Recycle Transponder - no mode c

[AuntPeggy]

Our plane lives inside the New York mode c veil, so the mode c is required to go anywhere or to come home. For the past year, ATC keeps telling us to recycle the transponder because they are not getting mode c. Recycling puts us back on radar temporarily.

Since the problem began, we have replaced the transponder, changed the encoder 3 times, replaced the antenna, cleaned all the connections, and replaced the cables to the antenna - in approximately that order.

Any suggestions?

- Aunt Peggy

 

[Areeda]

Let me guess, everytime it's been tested on the ground it works fine.

We are having issues like this with some of the club planes and are very interested in suggestions also.

Right now we're trying to record where this happens to see if it's location dependent.

Good luck.

Joe

 

[SkyHog]

could it be something related to pressure or temperature?

I am talking from inexperience.

 

[poadeleted20]

ATC has been known to have holes in its coverage, especially for Mode C. Get with the ATC office at Northeast Region to investigate this further.

 

[wesleyj]

location, location, location,

had the same problem on a Twin Beech, Baron, Meyers 200, mooney, cherokee 6 and an AC114

next time find out where the radar antenna is located and lift a wing to expose the xponder antenna directly to the site, or if the site is straight ahead turn 45 either way and see if it goes away, if the problem goes away, relocate your transponder antenna.

I had problems first with the beech 18, after many hours of head scatching and mucho denaro, i discovered that when they lost the Mod c, it was on either wing tip, moved the antennae back 6 feet, never had another problem, when i experianced the same problem on a recurring basis with the others, moved the antennae back, problem went away.

 

[AdamZ]

Let me guess Aunt Peg Was it NY Center? My friend recently flew he Lance from KLOM to KUNV for a Penn State Game. He was fine unitl he reached NY Centers Airspace they they said they weren't getting his mode C and to turn it off. He was fine in Philly App, Reading App and Harrisburg App airspace . Then on the way back Same thing happend. As soon as he got out of NY Centers Space. Voila no problem with the mode C.

 

[HPNPilot1200]

As the others have mentioned, it was most likely due to your location and altitude.

Let me guess Aunt Peg Was it NY Center? My friend recently flew he Lance from KLOM to KUNV for a Penn State Game. He was fine unitl he reached NY Centers Airspace they they said they weren't getting his mode C and to turn it off. He was fine in Philly App, Reading App and Harrisburg App airspace . Then on the way back Same thing happend. As soon as he got out of NY Centers Space. Voila no problem with the mode C.

That's likely because Philly, Reading, and Harrisburg TRACONs were picking up the primary/secondary targets on their ASR (Airport Surveillance Radar) system which is specifically used in terminal environments.

Most ARTCCs use ARSR (Air Route Surveillance Radar) which has a longer range since it is 'tuned' for enroute operations and is the reason Center controllers are required to provide 5 nautical miles lateral separation for aircraft more than 40nm away from the radar antenna. (As always, there are exceptions to this. The most common, relating to certain sectors in enroute facilities that use ASR radar due to the sector's close proximity to the radar antenna which allows controllers to separate by only 3nm.) This "long range" radar works differently than ASR, and was most likely why ZNY couldn't receive the mode C.

Regards,
Jason

 

[AuntPeggy]

We are getting it all over the place, not just NY Center. Most recently HPN Westchester Tower. But we have had the problem intermittenly all along our long-distance routes, too. They lost us over the lake coming back from OSH, but they were losing everyone that day. They have lost us in Oklahoma, Pennsylvania, etc.

As I mentioned, it started about a year ago and has become a major hassle.

Makes it tough to plan IFR flights or training.
- Aunt Peggy

 

[Lance F]

What exactly is one supposed to do when told to "recycle transponder?" Turn it completely off for X seconds? Turn it to Standby for X seconds? Turn it back to 1200 and then back to the assigned code?

And regardless of what knobs you're supposed to turn, how could doing this change the Mode C output that ATC is not seeing?

And for more extra points, would there be any difference in this procedure between an analog and digital transponder?

 

[HPNPilot1200]

What exactly is one supposed to do when told to "recycle transponder?" Turn it completely off for X seconds? Turn it to Standby for X seconds? Turn it back to 1200 and then back to the assigned code?

Usually ATC phrases it: "STOP ALTITUDE SQUAWK" and will advise when they want to you start squawking mode C again. If they want you to "recycle transponder" they usually give you a new code, at least that's how ZBW (Boston Center) phrases it.

 

[Lance F]

Usually ATC phrases it: "STOP ALTITUDE SQUAWK" and will advise when they want to you start squawking mode C again. If they want you to "recycle transponder" they usually give you a new code, at least that's how ZBW (Boston Center) phrases it.

