Old Garmin GPS units

[Steve Brown]

I respect your view ( and I agree it is a sensible view point) but your earlier comments were regarding the actual legality of others choosing to use GPS as a primary nav ete etc in VMC VFR.
You having a personal view about the dubiousness of something doesnt mean that it is illegal under te ANO.

And the reliability of an un-reliable 'map system' in an open cockpit...........?

I think GPS may be a better more reliable system there.....

[Steve Brown]

So we are agreed then - dumb but not illegal.

[Islander]

Another pointed out, quite forcefully, that I was unaware of very recent changes regarding certified GPS systems (although this thread is about old GPS sets!).

Secondly, the recent approval for the use of GPS for primary navigation ......

No recent changes are relevant here ... GPS has been legal in the UK as a VFR primary navigation system since its very inception. Old GPS sets? The FAA started to approve GPS-based non-precision approaches 15 years ago! Is that old enough for you? [As an equally irrelevant aside, the luddites and nay-sayers in the CAA have striven to ensure that, whereas the FAA is poised to introduce GPS all-weather Cat III GPS approaches within the next twelve months (i.e. autoland capability), the country that pioneered autoland (ie the UK) still doesn't even have a single operational GPS non-precision approach!]

In terms of reliability it's pretty hard to beat a good pair of eyes and a map.

A good soundbite, maybe ... but in my experience of navigating aeroplanes solely by map, compass and stopwatch over the past thirty years, a complete travesty nonetheless. To achieve the consistently accurate navigation that's required in an environment of ever-increasing CAS, the reality for anyone of less than skygod status is that a 'good pair of eyes and map' is a hopelessly unreliable navigation system. It can be fun, it can be a great challenge, I would want to defend to the hilt our right to do it, but ... a more reliable accurate-navigation system than a GPS operated with the same level of planning and diligence? Categorically not!

It's also true to say that whilst C/A code GPS is incredibly sensitive to jamming (or worse, spoofing), good old radio nav aids are surprisingly hard to jam, so are, at least in terms of the technology, potentially more reliable.

Firstly, jamming. I know your background qualifies you well to comment on this and, as I run an RF engineering company, I'm not going to argue against the possibility. IMHO, however, your assessment of the relative risk is out of all proportion. ALL navigation systems are susceptible to failure (and none more so, in my opinion, than the humble map/compass, but because that's human fallibility rather than technical, the tendency is to discount it as something that only happens to other, lesser mortals). I predict that, outside of a time of national emergency, jamming experiences on aviation GPS units, certified or otherwise, will remain extremely rare (unlike significant map-reading navigational errors, which occur with predictable regularity every single weekend!). The important thing is to understand, and to allow for, the possible failure modes and, whatever primary system is used, to have wherever possible a suitable back up.

Turning then to 'good old radio nav aids' being potentially more reliable than GPS. You mean NDB? More reliable than GPS? Sorry to be forceful, yet again, but that's a ludicrous statement that says you've zero experience of flying with NDB as the primary navigation system! The difference for reliably-accurate navigation is orders-of-magnitude in favour of GPS. And VOR? Hopeless at low level, and +/- 5deg at other levels. That means 5nm or more potential divergence from actuality! Not something I would associate with the word reliable, other than in the context of being reliably wrong!

In my view it's fine to use recreational-type GPS units for confirmation of map position, it's still very dumb to use them as the sole means of navigation, as so many recreational pilots seem to.

Surprisingly, maybe, we come fairly close to agreement here! If we delete the word 'recreational', we'd be even closer, since I would argue very strongly that it's especially dumb to use any kind of non-aviation GPS for aviation activities, whether primary navigation or back up! I'd merely wish to re-word your statement to say that it's dumb to use ANY system as the SOLE means of navigation where alternatives exist that can be used for back up.

[Steve Brown]

Jeremy - now you're talking. However, concern over loss of basic airmanship skills due to lack of map reading practice is a whole different issue to the 'is primary navigation by GPS legal' discussion to date.

I understand your concerns completely and agree but saying GPS primary nav is illegal / not good flies in the face of what most of us expeience with the wonders of GPS and then most people then switch off their ears and won't listen to any more of ones argument.

[Islander]

I do wish you wouldn't be so bloody rude though. Perhaps stating your opinion without declaring me to be "ludicrous" might make you seem to be less offensive.

Fair comment, and I apologise unreservedly.

What's more ...

Nice rant, Islander, but it seems that it may be you that is woefully ignorant

... I won't call your statements ludicrous if you don't call me woefully ignorant!

So let's kiss and make up.

Islander

[Steve Brown]

Jeremy - a good discussion I thought - where both parties bring info and knowledge to te BB - long may you continue to post.
Regards
Steve

[Trevor Harvey]

Edited:
Scottish branch of the Royal Institute of Navigation is holding a talk, The use & Misuse of GPS in GA. Tues 11 March in Edinburgh. I shall attend & try to learn something.
http://tinyurl.com/2w7a26
Email the secretary if interested.

[Phil Burgess]

It's good when we can all play together nicely... By the way my GPS doesn't work too well upside down anyway!

[malcolm frost]

I'm just coming back into GA (building a Jabiru) after 25 years away in the airlines and I'm amazed by the attitude of the CAA to the use of GPS. IMHO any means of fixing your position is good. Which is better a map and a chinagraph line, or a map, chinagraph line and a car GPS to confirm your location. I have used my Garmin car Sat nav on a 744, if you set it up with a small scale, non 3d display and track up, you get a very good fix (accurate to 5m) from towns, roads and rivers that you can cross refer to the map.
If the CAA were really serious about stopping CAS busts they would provide a very cheap map that could be used on car satnav and give the appropriate warnings.
BTW I have just done my sim check and we're now authorised down to 500 feet ish for RNAV/GNSS with dual GPS and LHR will be starting next month on 27L.

[kenbishop]

I still miss my very cheap Decca (Yacht Navigator). That was good for 90kts and 1 mile! With nice big number display!
Ken Bishop.

[Rob Swain]

The only snag is that the 1/4 mil is too big a scale, which means I have to carry an additional OS 50,000 series map as well.
Jeremy

I think OS 1:50000 Landrangers are brilliant. I like the 1:25000 even more.
For walking.

In the plane I can cross an entire landranger sheet in about 10 minutes, which renders them pretty useless for aviation navigation. The only way I could used them is put several of them on a PDA or computer. Having done that I might as well link a bluetooth GPS to it. Still doesn't provide me with airspace boundaries, danger areas etc though, but my GPS III does. Ah!

It appears "All Roads Lead to Rome", and all prudent aerial navigation in todays complex UK airspace leads to including GPS.

It would be nice if the powers that be at the CAA would just accept this and include GPS in the basic flight training the same way as other RNAV is.