Fellow Legacy Builders,
It seems there is a lot of interest in my modification to the Legacy brake system and I am happy to share with you the changes I have made. First let me say that I heard from several builders who installed their brake system using the Lancair provided components and those people have not had any problems with their brake system. However, I have also heard from some who have "heard of" or have "first hand knowledge of" problems with the Polyflo tubing. The problem is rumored to be one of improper assembly of the tubing and fittings with the tube coming free from the fitting when the brakes are applied; over heating of the tubing thus causing softening and failure of the tubing; or maybe long term creep of the plastic resulting in the tubing coming out of the fitting when the brakes are applied. Regardless of the likelihood of failure, I have chosen to revise my brake system to eliminate all plastic tubing and install more standard hydraulic hoses. Additionally, I have installed a parking brake valve so I can exit my plane and place wheel chocks without the plane rolling away from me.
At this time I have not installed the rudder cables, which hold the rudder pedals in the proper position, nor have I filled the system with hydraulic fluid. Take all these recommendations as guidelines for helping you make your own decisions on your own brake system modifications. The following is a summary of the modifications I made or plan to make.
1. I installed the brake fluid reservoir nearly as shown on the plans. I think I moved the reservoir a little toward the center of the aircraft (3/4") to avoid putting a mounting hole in the upper left engine mount, but it is still mounted on the upper left firewall.
2. I decided to reverse the brake tubing configuration from what is shown on the plans. The plans show the reservoir attached to the left side pedals and then the left side pedals connected to the right side pedals and finally the right side pedals connected to the wheel cylinders. In my mind, reversing this configuration so that the reservoir feeds the right side first provides two benefits. One, it reduces the length of hose and the number of fittings between the left brake master cylinders and the brake cylinders, thus providing slightly better reliability and braking. Two, there is more reservoir fluid upstream of the left side master cylinders, or in other words, low reservoir fluid would be noticed in the right brakes before the left brakes. Of course, this assumes you will primarily fly from the left seat.
3. I installed a parking brake valve directly to the outlet of the reservoir and ran _" aluminum tubing from the outlet of the parking brake valve to a tee feeding both right side master cylinders. The valve is WagAero P/N D-213-000 and costs $32.50. This configuration will lock pressurized fluid in both sets of brakes and only requires that the reservoir line be valved. A word of caution should be noted if you use this WagAero valve. It is supposedly a surplus Chinese aircraft valve. The one I received had certification paperwork dated 1992 and the o-rings were old. I had to replace both o-rings to get the valve to hold pressure. I fabricated a simple aluminum bracket to support the actuation cable.
4. I purchased prefabricated brake lines from www.ANplumbing.com that have AN4 fittings on the ends. I used these lines from the reservoir tee to the inlet of the right side master cylinders and from the outlet of the right side master cylinders to the inlet of the left side master cylinders. You will need to install AN822-4D 90-degree pipe to flare fittings in the master cylinders to connect the hoses. I found that two 12" hoses (P/N 64191912) and two 30" hoses (P/N 64191930) work well, but you should verify your own hose lengths. The location of the tee from the reservoir will determine the shorter hose length and I had to bend the tee out from the fire wall a little to make sure I had enough hose travel to accommodate the adjustable pedals. A 13" or 14" hose may be better for you. Also, make sure you clear the gas strut that holds the canopy when the canopy is closed.
5. I installed hydraulic hose from the outlet of the left side master cylinders to the main landing gear oleos. The hose I used is Weatherhead H10404 purchased from the local NAPA auto parts store and which cost much less than Aeroquip hose. I used Stratoflex 303-4S hose ends purchased from Aircraft Spruce on each end. I routed the hose along the _" fuel line and attached it to the fuel line with tie-wraps. I also installed adel clamps and grommets where appropriate for holding the line and where it passes through the load panels.
6. I attached the H10404 hose to the Lancair provided brake cylinder hose using a steel AN832-4 union that fit the oleo bracket without any problem. I used steel because I didnt want it to break through vibration or if struck by FOD.
As a result of this, I feel I have a high quality brake system that includes a parking brake, which should provide reliable service.
If you have further questions don't hesitate to ask me,
Jim Thomas #166