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Traffic on ND Display

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Author Post
Member
Registered: Jun 2009
Posts: 187
Location: Devon, UK
Hi Hardy,

I have been revisiting the code for this and I have a problem. I have got traffic externally controlled set and I am sitting on the tarmac. A traffic plane generated by X-Plane is approaching me down the runway.

I can see the strobes in your out-of-window display, so I have injected it correctly, but the traffic plane doesn't appear on the ND. (TFC and TA ONLY is on the ND).

However, if I go into X-Plane and increase the height of the traffic, it appears when I increase the altitude by about 50 feet. Is this the expected behaviour as I am sure I have seen taxiing traffic on the ND in the past?

Mike
Member
Registered: May 2010
Posts: 843
Quote
Is this the expected behaviour as I am sure I have seen taxiing traffic on the ND in the past?


Is this in real life or in the simulator?

There are a number of ways that TCAS can detect intruder aircraft. If the intruder aircraft is fitted with a Mode S ATC Transponder, the intruder aircraft will send "squitter" messages once each second which can be heard by your aircraft. Also, if the intruder responds to a ground station ATC interrogation, your TCAS will pick this up (by "eavesdropping"). Your aircraft can also eavesdrop on an intruder aircraft if it is responding to TCAS interrogations from another aircraft. Your aircraft will also actively search for intruders by making periodic Mode S "All Calls". On the ground, the intruder aircraft's ATC should automatically stop transmitting A and C mode signals and also stop responding to Mode S "All Call" interrogations.

This is the part where I get confused... Once the intruder aircraft has been found, your TCAS continually sends Mode C and Mode S transmissions to track the intruder aircraft. The Mode S tracking involves discrete Mode S signals to individual aircraft (not "all call" signals). This appears to leave a window open for tracking intruder aircraft after they have landed. However, it may be covered by the following:

If your aircraft is below a certain RA height, your aircraft looks at the relative altitudes of intruder aircraft and deems them to be on the ground (using RA and Baro data) and subsequently ignores them if they are within 380 feet of the estimated ground level.

Some ATC control panels have an OFF, AUTO, ON position. In the ON position, the ATC will respond to interrogations even though the aircraft is on the ground. Putting the switch to ON is sometimes requested by ATC or by user error or through maintenance action. Maintenance personnel should use this switch with discretion, especially if the maintenance area is close to an active runway.

Rgds
JHW
Moderator
Registered: May 2009
Posts: 5140
Hi Mike,

since PSX version 10.0.2-beta13, the ND doesn't show traffic that is lower than 50 feet AGL while the own aircraft is on the ground.

These conditions have been added to avoid unrealistic ground traffic clutter on the ND when Balt's traffic injector is running. This effect was irrelevant before because PSX's own traffic generator never places intruders on the ground.


Cheers,

|-|ardy
Member
Registered: Jun 2009
Posts: 187
Location: Devon, UK
mikeindevon wrote
Is this the expected behaviour as I am sure I have seen taxiing traffic on the ND in the past.


I was referring to what PSX displayed. I have no real life experience of this.

Does this mean then that as you follow the guy in front down the glide path he vanishes off the ND at touchdown and would reappear at 380 ft on a go-around?

Interesting input John, thanks.

Mike
Member
Registered: Jun 2009
Posts: 187
Location: Devon, UK
Thanks Hardy, I will stop looking for the bug! Mike
Member
Registered: May 2010
Posts: 843
Quote
Does this mean then that as you follow the guy in front down the glide path he vanishes off the ND at touchdown and would reappear at 380 ft on a go-around?


I'm afraid I'll have to leave that question to the experts and those who happened to be watching the TCAS at the time another aircraft was going around (quite a rare occurence as you can imagine) :mrgreen:

All of my personal observations were on the ground and where the manuals didn't quite seem to match reality. I often saw aircraft painted on the displays with relative heights below 380 feet, but I can't recall the details. Perhaps my aircraft would have to be in the air for the 380' logic to apply?

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