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Author Topic: Track or Heading?  (Read 27722 times)

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DaveReid

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Re: Track or Heading?
« Reply #15 on: November 25, 2008, 03:23:06 PM »
Someone in the US should get plenty of them

Or indeed any RB user in the southern UK - I've had 17 different UAL B772 flights so far today on SBS.

I take your point that it needs to be a user who gets them locally and not via the network - anyone using RB near Heathrow ?
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Cumulus

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Re: Track or Heading?
« Reply #16 on: November 25, 2008, 04:35:01 PM »

Approx 1614z two aircraft LX-N90443 and S2-ADK showing IAS



Cheers,

Peter

AirNav Support

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Re: Track or Heading?
« Reply #17 on: November 25, 2008, 04:37:50 PM »
Thanks Peter, What have you picked up which is at 84,600ft?
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Cumulus

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Re: Track or Heading?
« Reply #18 on: November 25, 2008, 04:48:10 PM »

Must be that guy with the white beard and red coat, they were building his grotto in the shopping centre today.

DaveReid

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Re: Track or Heading?
« Reply #19 on: November 25, 2008, 04:57:42 PM »
Thanks, guys - that's impressive, and also something that the SBS can't do.

I'm worried about that Bangladeshi, though - the A310's Vmo is 360kt, so the wings must have been in danger of falling off at 456kt IAS !!

Dave
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viking9

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Re: Track or Heading?
« Reply #20 on: November 25, 2008, 06:25:37 PM »
Thanks, guys - that's impressive, and also something that the SBS can't do.

I'm worried about that Bangladeshi, though - the A310's Vmo is 360kt, so the wings must have been in danger of falling off at 456kt IAS !!

Dave

I thought that the A310 series had a max cruise speed of around 0.85 mach, 485 kt at 35,000 ft!

Tom
Tom
Bury St Edmunds, Suffolk UK
15 miles SE of EGUN
32 miles SE of MAM > DIKAS track
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DaveReid

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Re: Track or Heading?
« Reply #21 on: November 25, 2008, 06:33:44 PM »
I thought that the A310 series had a max cruise speed of around 0.85 mach, 485 kt at 35,000 ft!

At 35,000ft 485kt TAS equates to approximately 285kt IAS.
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viking9

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Re: Track or Heading?
« Reply #22 on: November 25, 2008, 06:45:26 PM »

At 35,000ft 485kt TAS equates to approximately 285kt IAS.

You are of course correct. Senior moment on my part. :(

Tom
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Bury St Edmunds, Suffolk UK
15 miles SE of EGUN
32 miles SE of MAM > DIKAS track
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DaveReid

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Re: Track or Heading?
« Reply #23 on: November 25, 2008, 07:26:20 PM »
You are of course correct. Senior moment on my part.

I know the feeling  :-)

My original comment about the wings falling off was simply meant to illustrate that the column in the display labelled "IAS" isn't IAS at all, it's TAS which, as we know, is something completely different.

AirNav ?
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AirNav Support

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Re: Track or Heading?
« Reply #24 on: November 25, 2008, 08:16:03 PM »
The Enhanced Mode S IAS is where we are getting the data from for that column but as the 86,000ft and various other anomalies we see in some of the Mode-S Enhanced or ADS-B data it all depends on the actual aircraft and whether its correctly setup.

However we have seen some American aircraft display values in the 250-280 but can't remember whether these were descending rather than at cruise level.

Unfortunately the aircraft giving this extra information are rare at the moment.
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DaveReid

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Re: Track or Heading?
« Reply #25 on: November 25, 2008, 08:27:41 PM »
The Enhanced Mode S IAS is where we are getting the data from for that column but as the 86,000ft and various other anomalies we see in some of the Mode-S Enhanced or ADS-B data it all depends on the actual aircraft and whether its correctly setup.

Are you correctly decoding Bit 25 in the Airspeed/Heading Squitter ?
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AirNav Support

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Re: Track or Heading?
« Reply #26 on: November 25, 2008, 08:39:36 PM »
As far as I am as aware yes :)

I will pass on the query to the Development and Hardware just in case though.
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DaveReid

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Re: Track or Heading?
« Reply #27 on: November 27, 2008, 10:32:37 PM »
As far as I am as aware yes :)

I will pass on the query to the Development and Hardware just in case though.

Any resolution on this ?

Over the past few days I've captured nearly 140,000 Airspeed/Heading Squitters from 97 different aircraft and not one contained IAS, all were TAS, which begs the question of where you are finding aircraft that transmit IAS in the squitter?
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AirNav Development

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Re: Track or Heading?
« Reply #28 on: November 28, 2008, 08:16:47 PM »
Hello Dave: can you tell us which Mode-s/ADS-B frame number contains that information?

DaveReid

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Re: Track or Heading?
« Reply #29 on: November 28, 2008, 10:29:51 PM »
Hello Dave: can you tell us which Mode-s/ADS-B frame number contains that information?

DF17 (Extended Squitter) Format Type Code 19 (Airspeed and Heading) Subtype 3 (airspeed/subsonic aircraft).  Bit 25 has values 0 (IAS) or 1 (TAS).

But surely you must know that already if you are currently displaying airspeed in RadarBox ?
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