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Continuing problems seeing ATCRBS transponders with Mode Sinterrogators



 
 
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  #1  
Old September 23rd 08, 09:47 PM posted to rec.aviation.products
[email protected]
external usenet poster
 
Posts: 8
Default Continuing problems seeing ATCRBS transponders with Mode Sinterrogators

Continuing problems seeing ATCRBS transponders with Mode S
interrogators

Hey all, I work in, lets call it 'an associated industry' and we are
still seeing ATCRBS transponders that reply to some interrogators, and
not to others.

At one time this was known as the 'P4 problem', sometimes as the
'Terra problem', just want to ask if anyone out there flying with an
ATCRBS xpdr is still having trouble being 'seen' by some
interrogators, but no problem with others.


Thx-

Dave
Ads
  #2  
Old October 7th 08, 03:31 AM
tomlusch tomlusch is offline
Junior Member
 
First recorded activity by AviationBanter: Oct 2008
Posts: 3
Default

Quote:
Originally Posted by View Post
Continuing problems seeing ATCRBS transponders with Mode S
interrogators

Hey all, I work in, lets call it 'an associated industry' and we are
still seeing ATCRBS transponders that reply to some interrogators, and
not to others.

At one time this was known as the 'P4 problem', sometimes as the
'Terra problem', just want to ask if anyone out there flying with an
ATCRBS xpdr is still having trouble being 'seen' by some
interrogators, but no problem with others.


Thx-

Dave
Funny that you should pose such a question Dave. Just yesterday evening I observed a primary target with our ASR-9 (Mode S) moving ENE at a decent clip. Used a different display and selected our nearby ARSR (an ATCBI-6) sensor, and saw a rock solid beacon reply, showing that it was an aircraft at 13,000 ft msl. Never did see a transponder return using our ASR-9.

Take a look at my previous experience with this type of transponder behavior...

http://home.columbus.rr.com/lusch/talotta.html

...and get in touch with me.

Tom Lusch
http://tomlusch.com
  #3  
Old October 8th 08, 06:06 PM posted to rec.aviation.products
[email protected]
external usenet poster
 
Posts: 8
Default Continuing problems seeing ATCRBS transponders with ModeSinterrogators

On Oct 6, 10:31*pm, tomlusch
wrote:
;663552 Wrote:



Continuing problems seeing ATCRBS transponders with Mode S
interrogators


Hey all, I work in, lets call it 'an associated industry' and we are
still seeing ATCRBS transponders that reply to some interrogators, and
not to others.


At one time this was known as the 'P4 problem', sometimes as the
'Terra problem', just want to ask if anyone out there flying with an
ATCRBS xpdr is still having trouble being 'seen' by some
interrogators, but no problem with others.


Thx-


Dave


Funny that you should pose such a question Dave. *Just yesterday
evening I observed a primary target with our ASR-9 (Mode S) moving ENE
at a decent clip. *Used a different display and selected our nearby
ARSR (an ATCBI-6) sensor, and saw a rock solid beacon reply, showing
that it was an aircraft at 13,000 ft msl. *Never did see a transponder
return using our ASR-9. *

Take a look at my previous experience with this type of transponder
behavior...

http://home.columbus.rr.com/lusch/talotta.html

..and get in touch with me. *

Tom Luschhttp://tomlusch.com

--
tomlusch


Hey, Tom. Yeah, I'm familiar with your reports on this / these issues,
back when I was building a simulation model of transponders.

Seems there are some really old transponders out there, or
'some' (heh) that just don't meet spec.


Dave
  #4  
Old October 9th 08, 02:30 PM
tomlusch tomlusch is offline
Junior Member
 
First recorded activity by AviationBanter: Oct 2008
Posts: 3
Default

Quote:
Originally Posted by View Post
On Oct 6, 10:31*pm, tomlusch
wrote:
;663552 Wrote:



Continuing problems seeing ATCRBS transponders with Mode S
interrogators


Hey all, I work in, lets call it 'an associated industry' and we are
still seeing ATCRBS transponders that reply to some interrogators, and
not to others.


At one time this was known as the 'P4 problem', sometimes as the
'Terra problem', just want to ask if anyone out there flying with an
ATCRBS xpdr is still having trouble being 'seen' by some
interrogators, but no problem with others.


Thx-


Dave


Funny that you should pose such a question Dave. *Just yesterday
evening I observed a primary target with our ASR-9 (Mode S) moving ENE
at a decent clip. *Used a different display and selected our nearby
ARSR (an ATCBI-6) sensor, and saw a rock solid beacon reply, showing
that it was an aircraft at 13,000 ft msl. *Never did see a transponder
return using our ASR-9. *

Take a look at my previous experience with this type of transponder
behavior...

http://home.columbus.rr.com/lusch/talotta.html

..and get in touch with me. *

Tom Luschhttp://tomlusch.com

--
tomlusch


Hey, Tom. Yeah, I'm familiar with your reports on this / these issues,
back when I was building a simulation model of transponders.

