help needed with Nav!!

[fudgy2000]

Hi,

Im having a few problems with navigation (for PPL). My instructor has told me to divide my track into 4 segments- My departure point- check point a, check point b and then my arrival point. All at equal distances.

If I'm 4 degrees off at checkpoint "a", i double this, so its 8 degrees and turn back on track by this amount. I then hold this for the time it took me to travel from my departure point to checkpoint a. When ive regained track, I then adjust it by 4 degrees in order to hold it!! I also use fan lines to assess my drift, although my FI tells me just to estimate

Is this the correct method im being taught??

thanks

[Tinstaafl]

It's one of many correct methods. 'Cats' & 'skinning' applies. He's using one variant of 'proportional track correction'. Why would you think it's isn't correct?


If you're interested - or just don't seem to 'click' with this variant - you could ask him to show you alternatives eg a different proportion (half &/or quarter way), 1 in 60, standard closing angle etc

[BEagle]

fudgy2000, your misfortune in being taught an outdated and stupidly complicated system of navigation - probably by a dinosaur? Tell him you want to use the Standard Closing Angle technique - it is vastly easier!

[fudgy2000]

you are right Beagle. I just wanted to be sure this was the correct method- or one of them. Ive read about the standard closing angle- i think it sounds complex. i'm probably wrong.

I think this method hes taught me is simple. i think?

[Send Clowns]

This is very personal! Different people like different methods, you may like this onw even though BEagle doesn't. I am a navigation instructor (ATPL groundschool) as well as a flight instructor, so can describe a dozen slight variations on pilot navigation.

I use the 1:60 rule myself (military technique, very flexible), but generally teach a method similar to the one you have been shown for my students, except on a leg less than about 20 minutes long I will rarely use more than 1 check feature. I always start by teaching the "double track error" method for regaining, as you have been taught. However with most students (at least those whose navigation teaching I start, rather than inherited students) I try to avoid even track splits, where the check is exactly half or a third of the way along, and instead choose indentifiable features at about half or 1/3 of the way along. For estimating angle off track by your method I suggest marking a line (in a different, pale colour so as not to obscure the chart) at 10 degrees off track on one side.

[BEagle]

His method is archaic, complex, inflexible and hardly simple.

The Standard Closing Angle method is simple, flexible and requires no complicated mental arithmetic.

Your choice - ask him to explain the Standard Closing Angle technique to you. If he's ever heard of it, that is.

[fudgy2000]

Send Clowns,

If you leave your checkpoint till halfway point, when you come to double your error, it will bring you, so that you resume your track at your arrivial point. Is this ok??

[2604]

Let's not forget that a pilot and further more a student pilot cannot do calculations in flight. 2+2 suddenly becomes 5 or even nothing at all. So I would keep it very simple and forget about the numbers. There's enough to concentrate on when you have 2000 hours let alone 20 hours.

An good instructor should be able to adapt his teaching method to the student.

[stillin1]

Standard closing angle is the simplest and most flexible.
By the way, it is also the technique taught as the preference to military (RAF) students these days (most of the others are offered as options too). Investigate wot works for you!
KISS:cool:

[homeguard]

Closing angle as Beagle refers has rules of thumb that may be applied effectively without the need of inverse fraction mental arithmetic calculations as sometimes taught.

However, regain track is my prefered method for students and myself. Don't understand how 'fashion' comes into it.

Send Clowns makes a point which I agree with. Nothing to gain by halfway, quarter way pinpoints or military time marks if there isn't a suitable number of distinctive features to ensure that is in fact where you are. I teach that the pinpoint must be abeam a distinctive group of features (preferably 3) whether or not it is halfway or whatever. It is easy enough to premark the point at which you will regain your track, following in flight track error correction using the double error rule to achieve the Isosceles triangle drawn ( ten degree fan lines abeam the pinpoint with a small cross where track will be regained) during the pre-flight planning stage.

[fudgy2000]

hiya, ive just read all about the SCA method. It looks really good!!! A few questions, how can I tell how many miles off track I am?? By just looking out of the window of my PA28?? Also when should I regain my track using this method. Would I wait until halfway or before?? Whens a good time??

[stillin1]

Fuggy2K
yer not really thinking this through mate!
you know you are off track cos you have "fixed" not on track. Doh!

Measure the distance you are off track from the map scale!!! Doh!

