GPS APPROACHES
Join Date: Aug 2001
Location: Cornwall
Age: 75
Posts: 1,307
Likes: 0
Received 0 Likes
on
0 Posts
We get there eventually
This is an extract from a paper presented by Dave Howson (UK CAA SRG) last October in Montreal.
We're working on it.
G
Use of GPS for Offshore Helicopter Operations - Low Visibility Approaches
Background
Low visibility approaches to offshore platforms are currently based on the use of weather radar for navigation and as a means of detecting obstacles on the approach path. Although it has been used for this purpose for a number of years, weather radar is neither designed nor certificated for such operations. In addition, these operations were identified by the Human Factors Working Group [2] as an area of potential safety improvement. Consequently, UK CAA has been investigating alternative means of conducting these operations. These investigations have focussed on the use of GPS, and have included a series of trials activities and follow-on data analysis exercises which have been reported in CAA Papers 2000/5, 2003/2 and 2003/7 [34, 35, 36]. UK CAA believes that the results of these investigations have demonstrated GPS to have significant potential for use as an offshore approach aid.
Following on from this work, a hazard analysis of the use of GPS for helicopter offshore approaches is being conducted. This exercise has been split into two parts; the first deals with the use of existing North Sea helicopter GPS equipment to enhance the existing weather radar approaches; the second will focus on a GPS-based offshore approach for which new aircraft equipment will be required.
Background
Low visibility approaches to offshore platforms are currently based on the use of weather radar for navigation and as a means of detecting obstacles on the approach path. Although it has been used for this purpose for a number of years, weather radar is neither designed nor certificated for such operations. In addition, these operations were identified by the Human Factors Working Group [2] as an area of potential safety improvement. Consequently, UK CAA has been investigating alternative means of conducting these operations. These investigations have focussed on the use of GPS, and have included a series of trials activities and follow-on data analysis exercises which have been reported in CAA Papers 2000/5, 2003/2 and 2003/7 [34, 35, 36]. UK CAA believes that the results of these investigations have demonstrated GPS to have significant potential for use as an offshore approach aid.
Following on from this work, a hazard analysis of the use of GPS for helicopter offshore approaches is being conducted. This exercise has been split into two parts; the first deals with the use of existing North Sea helicopter GPS equipment to enhance the existing weather radar approaches; the second will focus on a GPS-based offshore approach for which new aircraft equipment will be required.
G
Geoffers - the last line means 'we're working on it - but it'll cost you a load more money to comply with the regulations we eventually impose'
Crab,
No, it is saying that Differential GPS will be required.
However, these approaches will still need some 'device' to establish the obstacle environment - that device is presently the Airborne Radar. What DGPS achieves is to more accurately position the aircraft than with existing nav aids - this will permit the MAP to be closer to the platform; and of course there is the provision of vertical guidance.
One of the continuing issues is the loss of the ability to approach from any direction - once that has to be decided by the software, it will require extensive modification.
Jim
No, it is saying that Differential GPS will be required.
However, these approaches will still need some 'device' to establish the obstacle environment - that device is presently the Airborne Radar. What DGPS achieves is to more accurately position the aircraft than with existing nav aids - this will permit the MAP to be closer to the platform; and of course there is the provision of vertical guidance.
One of the continuing issues is the loss of the ability to approach from any direction - once that has to be decided by the software, it will require extensive modification.
Jim
Join Date: Jul 2005
Location: Spain
Posts: 273
Likes: 0
Received 0 Likes
on
0 Posts
Crab
From USCG NAVCEN report!
“New technology has allowed the Coast Guard to establish centralized control of the continental U.S LORAN-C system at two locations...........It should read “From” two locations.
The posturing from USCG NAVCEN is about empire building. It was a reasonable navaid (when it worked) but its time has come and gone.
170
From USCG NAVCEN report!
“New technology has allowed the Coast Guard to establish centralized control of the continental U.S LORAN-C system at two locations...........It should read “From” two locations.
The posturing from USCG NAVCEN is about empire building. It was a reasonable navaid (when it worked) but its time has come and gone.
