GPS - Why Not????
 

Having read a few threads on GPS it seems that we pilots in the UK are absolutely **** scared of using GPS as a means of navigation.

Having used GPS in the US for both navigation and approaches I dont really seem a problem with it. There is a current thread on GPS jamming but lets it face, choice of flying blind in IMC with GPS or GPS that could be jammed at any moment, I would take the GPS every time - if you fly an approach in the US then its integerity is certified via RAIMS so you know you arent getting false data, if it fails you go missed.

I think this is one area where the US wins hands up and we are (sadly) lagging behind.

From my experience GPS is widely used in the UK both for VFR and IFR flight. I'm have been surprised several times by who just whips one out.

Often seems that people are a little shy of admitting they use one though!

They are probably the same people who wont admit they shop at Kwik Save.

I use a GPS all the time, best part is when you get home and look just how great your circuit was. <that dont read well. ho hum>
Walt,,

I dont know why there is so much resistance to GPS in the UK ,I suspect that most of it comes from the "old guard of navigators" in the CAA.

If the took a walk down the corridor in aviation house to the aircraft engineering people they would find that most of the airliners flying about are using GPS as the primary navigation sorce backed up by DME/DME , VOR/DME ,VOR/VOR and inertial ref.

GPS is the most widely used system to comply with the european B-RNAV requirement and when a TSO unit is fitted into the pannel of an aircraft and rigged to the proper instruments then it can be used to fly an aproach that is in the data base.

Unfortunatly no one seems to want to set up a GPS aproach in the UK.

I can see the authoritys reluctance to except hand held GPS units because the instalation is not tested can be subject to interference from the VHF com system or simply the passenger accidentily pulling the power lead out of the cigarette lighter socket.

One very simple reason GPS is not used for approaches in the UK....not invented there. 'Tis a US system and therefore cannot be trusted.
And for those that mention jamming, these schedules are published well in advance (in the USA) so ops can be planned accordingly.
Have used GPS in my private aeroplane for the last five years and have found it dead-on, every time, approaches included.

I understand that CAA trials with GPS approaches are at quite an advanced stage, but it would appear the problem of ensuring that the system is free from interference has yet to be overcome.
Additionally, although improving, the coverage of sattalite reception is still not 100% throughout the UK.

Airport operators would leap at the chance of GPS approaches being approved, as long as they still had a radar back up, this would then negate the need for having and maintaining ILS systems, which are very expensive to buy and involve a lot of monitering and maintenence.
Equally, I'm sure that airline operators would be equally receptive, for much the same reasons.

It should be borne in mind that when it all does come about, as now, pilots and aircraft will be restricted to certain limitations, so it isn't necessarily the panacea that some may believe it is.

However, whilst there is no doubt that the accuracy of the system is capable of exceeding present instrument approach aids, until the provision of the service can be proved to be as reliable as current systems, AND, a suitable back up is maintained by aircraft and airport operator, it will not be approved.

Although I'm a big fan of properly-used GPS (but not 'moving map' GPS as that encourages too much 'head in' time), I've noticed the odd glitch in the VFR-only GPS equipment in my 4 PA28s and also the occasional GPS wibble in the Y-code GPS element of the embedded GPS and laser INS in my 'day job' aeroplane. Which is why GPS-only is never used for navigation, GPS blended with LINS or GPS blended with a secondary INS through the Flight Management System is used for LNAV autopilot steering.

Nothing to do with 'not made here' - everything to do with safety of air navigation!

As I see it if you have a aproach aproved GPS fitted to your aircraft ,the aproach is in the (up to date) data base then you can make a non-precision aproach.

The CAA published an AIC on the GPS some time back and if you read deep in the small print you can find the aproval.

BEagle, do you really mean that you think that it is better
for a pilot to be working out lat/long coordinates rather than
have their position indicated on a moving map? That
has got to be a difficult position to justify...

If you are flying with an approved IR GPS setup in the US
you can perform the whole enroute element of the flight
on GPS, switching over to ILS for the landing phase.

Alternatively as A&C states you can make a non-precision
GPS approach to a beacon using the NDB procedure.

Having had the pleasure of recently doing a stack of NDB
tracking I am convinced that GPS approaches are far more
accurate than the NDB equivalent and less prone to systematic
errors.

-- Andrew

BEagle states that...GPS- only is never used for navigation.
Cannot speak for the UK, but in the USA it IS perfectly legal to depart IFR with GPS only, fly enroute (below FL180), approach to and land at an airport using an approved GPS approach. The GPS installation in the aeroplane MUST be IFR approved AND be fitted with a current database.
In addition, in these days of proliferating TFR's and restricted airspace, a moving map display (which I also have incorporated in the GPS) allows a positive way to avoid these areas so that one does not get close and personal with an F-16.:eek:

Our Company Falcon has dual Universal 1D FMSs with imbedded GPSs. They are fully stand alone enroute and approach approved. They can also use rho/rho and rho/theta but our navs need an upgrade to do that, hence we are flying the length and breadth of Asia on GPS only the vast majority of the time. I've yet to see anything less than 'Approach' when conducting enroute RAIM checks. The same applies to pre departure RAIM checks using the US Coast Guard RAIM prediction software/website.

My personal A36 Bonanza has a Garmin 100(like the aircraft itself, oldy but a goody) which one of these days I'll upgrade to an IFR one now that Australia has dozens of GPS NPAs scattered all over.

