In Flight Navigation techniques

[Teroc]

Hi all,
Does anyone have a really nice simple easy way of in flight vfr navigation / ded reckoning / off course corrections etc ?..im fairly new to all this and between flying the plane, monitoring the instruments, checking for traffic, noisy cramped cockpit / squeeling radio etc i sometimes find it hard to remember what 7 x 8 is never mind trying to remember and implement the 1 in 60 rule / ratio method / revised etas etc etc...arrghhh !! help !!!
So c'mon all you oul grizzled 20 million hour instructors / flyers :) ...how do you all do it and still stay up :)

[Wee Weasley Welshman]

Wait 'till you're half way onthe leg - assess the angle off and double it to correct. Its cheap and easy but it works every time and on the legs you fly on the skilltest it is good enough. You should also revise your ETA at the same time. Do this in one go with a reasonable degree of accuracy and that'll be good enough for the examiner.

Come on then - shoot me down! WWW

[DB6]

As WWW says, that's the easiest way for me too - forget trying to do sums in the head - and the easiest way to estimate your angle off track is to draw a couple of lines either side of track, 10 degrees off, radiating out from your departure point and destination. Then all you have to do is look over the side at your halfway point, see where you are with respect to your track and 10 degree lines and double it etc, etc. Also of course your ETA is revised by twice whatever the difference is at the halfway point.

[Charlie Foxtrot India]

The 1:60 rule works great on the ground.
In the sky, well if someone is far enough off track to make a 1:60 necessary then chances are they can't hold a heading well enough to make the calculation worthwhile. While they have their head down trying to work it out...whoops, there goes another 10 degrees...
Using the "Big Picture" eg hills, lakes, navaids etc and getting relative bearings then working out "It's Over There" and going for it usually works better than complicated course corrections.


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[Meeb]

The inverse rule which WWW purports is fine, but if on a commercial test you find yourself off track before the half way point an easy way to get back on track is to use the 'standard closing angle technique'. Simply assess your distance off track in Nm, then use that figure in minutes to get back on track using a 30 deg angle.
For example: if you are 2Nm off track, turn 30 degrees towards your track and hold that heading for 2 minutes, you will then have rejoined your original track, but remember to correct your heading or you will again drift off track. The angle of 30 degrees works for most light aircraft used for training, but the angle can be worked out for other types if required. 30 deg is the minimum that should be used.
Hope this may help you a bit Teroc!

[Wee Weasley Welshman]

Meeb - that's interesting, I had never heard of that. I'll try it out next week. WWW

ps - yeah Big Picture is the key, if I could stop students from trying to identify the B2486 directly below and instead notice the 4 mile wide lake with a lighthouse and cablecar system passing abeam at 9 miles I'd have this job cracked!

[Checkboard]

Getting students to hold heading can be difficult as they tend to look at the DG all of the time, you have to get them to set their heading on the DG, then pick a point on the horizon to fly to. This way it is immediatly obvious to them if their heading drifts off.

In judging distance, in a normal seating position & with most aircraft, the nose covers one mile for every 1000' AGL. (i.e. If you are at 5000' AGL, then when something dissapears under the nose, it is 5 nm away.) As the attitude is usually "four fingers", then anything out to the side that is "four fingers" below the horizon is also 5nm away.

For short legs, you can use a "Known drift" technique - set your track as your heading, when your watch says you have arrived, then the point you want will be located into wind.

[Meeb]

Ahh, to cruise along at 5000' in a bug smasher! Easy to see you are in Oz Checky! I remember climbing to 8000' trying to escape the heat in Oz. Unfortunetly here in the UK the most a student can hope for is 2500' due to the very congested airspace!
Sure WWW, try it out, then I can promise you you will not use any other technique again! ;)

[Meeb]

Or due to the cloud base the most you can get is 2500'! ;)

[This message has been edited by Meeb (edited 27 June 1999).]

[Checkboard]

I thought that was a little low actually!

For the PPL five hour nav, I used to ask students to select their cruising height (in thousands of feet) at 10% of their distance (in NM) ie 80nm leg = 8,000'.