Now regain track. If you wait - you will be further off track and therefore all the How long to regain track sums will be bollox.

using SCA the only real choice you need to make is how soon down track do you want to rejoin the planned route. Realistically - take a look at the map and make life easy - plan to rejoin at / just before a good "fix". Something of as unique-a-feature-as-possible, on or very near to track.

KISS :cool:

[fudgy2000]

I see!!

how would the ETA be affected?

Would I need to make anymore corrections to my heading later- i.e. something has occured to blow me off course to start with. How would I resolve this??

Would I still have a halfway mark for purposes of ETA calculation??




Sorry for asking so many questions!!

[BEagle]

Herewith my idiots' guide to the SCA method:

Most PPL text books give students a number of suggestions concerning methods of visual navigation. All these are based on the well-proven ‘1 in 60’ method which is a technique for calculating correction angles using estimates of off-track distance errors. Equally, it is also possible to make track corrections based upon estimates of angular track errors, a technique which is still quite popular.

However, most of these methods suffer from the drawbacks of either requiring relatively difficult mental arithmetic or correcting not back to the planned track with its associated pre-planned visual fixes, but direct to the next planned turning point. Recent advice from senior ex-CAA Examiners suggests that a rigorous navigation technique is required which instead does allow pilots to correct back onto their pre-planned track. Traditional techniques have not provided pilots with a simple method for achieving this; however a method originated in the RAF is available which makes track correction from observed off-track distances extremely straightforward.

Those of you whose eyes glaze over at the thought of trigonometry can skip thes paragraph as far as the bold portion if you like, but for the rest of you it works like this: If you realise that you are a miles off track and wish to fly b miles back on to track, then you need to turn through an angle φ whose sine is equal to a/b. Now the 1 in 60 rule tells us that φ is more or less equal to (a/b)x60 and if you fly your distance b at v miles per minute for t minutes, then φ = (60/v)x(a/t). If a and t are made numerically the same, that is you fly for the same number of minutes as your number of miles off track, then a = t and a Standard Closing Angle φ of (60/v) can be used where v is expressed in miles per minute. Hence the SCA at 360 kts is 10°, at 120 kts it is 30° and at 90 kts the SCA is 40°.

This method is really only completely accurate when TAS equals GS; it was originally used for navigation in fast aircraft at low level where the difference between these two values is not significant. The error will be greater at lower speeds, but is quite acceptable as the SCA technique assists pilots in reducing track error to a point from which readily identifiable pre-planned visual fixes can be observed and overflown. Similarly, timing errors will be introduced with a large SCA as the aircraft’s along track velocity (more trigonometry, sorry!) is v cos φ rather than v. This can be overcome either by reducing the SCA and increasing the correction time correspondingly, or by making an appropriate timing correction. In practice it is better to return to track as soon as possible, but only if a simple method for correcting the timing error can also be achieved.

Considering the PA28 with a 90 kt cruising speed, things now become quite simple. The SCA is 40° and cos 40° is 0.766 which is as near as makes no odds 3/4, so what should have taken 3 minutes on track will now take 4 minutes on a 40° SCA, i.e. 1/3 longer. These values will later be used in summarising the SCA method for use by PPL students cruising at 90 kts. (In a Warrior at 105 kts, theoretically the SCA is 34° and the corresponding ETA delay is 1/4 the track correction time, but for all intents and purposes it’s easier just to stick to the same 40° and 1/3 as for the Cherokee).

It is also necessary to examine why the aircraft was off-track in the first place. Assuming that pre-flight planning was correctly completed, several factors could have caused the aircraft to be off-track. For example, was the DI correctly set against the compass and was the slip ball properly centred? Did the pilot fly the aircraft accurately on the planned heading? If the answer to all those questions is yes, then the only possible cause of the error (barring ATC or divine intervention) must be that the wind velocity was other than the forecast value – a not unknown phenomenon! Having regained track, due correction can also be made for the change in drift which can readily be deduced by reference to a drift line drawn on the map. Because, if the pilot flew the aircraft accurately and yet discovered a track angle error of ψ°, then when back on track and with the DI re-aligned, the heading may be altered by the same angle ψ to correct for drift. In the correct direction, of course!

To assist in making these estimates, consider now the subject of map preparation. The start point and turning points should be marked with a circle and the track between drawn in. Timing marks every 6 minutes may be added as must the exact elapsed time at readily identifiable visual fixes roughly corresponding to easy fractions of the way along the leg (to make proportional timing correction reasonably straightforward) and at the turning point. A single 10° fan line from the start point for each leg should be drawn, to allow assessment and correction of drift error as described above. Finally the heading (not track) for each leg should be written on the map and a note made of the W/V at the level being flown together with the associated max drift value, as well as the safety altitude. Estimating distance from the CAA ½ million chart is straightforward enough by reference to the known dimensions of ATZs, MATZs and, of course, the latitude marks.

