Old transponders and cold weather

[Fearless Tower]

So, my xpdr appears to be acting up again. Went flying early Friday morning and MYF tower wasn't picking me up as I was heading out of the delta (I had planned to fly over to Brown field to do some stop and goes on the long runway). So, not being able to go flying around the San Diego Bravo, I elected to just stick around in the pattern. After the first trip or two around the pattern, tower informs me that they were now picking up the xpdr and it squawked normally throughout the rest of the flight. I joked with the controller that maybe the box just didn't like the cold (For San Diego it was fairly cold - about 39-40 degrees that morning).

So, being a bit fed up with this box (I've had it repaired about 3 times in the last 5 months (a couple hundred bucks each time), so I started thinking that maybe I should just buy a bloody new box.

My current one is a NARCO AT 150 TSO.

Now, as I'm searching online, looking at some newer xpdrs, I noticed that some of the solid state xpdrs do not require 'warm up' time. I went back and did some digging and found that the AT 150 is indeed a vacuum tube based box.

So, for the experts out here...does it sound plausible that the temperature was the reason for my box's lethargy?

I guess I'm trying to figure out whether or not I should pull the plug and buy a new box or if I should just wait for warmer days and save the money for a future comm radio upgrade.

 

[taters]

My current one is a NARCO AT 150 TSO.

Never again,
Those are the crappiest transponders Ive ever owned, For about 500 bucks you should be able to find a yellow-tagged King KT-76 that will last a very very long time. If you need to be in radar environments this will be money well spent, Im also a fan on the KT-79 (all digital) on the used market these are still a great value.

 

[bsdunek]

I believe the AT150 has a 'cavity tube'. These are pretty sensitive to temperature as I recall, so that could be the problem, considering it's age. I would think it would be more practical to replace the transponder than replace the tube.

 

[Ted]

Given the fact that Narco transponders are known for being junk and it will end up costing you about the same money to do a new install regardless of which transponder you get, I'd look at a Garmin 327 or 330, depending on whether or not you have a 430/530 you could hook it up to for traffic. The Collins transponder in the 310 has been acting up some. I've been advised it is probably an easy fix, but if that doesn't work, we will probably be getting a 330. I'd prefer real TCAS, but for what that costs, the TIS will suffice.

 

[RotorAndWing]

I believe the AT150 has a 'cavity tube'. These are pretty sensitive to temperature as I recall, so that could be the problem, considering it's age. I would think it would be more practical to replace the transponder than replace the tube.

Correct.

 

[MarkG]

Yes cold weather can cause it to take longer to warm the tube and start operating. Same goes for the old analog encoders. Particularly if you taxi out with it in off instead of standby - it has no warm up time. Even on a warm day these units take a few minutes before they start working. Most folks don't realize it because their taxi out and run up allow enough time to warm up as long as they are in stby.
I would not waste money on another repair of the 150 or even a Kt76. The Garmins are good products. However anyone buying a new transponder now needs to consider the ADS-B requirement coming down the pike in 2020. My personal opinion is going with a Mode S transponder with ADSB output will probably be the most cost effective, but time will tell. The Garmin 330 with ADS B and Becker are putting out some good units. The point is no sense buying a Garmin 327 and then needing to upgrade to the 330 in a few years. Of course you need to factor in how long you will own the aircraft and if you already have a Navigator installed for the ADSB inputs.

 

[Fearless Tower]

I'd look at a Garmin 327 or 330, depending on whether or not you have a 430/530 you could hook it up to for traffic. The Collins transponder in the 310 has been acting up some. I've been advised it is probably an easy fix, but if that doesn't work, we will probably be getting a 330. I'd prefer real TCAS, but for what that costs, the TIS will suffice.

FWIW, it is a 1948 Cessna 170.....a G430/530 with a 330 could cost more than the entire airplane is worth!

For this airplane, a Mode S xpdr is just not worth the money, but I might consider the 327

When changing out different brands of xpdr, are there additional required accessories or other equipment that must be purchased?

 

[MarkG]

Fearless, the short answer is yes. If you do the 327, you will get a new tray and wire harness. If you have an old encoder, it would be a good idea to change that out at the same time - go with the Trans Cal. I would also recommend changing your coax to the antenna. They probably need to change the end of the coax to adapt to the new tray. If its really old stuff, coax has improved greatly over the years. Kind of a waste to put in a new transponder and loose some signal strength because of old coax or antenna. Good luck.