In 12 years of using GPS daily I've yet to see one glitch in any way that wasn't finger trouble. The classic finger trouble is when, in the older non database ones (Garmin 100) you input an incorrect latitude, i.e. North instead of South, but easily picked up if you note the track distance and find it is several thousand nm out.

IMO GPS will never replace ILS or where it's used MLS but for enroute and NPAs it cannot be beat...the whole world relies on it nowadays...The US couldn't turn it off if it wanted to.

Chuck.

andrewc - first the VFR-only use of GPS at, say, PPL level. In my opinion you should draw your route on the map and calculate track and groundspeed in the conventional manner. In the ac, enter the GPS route with turning points. Select the data fields to give DTK, GS and ETA plus have the mini-CDI bar displayed. When you are airborne, start your navigation and use the GPS to cross-check your pre-flight work. You can keep an eye on the mini-CDI from time to time, but your primary navigation is by map and time, backed up by GPS.

However, if you have an IFR-approved GPS with all the relevant requirments, things will be different. As far as I'm aware, the UK hasn't published any GPS non-precision approach procedures yet though.

The 'day job' ac uses basically twin INS, one of which is GPS blended. We do not use GPS-only for LNAV, we use the best FMS-derived steering solution to navigate between database or manual waypoints. That's because the GPS element does not have RAIM (astonishingly), nor does it have adequate stability to be coupled directly to the autopilot.

Other ac with infinitely more modern GPS/FMS would not be so hampered, but my point was that not every GPS is suitable for IFR navigation and approach - although it might seem to be very accurate, there's still a chance of it going out to lunch at an embarrassing moment unless it has the appropriate mandatory certification.

In the US there are ' GPS Overlay' approaches which are basically a NPA such as VOR but overlayed on top is the GPS prcedure...which is exactly the same...

So if I was shooting a NPA in the UK and I had an IFR GPS fitted I would set up the approach in the GPS, and use this alongside my conventional nav equipment. If I had a problem with the conventional equipment, I'd follow the GPS....

Cheers
EA:)

The other advantage with using GPS in conjunction with standard nav equipment is that any mistakes you make will become obvious.

By this I mean dialing in say 123.05 instead of 123.50. I was once onboard an aircraft, the pilot was shooting an ILS (can't remember the exact frequecy) something like 123.50 and a nearby VOR had the freq 123.05. The wrong freq was dialed in, and should have been picked up when 'identifying' the navaid...but wasn't...so we had intercepted the 'localiser' which in fact was the VOR....ok there were other clues, like the inbound course, lack of GS etc...but in this situation, the pilot was under pressure and didn't pick up on these things straight away. The thing that made it obvious to me was my handheld GPS (Garmin eTrek) which I was monitoring to confirm the accuracy of the waypoints just downloaded from the web. I could see we were heading away from the airport and towards the VOR...which could have been a fatal mistake as the VOR elevation was significantly higher than the airport....when I checked the approach plate it became obvious what was going on....In this instance the error probably would have been picked up before a dangerous situation arose, even without GPS, there were 3 of us onboard and although vis was ***** it wasn't on the deck. Now imagine the pilot, on his own, in turbulent IMC, apprehensive.....

So I'm inclined to trust GPS and if not use it as a primary navigation system, to certainly use it as a secondary system. The more info you have the better...

Cheers
EA:)

BEagle

Do you really mean:

"Select the data fields to give DTK, GS and ETA plus have the mini-CDI bar displayed."?

If DTK (desired track) is the same on your GPS as on mine, it's the track between the last waypoint and the next one, which is probably written on the PLOG anyway. TRK is the one you want to tell you which way you're going, and therefore whether your heading is working or not. I find that much more valuable.

mis-quoted
 

A few people have mis-quoted me in post above so lets make this clear A GPS aproach is leagal in a UK registered aircraft ONLY if the aproach is in the data base.

This is because when the unit enters the aproach "ARM" mode the cdi scale reduces to 2.5 miles fsd at the FAF the unit goes from ARM to "ACTIVE" mode this slowly reduces the cdi scale from 2.5 mile fsd to 0.3 mile fsd by the time the aircraft reaches the MAP. the scale will also change back to 2.5 mile in the case of a missed aproach.

As you can see there is a lot more to a GPS aproach than first meets the eye and to be safe the up to date database for the aproach must be in the box.

At the moment I know of no GPS aproaches in the UK.

bookworm - I do indeed mean 'DTK' and NOT 'TRK'! The idea is that you should check the GPS value against the planned value at the turning point to show any gross error. The mini-CDI will show cross-track error which can be very useful if you have to deviate from track for some reason - such as a rain shower, for example.

A very common mistake is to have 'DTK' and 'TRK' displayed. All that will do is to tell you (from a rather inaccurate GPS-calculation of track angle) that, when the values are equal, you are parallel to your desired track, not maintaining it!

BEagle, yes that is in fact how I do organise myself for
flights of any significant distance. My GPS gear, a pair
of 430's is rated for IR approach use in the US when a
current database is installed.

This year I've done an IMC, the experience of which
I'm going to spend some time converting to my own
aircraft.

The plan next year is to do a US IR that will give me
full airways and approach access in the UK with
my (N-reg) plane.

-- Andrew

andrewc - you lucky chap! A pair of 430s indeed! We still have GPS150s and GNC250s.

Using a US IR in your N-registered aeroplane is a very sensible thing to do. But isn't it amazing how the aeroplane's registration makes soooooo much difference to IFR/IMC flying - if it has a 'G' painted on the side you can't use your IR, but if it has a 'N' then all is fine!