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PPL NAV cockpit calculations

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PPL NAV cockpit calculations

Old 8th Apr 2018, 16:10
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PPL NAV cockpit calculations

Hi all

I've completed a couple NAVs as part of my PPL training. One went really well. I went off track and made an error correction and also completed a diversion. The conditions were perfect.
The other NAV didn't go so well, there was a lowering cloud base, lots of radio work plus a diversion. I made a mistake in my diversion calculations and didn't get the right heading because I was under a lot of pressure.
A friend showed me a ruler they acquired called the blind spot ruler it looks like it would help an awful lot with in-air calculations, especially with diversions. It has a flying time table, double protractor, ground speed calculation etc. I feel like it could make some of the tasks in the cockpit easier. I've not asked my instructors yet but would using something like this be acceptable to use in PPL training and examination?

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Old 8th Apr 2018, 17:42
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Welcome to PPRuNe Joea,

Though gadgets look attractive, I have found during my VFR GA flying career that simpler is better. I gave up on gadgets, and just focused more of my attention on forming a mental image for situational awareness. If you can remain situationally aware in the big picture, things like diversions are not such a big deal. You can sort of guess the heading and distance based on your continuing awareness, and then your calculation at the time of diversion more becomes a confirmation of the awareness you were maintaining anyway.

I hope than helps. Others will be along with their varying opinions shortly, Pilot DAR
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Old 8th Apr 2018, 20:03
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Yes. That is right. Visualise the sky as a dark room. Your room. The torch is on the mantlepiece but somebody put a new table in there so you will have to alter course to get to it. You will, without difficulty because you know where you are and where you intend to end up. Flying is much the same. A process of continuous approximation that gets more exact with practice.
Get within ten degrees and you are going in about the right direction.
Calculate your route to fourteen decimal places and by the time you have worked it out, you'll be lost.

Navigation is easy if you follow one golden rule. It sounds like a wind-up but if you pay attention, it becomes second nature very quickly:

Always know where you are.
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Old 8th Apr 2018, 20:37
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Yes, all good advice. Two more things to consider. Sometimes navigation is about knowing where you are not... Not in controlled airspace without permission, not about to fly into a lowering cloud base, not about to hit a mast or pointy hill.

Second point. On a diversion, if there is a unique unmistakable feature to follow, that goes to where you want to be, then use it.

Sorry, one more point. Don't rush. As long as you have fuel and daylight you are good. You can get a rough fix on a vor, at least along a line, even if you can't plot two VORs to any degree of precision. You can even fly to the beacon (or big unmistakable town, island, airfield, whatever as long as it is a positive fix ) and then start from a known position.

Know how to use the equipment in the aircraft. It cost someone a lot of money. You are paying to hire it, so may as well make use of it. That includes the radio. If you are really not sure about nearby airspace or obstacles then get help early, before you bust the Heathrow control zone.

If you are lost, you won't be the first or even near it. If you can't get unlost by yourself, admit it. It's not easy psychologically, but it's much easier than explaining to the man from the CAA how you ended up overhead Paris when you meant to go to Le Touquet.
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Old 8th Apr 2018, 21:21
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I also wouldn't go for any extra gadgets - just make more work, more to learn, more drop on the floor of the aircraft (and jam the control runs and kill everyone), more scope for error.

Don't forget the gross error check after turning onto a new heading - does it make sense, and does it all look right?

There was a post here within living memory of an airline first officer who'd done all the calculations for a flight from Oz to somewhere civilised, but didn't think about what the numbers he'd calculated actually meant, and was about to head off on the calculated heading when the captain asked him to think about it in relation to the map, and then to say whether he really thought that heading in the direction of the south pole, however carefully calculated, would actually get them to Singapore?
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Old 8th Apr 2018, 23:03
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Originally Posted by Council Van View Post
Nice story but you are perhaps refering to to this incident https://thewest.com.au/travel/air-av...-ng-b88678220z
I don't think so, I think it was just an anecdote on PPRuNe, I don't think it went as far as being a reportable incident, and I don't know how many decades ago it happened. My recollection is that the captain didn't actually let the FO steer the course he was proposing.
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Old 8th Apr 2018, 23:41
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The one gadget I would strongly recommend is a VOR plotter - one of these...