Seems there are some really old transponders out there, or
'some' (heh) that just don't meet spec.


Dave
Dave,

Of course, those "really old" transponders met the _original_ TSO spec before Mode S came on the scene. I personally put in a lot of time and effort back in '95 to get a King KT76 fixed, when there was no problem with it (other than it was acting like a Terra TRT-250 at the time).

I've been noticing that it seems that more and more transponders *appear* intermittent on our ASR-9 these days. They'll show as a good beacon target, then become a RDR (primary "skin paint") target, and flip flop between these two states. It is as if they have weak signals. I notice this on typical low-end aircraft (especially on 1200 squawks on nice VFR days). I haven't observed this phenomenon on higher-end aircraft.

Yet, when I view these same intermittent beacon targets *simultaneously* using our nearby ARSR, it shows rock solid beacon replies. It seems to have no problem seeing them. There is a definite difference.

I recently came across the following statement...

"Turning off Mode-S: A Maintenance Alert was issued on 6/1/2006 instructing BI-6 sites to stop interrogating Mode-S."

That note is still present at...

http://www.aos.jccbi.gov/atcbi-6/faqs.htm

*IF* the ARSR I'm watching with is using classical interrogations, and our ASR-9 is in Intermode (Full Mode S), that *may* explain what I'm seeing.

Conversely, I wonder if possibly an *Interim* Mode Interlace Pattern (MIP), which must've been implemented on our Mode S sensors to deal with the "Terra problem," has been adjusted, and they aren't doing as many "classical" (i.e. without P4) interrogations. I have yet to determine if we're in "Mixed Mode" or are fully into "Intermode" (Full Mode S) with our ASR-9.

Tom
http://tomlusch.com
  #5  
Old October 14th 08, 04:11 PM posted to rec.aviation.products
[email protected]
external usenet poster
 
Posts: 8
Default Continuing problems seeing ATCRBS transponders with ModeSinterrogators

On Oct 9, 9:30*am, tomlusch
wrote:
;665691 Wrote:



On Oct 6, 10:31*pm, tomlusch
wrote:-
;663552 Wrote:


-
Continuing problems seeing ATCRBS transponders with Mode S
interrogators-
-
Hey all, I work in, lets call it 'an associated industry' and we are
still seeing ATCRBS transponders that reply to some interrogators,
and
not to others.-
-
At one time this was known as the 'P4 problem', sometimes as the
'Terra problem', just want to ask if anyone out there flying with an
ATCRBS xpdr is still having trouble being 'seen' by some
interrogators, but no problem with others.-
-
Thx--
-
Dave-


Funny that you should pose such a question Dave. *Just yesterday
evening I observed a primary target with our ASR-9 (Mode S) moving
ENE
at a decent clip. *Used a different display and selected our nearby
ARSR (an ATCBI-6) sensor, and saw a rock solid beacon reply, showing
that it was an aircraft at 13,000 ft msl. *Never did see a
transponder
return using our ASR-9. *


Take a look at my previous experience with this type of transponder
behavior...


http://home.columbus.rr.com/lusch/talotta.html


..and get in touch with me. *


Tom Luschhttp://tomlusch.com


--
tomlusch-


Hey, Tom. Yeah, I'm familiar with your reports on this / these issues,
back when I was building a simulation model of transponders.


Seems there are some really old transponders out there, or
'some' (heh) that just don't meet spec.


Dave


Dave,

Of course, those "really old" transponders met the _original_ TSO spec
before Mode S came on the scene. *I personally put in a lot of time and
effort back in '95 to get a King KT76 fixed, when there was no problem
with it (other than it was acting like a Terra TRT-250 at the time).

I've been noticing that it seems that more and more transponders
*appear* intermittent on our ASR-9 these days. *They'll show as a good
beacon target, then become a RDR (primary "skin paint") target, and
flip flop between these two states. *It is as if they have weak
signals. *I notice this on typical low-end aircraft (especially on 1200
squawks on nice VFR days). *I haven't observed this phenomenon on
higher-end aircraft. *

Yet, when I view these same intermittent beacon targets
*simultaneously* using our nearby ARSR, it shows rock solid beacon
replies. *It seems to have no problem seeing them. *There is a definite
difference. *

I recently came across the following statement...

