Capturing LOC/GS
8846,
I don't know if the Marham ILS was promulgated/flight tested in any manner you are familiar with. I DO know that approaches on Marham's Rwy 24 (it was 24 at the time anyway) came over a small chunk of flat old Norfolk and miles and miles of North Sea. In this particular instance, not a lot to interfere with it.
I don't know if the Marham ILS was promulgated/flight tested in any manner you are familiar with. I DO know that approaches on Marham's Rwy 24 (it was 24 at the time anyway) came over a small chunk of flat old Norfolk and miles and miles of North Sea. In this particular instance, not a lot to interfere with it.
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Nothing better than a little bit of Nahrfolk and miles and miles of ocean for the propagation of RF!
As I said in my post, I'm going to stick to talking about the systems I actually KNOW about so I'm not in a position to talk about military ILS. Promulgated ranges for the Marham ILS were surely published somewhere?It's got to be a different ball-game from a regulatory viewpoint anyway hasn't it? The CAA/ICAO lay down our standards in civilian life but I don't know what applies in the military.
If I remember correctly we only had an output power of about 25watts on the localiser array at Heathrow so plenty of room for improvement with a decent RF amplifier.
How is flight checking achieved in the military? I imagine that FRA up at Teeside are involved? Anyone from FRA care to add their h'apenny's worth?
As I said in my post, I'm going to stick to talking about the systems I actually KNOW about so I'm not in a position to talk about military ILS. Promulgated ranges for the Marham ILS were surely published somewhere?It's got to be a different ball-game from a regulatory viewpoint anyway hasn't it? The CAA/ICAO lay down our standards in civilian life but I don't know what applies in the military.
If I remember correctly we only had an output power of about 25watts on the localiser array at Heathrow so plenty of room for improvement with a decent RF amplifier.
How is flight checking achieved in the military? I imagine that FRA up at Teeside are involved? Anyone from FRA care to add their h'apenny's worth?
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Original Question..
And... just to come back to the original question, which worries me slightly as I re-read it....
As one of the blokes who used to be responsible for the engineering of the (civilian) systems that so many seem to be following outside the promulgated range... it is immaterial how far outside the correct range you can pick it up, it doesn't matter which aircraft type you are flying, if you use it then you are operating outside the certified parameters of the system. I know it goes on and I know it (mostly) works, but you ain't in a good position if something goes awry.
What can go wrong?
Well, the signal can bend all over the place, you could suffer from all manner of abberations and command reversals... I'm not suggesting it's going to fly you into a mountain but...
Just be careful now...
Now if you'll excuse me Mrs Doyle is coming in with some tea!!
As one of the blokes who used to be responsible for the engineering of the (civilian) systems that so many seem to be following outside the promulgated range... it is immaterial how far outside the correct range you can pick it up, it doesn't matter which aircraft type you are flying, if you use it then you are operating outside the certified parameters of the system. I know it goes on and I know it (mostly) works, but you ain't in a good position if something goes awry.
What can go wrong?
Well, the signal can bend all over the place, you could suffer from all manner of abberations and command reversals... I'm not suggesting it's going to fly you into a mountain but...
Just be careful now...
Now if you'll excuse me Mrs Doyle is coming in with some tea!!
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Well now, 8846, at least you seem to know what you are talking about, specifically, the ILS installations that you are familiar with.
I would certainly agree, in that context.
However, some who read here should realise that in other parts of the world, extended range high power ILS installations are available, and KLAX is one of them.
Arrival routes predicated on their use are published, and aircrews are expected to comply, by ATC.
If they do not....well, I suppose the concerned flight could be diverted somewhere else.
Anywhere else, for the betterment of all concerned.
I would certainly agree, in that context.
However, some who read here should realise that in other parts of the world, extended range high power ILS installations are available, and KLAX is one of them.
Arrival routes predicated on their use are published, and aircrews are expected to comply, by ATC.
If they do not....well, I suppose the concerned flight could be diverted somewhere else.
