Dual transponder

[PTK]

As I was getting ready to have the GDL 88 installed the GTX 345 came out. Cost is very similar so I decided to go with the GTX 345R.

I already have the GTX33R installed with the GTN 750 so I will have a two transponders.

Besides redundancy is there any other advantage to a dual transponder installation? Does anyone else have two transponders? 

[Jerry 5TJ]

I had two in my "C" and before that two in my "E."  But all those had tube transmitters.   I'm fairly comfortable with only one GTX33 as it is solid state throughout.  But the GTN750 will run two remote transponders....

Besides backup, no other reason to have two.  

[Mooneymite]

Well, you get to have two transponders certified every two years!  

Do they share a common altitude (gray wire?) source?

Edited June 2, 2016 by Mooneymite

[carusoam]

I like the R version... More rocks in the tail instead of in the panel...

Reliability is going to be important with everything going to the GTN display.

I'm going to be following Peter's guidance, just a few years behind.

Best regards,

-a-

[Marauder]

Well you get to have two transpondrrs certified every two years!  

 

Do they share a common altitude (gray wire?) source?

That is a challenge with these redundancy panels. My plane has 3 altimeters and I pay for them to be check during the IFR cert.

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[Mooneymite]

11 minutes ago, Marauder said:

That is a challenge with these redundancy panels. My plane has 3 altimeters and I pay for them to be check during the IFR cert.

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Yeah....confusing too!

If they all show a different altitude.

Since I  only have one altimeter, it might be wrong, but there's  no confusion....

[Bob_Belville]

The previous owner of my E had 2 KT76A. Only one tray. The 2nd one was in the back seat ready to swap out if the installed unit failed. He was retired AF, worked for NASA, was based @ VKX inside Washington's Prohibited Area. Flight in and out was by prior arrangement only and a transponder an absolute must have. His was the CB solution.

[kris_adams]

1 hour ago, PTK said:

Besides redundancy is there any other advantage to a dual transponder installation? Does anyone else have two transponde

I've recently had problems with my KT76A which I swapped out a few years ago in place of a different KT76A...so dual transponders sounds pretty useful to me right now!  I'm getting a new KT74 (readily admitting it isn't as good as the Garmin but I'm not 100% certain I'll have it in my panel "forever".)

-Kris

 

[Bob - S50]

Personally, two transponders is one of the last things I'd have on my list.  If I'm going to give up useful load, I'd rather have two battery backup attitude indicators first.  With solid state equipment these days, not much chance of failure.  I can live without ATC seeing me if it fails in flight, but I'd hate to have to fly IMC using a turn coordinator.  I'd also rather spend the money on Cies floats for my plane to have an accurate fuel gauge.  Or even an AOA gauge.

And ya, I know, a transponder doesn't weigh much, but as Everett Dirksen (I believe it was him) once said, "a million here, a million there, pretty soon we're talking real money."

[capthaak]

Airliners have two transponders because they can't go VFR. My guess is that 90% of the time, you'd get back home, or within 30 miles of it with one transponder.

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[N201MKTurbo]

4 minutes ago, capthaak said:

Airliners have two transponders because they can't go VFR. My guess is that 90% of the time, you'd get back home, or within 30 miles of it with one transponder.

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In '86 when I took my 67F to Topeka KS to get painted I needed to fly to Wichita to catch a flight back to Denver. The flight to Wichita was in a 727 at 5500 ft VFR! Weirdest thing ever. Quietest flight I've ever had in an airliner. On the way out I asked the captain about it and he said that he was given a long delay for a release, so he canceled and went VFR.

[Marauder]

I think the big problem would be if you are using the transponder to do the ADSB out. Do you not need two transponders that can do ADSB out to meet the mandate?

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[capthaak]

4 minutes ago, capthaak said: Airliners have two transponders because they can't go VFR. My guess is that 90% of the time, you'd get back home, or within 30 miles of it with one transponder.

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In '86 when I took my 67F to Topeka KS to get painted I needed to fly to Wichita to catch a flight back to Denver. The flight to Wichita was in a 727 at 5500 ft VFR! Weirdest thing ever. Quietest flight I've ever had in an airliner. On the way out I asked the captain about it and he said that he was given a long delay for a release, so he canceled and went VFR.

Back when fuel was cheaper! If he were to do that now, he'd be making a fuel stop as dispatchers only load the FAR minimum. When the started with the airline, we always filled the main tanks every leg. I think Gulf war 1 started the dispatch with just enough fuel.

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[LANCECASPER]

23 hours ago, PTK said:

As I was getting ready to have the GDL 88 installed the GTX 345 came out. Cost is very similar so I decided to go with the GTX 345R.

I already have the GTX33R installed with the GTN 750 so I will have a two transponders.

Besides redundancy is there any other advantage to a dual transponder installation? Does anyone else have two transponders? 

I would put one Avidyne transponder in just so it could envy the other Garmin transponder  

[N201MKTurbo]

8 hours ago, capthaak said:

Back when fuel was cheaper! If he were to do that now, he'd be making a fuel stop as dispatchers only load the FAR minimum. When the started with the airline, we always filled the main tanks every leg. I think Gulf war 1 started the dispatch with just enough fuel.

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I just looked up the 727 performance charts, they only go down to FL090, but for a 140 mile trip it uses less fuel staying down low  then going into the flight levels. The charts start favoring the flight levels at about a 300 mi trip.