I have a transponder Narco AT150 TSO. It seems to be quite old, it came with the plane I bought in 2008 and that plane was build in 1977. My guess is that the transponder was fit in the plane when built.
It has been working ok until this summer. I did a few trips in France and in the UK, most of the time in G airspace, and at times, when I wanted to cross C or D airspace, that means small area with a mandatory transponder, the ATC told me they could not see me. Last week, in the local area, I wanted to keep contact with the FIS and they told me a couple of times that they lost me, even though they could see traffic around and below me.
So I am going to see the radio maintenance guys next week, but I was wondering if anyone have had the same issue and what came out from it.
I know that Narco is dead, so I guess I will have to buy a new transponder if he can’t fix it …
The Narco AT150 TSO is normally a reliable unit. If the cavity goes bad, it is not economical to repair. If it is simply off frequency, most avionics shops should be able to tune it up. Check your antenna, if it is mounted in the exhaust stream or behind the oil breather tube, it can accumulate a soot and or oil covering. I have seen several times where this de-tunes the system sufficiently to obtain intermittent operation. Clean it off. Finally, buy a used replacement unit from eBay, just make sure it has a yellow tag.
AFAIR, at least on the D-reg, it is no longer allowed to install Mode-C transponders (new or used). France might still be different.
But Fred, I wouldn’t spend a single Euro on your Narco box. You like touring, don’t you? The Netherlands require Mode-S in most of their airspace. UK gets more and more TMZs these days. Germany requires Mode-S above 5000 feet. And so on…
In the UK you can replace an existing Mode C with another Mode C, but you can’t install a Mode C where there wasn’t a transponder before.
It’s really stupid because most UK ATC (that talks to VFR GA) cannot see the Mode S data, never will be able to (due to funding issues) and the policy helps to support the arguments of the “civil liberties” crowd who won’t install any transponder, because it would have to be Mode S which “can be used to track you”. So large chunks of UK GA fly without a transponder and always will. They won’t be fitting a FLARM product either, for the same reason. Fortunately most of them fly low – below 2000ft. It’s in the circuit where you cannot avoid them, and have no way of detecting them electronically…
Mode C transponders can be bought from US Ebay cheaply and a lot more people would install them if they could – it’s obvious to all that a traffic service from ATC is worth so much more with Mode C.
I don’t know the detail of the UK rule e.g. can you replace a Narco Mode C with a King Mode C? I recall hearing that you can’t, but obviously if you just do it, probably nobody will know because the original installation was most likely so many years back that there won’t be any record of it anyway.
Homebuilts and microlights can, I believe, install a Mode C unit.
But, as stated above, Mode S is the only way to go if you want to fly around Europe without major hassle.
If you decide to go with a new transponder I would recommend to go with ADS-B capable mode S transponder, instead of spending mode C. Mode S and ADS-B are the future. Have a look at the Trig TT-21 / TT-31 for a good price / quality transponder
Thanks for your answers. I have an appointment with the radio tech guys next week, and I’ll see what they can do. If it’s a problem with the frequency as NCYankee suggested, and they can fix it, fine. If not, I’ll definitely go for a Mode-S, but at 2500 euro a piece (plus fitting), I’ll have to convince the other 2 owners to put their money into it, and that’s not going to be easy, but as boscomantico said, I like touring, and Mode-S is a lot better and easier to use, and it makes contact with ATC much more efficient.
Have to purchase transponder and radio for my Onex now. Price is one thing, but to find one that isn’t too large (long) is rather difficult. This one from Dittel seems to be OK length wise, and rather nicely priced (relatively speaking) at US$ 1900.- Dittel also have EASA “approved” 8.33 radio at a reasonable price.
This Dittel KTX2 seems to be ok, however it’s really small. Is it not difficult during the flight, to change transponder code with those buttons ?
Make sure they also check the coax cable. Most of transponder related problems I have found during avionics testing are due to poor coax cable / connectors. If it is equiped with a monopole antenna instead of a vin make sure the antenna is still intact. They sometimes break.
This part must work ok with a new installation as well. Your avionics shop will be able to measure the antenna installation as well.
This Dittel KTX2 seems to be ok, however it’s really small. Is it not difficult during the flight, to change transponder code with those buttons ?
I have never used a Dittel before, I have no idea if it is a good unit, but I have used other 2 1/2" transponders and it’s no problem dialing with a rotary knob, essentially the same as a radio. A “flat” Garmin is easier/faster though, but will be impossible to fit in the panel of my Onex.
Homebuilts and microlights can, I believe, install a Mode C unit.
No. Probably different from country to country, but in Norway mode S will be mandatory at some unspecified time. It’s not at the moment. 8.33 kHz will be mandatory from 2018. Microlights and homebuilts have to follow the specs regarding avionics. I thought radios and transponders also had to be certified, but just received information that they don’t. Looks like all mode S transponders are certified anyway.