No, when my old KX-87a (I think that was the model) had its cavity tube slowly giving up the ghost, I was told many times by numerous Centers and TRACONs to "reset my transponder." I turned it off and then back on, but it rarely helped. Have a shiny new transponder now and they don't ask this any more.

 

[gismo]

Our plane lives inside the New York mode c veil, so the mode c is required to go anywhere or to come home. For the past year, ATC keeps telling us to recycle the transponder because they are not getting mode c. Recycling puts us back on radar temporarily.

Since the problem began, we have replaced the transponder, changed the encoder 3 times, replaced the antenna, cleaned all the connections, and replaced the cables to the antenna - in approximately that order.

Any suggestions?

- Aunt Peggy

Are they getting mode A (assigned code) but not mode C (pressure altitude)? If so you likely have a problem with the wiring between the encoder and the transponder. If they get nothing at all, I'd look at the antenna location.

Also, when you replaced the transponder and encoder did you go with new ones or used?

 

[poadeleted20]

What exactly is one supposed to do when told to "recycle transponder?"

Turn it completely off, then to STBY until it times in (in most cases, the reply light goes on during time-in and then goes off), and then back to ALT (or ON if the Mode C is supposed to be strangled for some reason).

And regardless of what knobs you're supposed to turn, how could doing this change the Mode C output that ATC is not seeing?

Just like PC's, transponders that aren't transponding sometimes respond to a shut-down/re-boot.

And for more extra points, would there be any difference in this procedure between an analog and digital transponder?

No.

 

[flyingcheesehead]

What exactly is one supposed to do when told to "recycle transponder?"

1. Pull it out of the airplane.
2. Separate it into parts based on the various materials used.
3. Take said parts to the local recycling center, where you might get $1.00 for it if you're lucky.



(In reality, I just turn it off and back to ALT...)

Usually ATC phrases it: "STOP ALTITUDE SQUAWK" and will advise when they want to you start squawking mode C again. If they want you to "recycle transponder" they usually give you a new code, at least that's how ZBW (Boston Center) phrases it.

What I've always heard from quite a few different facilities when getting a new squawk code is "November 271G, reset transponder, squawk xxxx..." Whereas "recycle" means to reboot because they're not receiving your code or altitude. (Or maybe they're just really bored and want to play with the puppet pilots. )

Oddly enough, neither the "reset" nor the "recycle" terms are in either the P/CG or the AIM. Any traffic in the area, please advise.

 

[gismo]

When ATC says to "recycle the transponder" they usually mean you should check your code selection and make sure your transponder is in the correct mode (EG alt). While it is possible that a modern transponder could get locked up and require a power cycle (off then on) to restore operation, but IME such a situation is extremely rare. Often times, the actual problem is a combination of antenna shadowing, poor radar coverage, and frequency drift and the problem will resolve itself in a few minutes if you do nothing. Of course if you turn the transponder off and back on during those few minutes and it begins to work again, you and ATC will probably assume that "recycling" actually fixed the problem whether or not it really did thus furthering the myth that such an action is useful.

 

[AuntPeggy]

1) When we recycle the transponder, we turn it off and turn it back on.
2) Mode A is received with no problem.
3) When the problem is occuring, the (R) light stays constantly lit.
4) Replaced old equipment with new equipment, not used.
5) Opened up old equipment, looked at parts and said, "Wow".
6) Replaced all wiring, not just to antenna.
7) Poverty precludes complete replacement of aircraft.
8) "Reset transponder" means to change the squawk code. That occasionally happens with flight following when handed off from one location to another and indicates a change in your status with ATC.

 

[gismo]

1) When we recycle the transponder, we turn it off and turn it back on.
2) Mode A is received with no problem.
3) When the problem is occuring, the (R) light stays constantly lit.
4) Replaced old equipment with new equipment, not used.
5) Opened up old equipment, looked at parts and said, "Wow".
6) Replaced all wiring, not just to antenna.
7) Poverty precludes complete replacement of aircraft.
8) "Reset transponder" means to change the squawk code. That occasionally happens with flight following when handed off from one location to another and indicates a change in your status with ATC.

If they are gettting mode A replies and you replaced the transponder & encoder with new, it almost has to be a wiring issue although there is a very slim chance your new replacement transponder is also defective. Some transponders (EG GTX-327) have a diagnostic menu that lets you see the encoder output as read by the transponder. If your's does I'd look there when it's failing. If not an intermittant wiring problem is extremely difficult to find. Basically you've got to get it to be failing and then trace the problem, all the while hoping you don't disturb the malfunction away. You said the wiring was replaced, but I suspect that some portion wasn't and that's where you problem is likely to be.