170
JimL my post was meant 'tongue in cheek' but is probably correct if what you say is right. Are GPS approaches approved in other countries without the need for Differential GPS (accepting that making an approach to an airport with predetermined obstacle clearance planes is not the same as making an approach to an ostacle like a rig)?
170' - the Loran users organisation (does that make them L-osers) is bigging up the new e-Loran as a complement and/or alternative to GPS and since the USCG seem to fund the LORAN chain in the US they don't seem about to dump it.
170' - the Loran users organisation (does that make them L-osers) is bigging up the new e-Loran as a complement and/or alternative to GPS and since the USCG seem to fund the LORAN chain in the US they don't seem about to dump it.
Hi Crab,
A number of States have a generic ARA (JAA, FAA, TC) which permits the approach guidance with a number of aids. These used to be NDB or DECCA but overlaying with the GPS is now more usual.
As was said earlier, DGPS will still rely upon the RADAR for clearing the approach and go-around sector as the obstacle environment is complex in offshore operations. Improving the minima depends upon more accurate positioning and vertical guidance.
Practical considerations will determine the outcome of this research - which is being undertaken mainly to legitimise what it presently being done today. The introduction of EGNOS and Galileo will result in WAAS for offshore operations in Europe within a couple of years.
The gap in RADAR cover will also have to be plugged in the near future -this could be achieved also by using satellite facilities; the GOM appear to be ahead of Europe in this - probably because they have a larger hole to plug.
Jim
A number of States have a generic ARA (JAA, FAA, TC) which permits the approach guidance with a number of aids. These used to be NDB or DECCA but overlaying with the GPS is now more usual.
As was said earlier, DGPS will still rely upon the RADAR for clearing the approach and go-around sector as the obstacle environment is complex in offshore operations. Improving the minima depends upon more accurate positioning and vertical guidance.
Practical considerations will determine the outcome of this research - which is being undertaken mainly to legitimise what it presently being done today. The introduction of EGNOS and Galileo will result in WAAS for offshore operations in Europe within a couple of years.
The gap in RADAR cover will also have to be plugged in the near future -this could be achieved also by using satellite facilities; the GOM appear to be ahead of Europe in this - probably because they have a larger hole to plug.
Jim
Join Date: Jul 2005
Location: Spain
Posts: 273
Likes: 0
Received 0 Likes
on
0 Posts
Crab
I think you could be on the mark with L-osers ;-)
….
It seems obvious to me that the best backup/alternate to GPS- has to be aircraft based…
Otherwise you’re back to square one. With someone having control of a switch somewhere. And we know this switch is not powered with electricity, but by politics.
Creating mirror technologies means there are now multiple switch-keepers to negotiate with.
So the best deal all-round, is something akin to INS/IRS platform technology, with fix updating via all available means such as GPS, vortacs, dme, etc…(already there in RNAV form)
Plus cell phone sites, Remote Satellite Measurement Units, for both arrival and en-route update…Commercial radio stns maybe. (Limitations notwithstanding). Radar …ad infinitum
Plus updating aircraft to aircraft.....(extension of TCAS)
Imagine I’m eastbound at 15West with 96% nav accuracy after crossing the pond (GPS is TU)…Your 4000’ below, westbound after checking Benbecula, where you updated from a RSMU or the VOR and have 99.9 recurring% accuracy…My widget transparently updates from your widget, and the 5 or 6 others in range…
Now extend this to an approach to a rig, where you have a bunch of Boeing/Airbus in LOS…. Speed bird 17 and his friends, are seamlessly updating your position if they have a minimum assured nav accuracy themselves.
The unit’s won’t accept one or two erroneous signals from terrorists, faulty or vandalized ground emitters etc, but (as with old INS technology) will only accept a limited position error update…from its last known position consistent with its INS position
Basically if it receives a signal that doesn’t match the mixed signal info it already possesses, it dumps the erroneous signal. Similar to running in triple mix mode on the old INS system…
All this is notwithstanding the great accuracy of current generation INS/IRS/RNAV as a stand alone system, particularly on the short legs involved in helo ops, where you do a manual position update on each rig or LZ.