"Turning off Mode-S: A Maintenance Alert was issued on 6/1/2006
instructing BI-6 sites to stop interrogating Mode-S." *

That note is still present at...

http://www.aos.jccbi.gov/atcbi-6/faqs.htm

*IF* the ARSR I'm watching with is using classical interrogations, and
our ASR-9 is in Intermode (Full Mode S), that *may* explain what I'm
seeing. *

Conversely, I wonder if possibly an *Interim* Mode Interlace Pattern
(MIP), which must've been implemented on our Mode S sensors to deal
with the "Terra problem," has been adjusted, and they aren't doing as
many "classical" (i.e. without P4) interrogations. *I have yet to
determine if we're in "Mixed Mode" or are *fully into "Intermode" (Full
Mode S) with our ASR-9.

Tomhttp://tomlusch.com

--
tomlusch


Interesting...

Was there any explanation for turning off Mode-S on those?

Dave
  #6  
Old October 16th 08, 10:49 AM
tomlusch tomlusch is offline
Junior Member
 
First recorded activity by AviationBanter: Oct 2008
Posts: 3
Unhappy

Quote:
Originally Posted by View Post
On Oct 9, 9:30*am, tomlusch
wrote:
;665691 Wrote:



On Oct 6, 10:31*pm, tomlusch
wrote:-
;663552 Wrote:


-
Continuing problems seeing ATCRBS transponders with Mode S
interrogators-
-
Hey all, I work in, lets call it 'an associated industry' and we are
still seeing ATCRBS transponders that reply to some interrogators,
and
not to others.-
-
At one time this was known as the 'P4 problem', sometimes as the
'Terra problem', just want to ask if anyone out there flying with an
ATCRBS xpdr is still having trouble being 'seen' by some
interrogators, but no problem with others.-
-
Thx--
-
Dave-


Funny that you should pose such a question Dave. *Just yesterday
evening I observed a primary target with our ASR-9 (Mode S) moving
ENE
at a decent clip. *Used a different display and selected our nearby
ARSR (an ATCBI-6) sensor, and saw a rock solid beacon reply, showing
that it was an aircraft at 13,000 ft msl. *Never did see a
transponder
return using our ASR-9. *


Take a look at my previous experience with this type of transponder
behavior...


http://home.columbus.rr.com/lusch/talotta.html


..and get in touch with me. *


Tom Luschhttp://tomlusch.com


--
tomlusch-


Hey, Tom. Yeah, I'm familiar with your reports on this / these issues,
back when I was building a simulation model of transponders.


Seems there are some really old transponders out there, or
'some' (heh) that just don't meet spec.


Dave


Dave,

Of course, those "really old" transponders met the _original_ TSO spec
before Mode S came on the scene. *I personally put in a lot of time and
effort back in '95 to get a King KT76 fixed, when there was no problem
with it (other than it was acting like a Terra TRT-250 at the time).

I've been noticing that it seems that more and more transponders
*appear* intermittent on our ASR-9 these days. *They'll show as a good
beacon target, then become a RDR (primary "skin paint") target, and
flip flop between these two states. *It is as if they have weak
signals. *I notice this on typical low-end aircraft (especially on 1200
squawks on nice VFR days). *I haven't observed this phenomenon on
higher-end aircraft. *

Yet, when I view these same intermittent beacon targets
*simultaneously* using our nearby ARSR, it shows rock solid beacon
replies. *It seems to have no problem seeing them. *There is a definite
difference. *

I recently came across the following statement...

"Turning off Mode-S: A Maintenance Alert was issued on 6/1/2006
instructing BI-6 sites to stop interrogating Mode-S." *

That note is still present at...

http://www.aos.jccbi.gov/atcbi-6/faqs.htm

*IF* the ARSR I'm watching with is using classical interrogations, and
our ASR-9 is in Intermode (Full Mode S), that *may* explain what I'm
seeing. *

Conversely, I wonder if possibly an *Interim* Mode Interlace Pattern
(MIP), which must've been implemented on our Mode S sensors to deal
with the "Terra problem," has been adjusted, and they aren't doing as
many "classical" (i.e. without P4) interrogations. *I have yet to
determine if we're in "Mixed Mode" or are *fully into "Intermode" (Full
Mode S) with our ASR-9.

Tomhttp://tomlusch.com

--
tomlusch


Interesting...

Was there any explanation for turning off Mode-S on those?

Dave
Dave,

Thus far I have been unable to determine the reason behind that maintenance alert, or whether turning off Mode S for the long-range sensors back in 2006 was only temporary (and maybe the alert was accidentally left posted on that site). However, based upon what I saw with that 13,000 ft overflight just recently, it is very reminiscent of what I encountered when I wrote the following on AVSIG some 13 years ago...

