PPL Navigation - FAIL
 

Hi,

I have just taken and failed my PPL Navigation exam – quite frustrated by it all as the method I was using was fine, I knew what I was doing, but the answers were just slightly wrong – i.e. give the Magnetic heading of A to B…I’d answer say 071 and the answer was 073. Obviously getting things like the heading wrong to start with meant my calcs for drift, G/S, journey time etc. were off so the knock on effect was that I ended up getting a handful of questions wrong – but only out by a degree or 2, a kt or 2 or a couple of mins for journey times – but ultimately failing. I would know I was doing something totally wrong if the answers I were giving were miles out but they weren’t.

So my question is how have I managed this? Could it be a simple thing like using a chinagraph that was too thick to mark the chart meaning I was reading off the True track as a degree or 2 out to begin with? Same with marking the flight computer – sometimes its quite difficult to get the centre dot over 85 or 95 etc. as the squares are in units of 2…

I am just paranoid that I’ll take it again and exactly the same thing will happen, as I really couldn’t have studied any more, I know all the methods to create a flight plan, and how to use the inside out for all calculations. Am I missing something vital or is it just a case of being a bit more careful when drawing my chart lines and marking my CRP?

Any advice most appreciated.

Thanks.

Navigation is all about accuracy. Never use a Chinagraph on a Dalton Computer, use a 2B pencil!

I agree with the above post. DO NOT use chinagraph on the old whiz wheel, a pencil will be much better at doing the trick! Also, re-check when doing the planning stage before going onto answer the questions. As you said, if your planning is wrong/inaccurate then your answers will follow the same path! Just take your time and don't rush. I'd recommend a good 20-30 minutes planning before attempting the questions.

I'm sure your instructor will be willing to offer advice. Hope the next one is a pass! Good luck!

I found the same thing when I was practising for my nav exam.

You have hit the nail on the head in your post on the subject of why.

You're methods are apparently fine if you are coming in a couple of degrees/knots/mins out.

Your problem will instead be with your accuracy, and this can be affected by many things. The most likely are:

1) Incorrect drawing on maps (Too big a chinagraph, 2 degrees out when measuring heading, two mm out when reading distance...)

2) Incorrect reading from maps (Rounding the numbers the wrong way or by too much when reading from the map)

3) Incorrect rounding during the calculations.

As a rule of thumb, you should maintain as much accuracy as you can throughout the calculation and only round anything at the very end.

For example, if you read a distance as 25.4nm, do your calcs with 25.4nm and not 25nm.

You should find that this will help you.

4015

The nature of the PPL navigation exam is such that it is very easy to know the correct techniques and use of the computer, but to have introduced cumulative errors from track measurement, magnetic variation interpolation and other sources. Those half degree errors can soon add up to an answer just outside the correct one....particularly when using a rattly old whizz-wheel.

But always plot as accurately as you possibly can!

Multi-guess 'digital' answers are wholly inappropriate for results obtained using 'analogue' methods; personally I think that a 2 or 3 degree tolerance value should be allowable for answers in the PPL exam - if the CAA want more accurate answers then you should be allowed to use an electronic navigation computer. It's only about 40 years since they first appeared on the market, but there are still those who think that an astrolabe, quadrant staff and lodestone are essential tools for PPL navigation...

Incidentally, you ARE allowed to use an electronic calculator for arithmetical purposes only, provided that it doesn't have any 'navigation functions'.

Personaly, I use very fine non permanent OHP pens on both the laminated charts and the whizz wheel, black on the chart which can be read under white, red or blue light (one of the aircraft I rent has a blue interior night light) and blue on the whizz wheel (blue is easier to differentiate from the black lines printed on the wheel). Electrical contact cleaner cleans the chart and a damp tissue the wheel (dont leave it on the wheel too long).
This gives very accurate and legible markings which should be easy to measure to the standards required.
All the best for the re-take.
Nigel

For measuring bearings, you may do better not to draw the line. The Jeppesen folding nav plotter and the ASA CP-R plotter both have lines printed on them which you can line up with your end points. These lines will be straighter than anything you draw! The idea is you slide the line along the track till the protractor bit can be lined up with a True North line. The CP-R plotter has a grid of North lines which make this easier.

It is a very personal choice, though - choose whatever works best for you.

For the calculations, do as much as you can with a calculator, it is much more accurate than the Whizz Wheel.

And good luck!

Thanks for all the advice guys, much appreciated. Fingers crossed for the next attempt! Cheers.

