UK GPS approaches

[funfinn2000]

Hello has anyone used the GPS approaches in Uk yet. I heard they have one in Blackpool and EGBJ. are they of any use? and where else are they approved?

[malabo]

Gloucestershire, Gatwick, Heathrow, Blackpool, Durham Tees Valley, Exeter all have RNAV/GPS Approaches. There may be more....

Here's a comment from another thread on UK GPS Approaches:
"........without splitting too many hairs over this, what the UK calls a GPS Approach (RNAV or RNP .3), doesn't quite qualify with standards in the rest of the world.

The UK GPS approaches do not provide guidance for the missed approach segment. It is either climb straight ahead and ask center for help (Gatwick, Heathrow, etc), or "LCTR required for missed approach" (Gloucester, etc). A good FMS system should be able to provide constant overlay information, but compared to what's going on this side of the Atlantic it looks bush league and half-hearted. If it is any consolation to UK pride, the Norweigans have a similar restriction on their LPV (localizer precision with vertical guidance) precision GPS approaches, and also require conventional navaids for the missed approach segment.

Must be something regulatory over there, and maybe somebody has some explanation. We're busy decommissioning NDB's, Marker Beacons, LCTR's, VOR, Radar etc. here, so designing a new procedure requiring existing ground based navaids seems pointless to us."

[SASless]

Keeping terminal VORs and associated DME would seem a fair compromise. Enroute reliance on GPS and ground based radar souinds reasonable. I would hate to think there was no backup system even as dependable as GPS is.

[Gomer Pylot]

Yabbut... just because other navaids exist, they shouldn't be required for missed approach procedures. ISTM you either embrace GPS or you don't. Having approaches but no missed procedures seems rather short-sighted, or perhaps just bone-headed. Perhaps the feeling is that GPS is a colonial thing, and the seat of empire can't permit its complete use. :E

[SASless]

Yo Gom,

I will quote one of our cousin's comment re GPS....."Never happen, give up going on about it....after all it is an American DOD thing!"

Then.....the Nigerian CAA made it a requirement.

The next comment was...."Well when they go U/S (unserviceable)....we will not repair or replace them!"

The major thing was not to disturb his serviette...as he got very cross.

[[email protected]]

If GPS is so reliable, why are the USCG looking at developing LORAN with a sort of DGPS twist as an alternative with similar quoted accuracy?

[SASless]

Crab,

A large part of the Coast Guard budget involved maintaining the LORAN system....it is as much politics as perceived need. Add in the fact all the existing LORAN sites can still be used but would only continue to be used if it can be made as accurate as GPS. Thus if the Coastie's are going to retain that part of their budget they have to be able to compete with GPS.

[Gomer Pylot]

Reliability is not the issue. If it's reiable enough for flying an approach, it's reliable enough for flying the missed. If it's unreliable, then why allow approaches in the first place? In the US, we're flying precision approaches using GPS, every day, onshore and offshore, fixed and rotary wing, including airliners. i understand that other countries distrust the US government, and I don't blame them, but allowing GPS approaches but not allowing its use for the missed simply makes no sense to me.

Everyone recognizes the need for a backup system, but maintaining thousands of navaids all over the US is very, very expensive, and it's cheaper to use enhanced LORAN for the backup than maintaining, and soon replacing, all those aging, obsolete navaids.

[212man]

Maybe - and purely speculation - it's quicker/easier to certify the missed approach if based on a pre-existing ground aid based approved procedure? Just piggy-back it on to a GPS approach and Bob's your mother's brother.

[jemax]

Having done both the JAR and FAA IR's in the last 6 months I cannot understand why we JAR land persist with outdated NDB, the needle gently meandering +/- 5 degrees of track on finals if you are lucky, and that's without any Coastal/Lightning/any other effect. As well as the potential for short term errors by pushing/pulling the needle in the wrong direction dependant on its orientation.

You have the option of GPS with RAIM Integrity, backcourse ILS, with vertical stepdowns etc. why on earth aren't we using it? Astonishing! Christ my mobile phone is good to about 3 metres these days.

[212man]

Can't answer your question directly, but have you ever considered the clock error required to generate a 200 ft vertical error? Clue - speed of light = 186,000 miles/second

Maybe the regulators took a conservative approach (pardon the pun) to relying purely on GPS.

