September 18, 2005

I’ve also put some more thought into mounting the FADEC ECU’s. I decided to turn the units through 90 degrees so that the connector faces to the right side and thus the centre of the aircraft. In the Aerosance manual, they specify that the units should be mounted with the connector pointing down. I presume that this is to prevent any water ingress. I doubt that there’ll be much water there, so I think it’ll be OK. I might put a small water shield over the connectors just to be sure. They do have seals in them too though, so it should all be fine.

Well, I had a think about it all, and put them in position. Then I had a think some more. There’s an issue with the prop control cable coming out right about where the ECU’s are supposed to be, so to be sure I mounted the prop control bracket. Now in reality, this will be closer to the firewall than where it currently is in the photos, because there should be a governor in there too, but it gave me the info I needed as to how high I needed to mount the upper ECU. I had to slide it up quite a way in order to get a good cable routing.

Here I have the top of the ECU mounting plate about a half inch higher than the bend in the firewall. Unfortunately, that’s still not enough.

In the end, I ended up moving it up another 3/4" or so. I had to remove some of the mounting plate in order to clear the firewall as it angles forward. Having the two ECU’s mounted like this makes for some ease of mounting too. The inner flanges of the mounting plates sit right on the angle the runs down the side of the firewall recess, so all I need to add is one piece of angle running vertically between the upper firewall angle and the cross brace angle. Everything will then be super rigid. Simple and easy.

Here you can see how I trimmed the mounting plate. There are two holes in each corner of the mounting plate. I basically added another hole closer to the center by the same distance, so the holes had equal spacing. Then this new hole sits on the centreline on the upper firewall angle.

Here you can see the clearance I have for the prop cable routing. It’s hard to see, but the bracket seems to orient the cable slightly upwards. I’m glad I thought of this when I did, otherwise it would’ve been a right mess later on!

In the next shot, you can see how close it is to the fuel pump outlet. It’s OK though as there will be a 90 degree fitting here anyway so it will miss by miles. Well, maybe not miles, but more than the engine will move at least! I could probably move this ECU a little higher, but I figure it’ll be fine there. I chose this spot to keep the ECU clear of the hot air blast from the cabin heat selector if the cabin heat is off. When cabin heat is off, it dumps the hot air overboard.

Here’s a shot from underneath just for good measure.