Wind & weather consids come first of course! Used to wander up to 10,000 feet for the longer bits (although going above 8,000' is really only worthwhile (normally aspirated) if there is a wind advantage....

[Teroc]

Thanks folks
Good solid practical stuff....
Never heard of that 30 degree one meeeb...
pretty neat...
Thanks again...see you all up there..not too close though :)

Teroc

[Grandad Flyer]

I agree with the 1 in 60 rule. I have never understood it, and probably never will now!! Mind you, I have always got by without all the hassle. The simple drawing deviation lines on the map one I can cope with. But hey, give me two VORs any day. It is so mindboggling easy to navigate using VORs. I do fly an aircraft with no navaids whatsoever sometimes, and with that I must admit to doing the basic "look over the side/ front and head for something obvious" rule of navigation! But if I have a VOR receiver aboard then it does it for me everytime. Probably coz I learnt in the USA, where people are practical.

And don't forget your chinagraph pencil, huge flight bag, pens, pencils, calculator.... Good, lets just a) look out the window and b) use VORs and NDBs. I haven't been lost yet and I have hundreds of hours of x-c time.



[This message has been edited by Grandad Flyer (edited 01 July 1999).]

[Brit Abroad]

Very interesting thread. I am a PPL holder but admit that my in-flight navigational skills need a bit of fine-tuning :)

Can anyone recommend a good book which explains practical in-flight techniques such as the above ?

Many thanks and safe flying

Brit

[KingAir]

Just briefly read through the postings but I don't remember seeing this method--double the track error. Basically, this method is to be done BEFORE the half way point. After map preparation--10 degree drift lines, etc...find out how much off you are, in degrees, from your track (ex. You are flying 360 degrees and you find yourself 5 degrees off to the right of track) and also, how long you have been flying off your track (ex. 5 mins.). All you have to do is double the error (5 degrees x 2 = 10), then fly the new heading (in this case, since you are to the right of track, you will need to fly 10 degrees less...if to the left, add.) for the same amount of time. Therefore, fly 350 degrees for 5 mins. After 5 mins., you should be back on track so now you will just need to correct for drift...fly a heading equal to half of your correction (ex. since you have been flying a 10 degree correction to the left, you will only need to fly a 5 degree correction to the left.) Therefore, fly 355 degrees.

[Oktas8]

Brit Abroad

In Aust & NZ the Trevor Thom series is v. useful at explaining stuff in a simple way.

Legal issues would be no good in the UK, but I imagine practical nav tips would be the same anywhere.

Look around on the internet for Trevor Thom...

O8

[Capt Homesick]

Grandad Flyer has a point, VORs are a great help: unless you're flying in a mountainous area, with only one VOR within 50 miles, in an aircraft with no DME or NDB, and a solid layer above!
Besides, I learned to navigate in an a/c with no VOR, DME, NDB or even transponder (although it did have both VHF and UHF Coms so I could call for help on lots of different frequencies).
Getting back to the question, the simplest method is the "2x Track Error" method as desribed by Kingair.
The trouble with this method is, it sounds complicated. See it on a whiteboard and you'd get it in a second, and once you've tried it in flight you'll be a convert, but it sounds a nightmare.
Most of the methods above work perfectly well- pick one and stick with it, whichever one you're used to will be ok if you practice!

[This message has been edited by Capt Homesick (edited 27 July 1999).]

[Oz_Pilot]

1:60 can work - just that working out the answer is a pain. I found myself a nice WAC ruler which does the 1:60 using splay lines drawn on it... place ruler, read splay, turn onto new heading...

Advocating the use of gadgets is not something I'd often do, but you carry a scale rule anyway...

[Meeb]

Double the track error is not the simplest method Capt Homesick, because it does not work after the half way point, you must use the inverse proportion rule then. My earlier posting on the SCA technique cannot be faulted. As an ex-509 instructor I often had to simplify things down to the lowest common denominator to get students to understand, the SCA worked every time, under all conditions and phase of flight.

BTW, I do not like the idea of using VOR's, best to foster good raw nav techinique in students, VOR's are just too easy. When I worked in Oz, the state was the size of the whole UK, and had around 6 VOR's!!