Using the SCA technique is very straightforward. Let us imagine that we have been accurately flying the first leg of our navigation exercise at 90 kts on a heading of 040° when we notice that we are 4 miles left of track with some 7° of drift error as deduced from our single 10° fan line. The first correction is to turn right onto a heading of 080° and then to time for 4 minutes as we head back towards track. During this 4 minutes we can first reassess that it really was a 4 mile error and then jot down on the log that our ETA at the turning point will be 4/3 of a minute later than calculated and that there’ll be a 7° drift correction to apply when we’re back on track. When our 4 minutes are up, we turn back onto our original heading plus our drift correction, i.e. on to 047° in this example and recheck that the DI is properly aligned with the magnetic compass. With any luck and assuming that the wind doesn’t change yet again, our navigation exercise should now continue pretty well on track and we should only need to note the passing of visual fix points to revise the ETA at the turning point.

Although SCA has its sceptics, it is a very simple and easy way for pilots to correct navigation errors and to regain their pre-planned track and it’s the method I require to be taught to all new students. But none of this is going to be much use if a pilot hasn’t planned accurately in the first place, flown accurately or thought ahead!

BEags

[fudgy2000]

Many many thanks for opening my eyes to this method Beagle!!!

I did speak to one chap who did his CPL, he told me that on his CPL skill test the examiner wanted him to regain his track at the destination point. Is there any truth in this??

[stillin1]

Re your CPL dude Q - who knows, I wasn't there!

Daft idea though. Would you drive to point B using all the wrong roads just cos you had been forced off route by a little diversion?

Why be off track & therefore off of all you have planned. get back on the plan and fly it - things will then happen as planned and you will be a happy chappy.
KISS:cool:

[BEagle]

There is no such formal requirement. From Standards Document 3 Version 6 (Guide to the CPL Skill Test):

3.6.5 The En-Route Procedures (Section 3)

Section 3 is usually flown after Departure to ensure an efficient flow to the flight. During this section of the flight the aeroplane is assumed to be on a passenger carrying operation under Visual Flight Rules. When the aeroplane has achieved cruising altitude, normal cruising speed and is on heading for the first destination, the applicant should confirm to the Examiner the heading, altitude, and ETA, thereafter advising any changes. For example, "2 minutes late at my halfway point - the revised ETA is now. . ." Corrections to heading or ETA shall be calculated rather than based on track crawling, impulse or inspiration. The applicant is expected to navigate by visual positioning in a practical way, not to feature crawl. Numerous heading or altitude changes that are the result of poor flying may constitute a fail in this section. The applicant is expected to make changes to his heading and ETA in order to correct deviations from his plan. Radio navigation aids may not be used during the first leg of the en-route section although they may be tuned and identified in anticipation of their use later in the flight.

3.6.6 At or before the first destination the applicant will be instructed to carry out a diversion to an alternative destination or airfield. This is not an emergency procedure. A prominent alternative destination or airfield will be pinpointed on the applicant’s chart. The applicant may be asked to commence the diversion at or before the original destination. The applicant should nominate his heading, altitude and ETA for the diversion and again use recognised techniques and visual positioning to navigate to the second destination.

3.6.7 During the diversion leg the applicant may supplement visual navigation techniques with the use of VDF, VOR, NDB, DME and/or GPS information. Only GPS raw data (latitude and longitude or range and bearing from a waypoint) may be used. GPS map displays or “GOTO” facilities will not be permitted. The examiner will deny the use of any aid that would allow the applicant to track directly to the diversion destination. If navigation aids are used, the applicant will be assessed on their correct use.

3.6.8 Demonstration of radio aid tracking in VMC will be required at some stage; the Examiner will decide when to ask for this exercise to ensure efficient use of time and airspace. He will nominate the facility to be used and the track to be intercepted and maintained. As this item requires the demonstration of satisfactory skill in heading selection and drift assessment, it must be completed using an RMI, RBI, HSI or CDI display. This is a visual flying exercise using radio aids to assist navigation.

[homeguard]

NO!

