Track error correction & ATC question

[pilot in command]

Hi everyone,

Just got a few questions regarding Track error correction & ATC.

If I am flying, say a 40nm leg, I will split the leg up into quarters to give me 3 check points along the route. I would just like to check I am calculating the correction angles correctly so here goes: Please correct me if any of these are wrong:

1/4= Track error X 2, brings you onto the 1/2 marker, then resume original heading + 1X track error.

1/2 = Track error X2, brings you onto the 3/4 marker then resume original heading + 1X track error.

3/4= Track error + closing angle until destination.

These are the methods I was taught during training however some PPL notes/instructors say otherwise. A lot of instructors seem to say when you get back on track resume your original heading and other instructors recommend original heading plus the track error.

Also, if the leg is shorter, say 20nm and you only have a 1/2 marker, is the correction angle just TE X2 at the half way point which will take you to the fix?

ATC question:

When on an Information frequency and you wish to select another frequency, should you "request freq change" or say "changing to...." I've always been taught to "request" when on an information service, but when flying with some other PPLs some of then use "changing to". Which one is deemed to be correct?

Thanks

[wb9999]

I'll leave the first part of your question to somebody more experienced than me. But for the second question, I've been taught that if you are in controlled airspace then you request a frequency change. Outside of controlled airspace you can talk to whoever you want, so you would say "Changing to...".

[Mark 1]

Doubling the track error at the half way point will converge you onto your final destination, not the 3/4 point. (assuming you had flown a constant compass heading since start of nav).

The only problem with these techniques is that assumption of precise compass heading from your last overhead fix. Account for DI drift, less than accurate track keeping etc etc, then the calculations become more complicated.

There are many schools of thought on this. If you're not sure of the cause of the track error, then get back on track using standard closing angle, re-establish an overhead fix and treat that as a new start of navigation.

If you're sure that the track error is due to wind variation from your plan, then your method is as good as any.

[riverrock83]

RE ATC see CAP 413 Radiotelephony Supplement 3: A Reference Guide to UK Radiotelephony Phraseology for General Aviation Pilots | Publications | About the CAA (http://www.caa.co.uk/application.aspx?catid=33&pagetype=65&appid=11&mode=detail&id=3749) page 10
Changing Frequency
You will normally be advised by the appropriate ground station to change from
one radio frequency to another in accordance with agreed procedures. In the
absence of such advice, you must notify the ground station before changing
frequency, using the expression ‘changing to’ followed by the name of the next
air traffic services unit. However, pilots flying in controlled airspace must obtain
permission from the controlling authority before changing frequency.As for getting back on track, there are various ways, but what your are doing sounds very like what I was taught.
A brief glance though, suggests that your numbers aren't quite right. However - this is just a quick glance!

If you are 1/4 of the way down the track:
If you turn 2x track error, you should get back to the track at 1/2 way point. If you then turn to 1x track error, you should then be following the track.

If you are 1/2 way down the track:
If you turn 2x track error, you should get back on track at the end of the track (ie your next waypoint).

The way I think of it, is that if you turn the track error, you will now be travelling parallel to your desired track (which is probably what you should have been on in the first place). If you turn 2x track error, you will move back towards your desired track at the same rate as you left it (so if you have been going wrong for 1/4 of your track, you will be back on track after another 1/4).

[BlueSkyLife]

Your Rule of the 2X TE works fine. Here is an expansion that before you may even reach the point of finding out your off course, you could fix it early.

Sound like nothing an old 1:60 Rule couldn't fix.

This is rather a complex explanation, however from this you can design your own rule of thumb.

1:60 Rule states that for every 60nm in distance a steadily held 1 degree deviation in Aircraft heading will place you 1nm abeam your checkpoint.
So, reduced to its lowest useful term is; 1nm~1Deg~101'.
Ex.10nm~1Deg~1010' or 30nm~1Deg~3030'/0.5 nm or 60nm~1Deg~6060'/1nm

Now, for the Ex.10nm~1Deg~1010', if we open that 1Deg deviation to 10 then; 10nm~10Deg~10,100'/1.66nm.

From here we have a base to work with.

Lets say your flying along a leg 60nm long with only 3 check points, which means approximate 20nm checkpoints. 10nm you check the MAP/GPS and estimate a 1nm/6076' XTE........10nm X 101' = 1010'per Degree. How many degrees are in the XTE of 6076'...6076'/1010' = 6 degrees. 6 degree is your XTE, however 6 degrees corrected turn will Parallel your course, so double the XTE=12 to meet your 1st checkpoint of 20nm over head.

A Quick Ref would be:

XTE (converted to feet)
Distance flown X 101'

Triple or Quadruple will intersect the leg (wont get into the details), but account for loss of time and extra fuel burn.

Hope this helps and not confuse you more.

[RTN11]

A lot of instructors seem to say when you get back on track resume your original heading and other instructors recommend original heading plus the track error.

You have to figure out why you were off track.

If it's because the wind is different from the forecast or plan, then if you go back to your original heading you will just get blown off track again, so you must correct the heading by 1 x drift.

If it's because your DI wasn't aligned to the compass, or you were just flying the wrong heading, then go back to the original planned heading.

[ozbeck]

BlueSkyLife

I'm afraid your explanation confused me a little.

What does the squigley horizontal line mean and what are the big numbers (101, 1010 and 3030)?

[RTN11]

I believe you could replace ~ with the word per, so 1nm per degree per 101'

and the large numbers are all distances in feet, ' being the symbol for feet, " for inches.

[ozbeck]

Thank you RTN11

[Piltdown Man]

The wiggly line was probably meant to be one of these ≈ ie. an approximate sign. The big numbers are feet. The starting point is that there are, as good as damn it, 6,000 feet in a nautical mile and that divides quite nicely by 60, the same number used in charts. Combine the lot and you have a navigation system.

PM