First Navex

[Oksinay]

As a relatively ancient mariner I started my first navex with a reasonable amount of confidence in my ability to get around with a chart and a compass. It all happens a bit faster in an aeroplane, doesn't it.

 

Everything went well, although I had an interesting experience at one point late in the flight convincing myself that what I was looking at was Nathalia when it was in fact Numurkah. Humans have a very strong ability to be subjective and make the facts fit the circumstances.

 

 

[J170 Owner]

Congratulations. My first navex was pretty easy but I was still 5 miles out after 100. That was 30 years ago. These days I still use the map and compass but must admit, the GPS gets used more!

 

 

[Chris Tarran]

Congrats Oksinay, I'll bet it's a great sense of achievment. I'm also a long time sailor and done 3 Navexs now, although the last one was 6 months ago. I've learnt something new every time. You're right about the perspective thing, at height and speed it is very easy to mistake one similar landmark for another. I fly out of Port Augsuta in SA and have used wheat silos as landmarks but I have picked the wrong one a couple of times particularly when they are (relatively) close together. Good luck with the rest of them. Cheers Chris

 

 

[facthunter]

You've picked a very relevent point. Any fix must be absolutely verifiable. Be wary if it turns up early (or late). Our mind wants to conclude a mystery and will accept any offer, to make things fit. The part of the brain that deals with the eyes does the same. It will always fill in the picture. Nev

 

 

[Chris Tarran]

My problem wasn't were I was, I knew that as I was carefully doing my time on distance checks to ensure I was on track. I had difficulty looking at similar landmarks in the distance and picking the right one. One example was a track from Cleve on the Eyre Pensinsula north-west(ish) to Wudinna. The actual vs forecast wind at cruise height turned out to be quite different so I was tracking north of my intended path. That took a few minutes to pick up and as a result I initially picked the Kyancutta silos to be Warramboo (some 10 km further South). As I got closer it resolved itself but it raised some doubts in my mind for a few minutes. No real danger as I was in an area I knew well but it certainly showed me how a simple error can be compounded. If it had gone on I would have been about 6 nm north of my intended turning point. Cheers Chris

 

 

[Jeff Gordon]

Long time navigator on the water and have been completely lost on more that one occasion. On one spectacular occasion we found ourselves off King Islands rugged West Coast going south...stormy night and thought we were going NE along the coast from Cape Otway...but really going SW. Pretty lucky that I am here today to talk about it.

 

So it was with great trepedation that I took my Nav exercises. One big hint that someone gave me that has helped is that one finger width on a WAC map is approx 10nm and when lost, the time from your last know point is the first thing to remember, then compute for 90 knots (my approx air speed) is about 1.5 distance. So 10 minutes flying will equal 15nm. Then using your finger width (or your trusty WAC ruler) and knowing your rough direction will put you on the map somewhere about where you are. then start looking for obvious landmarks that you can relate to the map.

 

 

[facthunter]

I've always said that " It is better to be roughly right than precisely wrong". Processing figures that don't have a high order of accuracy to decimal places is a waste of time.

 

It's the silly mistakes, like flying the distance as a track ot applying the drift or the variation, the wrong way that gets you in trouble. Do lots of planning on the ground where your head is clearer and double check all figures so you have a reliable document in the flight plan. Don't allow ferrous binders etc near the compass. Fly a fairly accurate compass heading. Establish actual track ( and by inference drift) when it can be accurately confirmed, by a positive determination of fixes ( or pinpoints if you use that term). It's not rocket science and individuals will to some extent work a system that suits them. . The basics remain fairly constant . Nev

 

 

[Guest davidh10]

Yes. It is easy to mistake Nathalia for Numurkah if you don't examine the surrounding roads closely, but if you check the angles of two distant landmarks at about 90 degrees apart, you will soon confirm which one you are above. Mt Major would be one such landmark and if you are at Numurkah, you should be able to see Katamatite on the diagonal Tocumwal - Benalla road. If it's Nathalia, the diagonal road just to the south leads to Shepparton. Of course it also depends on your altitude. Haze and cloud excepted, generally you will see much further from a higher altitude. The higher altitude also distorts distance. What was very distant at a lower level can look like it is only a few miles away from a significantly higher altitude. If the day is clear enough, you can also see the high country around Mt Buffalo / Mt Bogong in the distance, but if it is hazy, you won't see that far.

 

Don't just look down. Identify distant landmarks that you can use for bearings. I'm not talking about getting out protractors, but just dead reckoning. Don't wait till you get to your turning or check point. Always know where you are by following your progress on the map. If an emergency was to occur, you need to be able to give a location without getting charts out to figure it out.

 

I flew down to Violet Town via Benalla on Friday evening and then straight back to Yarrawonga. Mt Major was one of my key landmarks, as was the city of Benalla, because I was not flying a pre-planned compass heading, but doing dead reckoning from the Melbourne VNC. By looking at the map and the angle of these two key landmarks, I could pick the direction to fly and then check for road intersections and power lines that confirmed the track and progress.