PPL NAV cockpit calculations

[joea]

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?

Thanks

[Pilot DAR]

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

[m.Berger]

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.

[Piper.Classique]

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.

[Gertrude the Wombat]

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?

[Gertrude the Wombat]

Nice story but you are perhaps refering to to this incident https://thewest.com.au/travel/air-aviation/investigation-launched-after-air-asia-flight-out-of-perth-turns-left-instead-of-right-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.

[Genghis the Engineer]

The one gadget I would strongly recommend is a VOR plotter - one of these...

https://www.pooleys.com/media/6203/rnp-1-2016-side1.jpg

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.

G

[POBJOY]

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.

[Crash one]

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.

[Colibri49]

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.

[Gertrude the Wombat]

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.

[Crash one]

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?

[Molemot]

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 (http://www.microlightforum.com/archive/index.php/t-3164.html)

[m.Berger]

Thanks for that. I was a little rusty and enjoyed the revision.

[TelsBoy]

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 :)

[Gertrude the Wombat]

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.

[Piltdown Man]

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.

PM

[artschool]

https://www.pooleys.com/media/4285/1973.jpg

seems useful to me

I have this one
https://images-na.ssl-images-amazon.com/images/I/81hw0F3VL4L._SL1500_.jpg

[mikehallam]

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

[old,not bold]

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.

[horizon flyer]

I use a windpotractor invented by a guy called Olof Bakker from Holland. With a 1/2 mil chart headings can be made instantly, just by laying on the track line, and flight time worked out as well. I have two of them and regard them as must have items. So easy to use only requires the wind speed of the day converted to a percentage of cruise speed in knots. The disque has percentage lines scribed on it so using a china graph the wind direction is pencilled in, then lay this point on the track line on the chart referenced to north and the crossing point on the edge of the protractor is the heading. Take the cruise speed and regard them as degrees and on the inner edge is a time in minutes so 130 knots = 6 minutes which is the time from the wind dot to the edge of the protractor, so just work along the track in these time intervals for total time. It is very clever, so simple and easy to do in flight. Why does anyone use the whizz wheel it's so ackward to use in flight. To find one google it, about £17 pounds from Holland.

[Jhieminga]

The 'Olof Bakker' protractor is now this one: https://www.pilotshop.nl/contents/en-us/p408_Wind_Protractor.html

[hugh flung_dung]

Ditch the gadgets and learn the following:

maximum drift (MD) angle = windspeed x 60/TAS. MD is calculated during initial planning and written on chart or PLOG.
turn to track, use the DI to estimate the angle between the wind and track and turn towards the wind by 1/6th of MD for every 10 degrees (use full MD if angle 60 degrees or greater)
use the DI to estimate the head/tail wind by taking 1/6th of the windspeed for every 10 degrees from the beam (use full WS if angle 60 degrees or greater). Estimate groundspeed.
you will fly a distance equal to 1/10th of your groundspeed in 6 minutes so it's easy to estimate leg time

This completes all the necessary nav calcs. In the air it takes about 30 seconds to do and needs no distracting gadgets.
There's an explanation here (https://www.lightaircraftassociation.co.uk/2010/Coaching/Mag%20Articles/Crosswind%20Calculations%20made%20Easy.pdf)of how to use the DI to estimate proportions.

To correct to track use either of these techniques to get you back close to track:

estimate the error angle, turn towards track by double the error and fly for the same time it took to get to the point where you started the correction.
Before flight calculate a Standard Closing Angle for your intended TAS: SCA= 3600/TAS. In flight, if you are off track by y miles then simply turn toards track by your SCA and fly for y minutes.

Now decide why you were off track and act accordingly.

These techniques really are very simple once they're in your head, but they sound complicated when reading from the page. They work.

HFD

[jan99]

I would like to second the Olof Bakker windprotractor recommendation.
Having preferred doing the approximations in my head I was sceptical but ended up using it for the practical exam. Simple, quick and with little chance of confusion. That was more than 10 years ago (ofcourse I don't know where I have it now).

[rarelyathome]

HFD.

Good advice. Only comment is that, strictly speaking, SCA should be 60/GS in miles/min (which makes the mental arithmetic easier) or 3600/GS. Either way, it is the GS that you should divide by not the TAS. In reality, using the TAS won’t be far off most of the time. So for most training aircraft, estimate distance off track and turn L or R 40 deg and fly for number of minutes you are miles off track (as you say).

Use HFD’s method - it really is easy and far better than getting distracted with gizmos.

[TelsBoy]

HFD's method is exactly as I was taught and what I still use to this day.

[hugh flung_dung]

Rarely...: you're correct, but I learned to do this before GPS could give you a groundspeed. Given all the other vagaries and inaccuracies TAS is "good enough".

HFD

[old,not bold]

I agree re HFD's rule. But I think I put it more simply. It's just the 1:60 rule at work.............let's not overdo making it more complicated.

[Gertrude the Wombat]

If people really want to use "1 in 60" rules and suchlike they might, or might not (I might just be peculiar), want to remember where it comes from, which is simply that
sin x = x
to a reasonable approximation (ie as accurately as makes any difference to your flying) for small enough x. Where x is in radians of course, and one radian is roughly 60 degrees, so there you are.

[hugh flung_dung]

Gertrude: unfortunately even basic trig frightens-off quite a few studes so, at the PPL level, I think it's best just to get people using the practical guidance. Those who want to derive the MD and SCA stuff for themselves will do so.

