10 minute vs 10 mile markers

[Guest Flyer40]

I think you answered your own question Peter and I'm sure we're saying the same thing. If I keep Australia on my left I'll get where I'm going, sometimes at can be that easy.

 

I was thinking about the difference between flying in familiar territory where I simply know where I am, and flying where there’s some reason I actually need to navigate.

 

Moving map GPS contributes enormously to situational awareness and it's hard to get lost if you know where you are. But remembering that every accident features multiple failures I have no intention of falling victim to situations like; unfamiliar territory + GPS failure, or visual navigation error + GPS positioning error.

 

When I need to I protect myself by keeping a map handy and periodically recording verified positions, rather than placing all my faith in that beautiful 10.4 inch display.

 

But then again, my wife says I have a map fetish….

 

 

[Yenn]

While I wouldn't rely solely on the GPS it is a great help when you are West of the ranges. The country can be very flat with no major markers and the visibility can be poor with haze. Just being a few degrees off track may mean you fail to see your destination. Which way do you turn when the clock says you should be there. That is when the GPS pays for itself, especially if fuel is running short.

 

 

[Seal]

To go back to the original topic for a minute, I use 10 mile markers for a few reasons which make sense to me at least. Ten miles is ten miles on the map, always, where ten minutes is always ten minutes but it´s representation on the map varies constantly even during a flight. That means I can draw tracks and distance markers well before the flight and know that they will be relevant when I fly. I even have the chance to study the maps and look for key landmarks in the areas where I might plan speed and heading checks. If using time marks, then I can´t do any of that and I have an annoying series of calculations to do to put the markers on the map when I probably should be thinking about other things. I suppose I could put markers based on airspeed but I know these will be wrong and will give me a cumulative series of errors to balance during the flight

 

When the day comes and I´m zipping along I can use the distance marks, clock and whizz wheel to do GS checks, and I do see that the minute markers would do this directly but only provided the weather guessers were spot on. In the sort of aeroplanes many people fly the groundspeed errors can be a large proportion of the calculated value and my feeling is that time markers rapidly decrease in value as the difference between marks and reality becomes larger. How do I use them, keep some running correction in my head?

 

When my GS is not as predicted my mile markers are still miles, I can use them as the basis for GS calculations. If I have time marks, what to do? Go back and remeasure the map to get my distance? Just seems more awkward to me.

 

Now to the interesting part, GPS use. Ahh the full colour moving map, where, when, how fast, more information than you can poke a stick at. Wondrous modern technology or evil seductress luring real men away from the true path of navigation?

 

I think they are wonderful things but I don´t trust the installations to keep working all the time which means I need a backup method. My backup method of choice is the map, watch and whiz wheel. If I am going to use that then I need to keep in practice because unless I´m in practice the workload is just too high. To keep in practice use steam driven navigation as my primary tool and the GPS for cross check when I´m going somewhere I have to navigate.

 

The ¨use the GPS and if that fails I´ll whip out the map¨ school of thought seems popular and I have a couple of cautions for its adherents. The first is that if you don´t have a good grounding in navigating from a map the additional workload and unfamiliar procedures are enough to make other aspects of your airmanship deteriorate. The second is don´t underestimate the difficulty of orienting yourself to a map. If you are in the wide flat country it can be just about impossible and if you are dancing with control steps then the time taken and the distraction from other things can be critical. At the very least keep a map out and keep yourself located on it.

 

Other people use a second (3rd, 4th) GPS and that´s probably OK provided you keep all the map packs up to date, after all you are going to be relying on it for that too, make sure they have independent power etc etc.

 

I choose steam driven navigation because it is not hard to do and I find a certain satisfaction in having things turn up over the nose at the appointed time using such simple tools.

 

Cheers, Selwyn

 

 

[Guest J430]

shaula1247

 

10 mile markers :thumb_up:

 

your points are very valid, 10NM = 10NM......no matter what you fly. Now when you fly at 180-250kts you may want to use 20 miles, but same deal!

 

J:wave:

 

 

[antzx6r]

On the issue of a secondary GPS, I'm thinking of getting me a cheapy (no maps) as a a backup that will give me a simple track to hold if I can't position fix and get worried I'm completly lost. Primary Navigation with wizz, map and watch. Some planes I hire have a GPS and then my own hand held cheapy with the waypoints programed in as a last resort. Is this wise or should I think about spending more to get a map based one? I know as navigation goes you really need the map based units but as a simple insurance policy in the bottom of the flight bag, what do you recon???