Anywhere else, for the betterment of all concerned.
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From the Horses mouth!
Extract from the FAA Aeronautical Information Manual
Aeronautical Information Manual
Official Guide to Basic Flight Information and ATC Procedures
Chapter 1. Navigation Aids
Section 1. Air Navigation Aids
K. ILS Course Distortion
1. All pilots should be aware that disturbances to ILS localizer and glide slope courses may occur when
surface vehicles or aircraft are operated near the localizer or glide slope antennas. Most ILS
installations are subject to signal interference by either surface vehicles, aircraft or both. ILS CRITICAL
AREAS are established near each localizer and glide slope antenna.
2. ATC issues control instructions to avoid interfering operations within ILS critical areas at controlled
airports during the hours the Airport Traffic Control Tower (ATCT) is in operation as follows:
(a) Weather Conditions. Less than ceiling 800 feet and/or visibility two miles.
(1) Localizer Critical Area. Except for aircraft that land, exit a runway, depart or miss
approach, vehicles and aircraft are not authorized in or over the critical area when an
arriving aircraft is between the ILS final approach fix and the airport. Additionally, when
the ceiling is less than 200 feet and/or the visibility is RVR 2,000 or less, vehicle and
aircraft operations in or over the area are not authorized when an arriving aircraft is
inside the ILS MM.
(2) Glide Slope Critical Area. Vehicles and aircraft are not authorized in the area
when an arriving aircraft is between the ILS final approach fix and the airport unless the
aircraft has reported the airport in sight and is circling or side stepping to land on a
runway other than the ILS runway.
(b) Weather Conditions. At or above ceiling 800 feet and/or visibility two miles.
(1) No critical area protective action is provided under these conditions.
(2) A flight crew, under these conditions, should advise the tower that it will conduct an
AUTOLAND or COUPLED approach to ensure that the ILS critical areas are protected
when the aircraft is inside the ILS MM.
EXAMPLE - Glide slope signal not protected.
3. Aircraft holding below 5,000 feet between the outer marker and the airport may cause localizer signal
variations for aircraft conducting the ILS approach. Accordingly, such holding is not authorized when
weather or visibility conditions are less than ceiling 800 feet and/or visibility 2 miles.
4. Pilots are cautioned that vehicular traffic not subject to ATC may cause momentary deviation to ILS
course or glide slope signals. Also, critical areas are not protected at uncontrolled airports or at airports
with an operating control tower when weather or visibility conditions are above those requiring
protective measures. Aircraft conducting coupled or autoland operations should be especially alert in
monitoring automatic flight control systems.
Note: Unless otherwise coordinated through Flight Standards, ILS signals to Category I runways are
not flight inspected below 100 feet AGL. Guidance signal anomalies may be encountered
below this altitude.
Aeronautical Information Manual
Official Guide to Basic Flight Information and ATC Procedures
Chapter 1. Navigation Aids
Section 1. Air Navigation Aids
K. ILS Course Distortion
1. All pilots should be aware that disturbances to ILS localizer and glide slope courses may occur when
surface vehicles or aircraft are operated near the localizer or glide slope antennas. Most ILS
installations are subject to signal interference by either surface vehicles, aircraft or both. ILS CRITICAL
AREAS are established near each localizer and glide slope antenna.
2. ATC issues control instructions to avoid interfering operations within ILS critical areas at controlled
airports during the hours the Airport Traffic Control Tower (ATCT) is in operation as follows:
(a) Weather Conditions. Less than ceiling 800 feet and/or visibility two miles.
(1) Localizer Critical Area. Except for aircraft that land, exit a runway, depart or miss
approach, vehicles and aircraft are not authorized in or over the critical area when an
arriving aircraft is between the ILS final approach fix and the airport. Additionally, when
the ceiling is less than 200 feet and/or the visibility is RVR 2,000 or less, vehicle and
aircraft operations in or over the area are not authorized when an arriving aircraft is
inside the ILS MM.
