Approach "Not recieving Transponder recycle..."

[shenweas]

I have on quite a number of occations been told by approach control that my transponder is intermittant or "not picking up your transponder" but never from center. On one occation I happened to be talking to a friend who was working the approach rapcon and he said the transponter is intermittant then he went on to say "standby and I will check with center" I had just been on with center for about 15 min strait. When he came back he said center had a "solid hit on you all the way so it must be our equipment". Since that time I have had it happen all over the souteast and always so far has been limmited to approach and NOT center.

Has anyone else experianced this? Is the transponder not compatibile with the current approach radars?

The transponder is the SV-XPNDR-261.

 

[mmarien]

Could be the placement of your antenna. I have a antenna for composite aircraft that doesn't need a ground plane but is on the side of the fuselage. The signal can get blocked (by my aircraft) depending on my position in relation to the ground based radar. When they ask to recycle my transponder I just turn slightly to position the antenna better for the radar and then turn back when they are reading it. It's on my list of things to fix.

 

[shenweas]

Happened again today with Huntsville approach when checking on but within 2 min they had radar contact again with no problems. Was at 8000ft.

I never had this happen with the other planes I have been flying. I have a hard time believing that it is poor reception. the antenna is on the belly of the all metal airplane. RV-10.

Any other sugessions?

 

[jakej]

I've seen a similar sort of problem so bear with me for asking these questions  -

What sort of coax are you using ?  Is the centre conductor multi stranded ?

Do you have crimp fittings on the coax or screw type ?

Did you do a continuity check from pin to pin on the coax while flexing the cable at the connector ends ?

Lastly - check the antenna fitting on the antenna where the cable connector pin goes in.  A friend had a problem with his transponder system which was dropping out sometimes, but after others bench checked the transponder, replaced the coax & tested the system, they found nothing wrong.  However the fault was with the antenna where the cable pin goes into a 'socket'.  That socket is segmented into 4 pieces & spreads when the tapered pin goes in - I found that 2 of them were broken off resulting in intermittent ops at various times - never had any more issues once the antenna was replaced.  just saying - yours could be different  but it would be good to hear about the solution when you fix it.

Jake J

 

[shenweas]

I've seen a similar sort of problem so bear with me for asking these questions  -

What sort of coax are you using ?  Is the centre conductor multi stranded ?

Do you have crimp fittings on the coax or screw type ?

Did you do a continuity check from pin to pin on the coax while flexing the cable at the connector ends ?

Lastly - check the antenna fitting on the antenna where the cable connector pin goes in.  A friend had a problem with his transponder system which was dropping out sometimes, but after others bench checked the transponder, replaced the coax & tested the system, they found nothing wrong.  However the fault was with the antenna where the cable pin goes into a 'socket'.  That socket is segmented into 4 pieces & spreads when the tapered pin goes in - I found that 2 of them were broken off resulting in intermittent ops at various times - never had any more issues once the antenna was replaced.  just saying - yours could be different  but it would be good to hear about the solution when you fix it.

Jake J

1. I am using RG58. No it is multi stand.

2. Grimp Connectors

3. Yes I checked the continuity but No I did not "flex" the cable. If I dont find any other problems I may resort to trying that. (Hard to get to now)

4. This suggestion sounds logical. I will give it a check.

 

[dynonsupport]

From the SkyView side of things, you'll both get an alert from SkyView and the transponder status are will "red X" if the transponder has stopped communicating with SkyView for even a second. So if you still  have status, the transponder is still working.

Now, the other thing you'll get is the reply indication within the transponder status area. That lights up whenever the tranponder is reply to an interrogation request, so watching for that could be helpful.

But, have you had a shop test the tranponder after it was installed (as is required by FAR 91.413)? Reply rate, quantity, and signal strenth are all properties that are tested.

 

[preid]

Weasel, happen to be flying across the southeast in my RV-10, heading back to Ca. I got the same issue with a couple app/dep. in one case they told me to squawk Vfr, I called the next controller and never had an issue. I see the R on the sky view and everything looks normal. I think it's on their end and not us.

 

[shenweas]

From the SkyView side of things, you'll both get an alert from SkyView and the transponder status are will "red X" if the transponder has stopped communicating with SkyView for even a second. So if you still  have status, the transponder is still working.

Now, the other thing you'll get is the reply indication within the transponder status area. That lights up whenever the tranponder is reply to an interrogation request, so watching for that could be helpful.

