GPS approach have you flown one yet ?

[A and C]

Have any of you flown one of the trial GPS approaches ? ( in the UK) and if so what do you think of the system?

[IO540]

I don't know anybody who has (all IFR capable pilots I know whose kit meets the TSO129 requirements are FAA / N-reg owners) but a thread I saw on flyer.co.uk suggests that some people have had a go at it, and liked it.

The CAA is also reported as moaning that they aren't getting enough people doing it. Gosh what a suprise

http://www.flyer.co.uk/news/newsfeed.php?artnum=276

[S-Works]

I have done a couple now as my G-REG plane is certified and with an IR I seem to meet the requirements.

The are easy enough to do, you choose thw appropriate join for the procedure based on your direction of arrival. In my case going into Gloucester I join at UVNOP and then turn 157' to BJ09I. The distances take a little getting used to as they are distance to next waypoint and so only the last waypoint which is the threshold gives a quick indication of distance to go.

Each flight has a 5 page document to complete filled in by the observer recording CDI/HSI indication at distances?MDA/MAPt etc. Records messages from the GPS and asks how ATC performed and how easy the unit was to set-up.

A great step forward by the CAA and they should not be criticised for the effort. The trials have been extended as I understand it to allow more time. The problem of course has been they require to be flown in VMC and require an observer to be onboard which has made the take up slow.

It's a shame the N-Reg crowd have been omitted but then this is a British trial and so makes sense that they use "British" aircraft. You can't have your cake and eat it!

[A and C]

I used the GPS approach at EGBJ yesterday and found it to be very good, in fact far better than the ADF approach to the same runway.

The GA community in the UK is always very quick to blame the CAA for the problems in the industry but I think that we should all support this trial as the GPS approach is clearly the way forward and the sooner that we have them the better.

[IO540]

Sure we should be glad the CAA are doing something.

10 years too late is better than never.

However (and I know this is going over the same old stuff) I don't see that this is going to make a real difference to GA utility in the UK. This is because the CAA insists on full ATC for any instrument approach, and most non-ATC airfields absolutely do not want to pay the ATC salaries.

So, all we are going to get will be GPS approaches on top of existing VOR or NDB (or ILS) approaches. It would be useful if the MDH was lower on the GPS ones but the indications are that it won't be.

Especially when compared to an NDB/DME procedure which tends to be designed so that the DME stepdowns alone guarantee obstacle clearance (because everybody really secretly knows that an ADF can't be trusted for the bearing info).

While it is very true that a GPS is far more accurate than an NDB, the old NDB-based procedure is also in the GPS database as an overlay, and can be flown unofficially by flying the real one but in reality tracking the GPS track. Even a monkey can self-position to the FAF, using a GPS, along the conventional IAP track. Just as safe really, and foreign-reg planes can do it right now, under IFR

I am all in favour of anything improving, of course, but I fail to see what new mission capability we are going to get.

If we got GPS approaches into loads of non-ATC airfields, that would be great. In a recent presentation, one CAA official has said they are looking into it. I wonder how they will do the approach clearance delivery (i.e. separation of multiple planes flying the same IAP) given that UK ATC provides no service to IFR pilots flying outside the (mostly Class A) airways sectors. There is only LARS... when you can get it (rarely on Sundays, "due to controller workload"). Unless I am missing something obvious, this would take quite a re-vamp of the ATC system, and the only beneficiaries would be (as the CAA would see it) a small number of IMC Rated pilots. Unless they got a service from the IFR sectors.... can you imagine London Control handing out approach clearances to IMCR pilots flying a GPS approach into Deanland, in between vectoring 737s into Gatwick? That is what happens in the USA, of course But there every pilot doing it would have a full IR. A few things to think about!

[JW411]

A and C:

Yes, I have flown about a 8 so far (including 2 with the CAA watching) and they have all gone very well indeed. Mind you, having used dual GPS BRNAV in my old day job for years I would not have expected anything else.