(2) Glide Slope Critical Area. Vehicles and aircraft are not authorized in the area
when an arriving aircraft is between the ILS final approach fix and the airport unless the
aircraft has reported the airport in sight and is circling or side stepping to land on a
runway other than the ILS runway.
(b) Weather Conditions. At or above ceiling 800 feet and/or visibility two miles.
(1) No critical area protective action is provided under these conditions.
(2) A flight crew, under these conditions, should advise the tower that it will conduct an
AUTOLAND or COUPLED approach to ensure that the ILS critical areas are protected
when the aircraft is inside the ILS MM.
EXAMPLE - Glide slope signal not protected.
3. Aircraft holding below 5,000 feet between the outer marker and the airport may cause localizer signal
variations for aircraft conducting the ILS approach. Accordingly, such holding is not authorized when
weather or visibility conditions are less than ceiling 800 feet and/or visibility 2 miles.
4. Pilots are cautioned that vehicular traffic not subject to ATC may cause momentary deviation to ILS
course or glide slope signals. Also, critical areas are not protected at uncontrolled airports or at airports
with an operating control tower when weather or visibility conditions are above those requiring
protective measures. Aircraft conducting coupled or autoland operations should be especially alert in
monitoring automatic flight control systems.
Note: Unless otherwise coordinated through Flight Standards, ILS signals to Category I runways are
not flight inspected below 100 feet AGL. Guidance signal anomalies may be encountered
below this altitude.
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From UK CAA FODCOM 14/2004
1.2.1 In the UK, ILS Critical Areas are protected at all times that an ILS is in use. Additionally, the larger ILS Sensitive Areas are protected through ATC procedures when aircraft are making an ILS approach. The size of the Sensitive Area increases as the Category (I, II or III) of operation changes in response to decreasing visibility.
1.2.2 In the United States the ILS Critical Area is not protected if the weather conditions are better than 800 ft cloud ceiling and two miles visibility, as described in the extract from the FAA Aeronautical Information
Manual (AIM) at Appendix A.
1.3 Recommendation
1.3.1 Operators should bring this information to the attention of all their crews who are likely to fly to airfields in the United States.
1.4 Additional information
1.4.1 AIC 34/1997 (Pink 141) ‘THE USE OF ILS FACILITIES IN THE UNITED KINGDOM’.
1.4.2 JAA Temporary Guidance Leaflet ‘Section Four, Operations, Part 3: Temporary Guidance Material -
Leaflet No. 23: Use Of Autoland System On ILS Category I Facilities Or Category II/III Facilities When Low Visibility Procedures (LVP) Are Not In Force.’
1.4.3 FAA Aeronautical Information Manual
http://www.faa.gov/ATpubs/AIM/index.htm
1.2.2 In the United States the ILS Critical Area is not protected if the weather conditions are better than 800 ft cloud ceiling and two miles visibility, as described in the extract from the FAA Aeronautical Information
Manual (AIM) at Appendix A.
1.3 Recommendation
1.3.1 Operators should bring this information to the attention of all their crews who are likely to fly to airfields in the United States.
1.4 Additional information
1.4.1 AIC 34/1997 (Pink 141) ‘THE USE OF ILS FACILITIES IN THE UNITED KINGDOM’.
1.4.2 JAA Temporary Guidance Leaflet ‘Section Four, Operations, Part 3: Temporary Guidance Material -
Leaflet No. 23: Use Of Autoland System On ILS Category I Facilities Or Category II/III Facilities When Low Visibility Procedures (LVP) Are Not In Force.’
1.4.3 FAA Aeronautical Information Manual
http://www.faa.gov/ATpubs/AIM/index.htm
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Yup, that's all fine and dandy and thanks 411 for expanding my knowledge of ILS systems in other parts of the world.
Agent Orange is going up a slightly different path though...
To explain all the legaleese in the documents that you have reproduced...