But, have you had a shop test the tranponder after it was installed (as is required by FAR 91.413)? Reply rate, quantity, and signal strenth are all properties that are tested.

Tsponder test checkout was good.

I am becoming more convinced that it is on the app controlers end. Evedently they/we dont have completely compatible equipment.

 

[dynonsupport]

Transponders are TSO'd in order to guarantee compatibility. There really isn't such a thing as a transponder that is incompatible with specific ground station hardware, as that would be a huge saftey of flight issue.

Something else is up here, but I'm not quite sure what it s.

 

[DennisW]

I have had my transponder tested and approved for use by a certified avionics shop. I have experienced the same issues with Approach not getting my replies. I believe there are some issues at several approach control locations in the South East US. I think my transponder is working fine.

 

[shenweas]

UPDATE:

Over the last month or so I have monitored this problem and still have not found the cause.

I still have never had Center say to recycle the transponder.

I have had these approaches say it though and some of them when I was relatively close to them. (less than 20nm)

Columbus app
Huntsville app
Chattenoogga app
Tri Cities app

several otheres that I have forgotten.

I had the transponder checked by a certified avionics shop.

Question here. When they do the check with the close proximity of there testing equipment does it take into account antenna propigation?

Is there another test that I could do to test the efficiency of the antenna?

 

[preid]

I flew across the country and had 2 cases of the Approach tell me they were not picking me up, I have also received it in central California but what is interesting is that I return the same way and they seem to have me without an issue. In all cases I DID notice that a "r" was being flashed, so the transponder was picking up a radar signal the controller was simply not seeing me. I have only had one controller drop me and tell me to set to VFR, otherwise they all picked me up again after a short time.
I do not believe it is the transponder, it works 98% of the time and the rest seems to be a recurrent issue for others as well. I believe it's a ground based issue on a display and not the actual antenna or transponder.

 

[lolachampcar]

Avionics shop tested my install.
Short cable, continuity tested but not while flexing
Crimped ends (avionics shop as I did not have the correct crimper for the one end)
Palm Beach Approach has had an issue seeing me while Miami Center never has.
I'll monitor this thread.

 

[RVDan]

I have some background in transponders. Ramp checks done by avioics shops do little to check antenna coverage. Coverage is the signal distribution throughout all directions and with the aircraft in varying attitudes. A ramp test by its nature is done with the antenna in close proximity to the ground. Ground reflections can make the test quite successful while antenna coverage in the air is poor. I often see erratic transponder performance result from poor antenna installations with respect to ground planes and locations on the fuselage. Try to note the ground station direction from you and elevation angle to see if there is any comon thread as to when you get a problem reported by ATC.

 

[mmarien]

I agree. The success of ATC reading my xponder has a lot to do with the position and direction of my aircraft in relation to the radar ground station as noted in reply #1 to this post. I know for a fact that when the airport is at my twelve to two o'clock they will have a problem regardless of my transponder flashing a (R) reply.

 

[johnsteichen]

I have had this problem with 2 different composite aircraft with transponders. Almost certain it relates to position of the antennas and the site of the ATC site.
I have carried two transponders in both composite aircraft for that reason. $$solution I know. If the controller complains, I give him an alternate transponder. If you fly IFR frequently, you either need two transponders or need to be patient while they re acquire the signal of the one transponder you have. Recycling never really works IMHO. Switching to alternate transponder always works

 

[jnmeade]

What is special about a metal airplane vice a composite airplane? Does it mean the antenna ground plane in the composite is inadequate? If so, can't that be remedied?

 

[mmarien]

As I understand an antenna needs a metal ground plane with the size based on the frequency of the transmissions. In a metal aircraft the entire aircraft is a ground plane. In a composite aircraft there basically isn't a ground plane as there is no metal. A ground plane can be added. See this thread:

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1328697560/5

 

[jnmeade]

I understand about ground planes. The question was why a good ground plane can't be installed on a composite aircraft. The prior discussion implied that a composite had problems that didn't happen with a metal plane and I don't see why a good ground plane can't fix the problems.

 

[jakej]

I understand about ground planes.  The question was why a good ground plane can't be installed on a composite aircraft.  The prior discussion implied that a composite had problems that didn't happen with a metal plane and I don't see why a good ground plane can't fix the problems.

It can

Jake J