I use dental floss secured to the centre hole of my protractor. Something I learned in the military to give very accurate bearings between points. Unless you can find some fine tip lumi colours, I suggest you try this. It worked when I done my exam only getting one stupid question wrong about the 1:60 rule. It is still good practice to draw the track line in but a china-graph takes up 2 degrees of width not affording ultra accuracy. The Nav exam reeks of prehistoric values and once you get your license there is much more accurate devices for flight planning. I think its high time that GPS was integrated into the syllabus and pilots taught how to use it in conjunction with a chart. Not only does it increase situational awareness it keeps your head more or less where it should be L@@king out!

You have to learn how to use that stupid circular slide rule.

The CAA exams are rigged to catch out common slide rule mistakes - even if it is just 1 degree out. The fact that not even a £40,000 autopilot can fly to 1 degree is irrelevant :)

Also make sure you have the same VFR chart which the exam assumes. The magnetic headings etc have changed over the years and a current chart will yield the wrong answers.

How are you measuring the bearing on the chart?

The way in which the lambert conformal conic chart is projected, you actually get a different bearing if you measure at A and B separately.

Make sure you measure the track half way along the line to take the average bearing to be flown.

On a Southern England half-million chart, worst case (a 50NM East-West leg), I make the convergence error about half a degree, so it could indeed tip the balance in the exam.

Yet another example of Nav exams being different from real-life Navigation!

Exactly. All you need to do is make 2 small errors, rounded the same way and you come closer to the wrong answer. In real life, unplanned diversions which are cobbled together from rough guess work and estimations work perfectly well to actually get you from A to B.

Hi
I know exactly how you feel! I failed nav first time round due to the cumulative effect of track distances. To be honest, I don't think that the exam is totally fair as you can read the distances half a mile one way or the other. It doesn't make a whole lot of difference in the real world but can spell disaster in the exam! My second attempt was much better and I passed with flying colours so to speak but even then I had problems with the track distance as again I could have read it differently rounding it up or down. I worked backwards on the calculations in the end and got the right answer but of all the exams I wouldn't want to do nav again due to that reason alone. The calcs were fine and had no problems - it was just my interpretation of the measurement despite being totally anal with it and drawing the track line with a permanent fine liner pen.
I remember feeling quite gutted as I have never failed an exam before. If it makes you feel better I went on and got 90% + for all my other exams and ended up with a 95% average pass score. Its just one of those things but next time be very methodical and re-check your answers.

A low-tech, but effective, way to measure distances accurately is to use the edge of a blank sheet of paper. Make a pencil mark at either end of the leg, then measure the distance against a nearby line of meridian (1 minute equals 1 NM).

It remains accurate even if the chart has shrunk!

Were you hitting the correct dgree of accuracy when you did practice questions? I'm just wondering (as someone who will soon be where you are) whether one can at least practice to the point of perfection and then have confidence to know that you are exam-ready.

there is also a wide variaiton in the quality of whizz wheels. The one I used was great for actual nav but had too much movement between the wheel and the outer casing, so could lead to errors. Only afterwards I saw my instructor and it was a really close fit. You will also get differences depending on whether you are using wind up or wind down method. For the CPL I think they have to use wind down method, again ask the instructor.

When revising for my nav I made up several scenarios and did them using the whizz wheel, then cross checked against a piece of software, so I could see where any mistakes were.

Where are you based? any difficulties I am near York

Good luck

Plenty of good advice on here regarding check and re-check your answers. What I will add is that as it can be your lines AND/OR your calculations, if/when you have time at the end, re-do everything to check.

I had exactly the same thing happen to me, in fact, looking at the bearings you gave, it sounds the exact same question.

I brought it up with our CFI/Examiner at the time, as I felt the tolerances were rather too close. I remember that my answers came smack bang in the middle, maybe only half a degree favouring one side or the other :{

All I can say is RELAX when you resit, and don't let it bother you too much !

If only most compass's were swung with that much accuracy :ugh:

Best of luck !

Dalton Computer
 

I have been reading this thread with some amusement as I used the IIId-6B Dalton computer as an essential tool during my RAF navigational training sixty years ago. The oldest a/c was a Wellington T10 and the concept of flying to an accuracy of half a degree would have caused a good deal of mirth. It was a device which matched, in accuracy, the aircraft and the compasses which we used at the time - the DRC, distant reading compass - was temparamental, the gyros worked on alternate Thursdays when there was an R in the month and the autopillot had a disconcerting habit of losing 1,000 feet when switched in.

The IIID was very good, I could calculate a DR ahead, new track, course, ground speed and revised ETA in about 3 minutes after getting a fix.

Michael,

And yet, despite the challenges from your era, it would seem that the RAF were capable of mounting impressive missions requiring high accuracy. Did you see the programme on TV re the task faced by the Dambusters - at night!