Confused. Real time or not??

[superspotter]

Hi Guys;
Could somebody please explain this to me. I am running my Airnav Radarbox down here in Lagos, line of sight to the approach and the airport. Yet, on two occasions just now, an aircraft has actually landed yet Airnav still shows it in descent coming down the flightpath 2000 feet, 1950 etc etc??
It would appear that I am watching it with a time delay yet I can see the aircraft position and it does not tally with what is on the screen.
It's not the first time I have experienced this and before I posted this question, I closed down Airnav but I still get the same response?
I am not using the network before you suggest that!
Any reasoning?

regards clive.

[Runway 31]

Clive sometimes some aircraft stick in a position for a time when they get lost by the receiver, its been that way for years.  Maybe you are needing to adjust your time out settings.

Alan

[superspotter]

No Alan, not buying that! :)
The approach is less that a mile in front of me, line of sight so signal loss doesnt come into it. The only thing I can point out that both times its happened today, it has been bizjets......

[Runway 31]

No idea then Clive.  I was going to ask with them being a biz jet was it ADS-B or mode-s but as you can see them stuck they would appear to be ADS-B.  I presume this has never happened before?  As you are on the receiver they must be real time and cannot be delayed reception to answer your original question, you can only get delayed on the network.

Alan

[superspotter]

Ah, I never mentioned stuck!
The first one was turning off the runway when Airnav showed it as descending through 1650 feet, not stationary, but moving down the approach.
Second one I could see at about 500 feet about to land when Airnav showed it still at 2000 feet and about 5 miles out and moving towards the airport. That is what I am finding so confusing!

[superspotter]

Furthermore, just watched a Dana Air Md-82 landing and that was right on the nail with what I could see and what Airnav was telling me I should be seeing! :)

[Runway 31]

Were they OK until the hit the ground as there is a bug when the aircraft goes into GND mode

Alan

[superspotter]

I lose them when they are on the ground here Alan.

[superspotter]

Same thing just happened again, another Bizjet...
Turned off the runway and tower was instructing him to contact ground yet my Airnav still had him descending through 900 feet on a continual lessening of altitude.
It's as if Biz have a built in time delay....

[Runway 31]

When I take my box to an airport I have seen the altitude behaving OK until the transponder goes into GND mode when the wheels hit the ground and the aircraft shows altitude again going up to many thousands of feet and then showing descending altitude.  I believe that may be what you are experiencing

Alan

[superspotter]

Yes I have seen that too, many times and I have also seen two aircraft of the same airline next to each other on Airnav, in HKG for instance,  and they have both had the same height readout when its obvioulsy not been the case. I have always put this down to one anomaly or another and been very careful to corroborate what I am seeing.
However on the occasions today. I have been watching carefully the height descending and there was no jumping around, just steady descent even though the aircraft was already on the ground.
Airnav is a fantastic aid to spotting, it just needs to be treated with caution at times!