The examiner must take no part in the candidates planning. Each candidate - whoever the examiner is and whatever the examiners personal thoughts are - must be left free to plan their own flight but using only a recognised technique. The Examiner may wish to question the candidate on the particular technique to be used, prior to the flight. The candidate is then assessed on the performance that they achieved in accordance with their own chosen navigation technique. 'Track crawling' for example is unacceptable.

[Tinstaafl]

If you can count to 4 (or 5) & can measure a distance on a chart then you can do 1:60 very quickly & easily. To get the track error, for each n.m. off track:

if your distance run = 60nm -ish then multiply dist. off x 1 eg run 65 nm & 3 nm off track then track error = 3 deg

if dist run = 30 or so nm then dist. off x 2 eg 35 nm run & 3nm off track then T.E. = 6 deg ie 2 x 3

if dist run = 20-ish then dist off x 3. eg 22 nm run, 3 nm off, T.E. = 9 deg.

if dist run = 15 then dist off x 4.

if dist run ~45 then dist off x 1.5 ie add half the dist off to itself eg 48 nm run & 6 nm off track then T.E. = 6 + (half of 6) = 9 deg.

If you adjust hdg by the amount worked out above you'll parallel track - not always a bad thing.

If you want to close track at some point you can either double the T.E. worked out above and then you'll close track in the same time & same distance as it took to get off track, or pick a point ahead where you'd like to close track & do another 1:60. This time use the dist to go to get to that point on track instead of the distance run.

I prefer 1:60 for its no-brainer simplicity (ie remember 1 to 4 and multiply) and its flexibility to parallel or close track.

[bookworm]

I'm struggling to see why this SCA method is simpler than what fudgy has been taught.

It seems as though the pilot must fix her position and then use two numbers: the number of miles off track, and the number of degrees off track (drift error). She then applies the SCA for the number miles off track, and the drift error correction for the number of degrees off track. Once back on track, she applies just the drift error correction to maintain track. Two angles, one distance, one time. That feels like a lot of numbers to mix up.

By contrast, fudgy's instructor's method involves evaluating the number of degrees off track at a given elapsed time. She doubles it and turn back that amount towards track for the same elapsed time. Once back on track, she applies just the single drift error correction to maintain track. One angle, one time. It's also likely to be a great deal more operationally expedient, as the drift error will usually result in a much smaller closing angle than 40 degrees. For the same reason it's less susceptible to gross errors if the pilot gets distracted while closing the track.

Each one to his goat, I guess. :)

[BEagle]

Tinstaafl - you have just demonstrated what a total crock of $hit the 1:60 rule is for simple PPL VFR navigation. Something which most of the world accepted over 30 years ago.

The only trouble with the SCA method is that ageing dinosaurs can't believe that navigation can be so simple!

bookworm - now read my earlier post more carefully. After getting back on palnned track, apply only the observed drift error. No need to do both at the same time.

The 'not invented here' syndrome infests many of the gold bars on pullovers schools...

[bookworm]

BEagle

Whether you apply SCA and drift error or just SCA, the number of numbers to be dealt with remain the same.

FWIW, your geometry only works if you apply the drift error while getting back on track. It matters less only because the correction is so coarse for larger SCAs that continuing to drift happens for such a short time. If you envisage a 360 kt scenario with a 10 degree SCA and a 10 degree drift angle, applying only the SCA will simply parallel the desired track.

[DFC]

BEagle,

Having put nice 6 minute time marks on your chart, and having discovered in flight that the met officer gave you the wrong wind would you not agree that the marks you made are useless clutter for the average PA28 pilot since they were made with the wrong wind?

Personally I favour fixed positions based on recognisable features. You can mark your map once and use it on a thousand flights with different winds. It is also how airways are navigated using reporting points.

The RAF like SCA because in a fast jet it works well as you said. They also favour fixed time marks because they are very interested in achieving a TOT and they have the ability to increase or reduce speed as necessary to stay on time.

Instructors who use SCA or double the error agree on one thing, getting back onto the planned track is important. Thus both are in general achieving the important point of the exercise. As long as we don't have pilots 5nm off track correcting direct to destination then we overall agree.

I believe that correction should be made using the appropriate method within the first 15 minutes maximum.....about 10nm out in a PA28. That takes care of tracking. A Fix close to the quarter of halfway mark will sort out timing.

Remember that a PA28 pilot navigates far better than any fast jet pilot to achieve the same accuracy!

