help needed with Nav!!
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help needed with Nav!!
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
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
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
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
fudgy2000, your misfortune in being taught an outdated and stupidly complicated system of navigation - probably by a dinosaur?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!
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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?
I think this method hes taught me is simple. i think?
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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.
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.
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.
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.
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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??
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??
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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.
An good instructor should be able to adapt his teaching method to the student.
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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
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
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Nav
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.
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.
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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??
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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
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
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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!!
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!!
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
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
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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??
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??
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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
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
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.
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.
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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.
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.
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.
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.
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.
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.