GEA24 and Other Wiring

Time: 8hrs

Over the past few days I’ve been doing some wiring while waiting for the parts from TAF and the hoses from Aircraft Specialty. I’m not done with the work I wanted to get done, but I figured I should post the progress since I haven’t posted in a while. I’ll be using the Garmin G3X so the Engine Management System module that is used with that is the GEA24. There is also an older GSU73 EMS that incorporates the ADHARS and a few other components, but the GEA24 seems to be more of the standard now. The wiring of the GEA24 is fairly straight forward, there are a few instances where some extra electronic components are needed. One connection is the Tach (RPM) input from the Rotax trigger coil and also a resistor need for the oil pressure sensors. There is a Garmin kit #011-02348-00 which contains all fo the these miscellaneous diodes and resistors, but it’s a bit hard to find. I did manage to find it on a site called Gardner Lowe Aviation Services so I’m hoping that works out. The kit also comes with the more encompassing Garmin Rotax Sensor kit, but I didn’t buy that since there were components that I wasn’t going to use from that. If all else fails I’ll buy the components separately.

One point of confusion for me was how to wire up the temperature sensors. Rotax provides the oil and cylinder/water temperature sensors (I added the airbox sensor). These are essentially VDO resistive sensors, they have one wired connection and ground themselves to the engine block. I did a little looking and found that the RV12 which uses the Rotax 912 uses a single conductor out to the sensor. I saw at TAF (and confirmed with a few other builders) that they ran a 2 conductor shielded wire out to each sensor. One conductor connects to the sensor and the other to the engine block close to the sensor. I also asked Garmin and they said that the “LO” pin needs to be grounded, however from the RV G3X wiring diagram this isn’t the case and even if the pin needs to be grounded grounding back to the main ground block should be sufficient since the main ground block also connect to the engine block. Now having multiple grounds out to each sensor does provide some redundancy which is nice, but it could also cause some potential ground loops. In the end I decided to follow the RV way and not ground the “LO” pin at all. If the sensors don’t work I can pretty easily run a ground from the 4 “LO” pins (one for each temp sensor) to the main ground block.

I also did quite a bit of organizing and clean up of the other fuselage cable runs. I needed to cut back the cable sleeves and permanently label the wire bundles. Grounds will run back to the main ground block on the inside of the firewall. I installed some wire tie brackets to run cables along the top rib. Additionally I made some brackets that I attached to the support which I used to bot a few adel clamps onto so that the cable can run up and out of the center console area without fear of having it rub on any metal edges.

Edge grommet installed for all the sensor wires to pass through the top rib. The GEA24 will be mounted to the right of the hole. I left a bit of wire as a service loop so it’s easier to work on the connectors.

The GEA24 connectors mostly wired up. I’ll need to finish up the RPM and oil pressure wiring once I get the Garmin kit.

I didn’t realize how blurry this photo was until now. I’ll have to retake it tomorrow. This photo has the GEA24 connectors pretty much done with the inexpensive Chinese knock-off GEA24 installed :-). I cut back the wire sleeves on all the cables and labeled them. The grounds are run through the center hole in the top rib (Need to install edge grommet). Now that the cable is all organized it doesn’t feel so daunting of a task to wire everything up.  I’ll need to purchase a few of the avionics that get mounted on the top rib now (GEA24, TCW battery backup, and the VPX)


Nothing Exciting

Time: 1.0 hr

Nothing exciting done on the plane today. I installed the -8AN to NPT stainless steel fittings into the oil thermostat and measured the hoses for the oil lines. There are 5 -8AN hoses that are needed for the oil lines and so I’m having Steve at Aircraft Speciality make those up. There is also one smaller hose that runs from the oil pump back to the oil tank for the turbo, for that I order a length of fluorosilicone hose from Viper Performance Hoses. Fluorosilicone is silicone, but it is rated to be used with oil and fuel so it should work well. The reason I went with regular hose is because the fittings on both ends is hose barb and it will just be a bit easier to use hose with clamps for this one connection rather than trying to replace the fittings with AN style fittings. But maybe I’ll change my mind will have to see when the hose arrives.

Coolant Hoses

Time: 1.5 hrs

I ran the two coolant hoses to the radiator. The left side may be cut back more once I get the exhaust installed and see if there is a way to anchor the hose to the exhaust. The left side also involved using and 45 degree hose since the angle was a bit too much for the super flexible hose that I’m using. On the right side I was able to directly connect the hose to the radiator since the hose was at a good angle to connect to it. The hose I’m using is really flexible and is made from silicone. It meets the requirements in the Rotax manual and  seems to be very high quality hose. I’m really impressed with how well the hose is able to bend and not collapse. I put some thermal sleeve on the parts of the coolant hoses that run near the exhaust. The exhaust is also wrapped so hopefully it won’t get too hot. The sleeve looks a bit nicer then the thermal wrap, but it’s kind of a pain to put on and if the hose bends then it’s even harder. If I did this again I’d probably do the wrap rather than the sleeve.