[funfinn2000]

Well at least the UK are using them, we are lucky if we could even get a weather report over here. They really could do with desiging and approving som e GPS approaches in Ireland, and yeah some more airports would be nice too.

[Boslandew]

I may be a little out of date as I haven't flown the route for a while but Penzance heliport has used a Decca/GPS approach for years; I seem to remember carrying out such an approach during my S61 conversion in 1976.

It requires cross-checking against VOR and DME readings from Lands End VOR, the NDB at the heliport and the aircraft weather radar showing the very prominent swimming pool on the Penzance shoreline. Its based on two decision points, at 250' in sight of the water and then visual with the coast. It works very well.

There is a similar simpler approach into St Mary's on Scilly.

It is, or was, company specific and requires a check with a Training Captain

Boslandew

[HeliComparator]

Gomer

You have to remember that you are lucky, you have WAAS in the USA (WAAS being wide area augmentation system, ie a geostationary satellite transmitting differential gps data). With WAAS and a tso 145/6 gps receiver the accuracy and integrity of the data is several orders of magnitude better than without. Here in Europe we still have no WAAS satellite - EGNOS is still under development and only radiating for test purposes. Hopefully it wil be on stream soon and then all we will need to do is to upgrade our equipment to tso145/6 to be able to fly LPV approaches. There is no way you should be flying LPV approaches with tso 129 gps / no WAAS.

There is a GPS NPA published for Inverness (down the road from Aberdeen). Of course it has NPA minima so on some days the ILS is a better bet, but on some days when the weather is not too bad and the radar is off, it offers a more expeditious approach than the full ILS procedure.

HC

[NavMonkey]

I believe that all of the GPS RNAV approaches that were being trialled in the UK by the CAA have now been withdrawn so you should probably be careful if flying them now! There certainly aren't any in the AIP today.

The approaches at Inverness, Shoreham, Exeter, Gloucestershire, Durham and Blackpool were set up for trials purposes only to be flown in VMC and the trial ended late in '06. It's down to the individual airports now. If they want to reinstate the procedures they need to apply to the CAA with all of the safety assessments, paperwork, etc.

All the best, NM.

[SASless]

NM,

Do I understand by your post....there are "no" currently approved GPS approaches in the UK? As in none...zip....zero....nada???

Also....am I right to understand all of the prior approaches were for trial purposes and were limited to VFR/VMC use only and thus never qualified as "GPS Instrument Procedures" as compared to the situation in the USA?

Have not British Operators used GPS for instrument approaches in Nigeria....and approved by Shell Aviation personn

Does Nigeria have WAAS coverage?

[212man]

believe that all of the GPS RNAV approaches that were being trialled in the UK by the CAA have now been withdrawn so you should probably be careful if flying them now! There certainly aren't any in the AIP today.

Top tip: check your f*****g facts

Jesus, where do these guys get off?

[NavMonkey]

SASless - yes, your interpretation of my post is spot on. None of the original 6 GPS approaches that were implemented for the trial are available any longer. The trial (http://www.caa.co.uk/application.aspx?catid=14&pagetype=65&appid=7&mode=detail&nid=1262) was intended to get operational experience primarily amongst the GA crowd with a view to approval. The trial finished in Dec 06, a report (http://www.caa.co.uk/docs/33/2007_06.pdf) was published but as I said its now over to the airport operators to go through the formal process (http://www.caa.co.uk/docs/33/notal42007rnavgnss.pdf) to get approval for them if they want them reactivated.

I understand NATS have been looking at the possibility of some GPS Baro-VNAV type RNAV approaches into EGKK but am not sure of the status - so as far as I am aware right now they are not promulgated.

In short there are *no* public GPS RNAV approach procedures in the UK at present. That is a different matter from saying that UK operators are not approved to fly GPS RNAV approaches overseas, as a number are. Just that there are no promulgated IAP's to UK airports.

Nigeria doesn't have WAAS coverage. If it will get any SBAS coverage that will come from the much delayed EGNOS system. There are plans to expand its service across Africa, but to be honest they have to get it working for Europe first :)

[SASless]

Now hold on here.....did not some folks tell us there were some GPS approaches in use?

I could have sworn someone said FMS nav units could overlay them on other Non-precision approaches....or is that only on S-92 aircraft flying for a Dutch based oil company?

