View Full Version : Plans to replace NDB with GPS NPA

24th Jun 2005, 15:26
Now that the FAA is planning to replace NDB none-precision approaches with GPS one wonders when will Europe follow.

Or will it be another case of the beaurocrats being unable
to deal with technology advancement....

Of course there are real training needs here for those of you renewing IMC rated pilots. Read this...



24th Jun 2005, 21:41
And about time too, this continual negative attitude about GPS and it's flaws whilst completely ignoring it's benfits over the NDB approach baffle me.

The argument was put very well to me by a fast jet pilot....

"have you ever heard of an NDB/VOR guided bomb?"

No thank god even if they could make it work.


26th Jun 2005, 21:52
"have you ever heard of an NDB/VOR guided bomb?"

RAF Valliant bombers used the Cairo NDB which had been left on during a raid in the Suez Crisis.

28th Jun 2005, 16:10
And the bomb used.....? :D

Sooner the UK stops all this "evil GPS must use Mk 1 eyeball" [email protected] the better. They both have their place and neither should be excluded.


28th Jun 2005, 18:59
They have stopped it, in some areas at least. I went to a CAA Safety Evening a couple of months ago, and it's no longer "Don't use the evil GPS"; it's "Don't use it as your only form of nav, and make sure you know how it works". Made sense to me.:ok:

28th Jun 2005, 22:10
NDB approach procedures are being progressively replaced by GNSS NPAs in NZ - and have been for some time. There is a planned one year transition period between GNSS implementation & NDB decommissioning (soemtimes it's a bit longer).
The GPS procedures have worked fine since they started to be introduced 11 years or so ago.....

30th Jun 2005, 20:53
Glad to hear it Whirly,

I look forward to flying an autopilot coupled GPS approach :E

1st Jul 2005, 10:26
With the rise in GPS the diminished role of ground based beacons is a challenge for authorities who use their control of such beacons as a mechanism for control.....

One could see why such bodies might be tempted to use the safety argument as a cover for protection of vested interest
but there is nothing new in that...


1st Jul 2005, 11:10
Reynoldsno 1. "GPS Procedures have worked fine since introduced.."

That is a sweeping generalisation. Few pilots will admit officially to a cocked up GPS/NPA approach and as a result there is a huge gap in our knowledge of what could have gone wrong. Fine if the approach is conducted visually in daylight, but not fine if the stuff up's were IMC or night.

There have been two fatal accidents in Australia which claimed the lives of passengers and crews where either GPS defects or more likely mis-reading of the GPS/NPA instrument approach chart were suspected. This may have been due chart design with its accent on distance to various inbound waypoints rather than distance to the runway. In both accidents, low cloud and poor visibility were a factor. There is little doubt of the accuracy of GPS in tracking, but keeping above each stepped safe altitude is the weak link.

3rd Jul 2005, 10:35
There have been two fatal accidents in Australia which claimed the lives of passengers and crews where either GPS defects or more likely mis-reading of the GPS/NPA instrument approach chart were suspected.

Could you provide links or references to the accident reports please? I'd be interested to learn more.

3rd Jul 2005, 22:20
That is a sweeping generalisation
It wasn't a generalisation, sweeping or otherwise. I specifically referred to the situation in NZ.

4th Jul 2005, 06:20
I think the procedures are fine, just some pilots haven't spent the same amount of time practicing them before using one in anger. It's definitely not the same as a VOR or NDB approach due mainly to the ability to put a turn into any part of it.

If pilots practiced ~50 GPS approaches before using one in IMC(like they do for NDBs before sitting their Instrument Rating initial issue) I think there would be both more acceptance of GPS and it's specific terminology as well as widespread rejection of NDBs. At least if the RAIM fails it actively tells you, whereas an NDB could fail and if you don't have the volume up and notice the lack of ident, or some visual sign pops up, you could easily continue somewhere you don't want to. Even when they DO work it's only an approximate direction. I've flown four NDB approaches in VMC (thankfully) in the last three months with perfectly good instruments that have put us over two miles off track.