Regards,

DFC

[that chinese fella]

why is track crawling so derided in lower level Day VFR flying? If my track line passes over or alongside prominent features why wouldnt I point the aircraft toward said feature, draw an imaginary line over the ground to the feature and follow it, as you approach it look for the next etc. etc.

You wouldnt need worry about poor or no available forecast, 1-in-60's, whizz wheels et al.

Of course, time checks and cross reference to compass and usual airmanship points apply.

Just a query.

[BEagle]

Actually, I wrote:

Timing marks every 6 minutes may be added as must the exact elapsed time at readily identifiable visual fixes roughly corresponding to easy fractions of the way along the leg (to make proportional timing correction reasonably straightforward) and at the turning point.

which means put 6 minute marks on if you wish (I don't bother), but do put times against readily identifiable visual fixes. You don't need many of these (one about every 10-15 mins should suffice), but choose them at some simple fraction of the leg length - i.e. a nice obvious fix at 30% of the way along the route can be treated as 'about 1/3 way along track' for timing correction, whereas an exact point in the middle of nowhere at exactly 50% of the leg is pointless.

Also, for the terminally dim who still seem unable to read, once you've established where you are to make the 'miles off track' estimate, you turn back to track for the appropriate time. In the time you are chugging back towards track, double check the distance and jot down the timing correction. No need to add it up there and then, do that later. When you're back on track, then and only then check that the DI agrees with the compass, that the ball is centred and ask yourself whether your flying had been nice and accurate thus far. If the answer to any of those questions was 'no', don't bother changing your heading from the original once you're back on track - blame yourself. But if the answer was 'yes', then the wind must have been the culprit, so use your single drift line assessment to correct by the same amount. No silly reciprocal-of-the-fraction-flown-multiplied-by-the-drift-angle to do in your head - just a single figure to add or subtract. If it's more than 10 deg, the weather-guesser must have been telling porkies!

Why is track-crawling frowned upon? One reason is that you spend too long staring at the ground and not looking out around you for other aircraft!!

[homeguard]

chines fella

track crawling is not derided but it is not 'Navigation'. Forecast winds are just that, forecast. It is important for the pilot to discover the actual w/v at the chosen flight altitude. Track crawling dosn't allow you to do that and wouldn't work over the North Sea.

The w/v is found by maintaining a constant heading and speed for a given time, following which any errors may be assessed for GS and drift using a number of differing techniques. You now know the actual w/v. This method is repeated at intervals throughout the flight. The pilot is able to revise and apply a good heading (even without surface features always being available) and of course the intermediate and final ETAs.

[fudgy2000]

what techniques would these be??

Also using the SCA method, how would this affect my ETA if I was off track and had to use this method??

[stillin1]

Read Beags post 20 Mar:mad:

[Tinstaafl]

Thank you for your considered opinion, Beagle. Now that that you've enlightened us all perhaps you could deign to explain your reasoning to support your emotive outburst. :rolleyes:


1:60 works. It works well, it's simple & it's flexible. Other methods also work. All methods have some disadvantages although I think on balance the 1:60 has fewest.

As far as I can see your favoured method offers no additional benefit.

Indeed, it locks you into a single correction factor. Bad luck if you wish to achieve track elsewhere eg a particularly recognisable point in relatively featureless terrain (this can also be a deficit for proportional nav & double the TE corrections). It also means you have to memorise a range of apparently arbitrary SCAs for a variety of a/c. How's that different to memorising the numbers 1, 2, 3, 4 (and '+ a half'). I would argue that your method, whilst useful at times, lacks flexibility and is no simpler particularly if you fly range of a/c. Granted, if you fly a single type then it can be a 'good thing'.

I would also wonder at the accuracy of SCA when there's a large difference between TAS & GS - a common occurance in light a/c.

[BEagle]

Since one can only fly one ac at a time, hardly much need to 'memorise a wide range of SCAs'.....

Personally I find 'right 40 deg for 3 minutes and delay ETA by a minute' a lot easier than trying to work out (3x60/17) + (3x60/38) in my head.....

