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Garmin G3X/IFR Antenna Access

KEG

Active Member
Patron
I am just completing the empennage. kit on my 12iS. Looking way forward to page 7 of section 42PiS in the digital plans, I see an issue with installing the aft-most antenna in my eventual Garmin IFR package. How are you supposed to reach the area needed to drill the hole in flange f-1238-R and route the AV-532-L cable? Do you have to remove a skin panel? It appears to me that when using the Garmin G3X/IFR package, the cable and necessary parts should have been provided with the empennage kit and pre-routed prior to riveting the last skins. I think my 7 year old granddaughter is the only one in my family that could reach that area in a completed tailcone. ANY SUGGESTIONS APPRECIATED.
 
It can be done. I had the wings standing in a homemade wing stand and mounted a piece of MDF to extend the length of the Wing Spars.
This made it possible for me to enter the empennage on the MDF and secure the cable to the AV-532-L.
I used a small drill to drill the hole in the F-1238-R flange via the opening in the aft bulkhead.

See pictures.

https://photos.app.goo.gl/aymWUGUjaZYGz2ks8

https://photos.app.goo.gl/3wU1Jr2mWcM2KseA7

https://photos.app.goo.gl/ztXCh7vfP4CskQAh9

https://photos.app.goo.gl/KjfF8eezAsDrcrKH7

https://photos.app.goo.gl/cMHXrWMyfz26wFMs5

https://photos.app.goo.gl/imvQqCYrndVH8wS57

https://photos.app.goo.gl/KwJWii1giKwNQ8JP6
 
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It is probably easier to accomplish before the cone's last skin is on. Failing that, then install it before the tailcone goes onto the fuselage.

Since the instructions came out after my plane was all assembled, I had to do a retrofit. I placed a workhorse under the tail and had the smallest person on the airfield crawl in there. thick blankets or foam blocks on the floor will help you to maneuver around the cone's ribs and prevent bending them as you're climbing or laying in the cone.
 
Recognizing I am a brand new newbie your mileage may vary and when I say new I am waiting for my empennage kit to ship next spring. Taking advantage of my inherent focus on detail I read the KAI instructions front to back. I noticed this same problem and thought gee would it not make sense to install this stuff short of the antenna while building the Vertical Stabilizer and Tailcone. It can't be very expensive and would save literally hours.
Thus my AV532L pre-installation kit. I am aware of the ELSA rules about modifications but this is not a modification and uses all Van's parts that would eventually show up if ordering the Garmin 3X with IFR package. If later I decide not to go that route there is no loss. The "prep kit" has the following:

Product Name SKU Price Qty Subtotal
F-00203 Nav Antenna Doubler
F-00203
$3.75
Ordered1
$3.75
F-00205 Nutplate Spacer
F-00205
$2.50
Ordered1
$2.50
Tie Wrap Clip (hole attachment)
ES-00301
$2.00
Ordered1
$2.00
Black Snap Bushing SB625-7
BUSHING SB625-7
$0.08
Ordered2
$0.16
MS21051-L3 Plate Nut
MS21051-L3
$0.80
Ordered2
$1.60
CCR-264SS-3-2 CherryMAX Rivet
RIVET CCR-264SS-3-2
$0.30
Ordered2
$0.60
K1000-3 Plate Nut 10-32
K1000-3
$0.50
Ordered1
$0.50
NAS1149FN432P Flat Washer
NAS1149FN432P
$0.04
Ordered1
$0.04
LP4-5 Blind Rivet
RIVET LP4-5
$0.12
Ordered2
$0.24
K1000-06 Plate Nut 6-32 "Figure 8 Shape"
K1000-06
$0.50
Ordered10
$5.00
MS21051-L06 Plate Nut
MS21051-L06
$0.80
Ordered2
$1.60
AN426AD3-4 - Countersunk Head Rivets (lb)
AN426AD3-4
$62.00 / LB
Ordered0.25
$15.50
5/8" Nylon Ducting 25'
DUCT NT5/8-25
$19.30
Ordered1
$19.30
MS21266-1N 12" Grommet Strip
MS21266-1N
$1.00
Ordered4
$4.00
 
antennea

good morning. i like your logic and your parts list. where in the manual are these instructions?

John
 
The AV532L Nav\Com antenna mount is covered in Section 42Pis GTN650 portion of the avionics install. In essence, there is a handful of parts that definitely would be easier to install as the vertical stabilizer is built. The parts list came from combing through KAI 42Pis and comparing it with KAI Section 6 Vertical Stabilizer and Section 10is Tailcone. The antenna cable routing would be significantly easier to do before the top skin of the tailcone is riveted in place. The cable as a separate piece is available from Aircraft Spruce for about $80. Even if the IFR option is not ordered, and I am not sure I will go that direction yet, the time and work saved even if the cable gets "abandoned" in the tailcone and vertical stabilizer is worth the money. I think its worth it to plan ahead if there is the slightest chance of installing the GTN650.

By the way sorry for the lack of pretty print in my prior post as I am stilllearning my way around the forum. JJR
 
The AV532 is a dipole antenna specifically designed to be mounted on the top of a vertical stabilizer. The free ends of the dipole are meant to be in free air away from metallic structures which can cause interference and radio performance issues. You may see similar dipole antennas mounted on the belly of the fuselage. There are other antenna styles that may be mounted in other locations. So far as I know, they are all external mounted. Frequency range is the determinant here as VOR/Loc is 108 - 118 Mhz. GS is up in the UHF range in the 330 Mhz range if I remember correctly. Frequency is inverse to wavelength, the higher the frequency, the shorter the wave length, the more line of sight the radio wave is and the less bounce and better the penetrance. Putting a mid-VHF antenna inside an aluminum can is asking for performance trouble.

If building as EAB there is more flexibility in choice of antenna and location. If building as E-LSA you have to build to the ASTM specs from Van's using their materials plans and kits. Van's says AV532L dipole antenna on top of vertical stabilizer, so that's where it goes for me.
 
Noticed today that Van's posted revision of tail cone instructions (Sec. 10is rev 9-29-2022) to mark hole in top skin and not to rivet top skin until antenna cable installed. Bet the SLSA guys figured it out a while back. Now to get the Vertical Stabilizer KAI edited in similar way and an option kit with extra parts available.
 
docjjrmd, you mention that the cable is available from Aircraft Spruce -- I'd like to order one (with fittings if possible) before closing the tail cone. Do you know how long it should be?
 
The entire length, from the farthest ring terminal to the BNC connector is 283". You'll need to order a BNC male connector (for RG-58 cable) and possibly a crimper for it too (A tool that I think everyone should have). There are BNC connectors which aren't crimp-on, and I think they should be sent straight to the trash bin.

The cable alone appears to be Part#11-14057 from Aircraft Spruce. And #11-03992 for the BNC male. You may also want to consider putting a 90 degree BNC connector on it instead though. Once you mount the GTN650, you may understand why. The cable comes out the back of the GTN650 and needs to make a 90 degree turn to go elsewhere as theres only a couple inches between the GTN and the firewall. I suggest leaving the end off until then.

Ideally, Van's would include this antenna kit (antenna/coax) as part of the tailkit..
 
Rob has it nailed down and yes I would wait until avionics install time to put the connector on the cable. If concerned about cable length and compatibility, then at least installing the flex conduit and mounting doublers along with the snap grommet in the skin would allow for snaking the cable in later as long as the vertical stabilizer has not been installed permanent like. The only tough part then would be the cable tie to keep the cable from catching the control cables on the guide support F-1238. - JJR
 
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