
Cheers,
mcdhu
Cheers,
mcdhu
Joined: Mar 2001
Posts: 4,563
Likes: 35
From: I wouldn't know.
We used to have tailored jepp airport booklets which in the end had the cat 3 minima as well. However earlier we just had the information in our performance manual.
Nowadays we use EAG charts (tailored as well i guess since they have the name of the airline group in the header) and lo and behold they have the cat 3 information on them as well, both for 3a and 3b.
Nowadays we use EAG charts (tailored as well i guess since they have the name of the airline group in the header) and lo and behold they have the cat 3 information on them as well, both for 3a and 3b.
Joined: Jan 1999
Aviation Qualifications: ATPL
Posts: 2,648
Likes: 410
From: Gatters.......
Flying for a large somewhat orange UK operator I have long wondered why the "local" policy was to check the documentation to see whether a given rwy was approved for Cat IIIb and then use the Cat I plate to execute the approach.
One of the prerequisites for using any plate is that it only "valid" or in other words safe if you stay within the "boundaries" defined on the plate. A cat I ILS plate by definition only provides obstacle clearance if you stay inside the limits. Ie. if the minima is 200ft, the missed app. proc. only provides obstacle clearance if you initiate your missed app. at DA and don't sink through more than..... is it 30 ft ??
My point is, if you go down to ie. 50 DH and then carry out a go-around you have effectively busted the foundation of the plate, and as I understand you are not guaranteed obstacle clearance.
Now I know this is a bit longhaired, but as I understand it the largest operator in Scandinavia has a proc.for this "G/A blw. published minima" and they use and brief the engine out proc. for that scenario.
OY
Ps: We just very recently got Airline tailored plates from jepp, so it is not really an issue anymore, still I wonder
One of the prerequisites for using any plate is that it only "valid" or in other words safe if you stay within the "boundaries" defined on the plate. A cat I ILS plate by definition only provides obstacle clearance if you stay inside the limits. Ie. if the minima is 200ft, the missed app. proc. only provides obstacle clearance if you initiate your missed app. at DA and don't sink through more than..... is it 30 ft ??
My point is, if you go down to ie. 50 DH and then carry out a go-around you have effectively busted the foundation of the plate, and as I understand you are not guaranteed obstacle clearance.
Now I know this is a bit longhaired, but as I understand it the largest operator in Scandinavia has a proc.for this "G/A blw. published minima" and they use and brief the engine out proc. for that scenario.
OY
Ps: We just very recently got Airline tailored plates from jepp, so it is not really an issue anymore, still I wonder