This is the third instance among friends of mine where a nylon brake line has failed inside the wheel fairings causing a fire, one of which destroyed the aircraft. I have preached about it for years. Nylon brake lines work well. I had them on my KR for the 24 years I flew it and never had an issue. I have them in my SuperCub and RV as well. But if you use wheel fairings, you always want to terminate the nylon brake line above the fairings and use either aluminum, stainless steel, or braided hydraulic lines where they may be exposed to the heat that is retained inside the wheel fairings.
One other note on nylon brake lines. 1/4" brake lines have a significant amount of stretch in the walls of the line and will use up much of your brake pedal with the line expanding rather than braking. I've seen this several times, and in every instance have been able to address it by swapping the lines out for 3/16" nylon lines. One vendor (Arion Lightning) recommends using 1/8" nylon brake lines in their kits for better braking.
The issue with the fluid expanding when heated and causing the brake to bind is another oddity. I have seen it happen when ATF was used in the brakes rather than 5606 hydraulic fluid. But it can also happen if you don't leave a bit of air at the top of your brake reservoir for expansion or have restricted venting on the brake reservoirs.
And one last comment on brake fires. Mill spec 5606 is the standard most of us, myself included, use in their brakes. It is flammable. There is a synthetic �� �(MIL-PRF-83282) that is nuch less flammable. Sold as Aeroshell fluid 31, it costs roughly $75 a gallon vs the more readily available Mil-spec-5606 at roughly $50 a gallon. If one wanted to switch to the synthetic fluid, keep in mind that most mechanics won't have any on hand if you have an issue away from home. You can't mix with 5606 fluid, so your system needs to be properly cleaned. And the synthetic fluid is not compatible with natural rubber products, so make sure of what you have for O-rings in your master cylinders and slave cylinders. Most will be Buna-N, which is a synthetic rubber and should be compatible.
Zach handled this fire well. He was prepared with a fire extinguisher in the aircraft. I am not so well-prepared and need to think about perhaps adding a fire extinguisher to my equipment list.
-Jeff Scott
Arkansas Ozarks
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