The ILS signal is subject to interference from anything close to the aerial. To protect the signal from corruption we establish areas around the aerials into which a vehicle may not go without permission from ATC.
It is adjudged that in good weather the extent of these areas is sufficient to protect the signal from significant corruption to allow an aircraft to follow the guidance down to Cat 1 minima. There may also be slight deviations in the signal at greater range, even when the critical area is not being infringed, but in Cat 1 weather this is considered acceptable.
If the weather worsens then a greater protective area comes into force - the Cat 2/3 holds e.t.c. to ensure that the signal is reliable down to Cat 2/3 minima.
This is different again to the promulgated range question posted originally, which refers to the signal in space at the extent of its range.
All very interesting..or perhaps not! You be the judge?!!
Agent Orange is going up a slightly different path though...
To explain all the legaleese in the documents that you have reproduced...
The ILS signal is subject to interference from anything close to the aerial. To protect the signal from corruption we establish areas around the aerials into which a vehicle may not go without permission from ATC.
It is adjudged that in good weather the extent of these areas is sufficient to protect the signal from significant corruption to allow an aircraft to follow the guidance down to Cat 1 minima. There may also be slight deviations in the signal at greater range, even when the critical area is not being infringed, but in Cat 1 weather this is considered acceptable.
If the weather worsens then a greater protective area comes into force - the Cat 2/3 holds e.t.c. to ensure that the signal is reliable down to Cat 2/3 minima.
This is different again to the promulgated range question posted originally, which refers to the signal in space at the extent of its range.
All very interesting..or perhaps not! You be the judge?!!
The Marha 24 LOC (not GS) did have an extended protected range published. it was in the order of 60 miles, I think.
The Cranwell 27 ILS had a set of power lines running under it at about 4 miles. When you got the about 1200', you had to increase the rate of descent slightly to stop you going above the GS!
The Cranwell 27 ILS had a set of power lines running under it at about 4 miles. When you got the about 1200', you had to increase the rate of descent slightly to stop you going above the GS!
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Military checking almost identical to civvy in the UK but the ranges are the same.
LOC- 25nm +/- 10 degrees of centreline
17nm +/- 35 degrees of centreline
Glide 10nm +/- 8 degrees of centreline
BE VERY, VERY, VERY CAREFUL USING THE SIGNALS OUTSIDE THESE RANGES!
Previous post stated that they follow the glide as soon as they intercept it, just check that range!!!!
LOC- 25nm +/- 10 degrees of centreline
17nm +/- 35 degrees of centreline
Glide 10nm +/- 8 degrees of centreline
BE VERY, VERY, VERY CAREFUL USING THE SIGNALS OUTSIDE THESE RANGES!
Previous post stated that they follow the glide as soon as they intercept it, just check that range!!!!
A few years ago, Airbus A300-B4 0400 ish. arrival at Dublin Rwy 28 Cat III, we intercepted the LOC at about 40 miles. Everything looked good until G/S capture about 9 miles.
V/L, G/S green, Land 3, etc. Aircraft then seemed to wander off the LOC by about 1 dot and did not correct itself. We left it to about 1500ft to see what happened and then decided to go around and have another go.
2nd approach from 9 miles was perfect.
So did the black boxes forget what they were doing having been on the LOC for so long? Maintenance said there were no faults.
Is this a problem with capturing the LOC from so far out?
V/L, G/S green, Land 3, etc. Aircraft then seemed to wander off the LOC by about 1 dot and did not correct itself. We left it to about 1500ft to see what happened and then decided to go around and have another go.
2nd approach from 9 miles was perfect.
So did the black boxes forget what they were doing having been on the LOC for so long? Maintenance said there were no faults.
Is this a problem with capturing the LOC from so far out?
One difference between an ILS course over empty ocean and one in a crowded airspace is that the latter can be more vulnerable to interference from another ILS using the same frequency.
It's something like receiving two FM stations on the same frequency.
It's something like receiving two FM stations on the same frequency.