[Tinstaafl]

I'm quite sold on 1:60 as a very useful method (but not the only one). It's even possible to memorise a few numbers to do 1:60 in your head - not hard if you know your times table from school up to about 4 or 5 http://www.pprune.org/ubb/NonCGI/redface.gif

Remember always that the method has its limits: 1. No good if the track error OR closing angle is more than about 15 deg. 2. It's an approximate method as the method makes quite a few assumptions but it's accurate enough.

Method by rote:

If you have travelled anywhere around 60 nm since last you were on trackeg 55 to about 70 nm, then your distance off track is also your track error. ie distance off track times '1'

If distance travelled since last on track is about 25 to 35 nm then track error = number of miles off track times '2'

If distance run is around 20 nm then track error is number of miles off track times '3'

If distance is about 15 then miles off times '4'

The only numbers that need to be memorised are the 'times' ones ie 1, 2, 3, 4. Didn't mention it above but for distances around 40 to 50 nm then track error is distance off track + half of that. If you want more distance then for 120 nm the track error is half the distance off track.

eg You have travelled 33nm since your last fix on track & now a fix puts you 4nm off track.

33nm means use '2' times so 2 X 4 gives a track error of 8 deg. Turn towards track by 8 deg to parallel


If you adjust heading by just that amount then you will parallel track until whenever you choose to turn further to close track.

To close on track you could just double the track error that you found above, in which case you will be back on track in the same time interval as it took you to get off track. eg. If your last fix on track was at 20 minutes ago & you now fix your position and adjust HDG by twice the track error you'll be back on track in another 20 mins & also the same distance since last on track. Don't forget to adjust your HDG by ONLY the closing angle when you're back on track - I learnt that one while wondering why my instructor was smiling so much!

You could also use the method to find the closing angle to regain track at any point further on that you choose eg a better navigational feature or the destination or whatever. You don't even have to get the closing angle immediately. It'll work from any point along your currently parallel track to the on-track point you eventually choose.

eg from the previous example you adjusted your heading by the track error a little while ago so now you're paralleling track. While parelling track you can now look ahead on the chart to find somewhere to base the closing angle on. This gives you some breathing space to work it out. So...From the map you notice a feature that looks relatively easy to locate. Measure its distance from wherever you want to regain track. If it's around 60 miles then for a 4 mile off track position you will need to adjust heading 4 degrees towards track ie 4 X 1. If around 45nm then adjust hdg. by 6 deg ie 4 + a half. If 30ish miles then CA is 8 deg ie 4 X 2. If 20 miles then 12 deg ie 4 X 3.

Don't forget to turn towards track when you get to this convenient feature & don't forget to turn back by this closing angle once you're back on track. You could also just do both the TE & CA at the same time & make a single heading change to get back on track.


Other uses include simple diversions: just treat the new destination as if it is along track & measure its distance off from your current position & get the amount of HDG change (max 15 deg still, but can be handy)

Also for finding the lead bearing for commencing the turn inbound after a DME ARC but you need to know the lead distance 1st (GS/200: ie half the GS then knock off a couple of zeros approx. At 120 kt then lead distance is 0.6 nm). Whatever the DME ARC distance is eg 10DME or 12DME divide 60 by it ie 10 goes into 60, 6 times; 12 goes into sixty 5 times. Whatever that comes to, use it to multiply the lead distance (the GS/200 figure). So the 0.6 lead distance example used above at 10 miles would equate to 3.6 deg or (call it 5 deg) lead bearing required.

The method is also useful to figure out if you are making the missed required missed approach or departure gradient. Just multiply your groundspeed by the % climb gradient to get ft/min required climb rate.

But even with the above diatribe, it is still only one of a number of methods. Some are more appropriate than others in different situations. The more you are comfortable with then the better you can respond to a variety of situations.

Other 'bits' that can come in handy are things like deliberate track error, where you purposely use a hdg that WILL take you off track by the time you would have reached the destination. If the destination is hard to find but lies along a cross track or nearly cross track line feature then when you get to the line feature you can be fairly sure that it will now be in the direction you would have to turn to get back on track.

