Control Cable Firewall Penetrations

[robcaldwell]

What is the standard firewall penetration for the control cables (throttle, prop, mixture)? Where would one find written instructions and details for this install?

Is this what everyone uses?

[jaredyates]

I used something similar for the big three. For the smaller controls I drilled lengthwise through a steel bolt and tightened it to the firewall with an all-metal nut.

[Ray Strickland]

E1A7D408-5587-442D-B23C-886D89F17F1E.jpeg226FD2A2-4F8C-4EBE-B3F3-69C7E542504B.jpeg That is the fitting I used for the big three (stainless steel). For cabin heat I used Bowden clamps. Both come in various sizes: need to measure cable diameters. For electrical and other small pass-thru items, I used steel lamp hardware (hardware store) which is hollow on the inside and threaded on the outside, comes in various diameters and lengths.

[BravoGolf]

I have used those eyeballs for firewall penetrations. Not all control cables are the same diameter, so I had to ream the hole slightly so it would not cut the protective cover. They came with a single sheet set of instructions. If your’s did not I can make a copy for you. In one case a machinist friend turned a new ball as I could not ream the hole wide enough. I believe that was a CS cable.

[whee]

I ordered Aircraft Spruce control cables and specified a threaded section be installed at the location where the cables penetrate my firewall. I then drilled the properly sized hole, inserted the cable, gooped on some sealant and tightened a washer and nut on either side of the firewall. I’m quite happy with the result but I didn’t have a need to penetrate at an angle.

I used a couple aluminum (I know 🔥) eyeball penetrations for my wires. They are sorta ok.

[Bcone1381]

I've often thought about applying what industry (I think) calls a "Flange Mount Spherical Bearing". If its properly applied and sized right I think it could save weight and cost of the fittings I see made special for our applications.

[zkelley2]

These. https://www.aircraftspruce.com/catal...?clickkey=8172 or these https://www.aircraftspruce.com/catal...owdenclamp.php

I know they're aluminum. I don't personally care. Check out a certified firewall sometime.

[Bdflies]

I used these: https://www.aircraftspruce.com/catalog/appages/eyeballfw3.php?clickkey=32868.

Worked really well. Just one hole required. When the cable is hooked up and relaxed, tighten the capture nut.

Bill

[Battson]

These. https://www.aircraftspruce.com/catal...?clickkey=8172 or these https://www.aircraftspruce.com/catal...owdenclamp.php

I know they're aluminum. I don't personally care. Check out a certified firewall sometime.

I just drilled small holes and poked the cables through, with bushes to stop them wearing. I sealed them up with some high temp RTV. Not the most fireproof solution, but perhaps the lightest and most cost-effective. The clearance is tiny. Certified planes have bigger weak-points on the firewall and so do we - have you looked closely at a cabin heater valve.... seriously. Also those fireproof bushes things used to be quite expensive from memory.

The tiny gaps are not going to let enough fire through to do any damage, maybe smoke but we have windows which open so... I felt OK with the risk. If there is that much fire then I have major problems. I would be shutting off fuel and diving steeply with cowl flaps open to put the fire out, then get on the deck immediately.

[James]

I looked at a mate's RV the other day: he used a 4" section of heat proof rubber sheathing, you know the orange stuff that goes over flex lines and stuff on certified engine installations. Passed all the wires / control flex cables through the sheathing. Bogged the inside up with RTV106 or whatever the red high-temp sealant is. He had two cableties on either end of the tubing. I said "cable ties? They'll melt." I guess if you're on fire, you don't really care. Maybe cinch it together with stainless lockwire. Looked super easy, and super light.

James

[zkelley2]

I just drilled small holes and poked the cables through, with bushes to stop them wearing. I sealed them up with some high temp RTV. Not the most fireproof solution, but perhaps the lightest and most cost-effective. The clearance is tiny. Certified planes have bigger weak-points on the firewall and so do we - have you looked closely at a cabin heater valve.... seriously. Also those fireproof bushes things used to be quite expensive from memory.

The tiny gaps are not going to let enough fire through to do any damage, maybe smoke but we have windows which open so... I felt OK with the risk. If there is that much fire then I have major problems. I would be shutting off fuel and diving steeply with cowl flaps open to put the fire out, then get on the deck immediately.

Ya did that with the three major cable and then did what you described at all the other places. It was more about securing them via the firewall then fireproofing.