lateral separation in DOC4444
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Glad to hear that in Australia they do not apply the DOC4444 exactly as written!
How is same track and reciprocal track defined?
If you use the DOC 4444 definitions it severely limits the use of lateral separation.
Regards,
DFC
How is same track and reciprocal track defined?
If you use the DOC 4444 definitions it severely limits the use of lateral separation.
Regards,
DFC
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Let's keep it simple. If two aircraft are established on two different radials, as long as one or both of them are outside the AREA OF CONFLICT, defined by lateral separation charts that the unit should have, they are separated. It matters not whether they are inbound or outbound. I used that separation for many years, no hassles!!
As a side note, my old unit had a sliding scale for lateral separation based on angular difference between radials. The closest lat sep point was 8DME based on a 24 degree spread, if I remember correctly. As the angular difference decreased, the separation increased out to many miles.
Ready for insults!!
As a side note, my old unit had a sliding scale for lateral separation based on angular difference between radials. The closest lat sep point was 8DME based on a 24 degree spread, if I remember correctly. As the angular difference decreased, the separation increased out to many miles.
Ready for insults!!
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At the units I worked all the lateral separation charts were listed with the maximum height to which each particular chart was valid - this to take into account aircraft slant height distance from the DMEs. With the arrival of modern radar the charts went the way of the dodo.
To cater for any radar unserviceability a readily accessible table is available on position to enable controllers to work out separation distances based on angular differences from an aid and aircraft height - not quite as flexible as the 'old' separation charts, which quite often had entry/exit distances from an area of conflict based on different DME's - but good enough to allow the 'now procedural' controller to work something out whilst the radar was being fixed.
I must admit that I enjoyed those old procedural days. Felt a great deal of satisfaction at the end of the shift.
To cater for any radar unserviceability a readily accessible table is available on position to enable controllers to work out separation distances based on angular differences from an aid and aircraft height - not quite as flexible as the 'old' separation charts, which quite often had entry/exit distances from an area of conflict based on different DME's - but good enough to allow the 'now procedural' controller to work something out whilst the radar was being fixed.
I must admit that I enjoyed those old procedural days. Felt a great deal of satisfaction at the end of the shift.
I can't see anywhere in doc 4444 where it says that lat sep can't be used between radials 180° apart & it doesn't say it in Airservices MATS either, which is why it has been perfectly legal in Oz to do it for 30 years that I'm aware of.
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Agreed.
However, some authorities apply different distances from the VOR (adjust the size of the area of conflict) when one or more aircraft are inbound compared to when the aircraft are outbound.
Regards,
DFC
However, some authorities apply different distances from the VOR (adjust the size of the area of conflict) when one or more aircraft are inbound compared to when the aircraft are outbound.
Regards,
DFC
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Agree with ANSA... it might be legal in the Australian MATS, or any other ATS Unit SOP's for that matter, but that doesn't mean it's safe... and there is always an alternative solution... you just have to think beyond the square of "expected practices".
Last time I saw a particular scenario in Oz... opposite-direction traffic approaching the same VOR (180 degrees between radials). Southbound aircraft at a lower level, Northbound Medevac aircraft (MED1) at a higher level approaching Top-Of-Descent to an airstrip where the VOR was located. Instead of an early descent with a requirement to be vertically separated 10mins prior to passing, the Southbound aircraft was re-cleared outbound from the VOR on a radial that was laterally separated from the Northbound aircraft.
End result, an unrestricted descent profile for the Medivac aircraft and no delay or restriction to the Southbound aircraft... because the amended clearance to track outbound on a different VOR radial was cancelled when vertical separation was achieved with the Medivac on descent and before the Southbound aircraft crossed the VOR.
Separation Assurance and no penalty to either aircraft.
An old phrase taught to me many years ago but one that I have not heard for a very long time...
"Provision for Radio Failure"
If you or an aircraft had a complete communications failure... or deterioration to Unreadable (we experience this every day at some hour in my ACC)... what would happen?
Last time I saw a particular scenario in Oz... opposite-direction traffic approaching the same VOR (180 degrees between radials). Southbound aircraft at a lower level, Northbound Medevac aircraft (MED1) at a higher level approaching Top-Of-Descent to an airstrip where the VOR was located. Instead of an early descent with a requirement to be vertically separated 10mins prior to passing, the Southbound aircraft was re-cleared outbound from the VOR on a radial that was laterally separated from the Northbound aircraft.
End result, an unrestricted descent profile for the Medivac aircraft and no delay or restriction to the Southbound aircraft... because the amended clearance to track outbound on a different VOR radial was cancelled when vertical separation was achieved with the Medivac on descent and before the Southbound aircraft crossed the VOR.
Separation Assurance and no penalty to either aircraft.
An old phrase taught to me many years ago but one that I have not heard for a very long time...
"Provision for Radio Failure"
If you or an aircraft had a complete communications failure... or deterioration to Unreadable (we experience this every day at some hour in my ACC)... what would happen?