I have no idea of the complexity involved, but I imagine a triple doctorate from MIT could probably draw it out on a napkin….
I guess time will tell! But I wouldn’t be buying shares in any Loran stock. ...170'
ps...No I can't help out with development costs
I think you could be on the mark with L-osers ;-)
….
It seems obvious to me that the best backup/alternate to GPS- has to be aircraft based…
Otherwise you’re back to square one. With someone having control of a switch somewhere. And we know this switch is not powered with electricity, but by politics.
Creating mirror technologies means there are now multiple switch-keepers to negotiate with.
So the best deal all-round, is something akin to INS/IRS platform technology, with fix updating via all available means such as GPS, vortacs, dme, etc…(already there in RNAV form)
Plus cell phone sites, Remote Satellite Measurement Units, for both arrival and en-route update…Commercial radio stns maybe. (Limitations notwithstanding). Radar …ad infinitum
Plus updating aircraft to aircraft.....(extension of TCAS)
Imagine I’m eastbound at 15West with 96% nav accuracy after crossing the pond (GPS is TU)…Your 4000’ below, westbound after checking Benbecula, where you updated from a RSMU or the VOR and have 99.9 recurring% accuracy…My widget transparently updates from your widget, and the 5 or 6 others in range…
Now extend this to an approach to a rig, where you have a bunch of Boeing/Airbus in LOS…. Speed bird 17 and his friends, are seamlessly updating your position if they have a minimum assured nav accuracy themselves.
The unit’s won’t accept one or two erroneous signals from terrorists, faulty or vandalized ground emitters etc, but (as with old INS technology) will only accept a limited position error update…from its last known position consistent with its INS position
Basically if it receives a signal that doesn’t match the mixed signal info it already possesses, it dumps the erroneous signal. Similar to running in triple mix mode on the old INS system…
All this is notwithstanding the great accuracy of current generation INS/IRS/RNAV as a stand alone system, particularly on the short legs involved in helo ops, where you do a manual position update on each rig or LZ.
I have no idea of the complexity involved, but I imagine a triple doctorate from MIT could probably draw it out on a napkin….
I guess time will tell! But I wouldn’t be buying shares in any Loran stock. ...170'
ps...No I can't help out with development costs
170,
It is probably correct that the most potent of combinations is that of the GPS and INS - at least for the most critical portion of flight, the instrument approach (where the horizon prevents other signals from being received). The INS - updated by the GPS - would provide the guidance signal; if the GPS signal were to fail, there would be sufficient accuracy left in the system to complete the approach or go-around.
Strange then that these installations are few and far between - which points to cost or technical problems. The only (almost) helicopter which I know that is equipped with one of these is the Bell X-15.
Jim
It is probably correct that the most potent of combinations is that of the GPS and INS - at least for the most critical portion of flight, the instrument approach (where the horizon prevents other signals from being received). The INS - updated by the GPS - would provide the guidance signal; if the GPS signal were to fail, there would be sufficient accuracy left in the system to complete the approach or go-around.
Strange then that these installations are few and far between - which points to cost or technical problems. The only (almost) helicopter which I know that is equipped with one of these is the Bell X-15.
Jim
170' - it sounds great - have it wrapped and sent round...
JimL - if DGPS will still require an improved radar to more accurately determine the obstacle environment then why not just improve the radar and get reduced minimas that way? Do the N Sea operators really need to improve their bad weather capability or will the number of times a DGPS approach gets used in anger justify the cost? If the CAA is willing to look at GPS approaches to rigs then why not to airports -those plates shown earlier seem to be standalone and not requiring additional navaids.
JimL - if DGPS will still require an improved radar to more accurately determine the obstacle environment then why not just improve the radar and get reduced minimas that way? Do the N Sea operators really need to improve their bad weather capability or will the number of times a DGPS approach gets used in anger justify the cost? If the CAA is willing to look at GPS approaches to rigs then why not to airports -those plates shown earlier seem to be standalone and not requiring additional navaids.
Join Date: Jul 2005
Location: Spain
Posts: 273
Likes: 0
Received 0 Likes
on
0 Posts
Jim
Yes, It's a shame the INS has always been very limited in helo ops.
