GPS based Landing System

[Superpilot]

Is there / will there ever be a GPS based landing system, i.e one that offers a glide to land path as well as a LOC?

If there are currently no plans, could such a thing be achieved at least theoretically?

Thanks

[HEATHROW DIRECTOR]

<<If there are currently no plans, could such a thing be achieved at least theoretically?>>

I don't see why not; it only needs software to calculate distance from touchdown to arrive at a descent profile. I've worked with pilots who used to follow a VOR radial and count the miles off using a TACAN 20 miles away for their descent. Seen them do that and land in a sand storm! GPS should be capable of far greater accuracy.

[stilton]

This has already been demonstrated, known as GLS and has functioned throughout landing and rollout, there was a recent article in an aviation magazine about it.

We had the director of flight test for the 767-400 with us to Hnl recently who was heading out to Guam to sell Continental Micronesia on the technology.

Understand they had the lateral tolerances down to less than a metre on touchdown.

[Aerofoil]

I may be off the mark here but during my ATPL ground school i was told that the Americans can turn off the GPS system at any time they so wish (for security reason etc). I believe that this happened during the Sept 11th hijackings. Another point is that the accuracy of the system can be manipulated, again by the Americans, so as to confuse the pilot as to where he is at the time, his speed and altitude etc. Again this would be for security reasons i presume.

Maybe the fact that the system may be turned off at any time without warning, or inaccuracies implemented into the system during an aircrafts final approach to land is the reason it has not already been implemented for use?

I await to be stood corrected! :8

Regards

The Foil :ok:

[Superpilot]

A scenario worth considering, definitely. But then consider the whole thing in the context of the upcoming implementation of the 'civilian controlled' European Galileo GNSS system. Which boasts accuracy down to the centimetre.

[Approaching Minimums]

<<I may be off the mark here but during my ATPL ground school i was told that the Americans can turn off the GPS system at any time they so wish (for security reason etc>>

The same thing was told for me during my ground school as well. Despite the fact that Clinton signed a contract earlier that the precision of the GPS will not be manipulated by Americans in any circumstances we can't rely here in Europe only for that. A system which could be manipulated by Americans "just by pushing a button" can't be the main precision approach system for aircrafts.

For that reason I believe we will not see GLS widely used in Europe for a long time. At the moment Europeans are planning to have the Galileo system operational in 2008, which would be a satellite system fully operated by Europeans. However, it might take still many years before the Galileo has enough coverage for GLS operations.

Due the these security reasons other regions might develop their own satellite systems as well.

Best Regards,
AM

[5711N0205W]

The United States DOD has recently stated its intent to block the European Galileo GPS constellation under certain circumstances where enemies could use the signals for military purposes.

[411A]

A fair bit of misinformation here about GPS.

1. The US GPS system was not in any way switched off during the 11 September 2001 period, nor was SA altered in any way.

2. WAAS has now been approved in the USA, and GPS receivers are now available that enable approaches to CAT I minimums, depending on the airport, and the approved specific procedure.

The USA acts...the Europeans just look on in amazement, and continue to cast stones, simply because they didn't think of it first

Par for the course.

[Intruder]

A system which could be manipulated by Americans "just by pushing a button" can't be the main precision approach system for aircrafts.
Under what plausible circumstances that you can conceive would the US "shut down" GPS? Consider in your response that the US military currently depends SIGNIFICANTLY on GPS for targeting of most tactical "smart weapons"...

[alf5071h]

I note that 411A has renewed his new-years resolutions for jumping in the deep end, blowing trumpets, and being ill informed.

The European position is being managed and well thought through by Eurocontrol; individual nations contribute to the plan, see a paper from the UK CAA,
GPS Integrity and Potential Impact on Aviation Safety (http://www.caa.co.uk/publications/publicationdetails.asp?id=1301)
A publication search for GPS in the CAA web site will find other documents.
I understand that the European position on the use of GPS for high integrity approach and landings (Cat1 +) is that any system will require dual channel integrity, which implies using both GPS and Galileo.