Photo of the right side hose. I was able to run it directly to the radiator without having to use a 45 or 60 bent hose. I anchored it to the clamp that holds the large air intake to the turbo using an M5 nut and a bit modified adel clamp. I modified a longer adel clamp by cutting it a bit shorter and drilling a new mounting hole on one end. I suppose I could have just bought a larger clamp, but I had a large clamp that I wasn’t going to use. The clamp helps keep the hose a bit farther from the exhaust and provides some strain relief on the connection to the radiator.

The left side hose is quite a bit longer than the right and I had to use a 45 bent hose to connect it to the radiator. I’ll probably end up cutting this hose a little shorter once I see where I can anchor it. I have one anchor on the vertical portion using two adel clamps tied to the white engine mount. Note: I’m going to redo the clear tubing for the overflows with a Y fitting instead of the T to get a better downward flow.

Photo of the join to the 45 degree bent hose. The join is made by using a short piece of aluminum tubing that fits inside of the silicone hose.

Misc Work

Time: 1.5 hrs

Just did a few miscellaneous things today:

  • Drilled 6mm holes for radiator
  • Added neoprene around edge of radiator mount
  • Fixed hinge on rear seat (I had it backwards)
  • Filled/sanded some rivets
  • Fixed small crack in nose wheel pant

I really need to get the parts from TAF that I order back in December. Once I get those I can finish up a lot of the engine items. I’m also waiting on the oil cooler from California Power Systems.

Added some neoprene to the edge of the radiator mount hole. Also drilled the holes for the M6 bolts.

Cut down some M6 bolts and screwed them into the radiator. The new radiator has rounded ends and the cowling seems to have been updated to fit the new radiator.

I’m wondering how difficult it’s going to be to get the lower cowling off/on with the radiator and oil cooler mounted. There will be a bracket that connects the two and then some camlocs will hold them to the cowling along with the 2 M6 bolt pins (above). It seems like it will be a bit of a challenge to get all the lined up when putting on the cowling.

Exhaust Wrappin’

Time: 1.5 hrs

Today I wrapped the 4 exhausts running between the cylinders and turbo with Design Engineering 2″ thermal wrap. I had read on the Rotax blog that guys are wrapping the exhausts and haven’t had any negative affects…yet. Also Torrance TAF is wrapping the exhausts on some of the planes their building so it seems safe to do.

The process of wrapping the exhaust was pretty easy. I first cut 2 5ft and 2 6ft lengths (the right side pipes are a bit shorter than the left) of the warp. I did one overlapping wrap to start and then you maintain (or try to maintain) a 1/4″ overlap as you wrap the material around the exhaust. You don’t want to over do it because you could end up putting on too much material and cause too much heat to be retained in the exhaust. I wrapped the 4 main pipes down to where they meet at the turbo. I then did some creative wrapping to try to get the best coverage over this area. It took some experimentation, but I think I got a decent wrap around it. The wrap ends are held down by some stainless steel ties. I’m thinking now about how I will wrap the turbo. The guy at Torrance TAF said he was going to use a 3″ wide piece of wrap to cover it, but I’m not sure how you secure it, I guess you could run some wire through the edges and tie the ends together to form a kind of doughnut. I also saw that you can purchase a boot that is custom made to fit around the turbo, but they’re pretty pricey (like $150) and I saw that some fall apart so I’ll have to think about it.

One tip is if you’re sensitive to fiber glass wear some gloves. It doesn’t bother me so I didn’t wear any, but you’ll definitely get some glass on you if you don’t.

First pipe wrapped. I used a temporary zip tie to hold the end, but it actually stays fairly well with out it. The trickiest part is getting it started after that it goes quick wrapping down the pipe. I tried to hold some tension on the material as I wrapped it around the pipe. It stays wrapped pretty well.

All the pipe are wrapped. Only the area where the pipes all meet before going into the turbo needs to be wrapped. I secured the end with stainless steel ties. I also left the front EGT sensor bolts accessible so if I need to use them I don’t hav the cut the wrap.

This area took some time. I didn’t;t want to over wrap it, but the way it’s shaped makes it hard to wrap it so the wrap wants to stay. I secured it with a few ties.