My exposure was mostly in FW days, with the old Carousel IV followed by the Litton 92. But in long range ops, the accuracy of even this aged equipment was sometimes startling.
I think the a/c to a/c update could be a real boon though...
It's little more than an extension of TCAS and imagine getting updates from a high flying heavy (ies) all the way down to MDA...If we say the LOS @ FL330 is roughly 220nm...It wouldn't be often you'd be out of LOS of someone who is getting constant updates themselves...
Yeah! Tooth fairy stuff
170'
Yes, It's a shame the INS has always been very limited in helo ops.
My exposure was mostly in FW days, with the old Carousel IV followed by the Litton 92. But in long range ops, the accuracy of even this aged equipment was sometimes startling.
I think the a/c to a/c update could be a real boon though...
It's little more than an extension of TCAS and imagine getting updates from a high flying heavy (ies) all the way down to MDA...If we say the LOS @ FL330 is roughly 220nm...It wouldn't be often you'd be out of LOS of someone who is getting constant updates themselves...
Yeah! Tooth fairy stuff
170'
Join Date: Oct 2004
Location: Scotland
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
GPS Approach Trial
Goldenhawk (or anyone who knows the answer), can you tell me where you found the info regarding GPS Approach Trials, please?
As someone who operates an IFR helicopter from one of these airfields I would like to find out more. Thanks.
As someone who operates an IFR helicopter from one of these airfields I would like to find out more. Thanks.
Crab,
I may have confused you and others by mixing text on two different RADARs; with regard to ARA, I was only commenting on the airborne (weather) RADAR.
When flying the approach with the NDB/ADF, weather RADAR is used for ranging as well as obstacle avoidance (something for which it was not designed). With the introduction of DGPS, the weather RADAR will be used mainly for obstacle avoidance and not for ranging (although it will still be a worthwhile aid providing redundancy in the event of failure of the main nav source). Thus there is little need to improve the RADAR.
There are fewer-and-fewer NDBs and this has to be factored into any re-equipment equation. The ARA is being flown using GPS overlays - probably outside the original design concept.
Experience indicates that (in Northern Europe) few approaches are missed because of the existing minima (simplistically 200ft/0.75nm) even though ARA is used on a fequent basis - mostly in a modified form. Will the introduction of DGPS therefore give operational benefits? That is a complex question because, with the advent of EGNOS and Galileo, it is likely that such equipment will be introduced for a number of reasons - only one of which will be the potential for reduction in the approach minima.
Because of limited secondary RADAR cover in offshore Europe, safety will improve if tracks are flown more accurately. The addition of vertical guidance in the ARA also has the potential to improve safety by reducing the workload on the pilot.
Any equipment review will also take into account other elements that could be provided by satellite technology. As with the GOM, there are gaps in secondary RADAR coverage which, when all helicopters are flying IFR, introduces unacceptable risk of collision. We are likely to see elements of 170's projection which will facilitate a form of collision avoidance, sophisticated communication with operations, flight following etc.
All of this is likely to provide large incremental improvements in safety and is likely to happen with or without the CAA research; it is good therefore that the CAA are providing the background research which will consider the operational requirement and undertake the risk assessment.
The results of the research are being awaited with interest.
Jim
I may have confused you and others by mixing text on two different RADARs; with regard to ARA, I was only commenting on the airborne (weather) RADAR.
When flying the approach with the NDB/ADF, weather RADAR is used for ranging as well as obstacle avoidance (something for which it was not designed). With the introduction of DGPS, the weather RADAR will be used mainly for obstacle avoidance and not for ranging (although it will still be a worthwhile aid providing redundancy in the event of failure of the main nav source). Thus there is little need to improve the RADAR.
There are fewer-and-fewer NDBs and this has to be factored into any re-equipment equation. The ARA is being flown using GPS overlays - probably outside the original design concept.