Compared to doing my first NDB in a Varsity some 45 years ago a GPS letdown is a very relaxing affair!

Although the Trials Questionnaire from Leeds University consists of 26 questions there are only a few that HAVE to be recorded by your observer whilst you are airborne.

[nouseforaname]

The next thing that the CAA need to do is incorporate GPS training into the PPL syllabus. For both PPL and IR candidates, I think anyway.

Pilots will need to completely understand the requirement of updating your GPS system and how to check for vadility of the database (important when hiring aircraft)

I understand all this stuff and I have an IR but my Dad who has a JAR-IR wouldn't pick this kind of stuff up to speedy!

[JW411]

nouseforaname:

You are absolutely right. I have been trying to drag the instructors in my local club into the 21st century even to the tune of giving them the 60-odd pages of bumph downloaded by me from the website. These include CAA instructions to instructors.

So far I have been greeted with polite "Thank You's" but, with one exception, (who asked me to show him one) I don't hold out much hope at that level.

I did show one of the local examiners how to do it and I suspect that GPS approaches are about to go on the FI sylabus - at least in that camp!

[A and C]

JW411

I am an instructor and encourage GPS use, the problem that I have is that examiners insist in turning the GPS off even if the unit is BRNAV approved and is only being used for GS and drift imformation.

Would these guys turn off a dopler if they could still find one ?

The problem is a "British" one , that is some of the British establishment insist in turning flying into a black art probably to make some of them feel that they are in some way better than the rest of us!.

[Chimbu chuckles]

We have had GPS NPAs in Australia for a considerable time...and we have had a few crashes when pilots were flying them.

There is one great failing in their design in my opinion (and it's a view held by many experienced IFR pilots in Australia/SWP) and that is the extra waypoint between what would be, in a traditional final approach, the FAF and the MAP.

This is viewed as sufficiently dangerous by Air Niugini Check and Trainers to forbid them as an option for their F28 crews (analog cockpits)..the F100 and Dash 8 crews are only allowed to fly them as an overlay approach using the FMC/EFIS Nav Display ...and believe me there would be very few airline/Jet crews on the planet that are as practiced and accomplished in Non Precision Approaches as those at PX...all baring one or two ports on the network are only served by NDB and/or VOR/DME approaches...and all suffer tropical weather and very high terrain close by the coastal airfields...not to mention no radar and worse than useless ATC.

A crew in a Metroliner crashed into terrain in the last 12 mths in Far North Queensland 2000' below the limiting altitude for that 'mid final' waypoint...that can only happen when a crew is confused about where exactly they are on the approach. That level of confusion would be hugely more difficult to achieve if GPS NPAs were designed in the same basic manner as every other Instrument Approach Procedure...with an entire final approach and descent referenced to the runway MAP. That combined with a published profile for finals and minimal training of crews would all but make it impossible to be so confused as to be as low as the Metro crew ended up being.

It will probably not make it into the official accident report (because to do so would be to admit the approach design is flawed and contributed to the crash) but anyone with half a brain who is an experienced IFR pilot will tell you that that crew thought they were in the final 5 nm segment to the MAP instead of the 5nm segment preceeding the one to the MAP.

I have been instrument rated for nearly 20 years and have been an IRE and in my view something that could have been excellent, GPS approaches, has been made more dangerous because the basic design criteria was written by someone who had no idea what the hell they were doing.

Be very careful using them.

[IO540]

anyone with half a brain who is an experienced IFR pilot will tell you that that crew thought they were in the final 5 nm segment to the MAP instead of the 5nm segment preceeding the one to the MAP

This "problem" has been picked up by everybody who wants to defend the CAA's slowness on this subject.

I don't see how it is relevant though. An IR pilot does need to have some sort of a brain, and there are loads of ways to kill oneself, by misreading the approach plate. Probably every multi-stepdown DME-based IAP will kill you if you descend on the stepdown before the one you are supposed to descend on.