Old,not ...: in my groundschool sessions I have to teach the 1:60 stuff so people can pass the exam, but I hope nobody starts doing the calcs in the air to work out a closing angle. It's far better to avoid awkward sums and use the MDR stuff I described earlier for diversions, or even (heresy!) for all nav calcs, and to use SCA to get back close to the pre-planned track ASAP.
The link I gave earlier shows a simple visual way of using the DI (or any compass rose) to estimate proportions of MD and GS on any heading.

As an aside, the closing angle technique used to be widely taught, but this gets you to fly down a direct line to destination from your off-track position. This new line is one that you haven't planned or checked and may contain dragons, or worse. Clearly, the double track error technique only works to the half way point in its simplest form, using it beyond the half way point requires you to have a sensible serious of "opportunity" fixes noted on your chart so you can use double track error on part of the segment.
SCA is simple and works almost anywhere. The only time it's worth fiddling with it is at speeds of less than about 100kt, when it's better to use half the SCA for twice the time.

HFD

[old,not bold]

HFD I bow to your greater knowledge.

I should shut up, really; this is a person who, on 3 consecutive days a long time ago, landed at Le Touquet in the dark (SRA) with 90 hours and no Night Rating having set off from LGW much later than planned, followed that on the next day by landing at Orange military (very pretty red flares) instead of Orange civil which had just cleared me to land (there was an active thunderstorm over both) and then to complete the hat-trick on the next day crossing the threshold at Fuimicino in the belief that it was Ciampino, and then - realising my mistake - flying to Ciampino at about 500 ft AGL for 15 NM/10 minutes to turn onto final and land.

I seem to remember using the "double the error" correction a lot; I had a pretty little circular protractor with two arms which enabled a better estimate of track error than the eyeball. But on a 1:500,000 map in a slow aircraft, both of which I used all the way to Sharjah, you had to give it a bit of time to get a good position fix.

One of the most useful tips I used was to always draw the planned route on the map, and then mark off every 10-miles, with the total miles from departure shown. Provided you flew the planned course, this, plus the clock, provided an immediate position +/- a mile or two, and a check against gross error. (I did try doing it in minutes, but the wind usually made that unreliable.) Of course GPS has made all that stuff history, until it stops working. And I haven't seen a GPS that will tell you what heading to fly to get back on track and counter the drift. But I bet someone will tell me there is one.

[hugh flung_dung]

Old,not ...: I think we're in sync, I just didn't want people to get the idea that MDR was complicated, or that nasty sums were needed, or that they need to understand the 1:60 stuff to use MDR.

I prefer 6 minute marks (rather than distance marks) because the distance is just 1/10th of groundspeed and it's easy to look at the clock and then straight to the approximate position on the line. Of course, in reality they don't turn out to be 6 minute intervals but after the first couple you know they are 5'30", or whatever, and that's just as good. It's even reasonable to mark them at 1/10th of TAS and then to modify based on observed intervals with actual head/tailwind - but I wouldn't expect a pre-PPL stude to be able to do that.

(SE to Sharjah means you must be fairly bold, despite your tag ;-) )


OP: nav is an attitude of mind. Learn 1:60 to pass the exam, learn to visualise how things will look from the air so you can see them, and then use the simple MDR techniques for practical Nav. Do not buy gadgets. Use GPS as an aid and not as a master. Always do a gross error check after setting heading. Lookout!

Here endeth the sermon ;-)
HFD

[old,not bold]

SE to Sharjah means you must be fairly bold,No, just young and very foolish at the time ("I've got 90 hours, what can possibly go wrong"), not least because it was a £700.00 Percival Prentice with an almost time-expired Gypsy Queen, a wartime 4-channel crystal-controlled VHF and a dodgy VOR bought for £25.00. My uncle Bob, who distinguished himself writing off one of the 3 Vickers Windsor prototypes in 1944, said it was the most stupid thing he had ever heard of.

[hugh flung_dung]

Excellent! I'm envious of what must have been a fun trip.

I did my fair share of dumb things, but it always strikes me as odd that the older we get the more risk averse we become, despite there being less lifetime ahead of us to loose if it all goes proverbials up. The (over) confidence of youth, I suppose.

HFD

[old,not bold]

must have been a fun tripIndeed it was, with its moments, of course; discovering that in a Prentice the magnetos would short out in cloud with the moisture, as they did over the Italian hills in an ill-advised attempt to get to VFR on top without knowing where the top might be (the duty God was kind that day); later on an engine fire climbing away from Baghdad due to a missing exhaust gasket, leading to the discovery that although a firewire was fitted, it didn't work. There was no extinguisher in any case and never had been.

Flying from Damascus to Baghdad was a navigational challenge which I failed. 'Fly in controlled airspace or be shot down' was an incentive, but without an ADF and an absolutely featureless desert following the oil pipelines was the only way, reporting the NDBs visually, while pretending to be IFR-equipped and licensed. They tended be be sited at pumping stations, so the airway (base 8,000 ft, pretty much the aircraft's ceiling on a hot day) followed the pipelines. That worked until halfway when the dust haze removed any sight of the ground. Dead reckoning is easy crossing the Channel at 5Kts in my boat, less so in a Prentice when you have no reliable wind information, and I wandered inexorably off track, until I passed over a lake that I could recognise, about 50 Nm SW of Baghdad, with the fuel getting very low. By that time Baghdad was calling me, but I kept stumm until I could call "airfield in sight" as I didn't want to have to explain where I was. (When I reported in to ATC, I muttered about unexpected headwinds making me late, and then they gave me a carefully plotted radar map of exactly where I'd been since crossing the border, and we all had a jolly good laugh, as we did next day after I had left the aircraft, smoking gently, in the middle of the runway waiting for a firetruck and tow, just in their busy period.)