---

Message: #852440, S/3 Air Traffic Control
Date: Sat, Jul 15, 1995 1:11:18
Subject: Xpdr problem @ 1 tracon
From: Thomas Lusch/CMH 76545,2004
To: ALL

Here's a baffling radar problem...

Around two or so weeks ago one of our club aircraft began to get bad transponder reports from ATC. Columbus Ohio (CMH) approach control would assign us a squawk, but they wouldn't "see" our transponder reply. Members began "squawking" g about the problem.

On Wednesday I took the "bad" transponder (a King KT-76) to Capital Aircraft Electronics at Port Columbus Airport. They let it run for several hours, running it hot and running it cold, and it "bench checked" with flying colors. They stated that the problem might be in the aircraft system. On Thursday I flew the aircraft over. Their test equipment showed it working just fine in the aircraft. They released it to me saying it was performing as per specifications.

Shortly thereafter I departed CMH and flew west for 25 or so miles. The transponder's reply light indicated it was replying to interrogations. However, not even once did any of my transponder replies show on CMH's radar! I was a primary target the _entire_ way.

Here's where it really gets interesting....

Directly after terminating radar, I called Dayton (DAY) approach, asking for a transponder check. They assigned a code and my transponder replies showed up on their radar just fine. I immediately switched back to CMH to see if they were seeing my DAY assigned code, but I still only showed as a primary target!

After a fuel stop, I departed and flew midway between CMH & DAY. DAY saw my transponder replies just fine. CMH didn't. I then checked with Indianapolis Center, and they saw my CMH assigned squawk just fine! CMH didn't see my transponder replies at all that Thursday.

This is particularly hard for me to understand, as I happen to be a controller at CMH. Nearly three weeks ago our new ASR-9 was commissioned. From my vantage point behind the scope I am very impressed with how much _better_ the ASR-9 is compared to the ASR-8 that we had been running. Our new radar has a much cleaner presentation. We see primary targets much more reliably, and the same goes for transponder targets. We can see aircraft much more reliably, at a greater distance, and at lower altitudes. (And the precip display is a quantum leap beyond the old ASR-8!)

As you may have ascertained, our club aircraft's transponder problem appears to be coincident with about the time CMH's ASR-9 was commissioned.

I took the aircraft over to CMH again on Friday. I spoke to the FAA radar techs about our problem, and they find it very strange. They hadn't received any other such problem reports. Capital Electronics ran their tests again, and everything appeared just fine. With a spare transponder in hand, myself and a Capital Electronics technician decided to fly it, and see if the problem was still there. We were prepared to swap out the transponder while in flight. As you might suspect, our "bad" transponder performed flawlessly.

We're all really baffled by this anomaly. If anybody out there might be able provide some guidance with this problem, we're all ears...

Tom

---

For those interested, I have posted the text of my most recent NASA ASRS report about the 13,000 ft aircraft that wasn't showing up on my display just the other day, on the bottom of...

http://home.columbus.rr.com/lusch/talotta.html

I have also shared my concerns with our local radar maintenance technicians, so this latest case of an "invisible transponder" is in the process of being elevated within the FAA.

BTW, in my research in trying to understand this "P4 problem" better, I have come across two somewhat different definitions for the term "Mixed Mode."

I'm using the definition for "Mixed Mode" to be:

"Interrogate Mode A and also interrogate mode S: Like having two radars in the one sensor, one interrogating Mode A/C transponders (but unfortunately Mode S transponders also reply) and another interrogating using Mode S to which only mode S transponders reply."

(This is what they had to do when they discovered the "Terra problem.")

I take this definition from an Aussie paper I came across at...

http://www.astra.aero/downloads/ABIT...ssues%20v2.pdf

BTW, I just posted this notice concerning my web site, "Lusch's Midair Collision Investigations" that I first launched on Feb 2, 2000...

"2008-10-16: I have just learned from my ISP that "Road Runner has launched a new Personal Home Page service." They seem really excited about this, but it leaves me extremely bummed out. All of the content that I have created concerning aircraft transponders that don't appear on radar displays, and the positive change that I wish to bring about, will no longer be available at this url...

http://home.columbus.rr.com/lusch/

Being as Time Warner doesn't serve the location where I've been living for the past two-and-a-half years, if I'm going to migrate to a new server, I may as well migrate to a server that also offers me cable service. I don't look forward to all the work such a migration will entail. Therefore, be advised that this content may be unavailable (or less easy to be found) for some period of time."



Tom Lusch

P.S. Dave...I'm really curious why you began this thread. Give me a call at 614-370-1437 if you don't mind sharing.
 




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