Even if SCA doesn't get you exactly back to track, you'll be close enought to recognise your position at the next visual fixpoint

[stillin1]

Some more fell on stony ground I fear.
Those that UNDERSTAND SCA - use it if you wish,
those that don't - don't
and those that have an open mind - check out all the options and choose for yourself.
You have disappeared in to the vortex of "my mind is made up and the rest of you are wrong"
Understanding is the key to knowing
Me - I'm a SCA kind-o-guy.
ENDEX
Not listening no more
La,la,la,la,:yuk:

[BEagle]

Ah - but should we not try to convert the unbeliever lest he continue in his ways of ignorance and superstition!;)

[Tinstaafl]

Er....where did you get the ".../17" or ".../38" bit fro6m??? :confused:


I've run 27 or 30 or 35 nm (ie near-as-dammit 30 nm) & find I'm 4 nm off track. That equates to 8 deg TE (ie x 2). If I double that I'll be back on track in the same time & distance. I'll also know how much to alter heading in order to maintain track once there. Do you really think that's difficult?

I'll repeat the table:

approx Dist run or to go..........multiply dist off x to get Tr. Error or Closing angle

60...........................1 eg 4 nm off then TE=4 deg
30...........................2 eg 3 nm off, TE = 6 deg
20...........................3 eg 3 nm off, CA= 9 deg
15...........................4 need I continue???
45...........................add half the dist off to itself. eg 6 nm off, TE=9 deg




If I need/want to regain track at a specific point (eg in the desert where fixes are few) or even parallel track without closing then I can do that too. How is that done using SCA?

ETIs require a groundspeed check anyway. Adding a minute IAW SCA doesn't seem to allow for altered GS for the remainder of the on track route. Have I missed something?

[DFC]

Tinstaafl,

With SCA or doubble the error, there is absolutely no requirement to have a feature on track at the point where the planned track is regained.

Using the SCA, you will be back on track in the standard time. Using doubble the error, you will be back on track in equal time.

Using the 1 in 60 rule to correct direct to the next checkpoint requires you to not only spot the next checkpoint because if you don't you are lost, it also has the problem that you are now following a new unplanned track offset from the planned track. You are comprimising you safety altitude calculations and possibly separation from regulated or special use airspace.

Furthermore, since the correction you made could be for a leg of 100nm or more to destination, any further error on the new track must be assessed with regard to the new track and not against the one carefully drawn on your chart.....or perhaps you think that having calculated the errors using 1 in 60, we should use a ruler to draw in our new track and make new checkpoints?

Get back on planned track asap has to win out....so SCA or doubble error whichever.

Track crawling has it's merits in some situations. It can be very appropriate in certain situations for example keeping clear on controlled airspace. If there is a decent feature - use it. Be aware that if you use traditional navigation you could drift off track between checkpoints so you must make an allowance for that ( a buffer) when flying close to regulated or special use airspace. If there is a well defined line feature (handrail) then pre-planned track crawling along that feature can ensure safe operation.

Another example is following the coast on the seaward side as when doing so, one can disregard obstacles inland for safety altitude purposes since you will not hit them provided you don't fly inland.....can reduse enroute weather minima for the route.

However, it must be an obvious feature and pre-planned with checkpoints...not, not, not the finger on map looking at map and ground and nothing else as we slowly descent towards that hill ahead narrowly missing the low flying military jet type!

Regards,

DFC

[BEagle]

(Dist.offx60/Dist gone)+(Dist.offx60/Dist to go) = change of heading....

The 17 and 38 were examples on a 55 mile trip. Change of heading to reach destination (but not to be on track before) would be 15 deg. Or to you, probably, 15.325077 deg......

Which is why 1/60 is NFG for pilot navigation.

[BigEndBob]

Simplest method i taught, draw fan lines 5 or 10 degrees either side of track from dep. and dest.. When off track fix position, then add the two fan lines that intersect that point. This is the heading change to reach destination.
Can be reduced to one set or even one fan line once you get use to the method
For timing use quarter or half marks depending on available features or length of legs.
These methods ok for UK terrain.

For crossing deserts or north sea...go buy a sextant, gps or Loran set!


Years ago on my commercial gft i marked on 3min points on my imc leg. when asked where i was these timing marks where spot on with my radio aid fix.
Plan a diversion...drop a straight edge from fix to div., slide to nearest vor rose, throw in a bit for wind, width of thumb 4min little cessna, 3min pa28
Also teach people to guesstimate headings without using protractor.
There are many methods...KIS.

[Jesus H]

Chaps (and Chapesses)

I'm amazed that you can get so steamed up about "The Best" navigation technique.

The best technique for any individual is the one that works best for THEM!

I have my favourites, but as an instructor, if the student is struggling with the nav technique I teach, then I sit them down and try to find out why.

Quite often the answer is to teach them a variety of techniques and after discusuion we can usually work out which one suits the student best and then get them using that one.

