Brake Fluid

[jiott]

Kitfox manual says to use Mil-5606 for the brake system. This is a high quality mineral based aircraft hydraulic fluid.

Van's has quit selling the 5606 for their brake systems and are now using Royco 782, which is a synthetic fluid. They say it is compatible with systems using 5606, but you must flush out the old 5606 first. The 782 has much higher temp rating and I am tempted to use it. Has anyone used the 782 in their Kitfox? Opinions? Problems?

Jim

[Av8r3400]

I use ATF.

[HighWing]

Jim,
Curious what your thinking is regarding the switch.
Lowell

[jiott]

Oh I am just thinking that if I ever have to get on the brakes really hard for more than just a moment, that they might get really hot and the synthetic fluid will give more reserve in that regard. Has anyone ever overheated the 5606 fluid? The symptoms might be a dark color and funny smell when you drain or bleed the system.

Jim

[SkySteve]

Brakes? Do you actually use them other than for steering?

[Dave F]

I have never had an issue with 5606

I would definately talk to Matco about this and use their recomondation.

You not flying the space shuttle and the 5606 works and no seal issues with it so I would leave alone.

http://www.cfisher.com/aeroshell.html

http://www.cfisher.com/milspecoilbleeder.jpg

[HighWing]

I guess the reason I asked is because of the what we considered when we were routing the brake lines on the friends Lancair IV. The gear is retractable and I must say probably the ugliest thing I have ever seen on an airplane. The gear legs are heavy walled tapered steel tubing. The brake lines ran down inside the leg, through the aluminum fitting at the end and then outside to the caliper. It was very tight there. On the forums some of the guys were opting for the SS braided shield lines where the factory called for Nylaflow tubing like his manual called for - as well as ours. We chose to go with the plans and use the Nylaflow. The Nylaflow tubing, I would think, is the most temperature sensitive component in the brake system.

Also consider that the Lancair IV is 100 kts. on base and stalls near 70 kts. My buddy that flies the Lancair is considering Idaho as his next home - his business is dead here - and he is constantly talking about all the airports there, but the scarcity of airports where he would be comfortable landing. This is a guy who will have frequent opportunities to stand on his brakes. I know he uses the 5606 because he bought a gallon when we were doing his and had me use it when I charged the brakes on my recent completion.
Lowell

[jiott]

Thank you all for the good comments. I have a lot of respect for Van's and just wondered if they know something we don't and made the switch to the Royco synthetic fluid.

Jim

[Dave S]

A couple points on the temperature deal.

The nylaflow tubing which we use on most Kitfoxes has a recommended operating temperature range of -65 Degrees F. to +150 Degrees F

The 5606 spec fluid has a recommended operating temperature range of -65 Degrees F. to +275 Degrees F

Those of us with nosegear KFs are most likely to warm up the brakes when having to taxi long distances in significant crosswinds - hasn't been a problem so far.

Sincerely,

Dave S

[akarmy]

When I had my RV I also switched to the Royco fluid. I also swapped out the o-rings in the pistons with new viton rings which also can hold higher temps. The issue at the time was brakes getting dragged on the RV's and lighting the wheel pants on fire. The orings would fail and push the fluid out into the fire. Not much fun.

On my Kitfox I also went ahead and replaced the orings and used the Royco fluid as I have a gallon of it now. Not sure that I'll ever need it, but hey, why not. As others have said you don't use the brakes much on the Kitfox.