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Navigation Paradox

I just came across this fascinating article as a result of reading about bits from my recent navigation thread. I linked to this from WAAS…

https://en.wikipedia.org/wiki/Navigation_paradox

It’s a subject that has been discussed with a few friends of mine in the past. When going on a long cross country, VFR:

Person A: Has a precision PLOG based on named waypoints, programmed into a GPS, and followed by Hand
Person B: Ditto, but using Autopilot
Person C: Uses “elastic band” navigation to very roughly plot the route deliberately avoiding any named waypoints (that’s me)

My theory is that i’m much less likely to run into any traffic conflict. In fact, my logic here drove me away from buying a Garmin G3X and steered me toward the Dynon Skyview because the Garmin’s route planning is very waypoint based and it’s tricky to use lots of custom waypoints whereas the dynon just lets you drag and drop a route OR just lets you WIFI it from SkyDemon. Using SkyDemon My usual way of navigating from, say, Shoreham to Gamston is to enter a direct routing – then drag my finger left/right around London Class A, around airfields, and trying to go through the middle of chokepoints rather than necessarily the precisely shortest point to point routings.

How do other people approach this?

EGKL, United Kingdom

Limited to class G airspace, I sometimes fly what we locally call “the corridor”: a narrow corridor indeed, between the CTR’s of Brussel and Antwerpen. Vertically, it is limited to 1500’ by the Brussels TMA. It becomes even more “interesting” with traffic from EBGB Grimbergen, bound for the North to East, joining in or crossing about halfway through.

This corridor can be easily navigated by flying a straight line between BUN (Bruno) VOR and MAK (Mackel) NDB – indeed I heard a rumour that Bruno had been relocated for this very purpose. It is however general practice among us microlighters to avoid both navaids, because they are known to attract old school PPL pilots plus the occasional bigger machine – especially BUN is often used for navigating to EBAW, though most planes doing this will be higher, in the TMA so as to be controlled.

EBZH Kiewit, Belgium

The GNS430W has a feature called “parallel track” that let’s you fly left or right of the direct course between waypoints.

The biggest thing is that traffic depends very much on altitude. If you fly at say 1500ft, especially in the UK, you will be having near misses all the time, on a nice day, and 10x more on a weekend.

What I do in reality is that I might plan a route via navaids etc but then when I fly it I do shortcuts which are done on headings which just miss the CAS. So most corners get cut. With an autopilot there isn’t much to do except keep an eye on stuff and take photos, so this is not an issue.

Or – another example – there might be a lot of low level cloud around. Say I am going Shoreham-Coventry, 2400ft. If that puts me in the cloud, it’s not going to be a nice flight. But say the tops are 4500ft. One can do that trip VMC on top, but one has to go further “out” away from the LTMA CAS “upside down cake”. So I might fly it at 5400ft, managing the track on the fly, using the GPS moving map. An IFR GPS like a GNS/GTN has far too poor quality mapping for this, and I then use the CAA 1:500k map running as a moving map on a tablet. Then I would fly the whole flight in HDG mode, and turning the heading bug as required.

Administrator
Shoreham EGKA, United Kingdom

carlmeek wrote:

How do other people approach this?

Except in the CTR of an airfield, I don’t think I have ever used a “waypoint”. Lakes, mountains, roads, vallies, islands etc is what I use, also in easy VFR. Interestingly the ippc fpl site has just now started using some autorouting (using waypoints), but only for IFR, so I won’t be using that.

The elephant is the circulation
ENVA ENOP ENMO, Norway

What I was getting at is that one may plan a flight using waypoints (navaids, airway intersections, whatever you can dig out of the GPS database and chuck in) and these will be on your plog, which will form a rough guide to the flight, so you have a good idea of where you will be flying before you get off the ground (always a good idea ).

Then, enroute, if you have a means of getting really good CAS/etc awareness, you can fly around as you wish, take shortcuts, whatever…

Apart from trivia like Shoreham to Lydd I would not recommend getting airborne without some sort of basic route plan which is definitely flyable and a look at the MSA along the route.

A large part of the enjoyment of flying is to remove the “WTF are we supposed to do” moments, and having a route loaded in the GPS is a big part of this.

The fact that a “cheap” IFR GPS like a 430/650 has a map screen way too small to be used solely for off-route flying is a separate issue.

Also consider that the pilot who got done 5000 quid for busting the Eastbourne air show a few years ago, from Belgium IIRC, had the good route planned, but diverted from it to do some sightseeing…

Administrator
Shoreham EGKA, United Kingdom

A friend of mine told me about an occasion years ago when he was flying a Falcon 50 across the Atlantic at night.

They were flying a GPS track on autopilot. They were in contact with someone going the opposite direction on the same track.

It was a clear night and the could see if nav lights for many minutes before they cross over.

At the moment that the other aircraft pass under them, all on autopilot, the radar altimeter suddenly called out “one thousand”!

Middle of the Atlantic yet crosses directly over one another because of GPS accuracy.

Personally I use GPS waypoints all the time, but I tend to not follow “common routes” such as VOR to VOR.

EIWT Weston, Ireland

It’s a ‘big sky’ and midairs away from busy airports are not the problem. Enroute nav on airways are more dangerous than RNAV using GPS and staying off the airways.

From a communication standpoint I think it is a lot easier to talk to ATC and (to keep it to Belgium) say you are inbound Nicky (NIK) than that you are flying north of whatever town. The ATC guys are used to these waypoints, so why not use them. Even if I fly IFR and am e.g. inbound NIK I can hear other aircraft being directed inbound NIK at the same time, but just at different altitude. I have never seen them though as the big sky is really big.

EDLE, Netherlands

I went from what person A is doing. Then installed a Dynon autopilot (with a D10A) in my Europa in order to do what person B is doing. At this time, I was thoroughly programming my GPS with waypoints.
Nowadays, with the help of Skydemon, I just write down frequencies, identify some critical points (typically 2-3 for a trip of 400nm) or border crossing points (typically IFR waypoints, easier to explain to controllers in CAS where you are flying to) and then let’s fly! When on autopilot, I now only use HDG mode and make adjustments when too much deviating from the track on skydemon. Next step is upgrade to Dynon Skyview and do what Carl suggests with “elastic band”. Also synchonise Skydemon and Dynon Skyview via WIFI.
That is well assuming that weather is fine and so no stress situation is expected.

Belgium
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