Crossing left to right

[bookworm]

In the context of an RIS where separation is not being provided, what does it mean when I'm told that traffic in, say, my 10 o'clock is crossing left to right?

That it looks as though it will pass in front of me from my left?

That it will pass behind me?

That it may pass in front of me, or behind me, or may indeed collide with me?

[panjandrum]

Any of those.

But hopefully the controller may give a little amplification if it does not appear it will get that close, ie 'crossing left to right, but will pass behind you on present track' etc.

If it looked like a dead ringer, then the controller would hopefully re-pass the traffic to you as it became more imminent.

What you do with that information is of course up to the pilot!

[whowhenwhy]

It means that on the conflicting traffics current track that it is moving from left to right in relation to your track. Generally speaking if a conflicting track is much slower than you I'll tell you that it is "slow left, right." If I think it is pertinent I'll tell you that it will pass behind; however, according to the letter of the law all I have to do is call the traffic to you, using "standard RT" and update you only if you request it or I deem that it still poses a threat to you, because you've not called visual or not done anything about it!

[Jerricho]

Normally one would hope if traffic like that is passed, a range would be passed as well:

"Traffic 10 o'clock, range 4 miles, passing left to right.........". Kind of helps a little more.

[SirToppamHat]

Intercept controllers used to be taught target information in the format

240 twenty, left-right heading 320

242 sixteen, 22,000 decimal eight

245 twelve, left right heading 320

The added information about relative motion was to aid fighter crews better to picture what was happening in the days (not long ago) before other systems, and when AI radars were less reliable than they seem to be now.

Obviously the use of the relative motion info is intended to enhance understanding for those without radars at all. In my experience, the call 'left to right' is not intended to indicate whether the confliction is likely to pass in front or behind you, unless additional info is given (eg 'crossing nose' or 'should pass behind')

[Avoiding Action]

Some alternatives, Bookworm, to that sort of amplifying information:

10 o'clock, 4 miles, slightly converging heading...

10 o'clock, 4 miles, opposite direction traffic displaced left 2 miles...

10 o'clock, 4 miles, manoeuvring...

However, as www said, the controller doesn't have to pass this info; he's just trying to increase your situational awareness.

Oh, and I'd like a ht with all those as well;)

[Spitoon]

Under a RIS, as has already been mentioned, the controller tell the pilot about other traffic and then it's up to the pilot to decide what to do.

The problem is that if the controller gives nothing but the position of the other traffic it's probably because he or she doesn't know anything else about the target - and further info would only be guesswork and, potentially, wrong or misleading. Any traffic info given by clock code is going to be accompanied by the range - I can't think of any situation where this would not be the case.

If you want more info you can ask for updates if you cannot see the traffic.

[DONer Kebab]

When providing traffic information to ac under a RIS I would hope that controllers give pertinent information that allows the pilot to build up the 3-dimensional picture of significant traffic. Standard traffic information under RIS should consist of:

Relative position of conflicting ac in terms of bearing (clock code) or compass points to a manoevring ac.

Distance in nm

Relative movement to subject ac. This is where the crossing left to right / reciprocal heading or suchlike comes in.

If known the level of the conflicting ac. Normally given as 'indicating FL??' or 'indicating ???ft if using SSR. If no height information is available 'no height information' might also be passed.

No further information need be given on the conflicting ac unless requested by the pilot or, in the opinion of the controller, the conflictor continues to pose a definite hazard.

In all of the deliberations on TI under RIS only pertinent information should be passed. Therefore, if another ac is definitely passing behind the subject ac and poses no hazard, unless it is likely to get reasonably close (5nm?) no TI is necessary.

[bookworm]

OK, time to revive this one a little with the follow-up question. Please bear in mind in what follows that I'm aware that the information delivered in a radar information/advisory service may be prescribed by regulation (in particular MATS Pt 1 Section 1 Chapter 5 15.1). If I question the status quo, I am not for a moment suggesting that ATC is doing it wrong, but rather that the system itself is not optimal.

The problem with the traffic info as passed is that the movement information (e.g. "crossing left to right") is of no use to me as a pilot.

Any aircraft on a converging track will have no relative motion with respect to my aircraft (or more correctly, the relative motion will radial -- directly towards my aircraft -- with no tangential component). If the relative motion is towards the rear of my aircraft (e.g. 11 o'clock to 10.30 or 2.30 to 3 o'clock) then it will pass behind. If the relative motion is towards the front of my aircraft then it will pass in front.

The action that I take to increase separation depends on which of those situations is the case. If it's going to pass in front, I'll turn towards it. If it's going to pass behind, I'll turn away from it. If it's coming straight for me -- well it doesn't really matter which way I turn, as long as I turn. :)

"Crossing left to right", or whatever, gives me no useful information. If the traffic is in my 10 to 11 o'clock then it's bound to be crossing left to right -- otherwise it's going away from me or passing harmlessly down my port side and there's little point in calling it.

What I need to know the answer to is "which way do I turn to increase separation?". Of course I can guess which way to turn, but that will as often decrease the separation as increase it. I'm not asking for 5 miles here, just an indication of which turn is going to make life better.

In an ideal world, you'll warn me if the other aircraft continues to be a threat, and I'll see it before the crunch. The only problem with that is that it's the aircraft with no tangential relative motion that are the hardest to see. So we need to work together to make sure that safety is maintained even if the world is less than ideal.

Two questions:

Is it usually apparent which of the three cases ("passing in front", "passing behind", or "coming straight at you") is happening? (I understand that aircraft don't always travel in straight lines, but most of the time they do!)

And if so, what phraseology should be used to help the pilot distinguish, in other words to help me know which way to turn?

[mainecoon]

it could be in your 10 or 11 and on a closing heading so not in every case crossing left to right and we will tell you this
also 10 11 oclock passing down your left hand side

we warn you where, the distance and direction (sometimes speed fast jet etc)
but under ris it's your call
we may be providing ras too many other aircraft but furnish you with the information to make an informed choice as to your course of action

information is as it reads in the dictionary as is advice:ok:

[StillDark&Hungry]

What I need to know the answer to is "which way do I turn to increase separation?". Of course I can guess which way to turn, but that will as often decrease the separation as increase it. I'm not asking for 5 miles here, just an indication of which turn is going to make life better.

Then you should have asked for a RAS:rolleyes: :rolleyes:

"Crossing left to right", or whatever, gives me no useful information. If the traffic is in my 10 to 11 o'clock then it's bound to be crossing left to right -- otherwise it's going away from me or passing harmlessly down my port side and there's little point in calling it.

Not necessarily - could be flying parallel to you??? (slim chance I know but possible):ok:

Any aircraft on a converging track will have no relative motion with respect to my aircraft (or more correctly, the relative motion will radial -- directly towards my aircraft -- with no tangential component). If the relative motion is towards the rear of my aircraft (e.g. 11 o'clock to 10.30 or 2.30 to 3 o'clock) then it will pass behind. If the relative motion is towards the front of my aircraft then it will pass in front.

EXACTLY MY FRIEND At least you now know which window to look out of to make your search for the conflicting easier:)