GPS vs NDB (does NDB really meet RNP)?
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Anyone heard about RAIM holes.
We check for them every day as I am sure every other pilots using approved GPS for BRNAV does of course!!
IAP's do require app controllers. However, cloudbreak procedures which are not published do not. How do people think that we get into places like Blackbushe on IFR flights during those dark winter evenings?
GPS is great for providing situational awareness. However, if there is a serious discrepency between the NDB and the GPS we go-arround because the NDB is the primary aid and we can't tell for sure which is giving the false info.
IO540,
The NDB is different from the VOR. As long as you get the ident then there is a signal for the ADF to point at. Unlike the VOR it is non directional (as the name suggests) and thus can not have any error. To check your aircraft's system you select "test" and move the pointer away from the indicated direction before releasing the selector and checking that the pointer returns to the expected bearing.
Perhaps you should think about my previous comments regarding the siting of the NDB and quadrantal error in westerly winds at Shoreham and then comment further on some radio theory.
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People who get caught out on NDB approaches are the ones to track inbound to the NDB from a VOR using VOR or even GPS without noting that the NDB pointer is constantly in a place that it shouldn't be.
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PANS OPS has the procedures for GPS approaches and we have a few drawn up ready to use ( we have tried some out in VMC). But while the accuracy is great the cloudbreak procedure minimum altitudes are no different from those we use with the NDB and DME.
Places like Shoreham would require very little work to publish GPS approaches - simply draw up some waypoints to describe the existing NDB procedure and make it a GPS procedure with the same minima.
regards,
DFC
We check for them every day as I am sure every other pilots using approved GPS for BRNAV does of course!!
IAP's do require app controllers. However, cloudbreak procedures which are not published do not. How do people think that we get into places like Blackbushe on IFR flights during those dark winter evenings?
GPS is great for providing situational awareness. However, if there is a serious discrepency between the NDB and the GPS we go-arround because the NDB is the primary aid and we can't tell for sure which is giving the false info.
IO540,
The NDB is different from the VOR. As long as you get the ident then there is a signal for the ADF to point at. Unlike the VOR it is non directional (as the name suggests) and thus can not have any error. To check your aircraft's system you select "test" and move the pointer away from the indicated direction before releasing the selector and checking that the pointer returns to the expected bearing.
Perhaps you should think about my previous comments regarding the siting of the NDB and quadrantal error in westerly winds at Shoreham and then comment further on some radio theory.
----
People who get caught out on NDB approaches are the ones to track inbound to the NDB from a VOR using VOR or even GPS without noting that the NDB pointer is constantly in a place that it shouldn't be.
-----
PANS OPS has the procedures for GPS approaches and we have a few drawn up ready to use ( we have tried some out in VMC). But while the accuracy is great the cloudbreak procedure minimum altitudes are no different from those we use with the NDB and DME.
Places like Shoreham would require very little work to publish GPS approaches - simply draw up some waypoints to describe the existing NDB procedure and make it a GPS procedure with the same minima.
regards,
DFC
simply draw up some waypoints to describe the existing NDB procedure and make it a GPS procedure
Those countries that have been using GPS approaches for 10+ years abandoned overlays some time ago.....
Anyone heard about RAIM holes
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NDBs to be phased out in favour of GPS NPAs in Australia!?
Hi all, check out this thread on the Dunnunda & Godzone forum: http://www.pprune.org/forums/showthr...hreadid=137070
Andy
Andy
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Unlike the VOR it is non directional (as the name suggests) and thus can not have any error. To check your aircraft's system you select "test" and move the pointer away from the indicated direction before releasing the selector and checking that the pointer returns to the expected bearing.
A dangerous thought for those that do not understand how MW signals can be bent.
Sure, there are failure conditions in VORs which do not produce a fail flag (not least the famous time when Alan Mann Avionics wired up my OBS to give reverse indications on both VOR and ILS) but at least some failures are trapped either by the TST ident or the fail flag.
On the ADF there is simply no way of telling that the direction from which the signal being received is the straight line to the NDB.
I am not going to regurgitate ATPL radio theory, but night effects, coastal diffraction, mountain effect, dip, thunderstorms, reflections/multi-path, quadrantal error all add up to an alarmingly inaccurate and unreliable aid.
It seems a shame that, because GPS is demonstrably imperfect, the CAA are chucking it out with the bathwater. It is much better than NDB/ADF.
The CAA polices by consent. When they take a position so radically opposed to that of many pilots who (in possession of all the facts) do prefer GPS over ADF, they risk their ability to regulate and control, in the same way that 20mph speed limits are ignored.
NDBs to be phased out in favour of GPS NPAs in Australia!?
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It's a curious observation that an NDB must be a very cheap thing to run (could even be solar powered), while the receiving bit, the ADF, is relatively expensive.
The typical ADF, even brand new, is a 1970s design. I've just seen the innards of some in an avionics shop. There is no reason why it should cost £3000. One could also implement it by signal processing and measuring reception delays, i.e. without the present directional aerial system.
A VOR transmitter in comparison must be hugely expensive to install and maintain.
So an NDB ought to be a reasonable navigation fallback choice for remote locations. Inland, with no thunderstorms about, they are pretty accurate.
The typical ADF, even brand new, is a 1970s design. I've just seen the innards of some in an avionics shop. There is no reason why it should cost £3000. One could also implement it by signal processing and measuring reception delays, i.e. without the present directional aerial system.
