Locating Firewall Holes for Engine Controls

[jaredyates]

I got spoiled with having a 360 in the 4-Place Bearhawk, there was so much space between the engine and the firewall, cable routing was no trouble. This week I've been going through 303AP and one of my tasks is to relocate the engine controls from the left side of the instrument panel over to the middle. This means also making new holes in the firewall. But the engine is really close so there isn't much room for error. Did anyone with a 540 take a picture of where they made the holes for the throttle and mixture especially? In this case the prop governor is up front so no worries on that one. If I come straight at the carburetor they will be in the way of feet, but it's not clear how high I can get away with and still make the bends smooth enough.

[Tim213]

Jared, here is how I did mine. I came directly across from the top bar as seen in first pic. Second shows where they penetrate firewall. No problems with the smooth bends, all controls work well.

[jaredyates]

Thank you Tim!

[svyolo]

I think it depends on the cables and penetrations as well. I used the same as Tim213. The eyeball style cable penetrations allow you to aim the cable downward. My throttle cable is about 7" below the upper engine mount bolt. Seems to work smoothly, but it isn't flying yet.

For a few other cables, I used 3/16 Bowden cables and straight penetrations. The straight ones were a lot cheaper, but the 3/16 cables are more flexible. Coming out at 90 degrees was not an issue with those cables but I think would have been with the larger 1/4 cables used for the throttle,prop/mixture.

[jaredyates]

I think it depends on the cables and penetrations as well. I used the same as Tim213. The eyeball style cable penetrations allow you to aim the cable downward. My throttle cable is about 7" below the upper engine mount bolt. Seems to work smoothly, but it isn't flying yet.

For a few other cables, I used 3/16 Bowden cables and straight penetrations. The straight ones were a lot cheaper, but the 3/16 cables are more flexible. Coming out at 90 degrees was not an issue with those cables but I think would have been with the larger 1/4 cables used for the throttle,prop/mixture.

Thanks John, today I pulled out the old ones but didn't yet drill holes for the new ones. I'll be able to reuse the mixture because it is the wire type and can be shortened, but I had to order a new throttle that is 2 feet shorter. On the last plane I made my own pass-throughs for the 3/16 Bowden cables by drilling a hole through a half inch steel bolt. That worked out well and they survived the fire much better than the aluminum eyeballs, which I had used for the throttle, prop, and mixture. I hope it's safe to say that an inflight fire will be over sooner and less of a problem.