[malabo]

Oddly enough, all those approaches are current as far as Jeppesen is concerned. For example, Blackpool RNAV (GNSS) RWY 28, is current on this nav revision cycle and had an original publish date of 24-Aug-07. Typically all the FMS and GPS units maintained through Jeppesen navdata updates would also show it as current. Any operator flying into those airports would expect those approaches to be available today.

The fact that the publish date is after the so-called end to the trial period would imply that we are talking about two different things.

In the US and Canada each RNAV plate typically offers three different limits: the LPV for which WAAS is required, and the VNAV and LNAV which are considered non-precision approaches and do not require WAAS. Waiting for WAAS capability from EGNOS before putting your toe into the pool of RNAV approaches seems like grasping at yet another straw to justify Brit intransigence.

[ShyTorque]

but allowing GPS approaches but not allowing its use for the missed simply makes no sense to me.


The one reason I can think of is that if an approach was missed because of a failed GPS it would be unwise to carry out the missed approach procedure using the same equipment.

[HeliComparator]

The UK GPS approaches have not been withdrawn. They are still in the UK AIP - but you have to look in the supplements (and realise that you have to click the "view" logo on the right on the supplements page) to find them. The airports with these approaches are Blackpool, Durham TV, Exeter, LGW and LHR. Dunno what happened to Inverness?

HC

[Bravo73]

This is a very recent supplement: (You might need to log into the AIS website to view the pdf)

http://www.ais.org.uk/aes/pubs/aip/pdf/sup/EG_SUP_2008_11_en.PDF

Regarding MAPs, here's an extract (my bold):

11.7 Missed Approach Procedure: To expedite the introduction of RNAV (GNSS) procedures, the Missed Approach Procedures will be conventional, using ground-based navigational aids. These will be reviewed in due course and, after detailed discussions with the airports to determine optimum hold locations and required tracks, will be converted to full RNAV MAPs. Environmental consultation will need to be considered for any new tracks. Until then, all MAPs will be straight ahead to a designated altitude with GNSS track guidance being provided towards the missed approach turning point only. At the designated altitude, or Missed Approach Turning Fix (MATF), whichever is the earlier, the pilot should revert to conventional navigation and route to the holding beacon, ie by making a turn to the beacon or a turn with continued climb to holding altitude at the beacon.
.
.
.
And here's the 'original' supplement from Nov '07:

http://www.ais.org.uk/aes/pubs/aip/pdf/sup/EG_SUP_2007_34_en.PDF

Time for a quick u-turn, NavMonkey? ;)

[SASless]

Shy,

If I use a VOR/DME approach....normally the Missed Approach usually has me trodding off for a hold at the VOR, some intersection, or a radial and DME distance.

Now how does that differ from GPS?

In your view I take it you differentiate between NDB's, VOR's and GPS for some reason. Are they not all the same concept....navigation using some sort of electronic means?

If we lowly country bumpkins can overlay a GPS approach on a VOR or NDB approach including the missed approach.....why not the UK?

I will bet you a donut to a dog dropping....you can hold the stakes in your mouth....and I will wager that a GPS approach without WAAS is still much more accurate than the VOR approach and for much...much...more accurate than any NDB approach.

[Gomer Pylot]

A GPS approach without WAAS is actually more accurate than an ILS, at least horizontally. A GPS fix without WAAS is, IIRC, accurate to 10 meters. and you get that all the way from the IAF to the MAP. WAAS doesn't help a lot with horizontal accuracy, it was implemented to get vertical accuracy good enough for use with precision approaches, giving a glideslope.

Like it or not, the current navaid system is going to go away, because it's simply not economically viable. The maintenance costs on aging analog systems, using vacuum tubes in many cases, are just too high to be kept up. We're no longer flying range approaches, and I predict we won't be flying NDB or VOR approaches that much longer. Technology advances, and we have to give up obsolescent parts of it.

[NavMonkey]

Hi Bravo,

You had me worried for a moment :ok:

The 2007 supplement you quote states that:

Currently six licensed aerodromes, as listed below, have approved designs for RNAV (GNSS) instrument approach procedures.
Notification of operational availability of these procedures will be through NOTAM action by the specified aerodrome.
Blackpool
Durham Tees Valley
Exeter
Gloucestershire
London Gatwick
London Heathrow

Note that the CAA are talking about "approved designs" for the procedure, not the availability of the approach to be flown. Also see the comment about NOTAM and the lack of mention of some of the former trial airfields e.g. Inverness.