Position lines are great & not just to try & get several to get a fix. A couple that happen to cross track are good for ground speed. Any feature that you can line up with another that you can see is able to give you a line feature. Also they don't have to be to the same side of the aeroplane as you can still get a position line from flying between 2 features.

And lots of others still!....


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Don't mess with the red switches.


[This message has been edited by Tinstaafl (edited 29 July 1999).]

[This message has been edited by Tinstaafl (edited 29 July 1999).]

[This message has been edited by Tinstaafl (edited 30 July 1999).]

[Atlantic bart.]

Brit Abroad

Best one I've seen for ages is Global Navigation for Pilots, by Dale de Remer and Donald W. McLean, published by ASA (probably available through Transair, Sporty's, other usual stockists). Don't be put off by the grandiose title: although the book covers a bunch of advanced stuff like INS & GPS, even a bit of celestial, Chapter 5 "Basic Navigation Techniques" is as good an explanation of how to do basic dead-reckoning as I've seen in a long time.

Happy landings.

[deadhead]

If you do as much figuring out in advance during planning then the 1:60 rule is easy to use in the air subject to the limitations described above.

Here's an example:

1. Find a feature on the chart on or close to track

2. Draw a line perpendicular to track that goes through it

3. Draw several tick marks 1nm apart on this line (say five each side of track

4. Use this interpretation of the 1:60 rule to find a "correction factor":

(60/distance dep-feature) + (60/dist feature-dest)

say your feature is 88nm from departure point, and there is 56 nm to go

then (60/88) + (60/56) = aprox 2.

Write this number next to the feature.


During flight if you find yourself off track at the same feature by say 4nm (boy, weren't you flying a constant heading?) then multiply 4nm by the correction factor (2) to get 8.

So turn 8 degrees in the direction of track to make good your destination.

So this minimises head down and works for corrections up to about 30 degrees so if you are off by more than this you probably shouldn't have left the flight planning room...

DH

[hugh flung_dung]

The "maxdrift" method is the best I know for planning and diversions. Before flight estimate the max drift (drift when flying at 90 degrees to the wind) using: (windspeed x 60)/TAS. Write the maxdrift angle on the top of your FLOG, draw the wind direction on your chart.
In flight assess the angle between track and wind and apply a sixth of max drift for each 10 degrees. When the angle is 60 degrees or greater use all of maxdrift
For groundspeed planning just apply the same "rule of sixths" to the windspeed but use the angle between the wind and the aircraft beam.
This sounds painful but it's really easy and accurate in practise.

Assume TAS=90kts, track=010, wind=050/21.
Maxdrift is 14 degrees.
Track-wind angle is 40 degrees, drift=4/6 of max drift (= 9 degrees). Steer 019T
Beam-wind angle is 50 degrees so use 5/6 of windspeed as headwind, groundspeed =73kts.

The different parts of this method also work well for assessing drift in the hold and the crosswind component for take-off and landing.

My experience of the various track correction mechanisms is:
1 in 60 method - fine on the ground but it's a sad fact that most of us lose 80% of our IQ when we strap on an aircraft - mamy studes (and I) have difficulty applying it.
Closing angle method - (invert fraction of leg flown and multiply by closing angle) works well at 1/3, 1/2, 3/4 points - most studes are happy with it.
Standard Closing Angle - (turn towards track by 40 degrees (90kts) or 30 degrees (120kts) and fly for a time equal to the cross track error). I've only just started using this; the downside is that the theory is based on flying constant groundspeed but we fly constant IAS, also it only works for 90kts and greater. The upside is that it seems to work reasonably well.
Known error - (fly track for planned time and then turn into wind). I would use this if trying to find somewhere in featureless terrain but have never taught it.

This is all a bit cryptic but hopefully makes sense. The BIG thing is teach them not to track crawl! Turn onto track, set DI, set speed, trim, gross error check, plan time to first check point, PUT THE MAP DOWN (and don't pick it up again until a few minutes before the fix time unless an irresistible unplanned opportunity fix presents itself), look outside, fly accurately.

[This message has been edited by hugh flung_dung (edited 16 September 1999).]