 

Ant

 

 

[Mazda]

Ant I'd suggest a map based one as there's less of a chance of gross errors! Even something like the old Garmin Pilot III (no longer made but probably available 2nd hand). Small, light, black and white moving map ... I can't imagine they would be expensive 2nd hand.

 

 

[Guest Baphomet]

I've been using a Magellan Explorist 100 for ages. If you can't get around without a moving map GPS, then you probably failed your NAV and shouldn't be flying x-country anyway. The only problems with the Explorist, are no ext power (batteries died on me once, and had to Nav the old way) and buttons are small, so changing waypoints if/when its turbulent is not easy.

 

;)

 

 

[Yenn]

I have never used a moving map GPS. I find the line on the screen to follow and if I need more than a Goto somewhere off track to one side will just about locate me. Basicly all I am doing is getting distance and bearing from my Goto point and have to add or subtract 180 to get position to advise others. It gives me distance and time to run which is all I need.

 

 

[Guest Howard Hughes]

You guys crack me up sometimes, you will see so much more without a GPS, I long to fly a machine without one, hopefully one day my time will come!

 

But back on topic, when flying VFR I always put marks at the halfway point for the sector and if it is long enough, then quarter way marks. IMHO ten mile and ten minutes is just overkill!:thumb_up:

 

Cheers, HH.

 

 

[antzx6r]

Thats funny. While this duscussion was progressing I was thinking that would be an easy logical distance/time/eta check and was going to give it a try next flight. But no-one has ever mentioned it before. Any reasons this is not common practice? Or does the 10min / 10mile standard just date back to early days?

 

 

[Guest Howard Hughes]

Or does the 10min / 10mile standard just date back to early days?

From what I understand this is a more modern technique! The only advantage is that tracking errors are recognised earlier, however in ten miles the deviation is often so small it is hard for most to pick up.

'Halfway' or 'quarterway' marks tend to make the 1 in 60's easier in flight!:thumb_up:

 

 

[Yenn]

It all depends on what you are flying. In a Thruster the halfway point may not be far but the time could well be long enough to have quite an affect from the wind.

 

 

[bushpilot]

I often get the urge to do an even earlier call - say at 15NM.. 10 sometimes seems close when you are moving into a busy aerodrome at 100kts and can see activity about... Do others get the same urge??

 

 

[BigPete]

That's not a bad question Chris. I must say I've been tempted at times, but experience shows that things happen fairly quickly in the circuit area. At 10 miles out you're still 6 minutes away from the circuit.

 

I can do a complete T & G circuit in six minutes or less, most people in the circuit will have landed by the time you get there. When I went to Narromine this year, I couldn't believe the traffic (also at Hopetoun Fly In), but by the time I arrived (at the circuit) it was relatively quiet.

 

You might even create a situation whereby other pilots hearing your call, (at 15 miles) tend to disregard you as you are not close enough to worry about. You may also add to unecessary "radio clutter" at a busy time.

 

It is very important that you have a good mental picture of the strip and its orientation and to be at the right height for joining or overflying the same.

 

Just my $1.20's worth.

 

regards

 

:big_grin:

 

 

[Admin]

The 15mile call is interesting and I would like to hear comments on this.

 

Firstly I switch over to the local at 10-11 mile, make my call and then listen to the traffic etc. I do this as I feel most people switch away from the local fairly quickly after departure and possibly when they get to cruise alt. Now if you switch away from area and over to local at 15m then you may be switching over a bit to soon - just a thought!

 

Also, it may have been an isolated case but one time when I was coming into Shepparton I switched over at about 15-18 mile out and heard nothing but as I got closer I started picking up some weak calls that became stronger as I got closer. I never asked but it may have been possible that if they were weak as I got closer, would they have heard my call especially if anything happened like colliding with an aircraft that was on area not local that had just left Shepparton - just another thought.

 

Is there an actual rule on this?

 

 

[blueshed]

I always figured you have to give your call by 10 nm

 

Cheers Guy

 

 

[Guest airsick]

Is there an actual rule on this?

AIP ENR 1.1 - "By 10NM inbound or overflying"

 

So it is ok if you do it earlier.

 

 

[antzx6r]

I always figured you have to give your call by 10 nm

You do. This is just a thought on the tendancy to want to make the call earlier when the area looks (or sounds) busy.

 

As Big Pete has already said, the more important thing I think is to have a good mental picture of the field, then visualize the aircraft in there positions as they call them. Calling too early will just make the area for which to visualize that much bigger. So for instance, someone calls inbound 15nm, you then have to rethink how long it will take for them to get where you next need to have them in sight. It just adds to an already confusing situation. I've been really working on this of late, because traffic around the ctaf in areas like Hoxton Park can get quite busy. And I hate being suprised to see someone nearby you didn't see till then. No real bad close encounters yet. But it only takes one. I say keep the calls as close to standard as possible.