Humans will make mistakes; that is human. The question is what type of procedure is more dangerous still. One can read about those Airbuses piling into some mountain near Katmandu; a total loss of situational awareness which would have never happened with a GPS moving map.

One can equally argue the opposite to the CAA view; there is nothing magical about the MAP reading zero on the distance to run. It is more important for the pilot to know he has x.x miles to run to the next waypoint, then y.y miles to the next one, etc. To those used to flying DME based approaches (incl. myself) this seems odd, but one has to get one's brain out and use it. There are DME approaches where the DME 0 reading is nowhere near the runway, too.

Objectively, this stuff can be argued both ways. The only difference is that those who don't get killed don't make the statistics. Think how many GPS approaches are flown routinely in the USA, and how many deaths there would be if the large numbers of IR pilots they have were flying DIY descents into those airfields, the way UK pilots do.

[Chimbu chuckles]

The point is they could have been better designed than they are

Probably every multi-stepdown DME-based IAP will kill you if you descend on the stepdown before the one you are supposed to descend on.

That is why experienced pilots use a descent profile previously calculated or published on the chart rather than the old 'dive and drive' method.

I have flown the Kathmandu RWY 02 VOR/DME approach in anger a bunch of times at it is a VERY steep approach...using a pre calculated descent profile, and briefing same, is about the only safe way to fly that approach.

In my view CAA are right to be very cautious...and as a general rule I usually dissagree with virtually every muttering that comes from CASA...these approaches are NOT designed as well as they could be.

Where the MAP is in relation to the runway in other types of approaches is not relevant...what is is the manner in which you descend from the MSA to the minima. If it is not a runway aligned approach you must be visual to proceed beyond the MAP. Having said that the great (potential) advantage of GPS NPAs is they generally are runway aligned and the MAP is so positioned so that a descent to the threshold is possible, if visual, using normal rates of descent.

Think about how much simpler and safer GPS NPAs would be if instead of the extra waypoint you had only a FAF and a 'runway' waypoint.

For argument sake the airfield is MSL and the approach commences at the FAF waypoint which is 3000'/10nm from the 'runway' waypoint. With a suitably placed 'runway' waypoint you could fly the whole approach using a 3 times dist=altitude profile. 3x9nm=2700', 3x8nm=2400', etc down to 3x2nm=600'. If not visual at 2nm/600 commence missed approach and sequence GPS into the missed approach procedure.

That is how experienced IFR pilots fly VOR/DME or NDB/DME approaches and it makes it essentially impossible to end up low....yes I know nothing is impossible but why design an approach in such a manner that it is easy to **** up rather than hard?

In Air Niugini this style of approach profile use was drummed into us until their use was second nature...in over 30 years of flying NPAs in all manner of airline aircraft from DC3 to F100 as a matter of daily practice/necessity they have yet to have a CFIT despite tropical weather, high terrain, no ATC radar and incompetent 3rd world ATC....in other words all the risk factors for CFIT.

How much easier and less confusing is the above compared to the way these approaches have been designed?

I have flown GPS NPAs in my Bonanza when circumstances warrant...but I am VERY mindful of the trap designed into them.

[411A]

Hi Chimbu

Strange, how these GPS approaches are apparently designed by CASA.

Could you possibly post an example?

Here in the USA, GPS approaches are widely used, with very few problems, save for the odd corporate KingAir (or similar) who don't do that many on a regular basis.

I fitted GPS in my private aeroplane nine years ago, and find it very useful...and quite franky, almost impossible to **** up, especially if you have a basic moving map display, ala the Bendix-King KLN89B or KLN90, and these are old units.
The new Garmin units (430/480/530) are really nice, and have everything in the display but the kitchen sink.

[nouseforaname]

We have a Garmin GNS 480, it's good piece of kit but difficult to learn the functions at first. It's got just about everything in it including control for 2 transponders.