 

[Jaybird180]

Any chance of getting some of your $$$ back from the avionics shop on your "repair"?

 

[gismo]

FWIW, it is a 1948 Cessna 170.....a G430/530 with a 330 could cost more than the entire airplane is worth!

For this airplane, a Mode S xpdr is just not worth the money, but I might consider the 327

When changing out different brands of xpdr, are there additional required accessories or other equipment that must be purchased?

I highly recommend the 327. Nothing else will have to be changed except the tray and radio but you probably should replace the antenna cable if it's not relatively new and the antenna if it's damaged at all. The 327 will work with virtually any encoder but if your's is an old Narco I'd replace that too. BTW I happen to have a nice used TransCal for sale pretty cheap!

 

[Fearless Tower]

However anyone buying a new transponder now needs to consider the ADS-B requirement coming down the pike in 2020. My personal opinion is going with a Mode S transponder with ADSB output will probably be the most cost effective, but time will tell. The Garmin 330 with ADS B and Becker are putting out some good units. The point is no sense buying a Garmin 327 and then needing to upgrade to the 330 in a few years. Of course you need to factor in how long you will own the aircraft and if you already have a Navigator installed for the ADSB inputs.

Can someone enlighten me on the real story with ADS-B?

I was under the impression that ADS-B equipment will be required for any aircraft that wants to use the IFR system, but I was just reading an article in the latest AOPA mag that seemed to state that the ADS-B 'Out' equipment will be required when operating in any airspace that currently requires a xdpr. While my airplane is IFR legal right now, it doesn't make much economic sense to spend the money to keep it IFR capable in the year 2020, BUT, an airplane that can't operate anywhere near B and C airspace may be difficult to sell in a few years.

What is the real deal?

 

[MarkG]

I read the article too. Mainly about ADS-B "in". What is required is ADS-b "out". It is not just Class B and C where it will be required. Anyone within the 30nm Mode C veil of a class B will need it as well, even if you are just flying underneath the class B.
The good news is options are beginning to appear for folks like yourself with an older airframe and no navigator installed. I just read somewhere recently Freeflight Systems is going to announce a new ADS-b box for around 4K. These firm ADS-B out requirements have only been out for a year, so alot of companies are working on finding the most cost effective solution. Whoever has the most cost effective solution, will profit greatly just because of the shear number of aircraft in your situation.
My personal opinion is it will be a stand alone box with a navigator just for ADSB, similar to how EGPWS used to be for the bigger jets. It had a GPS antenna that went right to the computer with no position display in the cockpit. I think the same will happen here. Mount a GPS antenna andrun it to the ADSB box which will also have a small navigator. It will broadcast the required ADSB info on a seperate antenna and it would be transparent to the pilot.
In your situation without a Navigator, this type solution will probably be most cost effective. Everyone without a compatible navigator needs to hang tight a few more years and see what develops.
However, you need to install a transponder and the 327 is a good option. Another piece of this ADSB puzzle that folks need to understand is whatever encoder is displaying your Mode C altitude, that device must also be feeding your ADS-B output for altitude. (part of the ADS-b out requirments).
So in your case, if you install the Garmin 327, make sure you install a digital encoder (because you can just about say with 100 percent certainty that the ADSB box will be digital). This has many benefits anyway - instead of a 15 wire harness from the encoder to the transponder it is 3 or 4. The digital encoders use a rs232 databus which is just a fancy way of saying it transmits info to the transponder digitally on a twisted pair of shielded wires. So when you need this same encoder for your ADSB output a few years from now in the future, it will be just a matter of hooking into the rs232 databus wiring. If you don't do this with the new transponder now, I think you will end up changing it out later so save yourself a few buck by planning ahead. On the trans cal unit the price difference having the RS232 vs analog is not much. ACK has got a RS232 unit as well, but I have not used it yet.

 

[Fearless Tower]

I just read somewhere recently Freeflight Systems is going to announce a new ADS-b box for around 4K.

Is that installed or just for the box?

If it is just the box, a GTX 330 may be a better deal.

 

[MarkG]

My understanding is the 4K is just for the box, not including wiring, antenna install or installation. You're right the GTX330 is cheaper, but you need to factor in a Navigator installation because the 330 with ads-b needs gps input. So if comparing options, figure both the 330 and a 430 navigator install vs the stand alone adsB. With older airframes I really think waiting a few years and see what products are developing is the way to go.