A VOR transmitter in comparison must be hugely expensive to install and maintain.
So an NDB ought to be a reasonable navigation fallback choice for remote locations. Inland, with no thunderstorms about, they are pretty accurate.
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an NDB must be a very cheap thing to run
If interested in ADS-B, there is another AirServices Australia link which explains the programme for this in Australia here: http://www.airservicesaustralia.com/.../adsb/adsb.htm
Andy
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At £40k somebody is making a mint. I would happily start up a business to deliver say 500 1kW 300-400kHz transmitters, at £10k 
I suppose there are power costs too, not cheap for a remote location.
I suppose there are power costs too, not cheap for a remote location.
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Good luck IO540, but don't plan to pay the mortgage with this plan!
I'll bet you wouldn't: your costs will be much more than the sum of the parts, especially taking into account the regulatory requirements (FCC, ICAO, CE, etc.) you'd have to meet. Also bear in mind that the total turnkey purchase price for an aiport operator would have to include the cost of commissioning and testing not only the NDB Tx itself but also the antenna array. You'll also need to produce a matching ATU (impedance matching unit) as well as UPS and remote monitoring facilities if the installations are to be reliable enough for say an approach procedure. You would have to sink considerable R&D investment in order to address a globally limited and apparently shrinking market! I can't think of a seed investor around these parts who I know that would help you raise the capital for that project!
This business is already well served by large diversified groups, such as TV/Radio broadcast transmission equipment vendors such as Nautel, whose economies of scale enable them to re-use modules from other designs and to leverage the approvals process from their main product lines in order to viably produce a range of NDB transmission systems for nautical and aviation purposes, from 50W to 4kW... see http://www.nautel.com/products/index...ygroup&group=7 for example. BElow is a picture of Nautel's 50W unit... just the housing may well cost £10k!?
I am surprised it can be done for average replacement cost of £40k!
Andy
would happily start up a business to deliver say 500 1kW 300-400kHz transmitters, at £10k
This business is already well served by large diversified groups, such as TV/Radio broadcast transmission equipment vendors such as Nautel, whose economies of scale enable them to re-use modules from other designs and to leverage the approvals process from their main product lines in order to viably produce a range of NDB transmission systems for nautical and aviation purposes, from 50W to 4kW... see http://www.nautel.com/products/index...ygroup&group=7 for example. BElow is a picture of Nautel's 50W unit... just the housing may well cost £10k!?
I am surprised it can be done for average replacement cost of £40k!
Andy
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From the CAA document:
So there it is: GPS might be good enough for the FAA (and others), but we Europeans obviously know better and will stick with medium wave radios until we have our own toy that we can charge our users for.
In the short to medium term ground-based augmentation systems (GBAS), aircraftbased augmentation systems (ABAS), space-based augmentation systems (SBAS)
and augmentation with stand-alone GNSS such as Galileo offer the possibility to achieve the RNP. This study has shown that GPS augmented with Galileo offers a user level monitoring capability through RAIM good enough to satisfy the integrity
requirements for en-route to precision approach phases of flight.
and augmentation with stand-alone GNSS such as Galileo offer the possibility to achieve the RNP. This study has shown that GPS augmented with Galileo offers a user level monitoring capability through RAIM good enough to satisfy the integrity
requirements for en-route to precision approach phases of flight.
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Last I heard was that the European GPS system (Galileo) will now be compatible with the American one, and that the basic Galileo signal (whose accuracy will be of the same order as the existing American one) will not be encrypted, i.e. it will be free.
Presumably the plans to charge for the higher-accuracy encrypted version will hinge on it being legally required for certain operations e.g. GPS approaches?
Now... how long will it be before the code is cracked? Won't be very long, considering how many "approach approved" GPS units will eventually be in free circulation. They will have to sell Sky-TV-type smartcards.
Makes one wonder why they want to bother charging for it, given that they will never get any significant money from the tiny group of GA "IR" pilots. The potentially big money would come from airliners and bizjets but they are doing just fine with ILS, and the major benefit of GPS approaches (getting an instant IAP into an airfield where there are no navaids) won't apply to them.
I wonder who wrote this business plan...
Presumably the plans to charge for the higher-accuracy encrypted version will hinge on it being legally required for certain operations e.g. GPS approaches?
Now... how long will it be before the code is cracked? Won't be very long, considering how many "approach approved" GPS units will eventually be in free circulation. They will have to sell Sky-TV-type smartcards.
Makes one wonder why they want to bother charging for it, given that they will never get any significant money from the tiny group of GA "IR" pilots. The potentially big money would come from airliners and bizjets but they are doing just fine with ILS, and the major benefit of GPS approaches (getting an instant IAP into an airfield where there are no navaids) won't apply to them.
I wonder who wrote this business plan...
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Prescott? His next triumph after the Strategic Rail Authority, perhaps.
All the CAA does by insisting on NDB rather than GPS is to reduce its own credibility. But I'm turning into an angry old man...
All the CAA does by insisting on NDB rather than GPS is to reduce its own credibility. But I'm turning into an angry old man...
I was reading a recent CAA publication which outlined the RNP for approval as a primary approach aid - and all of the reasons why the current GPS system does not meet these requirements. After monitoring the NDB 20 approach into Shoreham (with 35 knots declining to 20 on the surface from 280 and very gusty) on the GNS430 I thought - does this NDB approach meet the RNP requirements.
Any conclusions drawn by the Civil Aviation Authority merely underline their position as the brightest national aviation authority in the UK.
