10 mile markers - Why teach them ?

[eyeball]

As a person that has spent a significant amount of time in GA I must ask why students are coming out of some training environments preaching the benefits of 10 mile markers. This would have to be one of the most questionable navigational techniques I have heard of. It may be good in a 100kt aircraft because it equates to 6 minutes but that is where the buck stops. Pilots are trying to navigate using this system when they get into faster aircraft and get themselves into trouble. WHY? because they were taught that way and I can hazard a guess that their instructor was also taught that way. Why are 6 minute markers not taught as a basic usefull navigational technique that can be used in any aircraft. From a 152 to a Concorde 6 minutes never changes , only the distance on the chart. 150kts will equate to a 15 mile marker 450kts to a 45 mile marker and so on. Just knock the zero off and thats how far you will go in 6 minutes. If your departure airport is DME equiped you can grab a dme groundspeed before it falls over and throw out 6 minute markers on a WAC chart. Normally makes remote navigation a non event in comparison to the work load 10 mile markers create in anything over 100kts.

[rolling circle]

Then again, why use 6 minute markers when there may be nothing there to see? Try this in the desert states of the USA or even in East Anglia and you will find that most of such markers are useless. Surely it is better to highlight the most obvious and unique features, at about 6-10 minute intervals, and use the closing angle technique to calculate heading changes. There will, of course, be those who consider it more important to stay on the arbitrary line they have drawn on the map than to reach their destination, but it does take all sorts....

[Charlie Foxtrot India]

yes, they don't help much when you're crossing the Nullarbor.
Still, they are handy in the early stages of training to help students get the concept of distance/time/ETA/groundspeed checks etc. I find ten minute markers a bit easier than six minutes, ( always had trouble with that six times table) working backwards from the destination.
IMHO its simplest to use minutes as a common denominator for everything rather than some things in litres, others in miles etc. But theres lots of different ways of doing it, and they all achieve the same result, like the whizz wheel.

------------------

[Tinstaafl]

Odd, really. I agree with all of you!

But if pushed I tend towards not using 6 min/ XX mile markers, at all for my students. I certainly don't use them myself.

But just to be curmudgeonly, they ARE definately useful to 'ingrain' the concept of TIME as the initial identification indicator.

Still, I'm quite sure most relatively experienced pilots DON'T draw 10 mile / 6 min markers - instead using the time to the next most suitable navigation feature.

As CFI indicates, it's precious little use to have a marker (in miles or minutes) that doesn't have a terrestrial feature to match!



------------------
How surprising! Aircraft use the same laws of aerodynamics all over the world. Has anyone thought to tell the CAA?

[BEagle]

Agree wholeheartedly that the time adjacent to obvious planned fixes every 6-10 min is the best way to correct timing. There will be those who, having found they are off track, decide to go direct to destination rather than regaining the planned track - such as the chap who recently blundered into a busy CTR by 'cutting the corner' in such a way!! It's quite likely that many GA GPS users also take the easy option of selecting 'Direct To' rather than correcting XTK after discovering track errors - and this could also easily result in unplanned penetration!! Even if it does save the few pennies that some would allege are apparently so essential to them!!

[Ozgrade3]

I was taught to use 6 minute markers during my own PPL training. In my experiance on my own navs, they are more of a hinderance than usefull. For a start, they are only usefull if your ACTUAL ground speed matches your PLANNED ground speed. If your actual ground speed is more than a few knots off plannes ground speed, each sucessive 6 minute marker becomes more and more in accurate(and confusing). I know I spent more time trying to red the markers in flight to match the actual ground speed, rather than flying the plane.

After 3 navs, I abandoned that method in favour of 10 or 20 mile markers(just count the number of markers off the map and you have a good estimate of distance).

For more advanced students I teach the method of picking a single identiable on track ground feature(between 1/3 and 2/3 of the way along track) for a groundspeed check.
Greatly reduced workload is the advantage.

[climbs like a dog]

I was taught (still teach) 6 minute marks as it eases the arithmetical workload on the student and, most importantly, gives the student a 6 minute cycle into which a cockpit routine can be put.