 

And no calling 10nm when you're only 4!

 

This is hard enough as it is.

 

 

[facthunter]

When to call.

 

There is a suggestion that you call earlier IF you are faster. RPT do that. Groundspeed would be the real factor.If you are coming in in your drifter WB and there is a 25 Kt headwind, you might be 20 minutes. This brings in the time element. which is what it's about in this instance. I would see that there is benefit in listening out earlier, to get more idea of the runways being used,& level of traffic, provided I did not have obligation to listen out on another frequency. Mazda's point on overloading the airwaves should be noted.

 

If you are arriving on a track which might be frequently used by aircraft arriving/departing the particular aerodrome, then going to the frequency earlier might be a good idea, but rather than arrive on these more congested tracks, thought should be given to diverging a little and coming in from another direction.

 

Even if I am 10 miles away, or more and abeam, in some circumstances, I would give a call. I have had a few close encounters east of Mangalore with aircraft departing in that direction, so being on the APPROPRIATE frequency helps your chances of survival. The rules don't tell you everything. They're a guide... Nev..

 

 

[Yenn]

If you are going to call at greater than 10 miles out, remember to give a time of arrival in the circuit area and also height. That will help those already in the area. Nothing worse than sitting at the threshold looking for a plane that will not arrive for 5 minutes.

 

 

[dingduck]

What about 6min markers?

 

Why doesn't the poll list 6min markers? From 1979-2003 I used whiz wheel & GS checks. Tried 10nm markers, now use 6min markers & don't go past the training area without 'em.

 

!-- @page { size: 21cm 29.7cm; margin: 2cm } P { margin-bottom: 0.21cm } --> 6min markers are are easy to calculate – simply 10% of your ground speed gives you the distance you mark each leg off in on your chart. On departure, add 6min to your departure time, write this time beside the first marker. Add 6min to that time & write it beside the next marker & so on for the whole leg. Now you have what amounts to instant Dead Reckoning, you can always know where you are by just looking at your watch. By the about the middle of each leg you will know if you are late, early or on time. If, for eg. you get to half way 2 mins late, you will be 4 mins late by the end, so revise your next ETA by 4mins. Keeps the electronics honest too. Even if I haven't done wind calcu's I still use this method – just based on TAS & having taken note of the forecast wind, know whether to expect to early or late. For very short legs I use 1 halfway marker. If you always think in time you won't get caught out being behind the plane when going from slow to fast ACFT or with the 40kt tailwind we had coming home from Cowra last weekend. Time is also good for planning descents to your destination or for avoiding CTA – descent for Camden from 7500' last weekend was started with 9min to run - for all you mile junkies ;) that's 27nm to run with the tailwind or 13 nm if it had been on the nose!

 

 

[BigPete]

...or halve your workload and go for 12 minute markers @ 20%.

 

regards

 

 

[jcamp]

Also, it may have been an isolated case but one time when I was coming into Shepparton I switched over at about 15-18 mile out and heard nothing but as I got closer I started picking up some weak calls that became stronger as I got closer. I never asked but it may have been possible that if they were weak as I got closer, would they have heard my call especially if anything happened like colliding with an aircraft that was on area not local that had just left Shepparton - just another thought.

Issue at Shep is the transmitter to the N (Radio Australia? 50KW?). Apart from receiving audio occasionally, the strong signal can reduce the sensitivity of your receiver (via the Automatic Gain Control) or overload the receiver completely (same principle as a IED jammer). No transmitter has all its power on one frequency and no receiver works on only one frequency.

 

The exact effect depends on frequency they are using, where they are aiming, receiver design, antenna setup (inc bank and pitch), quirks in the transmitter, phase of Jupiters moons etc etc etc.

 

Short answer is radio comms at Shep for traffic should be regarded as even less reliable that elsewhere.

 

 

[K-man]

I like the thought of the 6 min mark. Seems easy to do the calculation. With regard to the GPS, our AvMap is notorious for failing at the most inopportune time. Last time was over the desert north of Coober Pedy. We make sure we back up all waypoint and route data before we fly to enable the information to be reloaded if required. That's ok if the weather is good but in rough conditions it would be very difficule to reset everything. We also carry a handheld GPS as backup, route etc loaded before we fly. The maps are always out anyway.

 

 

[wanabigaplane]

Whatabout....

 

Whatabout 10 litre markers ? Just a thought !

 

Jack. :big_grin: :big_grin: