1 mile right of track
 

Whilst I’m not one to read the refs in my spare time, I remember reading many years ago, that one should fly 1 mile to the right of the GPS track.

Realistically, does this get taught these days or at least followed by most?

With more and more pilots in the generation of the magenta line, it feels like heads-on’s would be far more probable. I’ve had many occasions outbound from my local, to find someone on the exact reciprocal track inbound.

While it is currently a little bit safer with most A380's sitting on the ground, it's still a great idea for smaller aircraft - when its available.

https://www.flightglobal.com/a380-wa...124052.article

The linked article refers to the Challenger that suffered a fairly serious upset approaching the Arabian Peninsular back in 2017 when it passed under an A380, 1000' above.

The aircraft was subsequently written off.

Squawk is right. GPS assisted collisions are a real danger if you use catalogued man made features as waypoints. I’ve been saved by hemispheric altitudes more than once. I now always offset by a random distance, never exactly one mile either. My instructors years ago criticised this, calling it, “wandering all over the sky”.

Was a recommendation for VFR flight in non controlled airspace. ( CAAP 179 ) when using GPS for navigation.

You might consider being on the upwind side of track as the wake will drift as it descends????

More for reciprocal tracks at same altitude on autopilot. Read up on the 737 vs. a Legacy in Brazil a few years back. Legacy crew accidentally turned off their transponder, ATC had them at wrong level. Lost their winglet but survived. 737 lost the outboard 1/3 of their wing and didn’t...

Uihttps://en.wikipedia.org/wiki/Gol_Tr...os_Flight_1907

If your identified and try to track a 1 mm offset without a clearance ATC will have a go at you. If you are really lucky they will also file a report on you when ADSB equipped.

Modern navigation equipment is so accurate that reciprocal aircraft on the same airway at the same level would probably collide. I’m used to watching traffic on the same airway, opposite direction, 1000’ above pass directly overhead without even being a wingspan off track laterally, the fuselages line up exactly.

Then a minute or so later you hit the wake turbulence and if you’re below same direction traffic you need to request an offset as you stay in it due to both aircraft tracking the airway so precisely.

Often ATC will instruct aircraft to offset as they are too close together to make out on the radar screen.

Part of the problem is for VFR drivers they have so much fancy stuff in their machines that not only does their flight pass by without hardly looking out the window they are heads down which actually puts them in a higher risk bracket for mid air collisions!
I recall the early days when GPS driven FMS's where being used for primary Nav flying across the ditch I watched an ANZ B767 opposite direction which looked like we where going to split each other down the middle!

Can recall passing opposite direction Ansett F28 & BAE 146 aircraft - either above or below our altitudes - both of us utilising VLF Omega & never within a bulls roar laterally of each other... GPS has made a huge difference to tracking accuracy...

Until you meet opposite way traffic with the same idea..... upwind is “upwind” for everyone.

The newer Garmin units allow a parallel track to be flown . You can set it at the chosen offset .

When all else fails read the manual :)

Strategic Lateral Offest of Position (SLOP) is now mandatory in Atlantic airspace. It's up to two miles right of track (it used to be 1nm or 2nm, but now it's in decimal increments - eg 1.2, 1.4 etc) - always right, to avoid a head on collision if someone makes an altitude error. In that airpsace, there's no need to notify ATC.

Nose to nose mid-air
 

I recall one of the first mid-air collisions relating to GPS tracking was in Canada. A Metro and another IFR twin, one on climb and the Metro on descent, nose to nose. I recall that the twin had rolled hard one way after what the investigators suggest was a late observation of the conflict. The report suggested that if he had pushed or pulled the collision may have been averted, but because he rolled the vertical profile of the twin was increased significantly causing its then upper wing to slice the wing of the Metro. Lesson there is don't roll to avoid in such circumstances. And yes a one mile offset is a good idea, especially in some airspace. I doubt if en-route radar could pick that up?

I found the ref, an interesting read and still valid some 25 yrs after the event...
https://www.bst-tsb.gc.ca/eng/rappor.../a95h0008.html

A bit harsh for 1mm :E

-SLOP can be applied in Australian Oceanic airspace as well, up to 2NM right of track in 0.1NM increments.
-When in Oceanic Airspace, a clearance for the offset is not required, but in CTA, a clearance is required to offset from track.
-When moving from OCA to CTA, you must regain centreline before leaving OCA.
-Don't offset without a clearance in CTA, the tracks are often not very far apart.
-Don't offset to the left, it seems obvious, but I've seen it done.
-You can't add a SLOP offset in addition to a deviation off track, that is, if deviating 50NM off track due weather, that's the limit, not 50+2NM.
-If in surveillance airspace (ADSB or Radar), track deviations can be seen.
-If in non-surveillance airspace, offsets will only be seen if ADS-C equipped.
-Take wake turbulence seriously, it breaks planes.

You beat me to it.

accuracy is dependant upon number of satellites the gps receiver is interrogating. On the civilian bands dilution of precision (the circle of accuracy) with just 3 satellites is accurate to within 30 metres, that halves with 4 satellites. In most cases even at maximum opposite error you would still be within each other wingspan. I remember when we were first introduced to gps, before there were enough satellites up for alt and in DR mode most of the time. How on earth did we ever manage before gps, brings back so many memories.

Xeptu, isn’t the problem that as aircraft approach each other, they both receive the same errors in the gps signals? The absolute accuracy is not material. Both receivers will try and direct you to the same point.

Please explain to this long retired army pilot what is meant by the magenta line

Yes that's right, so you will both be within that same 30 metre circle as a worse case error.

The flight planned track, that which the autopilot is following to the next waypoint

Thank you. Now I understand. In my day it was chinagraph on a map.

Classic video that spawned the phrase, from the dawn of Electronic Flight Displays in cockpits....

This is the FMS (Flight Management System) of your day scouah
https://cimg8.ibsrv.net/gimg/pprune....92c41b1e0b.jpg
The Pray Wheel

It's definitely a thing with VFR in uncontrolled airspace, even when hand flying because you keep coming back to the magenta line no matter how sloppy your flying. And it does not need much fancy stuff - an ipad is enough. But use of the 'advisory frequency' seems to effectively reduce the risk. Here in 5Y land everyone is very conscientious about announcing their presence as they progress (at least, the ones I hear are :) ), is it the same in Aus?

Triadic posted a link to an accident report where there was a midair collision. It is well worth reading - especially this extract: I must admit I had never thought of the situation where a collision is imminent and you have to decide whether to roll out of the way or climb/descend out of the way. See below


1.9.9 Pilot Avoidance Techniques

Assuming that a pilot will be capable of visually detecting another aircraft in flight and determining that the closing geometry represents a mid-air threat, then the final stage in the see-and-avoid sequence is to initiate an effective avoidance response. The aim of that response will be to increase the miss distance between the aircraft. The effectiveness of that response is dependent on a number of factors; in general, either pilot can alter the geometry of a collision by changing some combination of aircraft speed, altitude, and heading. Because each of these actions will affect the geometry differently, it is essential that the pilot choose an appropriate combination of actions that will merge to achieve a corresponding effect.Footnote7

The optimum avoidance response will differ depending on the time to impact. There is research evidenceFootnote8 to indicate that, outside 10 seconds to the point of closest approach, the pilot should use compatible manoeuvres combining speed, altitude, and heading change. However, once the aircraft are inside the range of approximately 10 seconds to impact, the pilot should employ an altitude change only. This conclusion is based on an argument that, when two aircraft are confined in close quarters, the essential action is to minimize the relative cross-sectional areas of each aircraft. Under these circumstances, it has been generally found that any application of bank will increase the relative cross- sectional area and thereby increase the probability of impact.Footnote9

As an example, a Piper Navajo aircraft similar to the one involved in this occurrence will have a vertical cross-section of approximately 13 feet when in level flight. At bank angles in the range of 45 to 60 degrees, the vertical cross-section will be in the range of 28 to 34 feet. The final value of the vertical cross-section will be dependent on the aircraft's wing span and on the applied bank angle.

Formal training on how to recognize in-flight collision geometry and on how to optimize avoidance manoeuvring is not part of the required syllabus for any level of civilian pilot licence in Canada.