[BEagle]

'Standard Closing Angle' is the simplest method we've found for correcting tracking errors and 'proportional correction' for timing errors. No need for lines on the chart such as those ancient 5 deg and 10 deg driftlines!! And no hard sums either. To summarise:
STNDARD CLOSING ANGLE
1. Establish your distance off track.
2. Turn towards track by a Standard Closing Angle of 60/(TAS in miles per minute) i.e. 40 deg for a 90KIAS Cherokee, 30 deg for a 120KIAS Bulldog.
3. Hold that heading for the same NUMBER of minutes as you were miles off track , i.e. 3 minutes if you were 3 miles off track.
4. Turn back onto original heading , recheck DI is synch'd and the rudder trim is correctly stopping flight with a constant yaw.
5. Adjust timing by adding 1/3 of the time spent on the Standard Closing Angle at 90KIAS or 10 sec per minute at 120KIAS.

It's easy and it works!!

PROPORTIONAL TIMING
Choose pre-planned visual fix times at approximately easy fractions of your track distance. Then, assuming that you've been flying accurately any timing error must be down to the wind. So adjust ETA accordingly, i.e. 3 times the error at a fix 1/3 the way along, twice the error at a fix about half way etc.

WWW - didn't you do SCA on the nav phase at your UAS?? Or did you leave before that phase?? I'm not being rude, it's just that I'm pretty sure that there isn't much enthusiasm for basic visual navigation at UASs - it was certainly not taught well at CFS. But low-level and/or aerobatics and formation were much more popular!!

[rolling circle]

Whilst the SCA technique is adequate for the military and PPL worlds it is not acceptable in commercial aviation. The requirement in, for example, the CPL Skill Test, is to make a heading alteration to make good the next turning point/destination, not simply to regain track. In fact track crawling is second only to misidentification of destination in causing a failure of the en-route section of the test.

[BEagle]

The reason why SCA is acceptable for the military and for private flyers is that it gets pilots back onto their pre-planned track as quickly as possible. For military pilots, this means that they will be back on a route known to be de-conflicted from known hostile hazards as soon as possible. For private pilots it means that they will be back on the track upon which they based their pre-flight planning as soon as possible. Quite why these common-sense principles should be unacceptable to the '4 gold-stripes on the woolly-pully' high and mighties is unfathomable to me!! And SCA works perfectly well for pre-planned radio nav as well!! Perhaps because SCA is so easy it's viewed with concern by those who like to fly PA28s like 747s - and who love selling those wretched PLOG clipboards and sticky pens to their students!! KISS - if SCA works well enough for a Tornado at 540 KIAS+ and a PA28 at 90 KIAS, it's good enough for Capt Pompous Sennapod in his nice navy pullover with all the imitation gold stripes!!

[MaxAOB]

;) Map read and don't get lost!! ;)

[rolling circle]

Oh dear, we do seem to have tweaked the BEagle's tail don't we?

If you stop foaming at the mouth long enough to re-read your own post, my excitable friend, you will discover that you have answered your own question. While military and PPL pilots have very good reasons for regaining track, the raison d'etre of the commercial pilot is to reach destination as economically as possible, hence the requirement to alter heading to reach destination rather than to regain track. It's a simple matter of economics, not a personal vendetta.

"Just because you're paranoid, it doesn't mean everyone's not out to get you"

[BEagle]

The foaming at the mouth of which you speak is at the tone of RC's original post which inferred that commercial aviation somehow required techniques superior to the mere 'adequacy' supposedly appropriate to the military or private pilot.
Try this then: Draw yourself a line from Earls Colne to Gamston. Now assume that you're 5 miles off track overhead March. Compare the distance remaining by your superior method and by using our inferior SCA of 40 deg. What answer do you get - and how much time does your method save at 90 KIAS??
Now repeat the exercise at 180 KIAS and a corresponding SCA of 20 deg and what answers do you get??
I'll post mine later - any one else care to have a go??

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[This message has been edited by BEagle (edited 18 September 1999).]

[This message has been edited by BEagle (edited 18 September 1999).]

[Dan Winterland]

SCA - it's what I learnt at Basic, and then I spent five years teaching it. Having seen other techniques, I woulndn't use anything else - except for flying directly to something on track that I can see.