And you can couple an autopilot to a GPS, but not to an ADF! (and why would you want to, it'd make you sick with all the swinging... :yuk: )

I agree with Centaurus though, I'd like to see the distance to MAPt as one constant throughout the approach, put the "DTMA" under each waypoint on final by all means but one steadily counting down distance is easier for the brain, especially at night in poo when you're tired.

4th Jul 2005, 15:14
NDBs have no fail flags and are, as some commentators above have pointed out, subject to a number of errors (5 in all). Why do so many people continue to support this rather outdated crude technology as preferable to the FAA approved modern alternative? Is it because we have much more rigorous tandards in Europe? I think not. The 'special weather' argument hasn't been used much these days.

As pilots start to build a level of trust in GPS for approaches all over the world it is becoming time for the slow moving regulatory bureaucracies of Europe to embrace this technology otherwise people will just use it outside the training loop - and that is dangerous. What is needed is an international organisational approach that would cover training in aviation for such matters.

Of course the slow move away from ground based approach aid provision presents challenges of control for the authorities that maybe like to maintain the status quo. The traditional approach that maintains jobs and income streams....

A and C
9th Jul 2005, 19:09
I can see why a GPS approach could end in disaster if the pilot was not fully conversant with the way the "box" works it has taken me a few hours of reading the manual and playing with the box on the take home simulator and I am now happy to do a GPS approach in VMC.

The whole GPS thing has to be better than the ADF but and it is a big but..........the aircraft has to meet the GPS approach TSO, this I suspect will be the downfall of a lot of aicraft GPS instalations as most owners seem to pennypinch and dont get the full TSO instalation done.

9th Jul 2005, 22:32
cautionary tale:
low level flight in a Dauphin flying cross country between two jungle/bush helipads on a GPS track.

GPS screen blinks a couple of times and then a message appears

"FACTORY RESET" it says!

There we are miles from anywhere and no ***** GPS. A quick look in the box shows that the system is working but it does not know where it is and all the waypoints have disappeared apart from all those on the Jepp card - useless when you are out in the bush. The story ended OK when we punched in the Lat and Long of the nearest landing site and hit the "Direct To" button.

It happened again a few days later so lesson learnt we changed the receiver and installed another GPS as a back-up.

Have also experienced blank-spots where we would regularly loose the GPS signal.

It's not all as simple as you might think!

11th Jul 2005, 05:52
Which is of course exactly the same that would happen if you were flying a route based on any single navaid that suddenly failed (more like went out of range).

Knowing that doesn't make it any less unpleasant of course, but planning for it (eg keeping a simple time-speed-distance log) can mitigate the effects somewhat...

I well remember the second check I did in the GPS equipped aircraft I used to fly, checker turned off the GPS and said, "It's failed". Took me a while to get my head around that! But really it shouldn't have.

(I was about to add, at least in a Dauphin you can stop and have a look around, but then I thought, hmmmmm, low level helicopter in a jungle, better not stop methinks := )

12th Jul 2005, 10:44
Of couse an ADF is often worse - it has NO fail indication so the advice is to have a distracting morse ident whining away sometimes interspersed with static and needle movement........:*

31st Jul 2005, 02:10
When you have used a Garmin 430 for a while, or a Lowrance or Bendix King Skymap, you realise what a misconception it is that such a GPS could be compared unfavourably to ANY nav aid available to the average GA aircraft.

But that is different from the pilot who is using a hand held and trying to find a field in conditions in which he/she should not be flying, and I think that is the reason why the CAA spent a long time knocking GPS. It is not the GPS's fault that the pilot is misusing the equipment, and I think this is where the education should be targetted.

If the GPS equipment is mounted into the aircraft, then I don't see why it should not replace NDBs and DMEs. Why we need a DME when we have a GPS, I don't really understand.