Experience indicates that (in Northern Europe) few approaches are missed because of the existing minima (simplistically 200ft/0.75nm) even though ARA is used on a fequent basis - mostly in a modified form. Will the introduction of DGPS therefore give operational benefits? That is a complex question because, with the advent of EGNOS and Galileo, it is likely that such equipment will be introduced for a number of reasons - only one of which will be the potential for reduction in the approach minima.
Because of limited secondary RADAR cover in offshore Europe, safety will improve if tracks are flown more accurately. The addition of vertical guidance in the ARA also has the potential to improve safety by reducing the workload on the pilot.
Any equipment review will also take into account other elements that could be provided by satellite technology. As with the GOM, there are gaps in secondary RADAR coverage which, when all helicopters are flying IFR, introduces unacceptable risk of collision. We are likely to see elements of 170's projection which will facilitate a form of collision avoidance, sophisticated communication with operations, flight following etc.
All of this is likely to provide large incremental improvements in safety and is likely to happen with or without the CAA research; it is good therefore that the CAA are providing the background research which will consider the operational requirement and undertake the risk assessment.
The results of the research are being awaited with interest.
Jim
If the CAA is willing to look at GPS approaches to rigs then why not to airports -those plates shown earlier seem to be standalone and not requiring additional navaids.
Join Date: Sep 2000
Location: Neverland
Posts: 33
Likes: 0
Received 0 Likes
on
0 Posts
So, the CAA are going to look at this (halle-f#@king-looyah) BUT they have stretched themselves so thin that it won't happen quickly AND do we trust the numpties they employ these days anyway?
In the meantime, boys and girls, please remember that it remains illegal in the UK to use GPS for primary navigation in IMC below MSA (for you NSEA chappies & chappesses, it means you cannot legally do an ARA coupled to NAV - never has been, still isn't.)
Arguments? - please do the research first, then fire away.
Zeb.
In the meantime, boys and girls, please remember that it remains illegal in the UK to use GPS for primary navigation in IMC below MSA (for you NSEA chappies & chappesses, it means you cannot legally do an ARA coupled to NAV - never has been, still isn't.)
Arguments? - please do the research first, then fire away.
Zeb.
Moderator
Join Date: Jul 1997
Location: Europe
Posts: 3,228
Likes: 0
Received 0 Likes
on
0 Posts
Goldenhawk (or anyone who knows the answer), can you tell me where you found the info regarding GPS Approach Trials, please?
Plus you need to visit the Trial website at https://www.gpstrials.leeds.ac.uk/ after the 10th May 2006, for full information before taking part.
JimL, it still seems like all that is needed is a better radar - whether it is used for ranging or obstacle avoidance it needs to be accurate, if it is good enough for one then it must be good enough for the other (there is no point in knowing there is an obstacle out there without knowing exactly where it is). Our minimum let down distance is 1/4 nm on the Sea King and that is with a radar that doesn't even face forwards and is very long in the tooth. I suspect that the use of a weather radar for let downs has never been tested in court regarding legality as to my knowledge there hasn't been a crash resulting from its use.
But since the final element of a rig letdown IMC is going to be pointing at or near to it, will using DGPS let the operators use reduced minimas or must they stay the same because the radar is still the limiting factor?
I take your point re separation between IFR helis - a sort of RVSM if you like.
But since the final element of a rig letdown IMC is going to be pointing at or near to it, will using DGPS let the operators use reduced minimas or must they stay the same because the radar is still the limiting factor?
I take your point re separation between IFR helis - a sort of RVSM if you like.
Join Date: Mar 2006
Location: Haiti
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
At least radar will tell you what's really out there, like a ship with a helideck on the stern swinging around the bow anchor line. Navigate using the GPS and use the Radar for obstacle avoidance (and maybe range for those ships swinging on anchors). That's kind of how the GOM looks at things.
Where is the approach being flown to 1/4 mile on an uncalibrated radar used for a purpose it was never intended for? That would seem to be very close - most MAP's offshore are 3/4 mile, sometimes down to 1/2 where they get used a lot.