Horses for Courses chaps!

Arm yourselves with the full gamut, throw away any prejudices you have about a particular method and be prepared to teach them all.

JHC

[Tinstaafl]

Beagle, it's not me that's overcomplicating the method - but you & your snide remarks. You & I both know that all these heading corrections derived by *all* the methods mentioned so far are nothing more than 'good enough' approximations only.

Anyway, to use your 55nm trip & 3 nm off track example & say, 20 nm run (or 22 or 23 or 19 etc.) AND using the table I outlined above.

3 nm off in 20. Straight off that's 9 deg to parallel track (ie 3 x 3 nm).

Another 35 nm to run? Near as dammit 30 nm so that equates to 6 deg (2 x 3 nm).

All up 15 deg heading change. No difficult formula to remember.

Alternatively alter HDG 18 deg & regain track in 20 nm & the same TI it took to get off track. BTW, the table can be easily expanded for other leg lengths eg dist run 120 nm, use half the dist off as TE ie multiply by a half.

An attendant benefit is that the same distances run and to go can serve a double purpose and be used for subsequent GS/ETI checks afte the heading adjustment is done.

Yes, it can have more to it. What if you've run 75 nm? I use my whiz wheel. Unlike some in the UK, using a whiz wheel isn't considered a 'bad thing' elsewhere in the world. And no, it's not difficult or time consuming. It takes a few seconds.

I can see the benefit of your SCA in some circumstances, but certainly not as the be-all-and-end-all-there-is-no-other method. Where do GS/ETI checks get a look in? Or are you presuming the planned GS is accurate? Not much of a problem on short hops since the accumulated error is small but not a good idea on longer sectors.

If you do conduct GS/ETI checks then how do you integrate them with your SCA gyrations? It may not be common in the UK but in Oz many PPLs use a variety of a/c from 90kt C150s to 160 kt A36s or C210s. How many SCAs would you have them remember (alternatively, would you have them only ever fly at a single speed per type?)


As for some other methods:

I dislike pre-drawn drift lines because they're limited to solving a deviance that commences or terminates at the same origin as the drift lines. They fall over if the off track deviance develops at some point along track or worse, if you divert. The flip side is that if you'r adept at judging angles (or have tool for doing so. I used to have a scale rule with one printed on it), drift lines can be quick & efficient.

Proportional nav can also be useful - particularly if the proportions happen to be simple ratios. Bit of a b@stard if the ratios aren't very cooperative.

Other places I've seen had the students plot two positions & derive the actual W/V then apply that to the TAS & TR to obtain HDGs & GSs. Then calculate ETIs. Bit of a major workload enhancer but do-able & can be extremely accurate. To much bu ggerising around for my liking. Interesting to do as an exercise on very long sectors.

Jesus said it best (never thought I'd ever say that. And me a devout atheist :ooh: ): It's best to have a toolbox of skills that has a variety of tools.

[BEagle]

The whole purpose of simplifying VFR naviagation by using SCA is to avoid having to use a whizz-wheel in flight or spend time 'head-in' looking at tables. In our crowded airspace we really don't need pilots fumbling about with the whizz-wheel when they should be looking where they're going - and all SCA work can be done head-out.

What is a 'ETI' check?

We don't require pilots to 'check' their GS, just to correct their ETAs. Hence proportional navigation is the most usual technique. Selecting such a suitable visual fix is rarely a problem - although I concede that it might be in the GAFA!

[Tinstaafl]

Sorry, Estimated Time Interval.

To clarify a point: you don't 'look up' the table. You remember it. I've met very few people who can't count from 1 to 4 or remember 60, 45, 30, 20 & 15.

[fudgy2000]

Beagle, what happens if the GS doesnt equal TAS?? For instance Im in a 30kt head wind??

Is this method taught at CFS now?

[BEagle]

Ideally use a larger SCA. But in practice it won't matter hugely as even with a smaller SCA, you'd be close enough to recognise the visual fixes when you'd finished your correction.

SCA is used by the RAF. Have to say the 'Visual Navigation' wasn't actually taught when I wen through CFS - they concentrated on low level navigation.

[fudgy2000]

I will mention this SCA method to my instructor. I hope he will be impressed!!!!:D

[tacpot]

He will be, if you can apply it! :p

[Send Clowns]

Children - no need to argue about techniques. They all work, all are accurate enough for the purpose. Some people find one easy, others prefer another. All have certain disadvantages.

