GTP59 Shield Wire

[rapid_ascent]

I suspect why they called out #16 wire for the shield attachment is since they are referring to the crimp terminal attachment. This allows the wire to be crimped onto the wire easily, it?s not due to current carrying capability. #22 wires don?t work to well in crimp ring terminals.

[TASEsq]

Originally Posted by rapid_ascent

I suspect why they called out #16 wire for the shield attachment is since they are referring to the crimp terminal attachment. This allows the wire to be crimped onto the wire easily, it?s not due to current carrying capability. #22 wires don?t work to well in crimp ring terminals.

Interesting thought - but why not use a red terminal instead?

[g3xpert]

Originally Posted by TASEsq

The other reason for this question, is i was thinking of putting the probe in the left wing - where the pitot tube hole will be in the skin. I wanted to be able to run the cables in the wing now, to save fishing it through the wing later. I was figuring a connector at the probe would be a good idea anyway in case the probe ever needed to be removed?

In the install manual they talk about extending the cable up to 25ft is fine, and it calls for ?three wire twisted shielded cable? - but unfortunately doesn?t recommend a gauge.

The gtp59 isn?t listed in the current draw table on page 2-14 but I would imagine it doesn?t draw anything. I was thinking a 22awg would have been fine? https://www.steinair.com/product/22-...ctor-shielded/

Here?s one from a citrus g1000 install - looks like 20 or 22 awg maybe in that little connector?

As Walt mentions, there is a reason the GTP 59 is fabricated the way it is. The use of a heavy gauge shield termination is not a mis-print in the manual. As a small metal appendage to the outside of the airframe, we had to design the connection from the GTP 59 accordingly to prevent the GTP 59 from becoming a HIRF/IEL path to the rest of your avionics. I do not recommend deviating from our guidance on this.

Steve offers some pretty good information in this post that I think is relevant to the discussion on this thread as well, in case you are interested. The discussion specifically mentions a suggestion on how to deal with the wiring of the GTP 59 from the wing to the GSU 25.

Please let us know if you have any other questions. You may reach out to us directly at G3Xpert@Garmin.com with any questions as well.

Thanks,

Justin

[TASEsq]

Thanks for the info Justin,

By HIRF/IEL do you mean getting struck by lightning?

So would there be any issues with cutting the GTP59 cable at the wing root and soldering on a 16awg pigtail and passing this through a pin? (and same on the other side of the connector?

If i wanted to run the cable before hand, instead of using the one that comes with the probe, can you advise what spec the cable is? (is it some kind of larger AWG shield to require a 16awg pigtial?). The g3X manual says the GTP59 cable can be extended, but does not give any clues as to what to use for this extension.

I had read that forum previously - but in my case i really want to be able to disconnect all wires from the wings easily - so had planned a wing connector in any case, was just trying to put the GTP59 wiring all in the same plug - for a 16AWG for this shield i will have to put it through the same CPC as the power pins for other devices (Series 2 CPC can't handle 16AWG as far as i know).

[LNSelf]

The GTP 59 is certified on business jets with Garmin Avionics such as the G3000 or G5000 systems. A part must meet the highest level of certification for where it is used. It is not us single engine piston guys driving the design.

Your experimental aircraft is less likely to get struck by lightning than a business jet, but it is still a good idea to follow best practices of maintaining the shielding of the GTP wiring harness. When necessary I use standard MIL 27500 shielded wire to extend the wiring. I typically do not wire through a connector, but splice the shield directly together.

Except for the RV-12, if you have to pull the wings, it is a major project. I personally would rather just have a small service loop of wires in the wing root. If you ever pull the wings off, you can cut the wires and splice, or put a connector on at that point. Remember that any connector is a possible failure point.

-Levi