Hard to believe the CAA is taking so long to get on board. If you want to watch a well flown approach, find someone with a GPS that can couple it to an autopilot. I don't understand the GPS vs DGPS issue either. On GPS Approach certification flights the GPS coupled to the autopilot is expected to split the numbers at the end of the runway. If it doesn't, then the installation is faulty. What's that, about 3 meters accuracy? On the last tests I looked at GPS had 95% confidence at 7 meters and DGPS had 95 at 4 meters. What is the CAA arguing about, 1/6th of a rotorwidth?
The luddite attitude towards GPS has certainly managed to keep the avionics of the North Sea fleet firmly locked in the past. All the pilots talk about using GPS because that is what really brings home the bacon, but they have to keep it in hushed tones because the CAA righteously thinks a windshield wiper ADF and "lucille" LORAN (as in " you picked a fine time to leave me") is a far more accurate and reliable navigation source. Even what is installed now would be greated by snorts of derision from any self-respecting American EMS operator. Those lucky enough to operate in jurisdictions that have recognized the benefit of GPS for approach are installing quite different avionics that what is installed in those places that do not have any official sanction, and hence no valid argument for improvement.
charron
Where is the approach being flown to 1/4 mile on an uncalibrated radar used for a purpose it was never intended for? That would seem to be very close - most MAP's offshore are 3/4 mile, sometimes down to 1/2 where they get used a lot.
Hard to believe the CAA is taking so long to get on board. If you want to watch a well flown approach, find someone with a GPS that can couple it to an autopilot. I don't understand the GPS vs DGPS issue either. On GPS Approach certification flights the GPS coupled to the autopilot is expected to split the numbers at the end of the runway. If it doesn't, then the installation is faulty. What's that, about 3 meters accuracy? On the last tests I looked at GPS had 95% confidence at 7 meters and DGPS had 95 at 4 meters. What is the CAA arguing about, 1/6th of a rotorwidth?
The luddite attitude towards GPS has certainly managed to keep the avionics of the North Sea fleet firmly locked in the past. All the pilots talk about using GPS because that is what really brings home the bacon, but they have to keep it in hushed tones because the CAA righteously thinks a windshield wiper ADF and "lucille" LORAN (as in " you picked a fine time to leave me") is a far more accurate and reliable navigation source. Even what is installed now would be greated by snorts of derision from any self-respecting American EMS operator. Those lucky enough to operate in jurisdictions that have recognized the benefit of GPS for approach are installing quite different avionics that what is installed in those places that do not have any official sanction, and hence no valid argument for improvement.
charron
Charron,
You should have had the joy of using Decca in a single pilot helicopter on the North Sea! (With no RadAlt either.....but three BarAlts!)
Did anyone ever perform the Decca approach to Sumbrugh at night in cloud, single pilot, and coped with the key and map change?
Talk about something that made Lucille look like Tammy Wynette....sssshhhhh it Doc....two flakes of snow and Decca left quicker than a Rat from an aqueduct.
It's been 30 years since those fun days and I think I can still remember how to operate the Decca due to all the practice one got trying to keep the thing working.
You should have had the joy of using Decca in a single pilot helicopter on the North Sea! (With no RadAlt either.....but three BarAlts!)
Did anyone ever perform the Decca approach to Sumbrugh at night in cloud, single pilot, and coped with the key and map change?
Talk about something that made Lucille look like Tammy Wynette....sssshhhhh it Doc....two flakes of snow and Decca left quicker than a Rat from an aqueduct.
It's been 30 years since those fun days and I think I can still remember how to operate the Decca due to all the practice one got trying to keep the thing working.
Sasless - now you're talking - Decca was great, as long as you didn't need it in a hurry, or at night , or in bad weather
I know someone who decided to compensate for the crosswind on a Decca approach by offsetting one lane to the right
Charron - we use 1/4 nm in the RAF Sea Kings as radar let down minima (although the theoretical minimum radar range is 75m) - my point was that a decent radar, ie one designed for more than identifying weather returns, would give reduced minima.
I know someone who decided to compensate for the crosswind on a Decca approach by offsetting one lane to the right
Charron - we use 1/4 nm in the RAF Sea Kings as radar let down minima (although the theoretical minimum radar range is 75m) - my point was that a decent radar, ie one designed for more than identifying weather returns, would give reduced minima.