Close up of the tie. The worst part is that the ends of the material want to fray after you cut it. To do a nice looking job you have to hide the ends. When you start you can do one full wrap to cover the end. When you end you can’t do that so I ended up folding back the frayed part under to hide it.

Avionics Shelf

Time: 2.5hrs

I found got some time to work on the plane. I’ve been so busy with work and then useably tired after that I haven’t had time to do any work on the plane. So today I made two shelves that some of the avionics will sit on. Mainly the GTR20 (Radio), GTX45R (Transponder), and the GMA245R (Remote Audio Panel)… This list might change, but I think this will be the way I’m going for mounting the avionics. Some stuff will mount directly to the rib and then of course a few components mount into the panel itself. The shelves are pretty straight forward. I used some aluminum angle and notched the ends so that it could be riveted to the fuselage stringers. I had to make sure that it didn’t get in the way of the air ducts and anything that will be mounted to the panel. I use .05 6061 aluminum sheets for the shelves themselves and made them removable just incase I have to get in to reach something behind the panel and can’t crawl under for some reason. Now I just need to start buying some avionics, which I will do now that the engine is on and getting close to being done. The nice part about the shelves is it keeps all the avionics out where you can get to them and not buried under the rib section near the firewall which is actually hard to get to when the dash is on.

Shelves are roughed in and mounting holes drilled. Next step is to clean up the parts and install some rivnuts for the M4 screws that will attach the shelves to the angle and rib.

The shelves are mostly installed. I still need to rivet the angle to the stringers and get some shorter M4 screws. I may also make a bracket for the center that attaches the angle to the center console supports or maybe some L brackets to beef up the connection to the stringers on the side. It seems pretty sturdy though so probably not necessary. This will be the basic arrangement of the avionics. I’ll see when I get the actual avionics exactly how everything will fit and how the weight is on the angle piece. I may also be able to cut a little off the end of the shelves to shorten them up for better access behind and less weight. Also I can mount things to the underside of the shelves as well.

Coolant Hoses

Time: 1 hr

I roughed in the two main cooling hoses that run to the water cooler. TAF supplies some custom made hoses that look pretty good, but I’m trying to use the least amount of rubber hoses I can for reduced maintenance. I found some super flexible 25mm silicone hoses that can be used with coolant and meet the specs in the Rotax manual (up to 257º F and 73psi burst). I ordered the hoses from a UK company called Viper Performance which had both reasonable prices and shipping. Shipping via DHL only took a few days so not too bad. I also order a few short bent hoses. The thinking was to use the bent hoses for maybe the tight 90 out of the coolant housing on the top of the engine and then some 45’s into and out of the water cooler. I found though that the super flex hose seems to work better because it’s able to bend in multiple directions so I ended up just using that for now. When I get the water cooler I’ll see how it works on that end. I also found some hose clamps on Amazon that expand and contract as the connection heats up. It’s probably doesn’t matter so much with this smaller hose, but I figured it can’t hurt. The only downside is that the clamps are a bit heavy and bulky.

To get the rear hose in you need to turn the water inlet on the back of the engine to point to the right side rather than the factory install left position. There are actually six different angles the inlet can be position. I ended up using the right facing 70º position (slightly pointing up). The 105º position (slightly pointing down) would have worked as well, but I didn’t like how tight the hose was bent right at the fitting. Moving to the slightly up pointing position allowed the hose to pass through with a bit more space and a better angle. I was kicking myself for not doing this prior to putting on the engine, but it seems like the easiest way to get the hose on the inlet fitting was to remove the fitting and put the hose on then install the fitting. Now that made the hose install easier, but then installing the fitting back with the hose attached proved to be a bit challenging. Though with this in mind I figured it really doesn’t matter if you do this before or after mounting the engine. I suppose if you have the coolant hoses then prior may be better.

The 25mm silicone hose attached to the coolant tank on top of the engine. I was surprised at how flexible the hose was and how well it all fits in the small space there is to run the hose. I thought this was going to be the hard one, but it turns out the hose only took a few minutes to run through. The hose on the back of the engine for the inlet was a bit more involved.

The hose runs down the left side of the engine. I’ll need to find points to secure it.

This is the hose on the inlet on the back of the engine. This took some maneuvering to get in. It’s a bit of a pain trying to get the two allen bolts that hold the inlet onto the engine since there’s not much space to work (but when is there ever?). The inlet is in the 70º position which seemed to work the best.

It’s a bit close to the exhaust, but the exhaust will be wrapped and I’ll put on some thermal wrap on the coolant hose as well.

Just a shot of one of the bent hoses I purchases and the clamp.TAF supplied some fittings to connect hoses together so if I end up using these hoses to feed into and out of the water cooler then I’ll use those fittings.