GPS as an approach aid

[Willowski]

Hi

I am a helicopter pilot in the Royal Navy and have been asked to do a presentation on the use of GPS as an approach aid.

We have used it once in operations, as an emergency procedure only, and to good effect. I know it will be legal as a non precision apporach aid in the UK from Sept 07 at 6 airports that have been tested.

We as 'Junglies', ie support helicopter pilots, have a vested interest in the development of this technology. I would like to find out more about the technical and indeed the legal issues behind current development.

If anyone could duscuss or point me in the right direction that would be appreciated.

Thank you,
Willow

[Lutefisk989]

By "approach aid," I assume you mean as an approved instrument approach procedure. GPS approaches are the best thing since sliced bread...such approaches are widely used in the U.S. And precision approaches are now being published... The technology is very mature and impressive in its capabilities.

The FAA's Aeronautical Information Manual (AIM) has some very good discussion on GPS approaches. There's an additional section that specifically addresses Helicopter Only GPS approaches. Google will point you in the right direction...

Good luck!

[Two's in]

Willowski,

Scroll to this chapter; 1-1-19. Global Positioning System (GPS)

On this website;

http://www.flightsimaviation.com/data/AIM/

Good luck, Remember good use of colors!

[Raf-CSB3]

Hi,

You probably find something in it...

http://www.tc.gc.ca/CivilAviation/commerce/circulars/AC0123_att.htm

It's the Canadian's regulation. We use GPS as a stand alone approach. You will find further information in the CARS section.

I am surprised in Europe you don't use GPS more.

Raf
CYUL

[chevvron]

No WAAS widely available. This is necessary (as I understand it) for general approvals. Otherwise the GPS approach is required to overlay an established procedure such as NDB with or without DME.

[reynoldsno1]

Has been used as a stand alone non-precision approach aid in NZ for 13 years - WAAS not required, works well - very few coverage problems. Operational rules cover requirements in case GPS not available.
The EMS helis love it - they reckon it has saved 4 lives to date using point in space procedures to strategic locations (school playing fields work well):ok:

[Raf-CSB3]

Hi,

Here in Canada, The GPS is used as non precision approach. It's used as lateral navigation (LNAV) so the minimum are highter than ILS but sometime lower than NDB. The precision is very good. In high terrain, the GPS is helpfully specially in the rocky (vancouver area).

GPS with WAAS capability is coming....

Good example is the set of approach charts of west USA in the rockies.

Raf

[GOLF_BRAVO_ZULU]

What happens if the GPS satellite owners want/need to turn Selective Availability back on?
http://www.ngs.noaa.gov/FGCS/info/sans_SA/docs/statement.html

[green granite]

What happens if the GPS satellite owners want/need to turn Selective Availability back on?

I don't think it matters any more as any system used for airfield approach will use Differential Sat Nav which nullifies the effect of SA and makes it more accurate than an ordinary receiver is when SA is off.

[reynoldsno1]

Raw GPS was used as an approach aid when S/A was on ... the tolerances used for the design of the approach encompassed the S/A induced inaccuracy (up to about 300m).
S/A can be directed to specified regions, so it's not necessarily indiscriminate.

[MarkMcC]

Just finished testing an FMS software upgrade to allow unrestricted use of GPS approaches on the Canadian C130. Our certification path has been long and winding...

The Transport Canada link provided earlier should have some good info, as would the FAA documentation on the design of RNP, LPV, and Baro VNAV approaches.

Drop me a PM if you'd like to chat and I can fix you up with some stuff...

[Lutefisk989]

The point on Selective Availability is an interesting one. It's supposed to be a non-issue, given the amount of commerical ventures, that routinely use (require?) it day to day. But since the system is owned/operated by DoD, I imagine that's why the Europeans are putting up their own system?

But it seems to me that when WAAS becomes more widely available, the issue goes away. As I recall, WAAS functions more or less like Differential GPS, which would reduce the error the S/A puts into the signal.

[NutLoose]

On the UK front, check out the CAA site, see

http://search2.openobjects.com/kbroker/caa/caa/search.sim?sr=0&nh=10&cs=iso-8859-1&sc=caa&sm=0&sf=&ha=318&mt=1&qt=gps%20approach

indeed they are looking into it for Helicopters, see

http://www.caa.co.uk/default.aspx?catid=978&pagetype=90&pageid=6368

[onthebumline]

I think it's important to remember when talking about these type of approaches that you tak...............................


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[Willowski]

Hi,

Thanks very much for that. Im off to Iraq again in Sept and we are looking at taking the GPS thing a little further. Will check out the FAA manual.

Much appreciate the reply.

Fly Safe,
Willow

[Willowski]

Hi,

Thanks for that. So you were a QHI then?

The trappers said my Whiteboard presentation was pretty crap and my handwriting worse. Still, there was lots of colour, and they are difficult to please.

cheers
Willow

[VinRouge]

Were you the Willow that was on 201 Cse near York?