[IO540]

Chimbu

That is why experienced pilots use a descent profile previously calculated or published on the chart rather than the old 'dive and drive' method

I agree with you, and that is exactly how I fly NDB/DME approaches using a GPS (fly all the way down from FAF to MAP at a constant -VS, with the MDA set as the altitude capture on the autopilot, while checking off the height/distance fixes as they pass by) and I can't even compare to your vast experience, but nevertheless it is true that obstacle clearance is guaranteed at each stepdown fix.

So doing a "plummet" immediately after each fix should be perfectly safe.

There is just a bigger chance of busting each minimum level doing that, presumably due to greater pilot workload.

[Chimbu chuckles]

411A I am away on a trip at present but when I get home I will scan an Australian GPS NPA.

As far as I am aware Australian GPS NPA approaches are not designed 'by CASA' in terms of their underlying design criteria but rather are designed to an International standard...so they should be the same as those used in the US and UK. This is apparently driven by the way the GPSs were designed in the first place.

A recent 'Crash Comic' (CASA Air Safety Digest) suggests it was not possible to have the approaches any other way without changing the way the logic of the GPS units works which was deemed impratical.

I have a KLN90B in my Bonanza, an excellent IFR GPS. My A/P is a Century 3. Certainly a really good moving map and modern digital autopilot would negate to some extent the design of the approach but not everyone can afford a Garmin 530 and a Stec 55X.

I will be home from this longhaul on Friday so I'll scan an approach from my Oz Jepps then.

[A and C]

I can't see the problem with the fix between the FAFand the MAP If you are flying the approach using vertical speed to provide a nominal glidepath (rather than dive & drive) then this fix just becomes another point to check the altitude and adjust the vertical speed if required, after all the altitude that you should be passing is clearly marked.

The problem is one of reading the chart, there have been a number of accidents and near accidents from VOR approaches when the VOR/DME is not situated on the airfield (the B747 crash at Guam and the two near accidents on the same day !with a HS748's at the Isle of Man) in all cases the crews did not understand that the DME range was not from the runway and decended to soon towards high ground.

As long as we have approaches without a glideslope mis-reading the chart will always be a risk but in my opinion the fix between the FAFand MAP is an attempt to encourage pilots to fly vertical speed nominal glideslope rather than "dive & drive" by providing a waypoint with an altitude to aim at marked clearly on the chart.

[IO540]

the crews did not understand that the DME range was not from the runway

Didn't they have the gold plated JAA IR? One only has to read the plate to discover gems like that.

Chimbu - I have a slightly dated version of Jeppview 3 (worldwide); what is the ICAO airport ident you refer to?

[Chimbu chuckles]

Can't think of it off the top of my head...Lockhart River is the name of the place.

Now sat on my arse in BKK for 4 days...yesterday was FRA....this longhaul is hard work

Will hunt it out when I get home.

[IO540]

I've flown one of the CAA "trial" approaches. Not being G-reg I flew it (with prior ATC knowledge) at a few thousand feet, level all the way. Outside the ATZ so outside ATC jurisdiction. Not descending makes no difference to the GPS performance, of course.

With a 20-30kt crosswind, on autopilot, it tracked the route perfectly. As the sensitivity zoomed up from 1nm full scale to 0.3nm full scale on approaching the FAF, the track error disappeared to something too small to see on a 1nm full scale setting on the MFD. This, and looking down, I would say the runway centreline was tracked to within a few feet.

Impressive.

To land, I would have only needed to dial in the MDA as the target altitude, dial in the descent of -700fpm (for 90kt), and start this off at the FAF, then sit and watch the profile.

It flies on, still within a few feet of the track, to the waypoint which is a few miles after the MAP, after which the pilot, if still awake, would turn back to the navaid.

The only comment would be that the turn onto the inbound track needs to be done a few seconds before the GPS tells you it has passed the waypoint. Doing it when it says so results in an overshoot of a few hundred metres (gosh how terrible; NDB approaches are so much more accurate ) but this hardly matters as one is still about 8 nm out.