Checkpoints on your leg

[Pilot16]

Hi...

I remember during my nav briefing, which happened a while back, I was given an example of a nav leg cosisting of FOUR checkpoints each at quarter intervals (1/4, 1/2, 3/4)
During flight, The remaining ETA's can be updated by using the ATA over a checkpoint...

However I noticed this is not convenient when there is little land feature to identify your position or the leg is too short...so in that situation it would probaby be best to use just a half-way mark...

However since the briefing, my instructor always seems to prefer one checkpoint at the half way :rolleyes: no matter how long or short the leg is...

How do you navigate? Do you always use halfwaymark no matter how long the leg? or does it depend on the land features?

I dont know what Im trying to get at :confused: I guess just your prefered method of navigation when it comes to a long leg, short leg, featureless leg etc.

:ok:

Thanks
P16

[Keef]

My preference is radio nav - a VOR, better yet a DME, and to make it all easy, the GPS.

DME groundspeed readout and my plogsheet, and I can update ETAs easily.

[redsnail]

When I was bush flying I would use all the features I could get.
Over a 100nm flight (1 leg) I would break it down into 2 halves and monitor from there. Other times I would stick to 30 min "checks" or if it was a shorter flight, 15 min checks.
If I had navaids, I would use them.

I guess it's important not to get too pedantic in this flying game. The rules that you described are more guidelines to assist you fly accurately.

[Evo]

Keef, as Pilot16 has an instructor he's probably not supposed to be using VOR/DME - it's supposed to be VFR nav at that stage ;)

I'd only use a halfway waypoint, unless the leg was more than half an hour or so (i.e. 15 minutes to the waypoint), at which point i'd divide it up to roughly 15 minute legs. Obviously I'd use an easy to identify feature somewhere around halfway rather than an empty field at the exact halfway point!

The problem with too many waypoints is that theres more plogging to do and taken to an extreme (e.g. <10nm between waypoints) the examiner may be less than convinced about your VFR nav - you're really just feature-crawling. With a 15 min leg you're only going 20 miles or so, and even if you really b*gger up the heading (or fail to check the DI :O ) you aren't going to be so far from the waypoint that you cannot spot it - especially if you picked a good'un in the first place :)

[FlyingForFun]

There's no such thing as a hard-and-fast rule. If there's an obvious checkpoint, use it. If there are no obvious check-points for a long way, look for a less obvious one. On a 500nm leg, one check-point isn't enough. On a 10nm leg, you probably don't need any checkpoints excect your turning point or destination.

If I find myself uncertain of my position, I'll often look at the chart in-flight for potential checkpoints coming up in the next few minutes to confirm I really am where I think I am. On the other hand, if I'm following an obviously line feature such as a motorway, with towns at regular intervals to check my progress, I probably won't plan any checkpoints at all, and if I want an update on my position at any time I can just look out of the window.

FFF
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[Julian]

P16,

Seems a bit of a strange way of teaching nav, if you get a series of short legs you are creating work for yourself, just break it down into manageable easy chunks and nav that way. At each checkpoint also try and fix on a prominent feature in the distance which will help keep you on course and hey presto your nav check points should turn up where they are meant to!

[IO540]

Keef is absolutely right, but it's totally the wrong answer :)

I think the way to do VFR navigation is to first plan the wind-corrected heading. This will usually be slightly wrong because a) the forecast is wrong; b) almost nobody can fly an accurate heading for very long; c) the DI in most school planes drifts around too much.

So one has to make adjustments as one goes along.

The trick is to not fly from one feature to the next. One always flies a HEADING. One attempts to identify ground features as one goes along (not just mid-leg or whatever). This heading is then corrected a few degrees either way, when ground features which have been POSITIVELY IDENTIFIED are seen to be somewhat off.

The key is POSITIVELY IDENTIFIED. A lot of things looks the same down there, and it's too easy to make a correction due to a mis-identification. I suspect this is the #1 reason people get lost, VFR.

[Keef]

Tongue was definitely in cheek with the "Radio Nav" answer - I thought I'd let the more recent learners give the latest wisdom ;)

I reckon waypoints any closer than 30nm (unless you're turning) are just overegging the pudding. If you pick reasonably recognisable waypoints (avoiding the well-known pitfalls), then you will see them after 30nm unless your course-holding is dire or the wind is horrendous.

Over very flat terrain, I'd go for 30nm (no closer). If there are mountains etc around that give a good "non-waypoint" guidance, I would probably stretch it beyond that.

Flying across Arizona from LA to Grand Canyon, I had waypoints at least 60nm apart and never a moment of "uncertainty". Mind you, that canyon is pretty obvious once you get anywhere near it.

The VOR on the airfield was nice, though, to give that extra warmth.

[Circuit Basher]

.. but I haven't got any checkpoints on my leg! :D

Will hairs / spots / moles [delete where applicable] do??!! :)

[big.al]

When I first passed the PPL I was tending to use checkpoints much too close together for fear of getting lost. This only resulted in too high a workload which could have resulted in me getting lost!

I now tend to use checkpoints at around 20nm intervals, but it all depends on the route. Having drawn the route on the chart I look for easy to spot features (such as a lake with a railway line running alongside it) either on-track or very close to track, and then mark off points along the route with numbers and put the corresponding numbers on the PLOG. Sometimes the checkpoints may only be 10nm apart, sometimes 30nm. The important thing is to be able to positively identify a landmark rather than confusing one lake for another, or one town for another etc.

[Pilot16]

So are your checkpoints all divided into equal distances e.g. four quarters? Does it always have to be EITHER two halves or four quarters?

[englishal]

I draw tick marks every 4 mins (one thumb width) along my track, then label every 20. Then if you are at about say 16 minutes, you should see the feature under the tick mark for 16 mins. If you have a head wind you'll be late, tail wind early, cross wind slightly off track, but only slightly for each tick mark. No big deal if you miss a couple either, you'll pick up on the next ones, the timers running.

This was taught to me by an ex-harrier pilot who did this sort of thing at 400kts 200' above the ground, and it works well. I still prefer navaids, but as a VFR navigation technique it is pretty good.

Cheers
EA:D

[IO540]

The biggest problem I found was that forcing oneself to look for a ground feature every X miles or minutes is that one ends up having to select many features which are ambiguous.

A PPL student doesn't have the spare brain capacity of a Harrier pilot; the latter is selected to be the best of the best from thousands of applicants and to him 400kt is just pottering along...

[Genghis the Engineer]

Ah yes, but bear in mind both that the Harrier pilot is managing an infinitely more complex aeroplane, but also that a lot of those systems are there to do much of the routine work - like navigation - for him (or her).


Personally I mark 12nm intervals, or 6nm in a particularly slow aeroplane. If one is over featureless terrain or I'm too busy I don't worry about it, but I can divide a time by 2, 3 or 4 easily enough in my head, and generally do most of my navigation in minutes per 12nm. I don't like time markers, since it's all too easy for en-route events to change that.

Works for me anyhow,

G