I think it's all too easy for an experienced pilot to dismiss the method, having since moved onto a technique that suits, but is a student going to have the capacity or experience you can draw on to sort out their pet method? I have been with students assigned to other instructors on navex's where the instructors' pet method has left the student thoroughly overloaded. They use the six minute marks and it all becomes a lot easier. Some of the alternative methods taught were quite good (and some not) and I could see myself using the better methods occasionally where circumstances dictate but surely it doesn't serve the stude in their basic navigation training if they're being overloaded doing the sums.

Anyway, why make it overly complicated?

------------------
0 to 2000ft in 10 minutes

[redsnail]

I was taught the 6 min marker technique. When I had the nav gig sorted and was working in the Kimberley (remote area Western Australia)
I found the method as described by Ozgrade 3 to be the most practical. Also makes a good poor person's DME. With the 10 or 20 nm markers the distance was fixed, ie didn't have to rub them out and start again. If you had 2 or more flights on the same day it could mean a rather cluttered map.
So, my point, it is vital that the student has at least one method that works. Then, with some experience they can modify it to suit them and their needs.
thank you.

------------------
reddo
Life is good 'till the next stuff up.

[eyeball]

I tended to determine my groundspeed by whatever method was appropriate at the time
DME , Radar , or two positive fixes. Then the markers went out and it was time to watch the world go by. A distance marker carries little substance unless a period of time is associated with it.

[4dogs]

Folks,

Time and distance are fixed so groundspeed is the issue. If you have little or no ability to vary the groundspeed then you need to determine your rate of progress to determine your arrival time at some point. Distance markers make it easy to determine that rate of progress. If on the other hand, you can vary the groundspeed to control your rate of progress, then time markers make it easy to achieve your time on target.

The only time that time and distance markers are interchangeable is when everything matches the plan. Otherwise, inappropriate markers create confusion, the very antithesis of marking the map in the first place.

Navigation cycles should be related to the clock.


------------------
Stay Alive,

[email protected]

[climbs like a dog]

Why re-mark your map with 6 minute markers if you're running fast/slow? I only use the original markers. It's no problem working out divergence from planned times so planned ETA can be adjusted accordingly. I disagree that the marks are confusing if groundspeed diverges from the plan. If the student is staying with the plot they'll be fine; if they're not then they're burggered anyway.

------------------
0 to 2000ft in 10 minutes

[puddlejumper]

Surely 6 minute markers are surely only to be used as a time graticule rather than expecting there to be anything necessarily at the fixes. Simply interpolate between them to work out your actual fix. Having said that - I tend to agree that working out a good fix which has both cross track and along track reference and the time to it seems to provide more accurate results. But that's just in my opinion ;-)

[4dogs]

CLAD,

I wasn't proposing remarking anything.

I have navigated aircraft to achieve many different outcomes at extremes of altitude and in vastly different environments. My comments merely reflect on how I determine what parameter to use as the "graticule", based on that experience.

If the magnitude of the discreancy is small, it may not matter much. However, if it becomes large, then confusion will reign. As an instructor, my aim is not to contribute to the confusion.

------------------
Stay Alive,

[email protected]

[deadhead]

Six minute markers are what I teach, and never had a problem with 'em, PROVIDED they are not recognised as the be all and end all. As for being useless over featureless terrain, that's not correct. It matters not that there isn't anything there every time - it's the continuous plotting ad re-plotting that is important. It matters not that things may change during the flight - (providing it is only the W/V!) And getting the trainee pilot into the groove with respect to good solid nav techniques is all important. Now provided you can use things in conjunction with six minute markers, ie not use them in isolation then there is no reason why they can't be used without overloading the student or getting them hopelessly lost waiting for a planned feature to turn up. If that happens then there are more serious problems afoot than using six minute markers.

[Thumperdown]

Well chaps lets not get flustered less we crash! Isnt it better to teach the student a system or method by which they can succesfully navigate. I teach 6 mins cos think it works well. I test many students for skill tests(which requires a system but no feature crawling)and I just want to see them get to the turning point on time using any methodical manner that works for them.
Some guys Ive tested in the past have no system and /or situational awareness cos they dont get taught any type of system

[Cpt_Fop]

Thumperdown, not track crawling !!!!!