>>The USA acts...the Europeans just look on in amazement, and continue to cast stones, simply because they didn't think of it first<<
Of course 411A this applied to the Microwave Landing System (MLS) didn’t it? Or was the situation that the US grand plan for GPS was to quickly supersede MLS, forcing its untimely demise in the early 1980’s, thus killing the European lead and commercial potential.

Edit: Also see a more digestible document, with some applicability to commercial operations Use of GPS (http://www.caa.co.uk/docs/33/SRG_GAD_SSL25.PDF)

[Groundloop]

GPS based landing systems use "differential" methods where a fixed receiver on the ground monitors its GPS derived position, compares it with its known position and broadcasts corrections to the GPS position. The inbound aircraft receives the corrections, applies them to its GPS derived position to obtain its correct position relative to the runway.

So, in theory, even if Selective Availability was switched on again it would not effect GPS based landing systems as the ground station would detect the GPS shift and broadcast corrections.

This is, I believe, the basis if the FAA's LAAS which has not yet been implemented.

[airborne_artist]

The USA acts...the Europeans just look on in amazement, and continue to cast stones, simply because they didn't think of it first

Not true when it comes to mobile phones. I've a load of US contacts who just loved coming to Europe when we got digital cellphones twelve years ago that worked across Europe on one number, automatically, with cross-network two-way text messaging. The GSM standard is pure European, and you guys Stateside didn't get near the functionality for between five and seven years!

The USA thinks it acts, and thinks that the rest of the world looks on in amazement, would be more accurate....

[ETOPS]

We are currently testing an RNAV/GPS approach to R26L at Gatwick (EGKK). I have completed the sim training and the aircraft FMS's are loaded with the software and ready to go. The initial approach minima will be 700MDA (500MDH) and the guidance is both LNAV & VNAV. In the tests we left the ILS displayed but engaged Autopilot in LNAV/VNAV. The program has a clever submode that "opens" the speed window on the MCP to allow pilot controlled speed and config changes. The tracking was so good that at decision there was a perfect match between the GPS derived position and the dislpayed ILS.
It is important to keep POS page 2 displayed on at least 1 FMS to monitor RNP limits.
No doubt that as experience grows the landing limits will reduce to match CAT 1 ..............

[411A]

Indeed they will, ETOPS, GPS is the way to go.

Now, not for just large international airports, which are aptly served by ILS, but the more remore airfields, that have now possibly and NDB or VOR approach...but sure could use a precission approach that GPS/LNAV/VNAV will provide.

Far too many folks forget about these less served destinations, where GPS will provide enhanced aircraft/crew/pax safety.

I find it strange indeed that those in Europe/UK still have their collective heads in the sand.

However, I suspect the Brits may be the first to cave, especially as they were the first with......RADAR, automatic approach/landings (hello, Trident...a superb achievement) etc, and put 'em to good commercial use, while the rest of Europe couldn't care less.

[dusk2dawn]

Written in a plain and simple language, see FAA Satellite Navigation info site (http://gps.faa.gov/gpsbasics/index.htm).

Sorry, couldn't find the site where the americans explain to the amazed world how they will avoid another California electricity shortage....:p

[c-bert]

I believe that the JPALS carrier bourne aircraft landing system currently in development is based on GPS.

[Norwegian]

Happy new year!.
In norway Widerøes is going to try out SCAT-1 which is a sattelite based approach system, with lateral and horizontal navigation like an ILS.
(Special category-1 like cat -1 ils)

This is what i think anyway.

[Crossunder]

For those who can read norwegian:

http://www.helgeland-arbeiderblad.no/nyheter/article1586702.ece

Those who cannot - in short: The Norwegian, US and Canadian Civil Aviation Authorities, Widerøe's Airline, Universal Systems and more, have been involved in the last stages of testing/approval of the Special Category 1, SCAT-1 system at ENBN/BNN , Norway, during the last few weeks. The equipment and procedures are expected to be approved during next month, and operational approval & implementation a couple of months thereafter.
Widerøe's already use GPS/VDF stand-alone approaches on several STOL ports, so the Europeans aren't that far behind, methinks :ok:

Cross.