Teach your students a technique you think is appropriate to their abilities, and if they don't get on well with it then get them some practice on the ground with other methods, until you find one that works! It ain't that difficult:rolleyes:

BEagleWhich is why 1/60 is NFG for pilot navigation.Is perhaps the most ridiculous statement I have seen in a supposedly serious discussion of instruction. You have decided it is no good because it is too difficult to work out to 8 significant figures, yet the method you advocate is (like 1:60) only accurate to the nearest couple of degrees. For anyone with any practice in mental arithmetic the maths is very easy, as long as you only expect a rough answer, which is all that is possible in the air.

Some of my ATPL groundschool students use 1:60 when flying. I've used it for a lot of flying, was taught in the Navy and believe me there were a few pilots who were not terribly bright. The reason it is in the ATPL exams is because the RAF use it, and they certainly aren't known for intelligence :E If they can manage it then it's worth offering your students as an option, and keeping an open mind.

[fudgy2000]

I tried SCA method in the sim. I was 4 miles off course heading north- I set the wind to 270/30 and my TAS was 90kts. However, I held this for 4 minutes turned 40 deg and I was still off course by 2 miles!!????

Anyone??:confused:

[BEagle]

Your original data set was incomplete and the conditions you used were non-representative. Basically, you did not emulate a navigation problem........

[DFC]

fuddgy,

Try the same flight however this time use drift lines to measure the angular error caused by following your heading. Having measured how long you have been maintaining that heading, doubble the error towards track and in a equal time you should be back on track.

With a wind of 270/30, the heading required to track North at 90Kt is about 337.

To look at it another way, if you steer 360 in that wind you will track 023 degrees.

Having maintained heading 360 for say 5 minutes, you turn left by (2*23)=46 deg heading 314 for a further 5 minutes where upon you will be reasonably back on track where you turn right by 23 degrees heading 337 to maintain a northerly track.

You don't have to be a genius to work out that correcting into wind will leave you a little short while correcting out of wind will make you overshoot slightly. However, the whole idea is to get you bak within a reasonable distance of your planned track and provide you with a correction that will keep you on or near that track.

---

BEagle,

I'll leave the SCA explanation for this case to you. :)

Regards,

DFC

[BEagle]

Track closure rate at 90 kts with a 40 deg SCA is 90 sin 40. In 4 minutes, XTK error would have reduced by (4/60) x 90 sin 40 nmiles, i.e. 3.8567 miles. He should have been only .1433 miles (871 feet) off track after following the 40 deg SCA for 4 minutes - hence I can only assume that he didn't model the problem correctly...

[stillin1]

F2k
If you did what you said you would have been back on track!:D
You must have erred somewhere:{
Did you continue deviating from track whilst calculating the correction? That would have, of course, allowed the distance from track to increase still further:oh:

I'm having a smileyfest

[fudgy2000]

I have tried this with RANT and it doesnt work!!!!

90kts, 40 degree turn, 270/30kt.

I set the alt to 0ft therefore not reading any slant distance with DME.

Moved my aircraft 2nm abeam DTY, pointing north. Applied wind and then turned 40 degrees, held for 2 minutes---still 1.2 miles off???:sad:

[BEagle]

You wrote earlier that you'd tried SCA 'In the sim'. I didn't realise that you actually meant with some PC toy 'simulator' program...

Practise it in the air, chum (dual, of course!) - you're obviously doing something wrong with your PC!

[Send Clowns]

BEagle - if a technique works then it should work on RANT, a system so simple that the variability even of a simulator has been removed, and results should be most consistent. I agree that fudgy must be doing something wrong, as although I have neither taught nor used the technique I am not aware of large errors, but that is not an excuse for being patronising. It in fact goes against your insistence that SCA is the only technique to use and infalibly simple! Perhaps fudge should simply be using a different method, that might suit him?

[Tinstaafl]

Unless I'm misreading your description, you positioned the a/c 2nm off-track then set a wind, turned i.a.w. the SCA method & flew for two minutes?

Where did the two minutes come from? From your description you started at the 2nm abeam position. I think the SCA method requires that you fly the track correctio for the same duration it took for the error to happen.

[BEagle]

No, you hold the correcting track for the same numerical number of minutes as you were miles off track. N miles off track, turn through SCA and hold for N minutes, then reverse to original heading and correct DI, rudder trim. But if both those were OK, correct by applying observed drift value.

'Pointing north' - does that mean 'heading' or 'track', 'true' or 'mag'?