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Dotted Line On MFD - Is It A Tcas Target?  
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Posted (11 years 7 months 1 week 3 days 7 hours ago) and read 2758 times:

Hi guys.

In the photo below of a 777's cockpit, you can see a green dotted line on both the captain & first officer's inboard Multi Function Displays (MFD).

Is this dotted line showing a TCAS target that's travelling from left to right ahead of the 777?

Also, is the dotted line green in colour because the TCAS target aircraft is not in a position of conflict?


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Chris  Smile


"Just a minute while I re-invent myself"
11 replies: All unread, jump to last
 
User currently offlineMandala499 From Indonesia, joined Aug 2001, 6968 posts, RR: 76
Reply 1, posted (11 years 7 months 1 week 3 days 7 hours ago) and read 2716 times:

Mr. Spaceman,

We meet again on an interesting question!

It's not a TCAS warning/target. It's either of:
1. Extended runway centerline...
2. a VOR crs line...

If you see see blue NAV rose pointers, NAV 1 is selected at an NDB (or VOR no DME) and NAV2 is at a VOR/DME (the vor shaped icon on the green line just slightly to the right of the aircraft planned track)...

It's rather hard to see at that size though...

Mandala499



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineAccidentally From United States of America, joined Dec 2000, 643 posts, RR: 0
Reply 2, posted (11 years 7 months 1 week 3 days 6 hours ago) and read 2704 times:
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An abeam point, maybe?




Cory Crabtree - crab453 - Indianapolis - 2R2 - 1966 PA-32-260
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 3, posted (11 years 7 months 1 week 3 days 6 hours ago) and read 2690 times:

Hello Mandala499 & Accidentally.

Thanks for your replies.

OK, so the green dotted line isn't showing the direction of a TCAS target. Instead it's either an extended runway centerline, or a VOR course line. Perhaps it's an abeam point, although I don't know what that is.  Sad

I've never seen a green dotted line like this on a MFD before, and I've looked at a lot of glass cockpit photos on Airliners.net and in aviation magazines. So, I thought it might be a TCAS target being displayed. Just a guess on my part.

Maybe someone will let us know for sure what the dotted line means. Big grin

Chris  Smile



"Just a minute while I re-invent myself"
User currently offlineSushka From United States of America, joined Nov 1999, 4784 posts, RR: 14
Reply 4, posted (11 years 7 months 1 week 3 days 4 hours ago) and read 2606 times:

It looks like a VOR course to me. But what do I know? Big grin


Pershoyu Spravoyu Litaki!
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 5, posted (11 years 7 months 1 week 3 days 2 hours ago) and read 2568 times:

Hi guys.

OK, well it seems to me that the green dotted line on the 777's MFD is likely marking a VOR course ..... because that's been mentioned twice.

Thanks for the help guys.


Chris  Smile



"Just a minute while I re-invent myself"
User currently offlineAJ From Australia, joined Nov 1999, 2397 posts, RR: 25
Reply 6, posted (11 years 7 months 1 week 3 days 1 hour ago) and read 2561 times:

As has been said the green dotted line can indicate a course line from a VOR or a course line from a fix entered on the fix page. The fact that the green dotted line appears to pass through a VOR symbol (in both directions) just to the right of the next waypoint, then through the next waypoint, would indicate to me that the crew has entered the VOR radial that denotes the waypoint's position as a cross check.
I'm sure CX Flyboy could verify this.


User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 7, posted (11 years 7 months 1 week 3 days ago) and read 2552 times:

Just for clarification, a TCAS target appears as one of the following:

Red Square: "Resolution Advisory" Traffic or "RA" (causes a "climb climb" or "descend descend" callout or variation depending on software and situation)

Amber circle: "Traffic Alert" or "TA" (causes a "traffic traffic" callout)

Cyan or White closed diamond: "proximate traffic" (No threat)

Cyan or White open diamond: "other traffic"

The traffic symbols are accompanied by a relative altitude tag and a trend arrow. (Up for climbing and Down for descending)

There is a new system being introduced by Garmin that is capable of using some advanced ATC systems that show a tail (small line) on TCAS targets that indicated the direction. I haven't as yet seen one installed, so for the most part don't expect to see any little lines on TCAS symbols.


User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 8, posted (11 years 7 months 1 week 3 days ago) and read 2554 times:

PS

Oh yah...the green line represents a selected VOR course. The airplane is flying towards it to intercept. The dashed portion represents the bearing to the VOR station, the solid represents the course from the VOR station.

The curved green arc in the display represents the VNAV bottom of descent.


User currently offlineAJ From Australia, joined Nov 1999, 2397 posts, RR: 25
Reply 9, posted (11 years 7 months 1 week 2 days 23 hours ago) and read 2547 times:

Airplay, the green arc, or 'dynamic' arc, is not a VNAV derived display, it is simply the point calculated that the aircraft will arrive at the MCP altitude at the present rate of descent. In VNAV sometimes it matches, sometimes it doesn't, for example the dynamic arc does not take into account decelleration or any other change in the rate of climb or descent.
VNAV bottom of descent, actually called end of descent, or E/D, is marked by a green donut, normally over the runway threshold after an arrival has been programmed.
In the above photo the aircraft is descending to 5000' in FLCH, flight level change, and is well below thje VNAV path displayed on the right of the ND.


User currently offlineCx flyboy From Hong Kong, joined Dec 1999, 6642 posts, RR: 55
Reply 10, posted (11 years 7 months 1 week 2 days 18 hours ago) and read 2514 times:

AJ is absolutely correct.

The green dotted line denotes a radial of a VOR that the crew have put into the radios aids page of the FMC to cross check that the route, which appears to turn to the right, over the VOR, is cross-checked.

An extended centreline of a runway shows up as a white dotted line, but only extends for 14.2NM in the ND scale of 10, 20 or 40 so would not appear right across the whole ND like that.

As for the green arc, AJ is also correct. The green arc is based on 3 things only. MCP altitude, current rate of climb/descent, and groundspeed. In turbulence, when the aircraft is being bounced around, the green arc comes in, and out and in and out as the aircraft fights to be stable. In these conditions, the green arc is a useless tool. In stable conditions it can be very useful, especially when doing a VOR approach to make sure that you reach a certain DME at a certain altitude while doing a continuous descent.



User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 11, posted (11 years 7 months 1 week 1 day 23 hours ago) and read 2426 times:

AJ...yes. Thanks for the correction on the VNAV.

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