Support Resources for Matco ALS Wheels & Brakes

Check to be certain that pressure is not being applied to the brake by a blocked hydraulic line by loosening the bleeder carefully. If brake fluid under pressure is expelled and the wheel now turns freely, check the hydraulic line for the block source. If this did not free the brake, most likely the brake guide tubes are bound up by the brake plate anchor. Fix this by cleaning any rust deposits off and lubricating the brake guide tubes. Check to ensure that the brake plate anchor Is not deforming when the bolts are tightened against the axle head. Some shimming may be required to ensure a flat fit.

Use a thread sealant on any tapered pipe fittings that is compatible with petroleum such as LockTite 567 Thread Sealant. Do Not use Teflon tape as it can be cut during installation and enter your hydraulic system.

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First, check to ensure that there is no air in they system. Air can be trapped in any high spot in the line and often cannot be “pumped” out. Ensure no high spots during bleeding. The following bleeding procedure may be used:

1. Open brake bleeder valve slightly on the brake caliper to facilitate bleeding of air from the system.
2. Attach a tube from the nozzle of a squirt can or bleeder tank of brake fluid, to the top of the brake bleeder valve. Pump the handle until oil flows bubble free from service hose before attaching.
3. Make sure that the master cylinder shaft is fully extended to open up the internal bypass valve.
4. Inject brake fluid (Mil-H-5606) or equivalent, into the puck housing and continue injecting until the fluid travels through the system in to the master cylinder.
5. Air in the system will be pushed up and out in to the master cylinder ONLY IF the master cylinder cap (if master cylinder has built in reservoir) or remote reservoir, if used, is at the highest point in the system, and there are no loops in the brake lines.
6. Fluid should be pushed through the system until it reaches approximately ¼ inch from the top of the master cylinder or remote reservoir.
7. Close the brake bleeder valve, and remove the service hose.
8. If the brake system is free of air, the brake pedal should feel firm and not spongy. If not, repeat steps 1 through 7 until system is free of trapped air.
9. Problematic systems (especially those with local high spots in the hydraulic lines) may be best bled using a vacuum source at the reservoir and hydraulic fluid supply connected to brake bleeder. Drawing hydraulic fluid up through the system often improves the removal of trapped air in local high spots. High spots may be in the caliper, master cylinders, fittings, or park brake valves.

Second check to ensure that your linings have been adequately broken in using a standard break in procedure. Your lining should produce a shiny transfer layer if properly conditioned. The following procedure should be adequate to condition the linings:

1. Apply brake pressure for high throttle static run-up. Note RPM at creep if any.
2. Perform 2-3 high-speed taxi snubs to generate 300-400 degrees at brake pads and rotor by accelerating the aircraft to 30-40 mph. Remove power and apply firm braking pressure until slowed to 5 mph and release pressure. Do not bring aircraft to a complete stop during the taxi snubs. After accomplishing the snubs, do not drag the brakes. Allow the aircraft to roll as brake free as practicable until back to the tie down area. Avoid stopping the aircraft completely as much as practicable and park with brake pressure off.
3. Allow brakes to cool 10-15 minutes.
4. Repeat step 1. There should be a noticeable increase in holding torque.
5. Repeat steps 1-3 if necessary. Properly conditioned pads and discs will have a uniform, shiny appearance on the surface.

Third ensure that the none of the o-rings has been damaged or is letting fluid out.

Fourth, check to see if you are getting adequate pressure from the master cylinders by attaching a pressure gage to the brake bleeder seat port and applying pressure. Pressure ranges from 450 PSI to 600 PSI are adequate.

Fifth, ensure that both linings are touching the brake disk. If both linings are not touching, check to see if there is adequate travel of the brake plate anchor along the guide tubes. When both linings are now, the brake plate anchor should be between the center line and the housing. See the caliper adjustment drawing for B3 & B4 brakes under Brake Assembly Drawings at www.matcomfg.com for more details on adjustment of those brakes.

There are many types of line material that can be used. The line should have a working pressure of at least 425 psi and a burst pressure greater than 1500 psi. Care should be taken in the installation to reduce the installed stress on the line by keeping bend radii as large as possible. This is especially true at the fittings. Thought should be given to the orientation of the fittings at the caliper to best align with the approach of the hydraulic line to minimize the stress on these important fitting. Also, the lines should be routed to be clear of rotating components of the brake for consideration of potential damage from interference as well as heat induced stress from proximity. Solid lines of aluminum or steel as well as braided stainless line or nylon line are available in these pressure ranges and can be suitably engineered for installation with the proper consideration. All lines are not alike and the user must be certain to select lines of the proper rating. Also, keep in mind that the caliper must be free to float in the brake plate. The caliper housing will move away from the disc as the pads and disc wear. This distance will be one half the total of the pad and disc wear and must be accounted for in the installation.

Overfilling is the primary reason for leaking around the shaft. Since the master cylinder vents around the shaft, the fluid level should be only 3/4 full to allow for master cylinder travel with the rudder pedals. The MATCO master cylinder is designed to function within fifteen degrees of vertical. If you cannot install within fifteen degrees of vertical, use a remote reservoir master cylinder.

MATCMatco Aircraft Landing Systems. Uses 1/8 tapered pipe fittings for all fittings.

Your hydraulic system is designed to allow it to self adjust as the pads wear. This is accomplished by having a by-pass valve in the master cylinder that opens to the reservoir when the master cylinder is at rest and the shaft is fully extended. With the by-pass open, the reservoir is connected to the hydraulic system and allows fluid to flow into the portion of the system below the master cylinder and supply additional fluid required as the brake linings wear and the brake pistons extend. The fluid can only flow to the lower portion if the system is vented. For aerobatic use, the vent may be plugged but will need to be manually vented (cap opened) after 15-30 landings or the cylinder may begin to draw a vacuum and introduce air into the system from the master cylinder end gland shaft seal.