If you had looked a little further through the 2008 supp (http://www.ais.org.uk/aes/pubs/aip/pdf/sup/EG_SUP_2008_11_en.PDF) you quoted you would see that on one hand is says that the NATS RNAV GNSS approaches at EGLL and EGKK will commence from 5 June 08, on the other it states that

Notification of operational availability of the procedures at Blackpool, Durham Tees Valley, Exeter and
Gloucestershire will be through NOTAM action by the specifed aerodrome.

Looking at the current NOTAMS we get:

Blackpool RNAV APPROACHES NOT AVBL
Durham RWY 05/23 GNSS APPROACH NOT AVBL
Gloucestershire RNAV (GNSS) APPROACHES NOT AVBL
Exeter TRIGGER NOTAM on 5th June UK RNAV (GNSS) INSTRUMENT APPROACH PROCEDURES, SUP S11/2008 REFERS :confused:

Still looks to me like nothing is available. Whilst the IAP may be available and in your databases it still doesn't mean that its available to be flown until the airports comply with the Notice to Aerodrome Licence
Holders (NOTAL) 4/2007 specifying the responsibilities and actions required of licence holders intending to introduce RNAV (GNSS)
approach operations.

More than happy to be corrected if my reading of the situation is wrong though...;) also good news that we will have RNAV GNSS approaches in the UK from 5th June too:ok:

Cheers, Nav.

[HeliComparator]

Gomer sorry but I can't agree with your comment that non-WAAS gps is more accurate than ILS, nor that its error is 10m. The whole problem with gps is that there is no maximum error. You could say "the error is no more than 10m for 99% of the time" but what about the 1% or even 0.1% when the error is 100m or more. The maximum error for 0.001% of the time is perhaps 1000m (making these figures up but you hopefully get my gist). GPS near the ground can be further degraded by multipath reception from buildings etc. So outside of 99% of the time, WAAS makes a big difference horizontally.

RAIM gives a certain degree of protection but for a tso129 receiver the best it can do is to tell you that there is a RAIM problem and the best you can do is to discontinue the approach - not very good if you are already at your alternate on minimum fuel with no other approach aids.

FDE RAIM for tso145/6 receivers deals more gracefully with RAIM problems by deselecting the faulty satellite and, if you still have enough satellites, you can continue the approach.

ILS of course has the advantage that it gets more accurate the nearer to the ground you get. Yes ILSs can fail too but its a so much simpler and more robust system than gps that the probability is remote.

HC

[212man]

FDE RAIM for tso145/6 receivers deals more gracefully with RAIM problems by deselecting the faulty satellite and, if you still have enough satellites, you can continue the approach.

Surely all RAIM kit does that? You need 4 SVs to get a 3-d position and 5 SVs to provide RAIM. More than 5 SVs gives you redundancy to maintain RAIM while deselecting SVs. If you start with 5 and then deselect one, you no longer have RAIM and will therefore have to discontinue the approach, no?

[ShyTorque]

In your view I take it you differentiate between NDB's, VOR's and GPS for some reason. Are they not all the same concept....navigation using some sort of electronic means?


SASless,

But I didn't say it was my view, nor that I agreed with it. It's the view of the CAA.

I use GPS and VOR/DME/NDBs routinely, every working day. Two GPSs, in fact, plus a nice moving map, also driven by GPS.

I use one GPS to back up the other and the other radio navaids to confirm that what I'm seeing is correct, in one contiguous package.

And I look out of the window a lot, too.

In my view, GPS is the best thing that's happened to aviation in decades.

[HeliComparator]

212 - no, I don't think "ordinary" RAIM identifies the faulty satellite - it just says there is a problem. Type RAIM into wikipedia and see if you agree with my interpretation. Its true that many GPSs allow you to deselect satellites but that is no good if you don't know which one to turn off.

CAA Spec 22 that we know and love, says that in the event of the RAIM alarm limit being exceeded, you have to navigate by other means (and that is just when using for en-route!)

FDE RAIM does it all automatically (that's part of the tso145/6 spec) and if you have WAAS (SBAS) then FDE RAIM is not really necessary because the SBAS signal tells your receiver to ignore dodgy satellites - even if it doesn't have enough for FDE RAIM

HC