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Miles from touchdown


Daniel Chester
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Daniel Chester

Does anybody have a quick and easy method for working out an aircrafts track miles from touchdown when starting approach? I am aware its something we should be passing to an aircraft on initial contact when working an approach position, but I often find it difficult to work out accurately - especially when busy!

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To calculate the minimum track mileage:

Anything from around 200kt to 310kt (by my rough calculations) is around 3nm per 1000ft to drop at a reasonable rate. Add 1 nm for every 10kt the aircraft must slow down.

So at Manchester:

Aircraft is at FL90, 260kt. Platform altitude is 3500ft, so its around 5500ft (QNH dependent) to descend. That'll require approximately 16.5nm (5500/1000 * 3) for the altitude. Then to slow to 180kt for an intercept speed, thats an 80kt reduction, or 8nm (80/10). Thus a rough minimum track mileage of 24.5nm. Now of course, this is a minimum and it will likely be more with winds and A320s existing.

 

How to estimate track mileage remaining:

What I generally do is drag the heading tool to a base leg, then a 10nm intercept from the stack. This gives an underestimation of the track mileage remaining. While inaccurate, if anything it gets pilots descending a bit faster. However, over time you get a "feel" for the actual track mileage from the stack to the runway.

 

Hope this helps!

Edited by Darren Hill
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Daniel Chester

Thanks guys - this is similar to what I’ve been doing but I’ve been using the ruler to draw my 10nm intercept, then drawing my base, then my track from the hold etc…which is time consuming. These tips will help speed things up!

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The above methods like measuring works if there’s 1 at a time or already different track miles between them. If there’s several arrivals at the same time then clearly they can’t all have the same track mileage so then I work out the track mileage for No 1 and add the intended final approach spacing on for each subsequent arrival.

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This reminds me, I wrote a guide on 'Counting the Miles' for a Heathrow context with some assistance from those who know what they're doing!! I'll make sure to get around to sharing that - as well as an updated 'Guide to Final Approach' - soon.

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When the approach includes a downwind leg, a useful cross-check at that stage is:- when the aircraft is abeam the airport, distance to run is about 20 miles plus the distance from the airport. So if an aircraft is downwind abeam the airport by 5 miles, distance to go will be 25 miles (10 out, 10 back and 5 on the base)

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Caspian Merlin

You can usually learn the common points at which you descend aircraft and memorise their distances from touchdown - you can tweak the track mileage as required but using those points as a starting point.

If you have a sequence going on, and you are going for, say, 6 miles spacing on final - if you know the track mileage for #1, if you're going to nail the spacing (which of course you are!) then just add 6 (or 7 if allowing for compression on final) whatever then you know how many track miles #2 is going to end up having. So, you can tell #1, say, "25 miles from touchdown" and then #2 "32 miles from touchdown".

The bonus is you've now commited to getting perfect spacing 😄

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  • 2 weeks later...

 I tend to be a bit lazy and have plotted the normal vector tracks with track miles to the  thresholds. Outside this vectoring pattern I can use the distance pointer to calculate  the distance of the aircraft to the start of my vectoring patterns and add this distance from this point of entry to get the total track miles to the threshold.

EGGP.PNG.a83eddb58ae83229b36678d0cd33b09f.PNG

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