KISS - It's the way ahead!

[BEagle]

Quite right, Dan!! OK - since no-one has been able to solve my question, I'll tell you:
At March (Cambs. - not March AFB!!), you've got 57.5 miles to go to Gamston. At 90KIAS and using an SCA of 40 deg, the error induced by not using the 'direct' track is that you'll fly 1.76 miles further and it'll take you 70 sec longer. At the higher speed of 180KIAS, the errors are that by using an SCA of 20 deg it'll be 0.91 miles further and take a whole 18 sec longer than using the 'direct' method. My, those commercial pressures must be severe if 18 sec really matters!!

Try it in your 757/767 some time, RC; at a GS of 450 kts your SCA is 8 deg, at 515 kts it's 7 deg. I've tried it at 600 kts and it works a treat!!

[Capt Homesick]

Meeb, I kept my reply simple. A full explanation of the 2x track error method includes the section about track error plus closing angle after the midpoint. You may notice that I stressed the need to see the method on a board before trying to fly it? Trying to teach a nav method (as opposed to a quick description) by typing is something I'm not even going to attempt.
And BTW, I was a 509 instructor too. The FTO I worked at used 2xTE because it most closely resembled the way you would fly airway corrrections- if you were unlucky enough to be flying a non-RNAV airway. Purely academic, I thought, until this July when the RNAV in the 146 died on us, and we had to fly the airway across the Alps by VOR!

[Capt Homesick]

BEagle, I would love to hear the response from LATCC when you turn 60 degrees to regain an airway centreline! Pax might get a little uncomfortable too...

[BEagle]

To turn through a 60 deg SCA, you'd need to be flying an aircraft with a GS of 60 kts as SCA = 60/(GS in miles per minute). Even an Airbus isn't that slow!! At a normalish GS of around 450 kts, your SCA is only about 7 deg!!
However, having heard LATCC's polite instructions to certain members of the UK jet-set to get back into Class A airspace, I'm sure that they wouldn't mind a gentle SCA turn. But how often are you allowed to proceed without extensive vectoring any way, these days. It's usually pretty efficient.
The great benefit of the SCA technique is that it's so easy and doesn't need pre-planned fixes. You can use it at any speed just so long as you can assess your cross-track error. It's a refinement of the 1 in 60 rule - which I can explain again if anyone needs the proof. Perhaps because it's so simple, it's viewed with suspicion by those who think that only complex solutions are the correct ones??

[rolling circle]

Sorry about the delay in replying but I was unavoidably detained.

Earl's Colne to Gamston? Hardly worth getting out of bed for. What about 300 miles out of Bermuda, heading for Lajes and the jolly old astro puts you 15 miles off track? How much are your four Hercules going to cost you then as you struggle back onto track?

[BEagle]

Bermuda to Lajes, 300 miles out and 15 miles off track (assuming that the 'astrologer' knows how to do his sums). Four Hercules?? - do you mean Bristol Hercules or C130s?? Hmmm - the only thing in living memory that I can think of which had 4 Hercules was the Hastings (which at least had passenger seats unlike the wretched C130). So a cruising speed of about 260 knots then. I'll work out the difference between SCA time/distance and the 'direct' method - as I'm sure you will - and will tell what my answer is later.
Of course, when the RAF was flying Hastings, the poshest thing on the North Atlantic was probably either the pre-INS 707 or the aaah - deHavilland Comet 4. Even the RAF has moved on since then, I guess! And Earl's Colne to Gamston on a nice sunny day is actually quite worth getting out of bed for!! I'd certainly prefer to do that than haul lager-louts from Lootnairpawt - except for the money!! Have a nice day - going anywhere nice today??

[hugh flung_dung]

Beagle,

A minor correction: the SCA method doesn't work for 60kts.
Sin(SCA)=60/groundspeed... so at 60kts SCA=90 degrees. For an SCA of 60 degrees the groundspeed would be 70kts.
I have to agree that it seems to work well at non-microlight speeds though.

[This message has been edited by hugh flung_dung (edited 22 September 1999).]

