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Overflying instrument approach tracks

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Overflying instrument approach tracks

Old 3rd Jul 2018, 20:38
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Overflying instrument approach tracks

Hi there,

Is there a safe height one can overfly an instrument approach track? And is there a procedure for gaining permission?

The reason I ask is because I am planning a VFR flight into Duxford from the north, and it’s very close to Cambridge airport with an approach track. I could just stay on the radio to Cambridge and ask permission, although i’ll probably need to be talking to Duxford at this point. The joining instructions are such that it’s awkard to totally fly around the track.

Any my specific advice on Duxford appreciated, and general advice to do with instrument approach tracks.

Last edited by PelicanSquawk; 4th Jul 2018 at 09:39.
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Old 3rd Jul 2018, 21:05
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Traffic above Cambridge could be at any height if they're practising holds.

But it's class G, so you don't need permission. Talk to them, and if there's a problem they might politely ask if you mind sticking to your current altitude so they know what you're doing and can keep the instrument traffic out of the way, that's the most likely outcome. You don't need to talk to Duxford until you're clear of Cambridge.
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Old 3rd Jul 2018, 21:11
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Originally Posted by Gertrude the Wombat View Post
Traffic above Cambridge could be at any height if they're practising holds.

But it's class G, so you don't need permission. Talk to them, and if there's a problem they might politely ask if you mind sticking to your current altitude so they know what you're doing and can keep the instrument traffic out of the way, that's the most likely outcome. You don't need to talk to Duxford until you're clear of Cambridge.

Thanks for this. Iíll probably just fly overhead Cambridge any way. I was more just curious about what height you can safely assume an instrument track isnít going to be an issue. I guess in every scenario you should be talking to them any way.
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Old 3rd Jul 2018, 21:14
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If this was about decent aerospace, the answer would be simple: in any controlled area, coordinate with the controlling authority. In class G, apply whatever the AIP says, and it never hurts to request advice from FIS.

But as I understand it, the Brits love to make things unsimple...
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Old 3rd Jul 2018, 21:17
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Are you talking about the ILS track on a chart? The gradient is usually about 300' per mile, so if there's someone on the slope, that's where to expect them. If you're VFR in uncontrolled airspace, just look out the window like normal - you can fly down it, across it or even up it - but common sense says avoid it especially if it's the active.

At 10 miles, it's around 3000' so you could fly under it at 1500', likewise at 3 miles it'll be around 900' so you could fly over it at 2000'
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Old 3rd Jul 2018, 21:59
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Originally Posted by rudestuff View Post
Are you talking about the ILS track on a chart? The gradient is usually about 300' per mile, so if there's someone on the slope, that's where to expect them. If you're VFR in uncontrolled airspace, just look out the window like normal - you can fly down it, across it or even up it - but common sense says avoid it especially if it's the active.

At 10 miles, it's around 3000' so you could fly under it at 1500', likewise at 3 miles it'll be around 900' so you could fly over it at 2000'
If more or less overflying the airfield, then the inbound leg - the one marked on the chart! - is indeed low enough not to have to worry about; it's the beacon outbound leg starting from 2,000' or 3,000' that's more likely to be interesting. Oh, and if Cambridge ATC is on one of its half hour breaks due staff shortages there will be people milling around at all levels in the overhead waiting for them to open again, but IME the "Cambridge traffic" calls work fine.

Suggest overflying Cambridge at 2,500' - that's what most passing traffic seems to do, cloud permitting. I've never heard this be a problem (well, instrument training traffic might be given "not above 2,000' on the go-around" to keep out of your way, but that's all good practice for the student).
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Old 3rd Jul 2018, 22:10
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Thanks all. All good advice, it’s got to know I’m ok to fly in the track, and about the various altitudes of it. I’ll probably opt to fly overhead.

Thanks
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Old 4th Jul 2018, 08:58
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Unless you are in a warbird, the circuit is to the south of Duxford airfield so it is easier to route in via the town of Royston, which Duxford like to use a VRP anyway. That helps keep you clear of Cambridge.
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Old 4th Jul 2018, 09:16
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PS,
You probably know this already but, just in case, if you want to get to Duxford early, you need to PPR the day before. They don't open until 1000 and that's a bit late if you want a full day there. I nearly got caught out by this but they kindly let me in as I had been there before.
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Old 4th Jul 2018, 09:38
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Originally Posted by pulse1 View Post
PS,
You probably know this already but, just in case, if you want to get to Duxford early, you need to PPR the day before. They don't open until 1000 and that's a bit late if you want a full day there. I nearly got caught out by this but they kindly let me in as I had been there before.

I didn't know that! So thanks for this.
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Old 4th Jul 2018, 13:29
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Originally Posted by PelicanSquawk View Post
Thanks for this. Iíll probably just fly overhead Cambridge any way. I was more just curious about what height you can safely assume an instrument track isnít going to be an issue. I guess in every scenario you should be talking to them any way.
It's a good question but a tricky one to answer. For typical conventional procedures, you'll cross both the outbound and inbound legs. As an example, the platform altitude for the ILS23 at Cambridge is 1700 ft, so you can expect inbound traffic to be not below that level until it has intercepted the glideslope at about 5 miles on extended centreline. On the outbound leg, which you'll also cross, aircraft may be descending to about 2000 ft from much higher levels, though most usually from about 3000 ft. If you talk to Cambridge Approach, they will be able to advise you as to any instrument traffic, and unless there's a conflict they shouldn't object to an early call to Duxford to out out your join.

You can find Cambridge approach plates in the AIP.
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Old 4th Jul 2018, 17:48
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If you are west of Cambridge you may not be crossing the approach but the 23 departures. If jets they may climb quite quickly so there is no conflict free height/alt. They are friendly and really appreciate a call. If there is no conflicting traffic they will pass you to Duxford quickly.
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Old 7th Jul 2018, 22:45
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Just a follow up on this, I flew into Duxford today via Royston. It was all very straightforward with Cambridge, and I must say Duxford were excellent, from the moment I called to PPR, to someone meeting us at parking and explaining everything. Great day out.
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Old 8th Jul 2018, 17:40
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Best bit of advice was from Gertrude - "talk to them". Simples.
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