Or a close relative - simply because it's a nice compact ruler / protractor that's hard to break and lives easily on your kneeboard, whilst if you really have to, is useable one-handed.

The basic principle of nav, particularly on diversions, are not to try and do anything too fast or too clever. If you need to divert, carry on en-route to somewhere known a few minutes ahead, or fly to a visible town a similar distance, or follow a line feature in a safe and vaguely appropriate direction. And plan not from where you are now, but from where you will be in a few minutes.

That means you can take your time, get it right, and not get stressed or confused about the whole thing. There are absolutely no prizes in PPL flying for handling anything except circuits and emergencies quickly - the rest you can take your time, burn a little more fuel, and then get it right.

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Old 8th Apr 2018, 23:55
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JO There are some items that 'have' to be complied with as part of your CAA approved training. Your instructor has to follow this system which will include how you are supposed to navigate. In practice there is very little scope to use 'gadgets' in a solo flown exercise as your time should be spent flying the aircraft, looking out, and monitoring the engines health. To that end Nav MUST BE KEPT SIMPLE and indeed I suggest that in these days of cluttered airspace, choke points, and expanding 'controlled' airspace, the simpler the better.
To that end I suggest choice of route can be looked at to avoid potential problems and remember 'Radio Work' does not really decrease workload so that may be a consideration when route planning. Also ensure your basic kit is serviceable compass/DI**, and ALWAYS do a double check when you line up on the departing runway. If you have some latitude in choice of turning points do so with the mind set of 'will it show up well in haze' or are there some good 'pointers' before I get there. Remember this is not a competition to make flying difficult it should be a PRACTICAL way of going somewhere, and being confident in knowing where you are all of the time. As you gain experience this will get easier, but the modern PPL course has got more demanding as regulations change so give yourself 'an edge' and adopt a system that works for you and delivers the results.
** If you fly multiple club machines the equipment will differ in each one, so ensure you are using the correct deviation information, and check that the DI is not wandering, and keep it set as required.
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Old 9th Apr 2018, 01:04
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If I spread my fingers out as wide as possible they are approx 15 deg apart. Thumb length is 10nm to the knuckle.
Heading north once in severe turbulence, my pax had a GPS of sorts, just Lat and long plus ground speed of 54knots, airspeed 90, no magenta line stuff. We were getting low on fuel so I estimated a right turn onto 060 ish deg heading for Eshott, just by fingers on the chart and thumb lengths.
Ignored the wind correction (290/40)
Although I expected to be pushed south of track.
Ten mins later Eshott appeared on my ten o'clock pretty much where I was looking for it.
Prob wouldn't suit the training system but we were never lost and found the destination with no problems.
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Old 9th Apr 2018, 11:59
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Beware the "Go Direct" button on many GPS navigation boxes, such as the older Garmins. This button sometimes is marked with the letter 'D' and has a horizontal arrow through it. I understand that you probably aren't allowed to use the GPS while doing navigation training, but my caution is for after you've qualified and want to lighten the navigation load by using modern technology in addition to map, compass and stopwatch.

The temptation when temporarily uncertain of position (lost) as can happen to even the most experienced, is to decide on going straight to the nearest waypoint/airfield which you believe to be in your vicinity and to press the "Go Direct" button, which will give you a straight line course to that point.

The trouble with that is that the straight line could be taking you into controlled airspace or a danger area, which your originally planned track would have avoided. I'm not in any way suggesting that you shouldn't be using this facility when necessary but as others have suggested, getting help on the radio is always a good idea in such situations.

Last edited by Colibri49; 9th Apr 2018 at 12:11.
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Old 9th Apr 2018, 12:13
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Originally Posted by Genghis the Engineer View Post
that's hard to break
Not that hard - I've broken every one that I've had.

