I've seen numerous failures of the plastic brake lines due to heat. One in a Rutan Defiant caused the loss of the aircraft due to a brake fire while braking during rollout after landing. The other was a RV-4 that popped both brake lines after a long taxi causing no damage to the plane, but ruining the fly-in weekend for the owner since she got to spend the weekend searching for parts and bleeding brakes. The nyloflow plastic tubing is rated for 1000 psi and holds up to braking pressures reasonably well. However, it will not tolerate hot brakes if the line is inside the wheel fairings or attached to an overheated caliper. If one wants to use nylaflow, nylaseal, or polyflow brake lines on your project (which makes for an easy installation), it is a good practice to terminate the plastic line outside of the wheel fairings and use aluminum, stainless, or properly rated pressure hose the remaining few inches down to the brake calipers. That eliminates any chance of having the brake lines fail due to heating, and eliminates any chance for brake fire with 5606 hydraulic fluid. Note that some builders choose to use Skydrol (TM) Hydraulic fluid rather than 5606, but the vast majority of light aircraft use 5606 and most FBOs will have 5606 in stock if you ever need it and are unlikely to have Skydrol on hand. The two fluids are not compatible and should not be mixed.
On my KR, I terminated the plastic lines at the bottom of the gear leg and used aluminum lines inside the wheel pant. You'll see the fitting location right at the top of the intersection fairing in this photo: <http://jeffsplanes.com/KR/2013-2/fairings%2021.jpg> One other note on the plastic brake lines. The plastic lines do tend to expand a bit under pressure. With the expansion comes a loss of brake pressure. I have fixed a number of brake issues on Experimental planes by swapping out the 1/4" Nyloflow brake lines for 3/16" lines. I noted recently that the Aerion Lightning aircraft are now using 1/8" Nyloflow lines for the brakes to prevent loss of brake pressure due to the tubing expansion under pressure. Jeff Scott Arkansas Ozarks ________________________________ -Please see LIST RULES and KRnet info at http://www.krnet.org/info.html -Change list delivery options at https://list.krnet.org/list/krnet.list.krnet.org/ Affinity List Info Board -Search recent KRnet Archives at https://list.krnet.org/empathy/list/krnet.list.krnet.org/ -Search John Boyea's decades of archive at https://www.mail-archive.com/[email protected]/