ANSA,
If you don't like it, fine, but I have shown how it is legal and safe and been done for 30 years that I know of and still used everyday in procedural towers (obviously not common on procedural enroute anymore, more's the pity, because it can be more efficient) - vertical requirement prior to first aircraft getting to lat sep point.
Quokka,
Yes you had separation, but it's not always no penalty, whereas a lat sep of 8 DME can be much more efficient, with no-one having to go off track. Provision for radio failure is not in the sep standards, but what's the difference between giving a requirement by lat sep as against 10 mins prior to time of passing - they both allow for radio fail as long as you give the requirement prior to radio fail and who knows when that may be!!
As for thinking beyond the square of accepted practices - I now work radar approach and it doesn't take much of a change in acft position for a completely different solution to be required.
If you don't like it, fine, but I have shown how it is legal and safe and been done for 30 years that I know of and still used everyday in procedural towers (obviously not common on procedural enroute anymore, more's the pity, because it can be more efficient) - vertical requirement prior to first aircraft getting to lat sep point.
Quokka,
Yes you had separation, but it's not always no penalty, whereas a lat sep of 8 DME can be much more efficient, with no-one having to go off track. Provision for radio failure is not in the sep standards, but what's the difference between giving a requirement by lat sep as against 10 mins prior to time of passing - they both allow for radio fail as long as you give the requirement prior to radio fail and who knows when that may be!!
As for thinking beyond the square of accepted practices - I now work radar approach and it doesn't take much of a change in acft position for a completely different solution to be required.
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Our operations manual specifically states:
"15 degrees between same direction, outbound aircraft ......."
and
"15 degrees between opposite direction aircraft provided they will pass at a point more than 15 miles from the facility"
I would never use this when A/C are on opposite sides of the VOR, when they are on the same side (still nose 2 nose) and established on radials that differ by at least 15 degrees, and will pass each other more than 15 miles from the VOR, then no problem. Some states publish a lat sep table with more radials and less distances, like 24R and 8NM as previously mentioned by someone else on here.
If they were on opposite sides of the navaid I would give the A/C in level flight a precautionary hold (paper / pretend) at the fix, then push the other A/C up or down as required achieving vertical sep prior the front end of the holding airspace plus an additional 3nm (NZ requirement if memory serves correct for opposite direction)
"15 degrees between same direction, outbound aircraft ......."
and
"15 degrees between opposite direction aircraft provided they will pass at a point more than 15 miles from the facility"
I would never use this when A/C are on opposite sides of the VOR, when they are on the same side (still nose 2 nose) and established on radials that differ by at least 15 degrees, and will pass each other more than 15 miles from the VOR, then no problem. Some states publish a lat sep table with more radials and less distances, like 24R and 8NM as previously mentioned by someone else on here.
If they were on opposite sides of the navaid I would give the A/C in level flight a precautionary hold (paper / pretend) at the fix, then push the other A/C up or down as required achieving vertical sep prior the front end of the holding airspace plus an additional 3nm (NZ requirement if memory serves correct for opposite direction)
"15 degrees between opposite direction aircraft provided they will pass at a point more than 15 miles from the facility"
I would give the A/C in level flight a precautionary hold (paper / pretend) at the fix
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I think that what we are talking about now is different from DOC 4444
DOC 4444 only requires one of the aircraft to be more than 15nm from the VOR.
To me indicates that firstly there is no provision for the situation where both aircraft are inbound but not opposite direction (perhaps included in another part of the requirements?)
Secondly, making a requirement that the opposite direction aircraft will pass at a point more than 15nm from the facility would mean that depending on relative speeds, one aircraft will have to be much more than 15nm from the facility so that when they pass, they are both more than 15nm.
Going back to my original stretching of the DOC 4444 words, it could not happen using this version of the sep standards since the pass would take place within 15nm of the VOR to have the sme situation with 1 B747 1nm from the VOR, the other would have to be some 16+16 = 32nm from the VOR so that the pass will happen between 15 and 16nm from the VOR...........thus the head to head separation is more than twice what DOC 4444 says and sounds far more reasonable.
Regards,
DFC
DOC 4444 only requires one of the aircraft to be more than 15nm from the VOR.
Our operations manual specifically states:
"15 degrees between same direction, outbound aircraft ......."
and
"15 degrees between opposite direction aircraft provided they will pass at a point more than 15 miles from the facility"
"15 degrees between same direction, outbound aircraft ......."
and
"15 degrees between opposite direction aircraft provided they will pass at a point more than 15 miles from the facility"
Secondly, making a requirement that the opposite direction aircraft will pass at a point more than 15nm from the facility would mean that depending on relative speeds, one aircraft will have to be much more than 15nm from the facility so that when they pass, they are both more than 15nm.
Going back to my original stretching of the DOC 4444 words, it could not happen using this version of the sep standards since the pass would take place within 15nm of the VOR to have the sme situation with 1 B747 1nm from the VOR, the other would have to be some 16+16 = 32nm from the VOR so that the pass will happen between 15 and 16nm from the VOR...........thus the head to head separation is more than twice what DOC 4444 says and sounds far more reasonable.
Regards,
DFC