I use it for planning, but have only every used it in the cockpit on the IR(R) exam. When the examiner as trying to get me to fiddle with it so much that I lost track of the aircraft's attitude.
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Old 9th Apr 2018, 13:08
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Originally Posted by Gertrude the Wombat View Post
Not that hard - I've broken every one that I've had.

I use it for planning, but have only every used it in the cockpit on the IR(R) exam. When the examiner as trying to get me to fiddle with it so much that I lost track of the aircraft's attitude.
Did you pass the exam or did the examiner fail you for losing the aircraft by fiddling with it too much?
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Old 9th Apr 2018, 16:17
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Allow me to recommend Mental Dead Reckoning and the Clock Code, as taught by the RAF. It's very useful for diversions, in flight corrections and checking that the numbers coming out of the WhizzWheel make sense. A good explanation can be found in the microlight world... Navigation question [Archive] - Microlight Forum
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Old 9th Apr 2018, 17:37
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Thanks for that. I was a little rusty and enjoyed the revision.
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Old 9th Apr 2018, 19:31
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We've all done it - fairly innocuous errors to catastrophic Nav faux pas. The only solution is simply practice and learning from experience so keep it up!

I'd echo the "keep it simple" philosophy. I've had many gadgets recommended to me over the years and seen pilots with gigantic flying bags crammed full of all-sorts. All these do is drain the flying fund, annoy the missus with "What on earth are you spending money on for your flying now?", increase your take-off weight and make things more complex. When it comes down to it DR and UnP Diversions are a bit of fairly simple arithmetic. No calculators or fancy apparantus needed.

Nowadays my flying bag consists of one of those little headset cases carrying my headset, kneeboard, checklist and chart. That's all. I like it that way
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Old 9th Apr 2018, 20:42
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Originally Posted by Crash one View Post
Did you pass the exam or did the examiner fail you for losing the aircraft by fiddling with it too much?
Without a word being said, it was clear to both of us that he'd made his point, and that I'd recognised it and done something about it, so it was a pass.
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Old 9th Apr 2018, 22:00
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I'm with the "less is more" brigade. Less gadgets allow you to focus on the basics. Simple maths, simple measurements and angles guessed by eye. For trigonometry use .5, .7 and .9. All of this is good enough for PPL and the majority of commercial flying. When kilos and seconds count in the air, something went wrong hours beforehand.

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Old 9th Apr 2018, 22:13
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seems useful to me

I have this one
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Old 9th Apr 2018, 22:37
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Fancy & pretty rulers etc. when needed in a hurry are probably on the seat in your bag, or dropped on the floor !

Moreover they need knowing well enough where to look for one's 'easy' answers. The one above has several speeds to suit many a/c, but in one's usual mount each 1/2 mill. chart inch is 8 nm. Thus at 80 kt takes 6 minutes.
Double speed e.g and 3 min's. So half way between 120 kt = 4 1/2 minutes.

TBH in my a/c I simply multiply miles distance to go X 7 which suits its pedestrian 80 and a bit speed.

Same idea for simplifying direction adjustments corrections, as several before me have recommended, and the '1 in 60 rule' is quite accurate really.

Measuring off the chart, one inch in my case is a thumb width,
Now you can't easily drop that on the floor !

Ground speed/drift etc. is naturally a component, but if not a hooley blowing, map reading and small course corrections works: as does marking the chart where you know you really are at every useful ground feature or each 5 minutes as you wish - then with a good eye & if temporarily uncertain of position, your time and heading since last fix is pretty useful.

mike hallam
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Old 10th Apr 2018, 00:47
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The most useful rule that I was ever taught is the 1:60 rule; it got me from Gatwick to Sharjah VFR more or less following a line on a 1:500,000 map marked off at 10-mile intervals, and a dodgy VOR, in an aircraft that cruised at 90 Kts for 300 miles between refuellings.
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