Even the most featurless country has some and it you stay on track you won't need to bend your brain around 1/60's, heading correction, inflight wind calculations.

Knowing how to use either method is obviously the preferred method but 10 mile markers are just way more useful and are not effected by GS. If they come and go at 3 minutes then you've just got more accurate navigation. Why not speed your cycle up. It surely can't take the 5 minutes after the 6 minute marker to sit relax and scratch ??

[BEagle]

No - between your pre-planned visual fixes you fly accurately having assessed your tracking/timing errors, re-compute your ETA, and then spend as much time as possible looking out of the window for other track-crawling idiots who are staring at their maps, the ground, their GPS moving maps - but are NOT looking where they're going. The number of times I've had to avoid PA28s and Senecas with bits of orange on them blundering about under VFR not looking where they're going because their pilots are buggering about with some tortuous and pointless flight log when they should be LOOKING OUT are quite a few!! You CANNOT use the same techniques in Class G airspace as in Class A if you want to avoid a collision!!

[Roller Merlin]

BEagle.....well spoken.

As long as a system of heading /IAS / tracking / timing / correction workcycle is taught, then there is time to fly the *amn aeroplane in safety. I have witnessed some sorry "instructors" struggling with a doona-sized and poorly prepared map trying to follow the aircraft's progress rather than directing it safely.

Also, the number of CTA infringements from wayward amateur pilots is getting beyond a joke on OZ! When one recent guy was asked why he busted CTA, he complained that the airspace wasn't marked on his road map!

Clock (time gone, I should be X mins/NM)
Map (I should see this feature at dist/brg) Ground (Big to Small, pinpoint, workcycle)
Next Event (Map away, pull it out at time XX),

...then lookout and enjoy until XX and do it all again. Soooo easy.

[Tinstaafl]

Elegantly put, Roller...

[Swamp]

10 mile markers, 6 minute markers and drift lines for that matter serve no real practical purpose.

Have we forgotten that we essentially have a scale rule on every navigation chart? Remember that one minute of longitude measured along a parallel of latitude is equivalent to one nautical mile. Even an average student will be able to eyeball a distance with 15 minutes of practice. This eliminates the need for any type of marker. Markers are messy and can be very confusing when the aeroplanes actual speed is not what your planned speed is. They are also impossible to use in areas that are denied of suitable landmarks.

I think the best method is to simply mark your position and time every time you get a positive fix on your chart. On every leg you should calculate your revised groundspeed and work out a revised estimate. If you become disorientated or unsure of your position you can simply refer back to your last positive fix and based on your actual groundspeed work out a distance from that fix.

I personally don't believe that techniques should be taught if they can't be applied to faster aeroplane types.

[BEagle]

Sounds like we're back to Standard Closing Angle again..........

[class-e]

I must agree with swamp on this one.
When I was learning to navigate and was having difficulties in accuratley fixing my position, my instructor at the time told me to use "halfway markers".
We would go on a nav....get to a turning point and mark the time. Within 10 minutes, I was to get another pinpoint and again mark the time.He would then take my map off me(or put me under the hood) and get me to maintain a constant hdg and constant alt...and not touch the throttle.
when we would get to the planned half-time on the leg, I would then be reunited with my wac chart and told:
1/ draw a line from the turning point thru the pinpoint and keep going.
2/ work out my groundspeed from the turning point to the pinpoint.
3/look at my watch and work out exactly how many miles we were from the turning point and then follow along the line I had drawn until I reached that distance
4/look at the map and find a feature that should be there and then look at the ground for it

This method I find works exceptionally well in any speed aircraft.(provided you maintain a constant hdg and alt!)It is also handy in teaching "lost" procedures.It also stops the student from constantly looking for features on the ground/map and gets him/her to just fly the plane!
With a halfway point...you already know how long the other half will take.Your closing angle will just be double your track error, and the workload is significantly reduced!

AVIATE , NAVIGATE , COMMUNICATE