[BEagle]

HFD - don't think so. Someone has possibly misread an earlier posting which said "Since SCA = 60/(GS in miles per minute)........." (NOT Sine SCA =60/GS), then, at 60 kts GS, SCA = 60/1, ie 60 deg.
Anyway, I digress. In the rather extreme example quoted by **** , sorry,"RC", the errors induced by using the SCA method (and being back on planned track 15 min later) droning along in a Hastings at 260 kts GS, with some 1600 miles to go to destination, would be about +3.15% further to go in still-air terms. By flying 'direct' you would be well over 5 miles off track for over 4 hours. He might accept that degree of flying precision, but neither I nor the mere military or private pilot prepared to accept the 'adequacy' of being back on track after 15 minutes rather than still over 5 miles off track after 4 hours would probably care to!!

[BEagle]

Sorry about the need for the moderating ****!!

[rolling circle]

Maybe I'm missing something here but I fail to see what is so special about a line drawn on a chart, particularly over the open ocean. Just draw another one from where you are to where you want to go, it makes no nevermind. I seem to remember the RAF used to call it the New Track Reference System.

Incidentally, the 'extreme' example involved only a 3 degree track error.

In reality the argument is somewhat pointless since SCA, whilst a splendid system I'm sure, will not get you through the CPL Skill Test.

And finally, no flight that I'm not getting paid for is worth getting out of bed for. Now where's that tin helmet?

[BEagle]

1. If you don't like the concept of getting back onto lines drawn on charts over the open ocean, please don't ever fly the NAT system!!

2. The RAF sh*tcanned the 'New Track Reference' method in favour of the Standard Closing Angle technique.

3. There is another word to describe those who demand payment for enjoyment.....

4. I will ask CAA SRG about the acceptability of using SCA for CPL Skill Tests - or perhaps if they're reading this (as I know they do!!!), they might like to comment?

[rolling circle]

1. 15 miles off a NAT track is insignificant, at least it was yesterday morning.

2. The RAF didn't 'sh*tcan' NTR, they simply decided, quite rightly, that it did not suit their purposes (I was a member of Exam Wing at the time).

3. Does not deserve a response.

4. Be my guest.

5. This is getting silly and not worth the effort.

6. Bye.

[The Scarlet Pimpernel]

Oooooh, Ladies!! Handbags at 5 paces methinks! IMHO (and experience)the RAF decided to stick to one method of regaining track to avoid confusing the s**t out of the studes! My advice is to stick to something that works for you: 1in60, New Track Reference, SCA...whatever. The biggest aid to navigation (as has been mentioned already) is the picture you see out of the window, provided you're not on the Bermuda - Lajes run (obviously no Herc pilots here - they never get out of Bermuda!)or something similar.
I'll shut up now before somebody throws a powder puff in my direction!

TTFN

[BEagle]

TSP - Mate, thanks for bringing this silly contest back to earth. I've had chats with chums various and the CAA are quite content for people to use whatever system they desire to assess whether they're off track and to recover to track with an ETA for the next turning point before they get there. I'm sure that I've quaffed at many of the same waterholes as RC (by the way, do you prefer to roll into or out of the turn?) and would hate to alienate a fellow pilot. But I do consider that anything more than the assumed 95% standard deviation of 6.3 miles from a NAT track IS significant, even though a Gross Navigational Error is considered to be 25 miles or more - I guess that I'm fortunate that my company's sparkly new Y-code driven system is good to within 0.02 miles. Let's not descend into the realms of mutual handbagging, but accept the fact that returning to the flight planned track is an acceptable technique for the goose as well as for the gander!! (Both of which places SUCK, by the way!!).

[hugh flung_dung]

Beagle - the SCA=60/GS is an approximation that only works for "reasonably small" angles. If you draw the diagram and dig out the skool trygunometree buks you'll find that Sin(SCA)=60/GS. This doesn't alter the fact that it works well down to about 70kts.

[BEagle]

100 lines for me - I must remember my Small Angle Theory!! I'm sure that you're right as I never considered the errors implicit in extrapolating the SCA technique down to speeds at which they would become significant!! Here comes the maths mistress with her cane....and leather boots....MISTRESS I NEED NO MERCY.......AAARGH!!