BRAKES
Airplane wheel brakes can be applied by depressing the brake pedals. When either set of brake pedals are depressed, hydraulic pressure from both the left and right hydraulic brake systems is applied to the main wheel brakes. A fully automatic, pressure modulating, anti-skid system is installed. The anti-skid system will reduce hydraulic pressure if necessary to prevent tire skidding and provide maximum braking. The anti-skid system is electrically controlled and has a touchdown wheel protection circuit that prevents braking action prior to main gear wheel spinup. The system is deactivated whenever the gear handle is not in the DOWN detent, parking brakes set, arming switch at OFF, or airplane is at low taxi speeds. When the system is deactivated, braking action is mechanically controlled by pilot input at the pedals.
Each main gear wheel is equipped with a disc type power brake, actuated by two independent sets of pistons (4 in each set); each set is powered by one of the hydraulic systems. In addition, each system has an accumulator that will supply reserve brake pressure in the event of normal hydraulic pressure failure. A dual pointer pressure gauge provides visual indication of hydraulic pressure in each system.
A BRAKE TEMP gauge and an OVHT light provide visual indication of brake temperature. If main gear tires are exposed to excessive brake temperature, fuse plugs in the wheel will melt releasing tire pressure. Each brake assembly is equipped with wear indicators so that visual checks can be made of brake wear.
The parking brakes are set by depressing the brake pedals, pulling up on the park brake control knob (located in the center of the nose-gear steering wheel), and releasing the brake pedals. This mechanically opens the brake control valves and closes the anti-skid return lines in both hydraulic systems, trapping accumulator pressure in the wheel brake system. When the parking brake knob is raised, it actuates a switch that disables the anti-skid system and turns on PARKING BRAKES ON light. If parking brakes are not set and one to four ANTI-SKID lights are on, a parking brake or anti-skid malfunction is indicated. If throttles are advanced to a takeoff setting with the parking brake set, the aural/vocal warning system will be activated.
Continental
Rev. 12/01/00 #29 Flight Manual
Automatic Brake System (ABS) (Some Aircraft)
When armed, the automatic brake system (ABS) will automatically apply brakes during landing and takeoff modes of flight. The ABS landing mode is armed prior to landing after the landing gear is extended by selecting MIN, MED, or MAX by the AUTO BRAKE selector switch and placing the AUTO BRAKE ARM/DISARM switch to ARM. The anti-skid system must be armed and operational as a condition for ABS operation. ABS landing mode is activated when spoilers are deployed either automatically or manually with throttle levers retarded and brake pedals released. Automatic braking is delayed after spoiler deployment for approximately 1 second in MAX position and approximately 3 seconds in MIN or MED positions to allow for normal nose wheel touchdown. ABS landing mode is inhibited if throttles are not retarded below 22 degrees. Pilot takeover can be initiated at any time, and the ABS will disarm and revert to normal anti-skid braking if either brake pedal is depressed beyond approximately 25 percent of travel, if throttle lever 1 or 2 is advanced beyond +22 degrees, or if the ARM-DISARM switch is placed in the DISARM position. The ARM/DISARM switch will drop to the disarm position and the ABS lights will illuminate for the above conditions. The ABS will also disarm and the ABS lights will illuminate if flaps are raised to less than 26 degrees with airplane speed above 70 knots. Stowing the ground spoilers will release brake pressure without disarming the ABS. The ABS lights will remain off and automatic braking will again be available if spoilers are re-deployed.
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