NORMAL, ALTERNATE AND ACCUMULATOR BRAKING
Braking combines a hydraulic source, a control path, wheel-speed sensing and tyre/runway friction. The reference architecture uses Green supply for normal braking and Yellow/accumulator arrangements for alternate and parking functions. Normal braking is electrically controlled through the braking/steering computer and relevant valves. A change of hydraulic source can preserve braking while changing automatic functions or indications. Braking capability should therefore be described by the actual remaining combination, not simply by whether a pedal still produces some pressure. [87, PDF pp. 88–91]
Anti-skid compares wheel behaviour with an aircraft-speed reference and modulates pressure to avoid excessive skid. Autobrake requests a deceleration objective and depends on its required sensing/control and normal-system conditions. A DECEL indication relates to achieved deceleration under its defined logic; it is not a hydraulic-pressure gauge or a statement that the wheel brakes alone produced all slowing. Reverse thrust, aerodynamic drag and runway condition influence the result. Selecting an autobrake mode establishes a request that must later be checked against actual arming and deceleration. [87, PDF pp. 89–91] [23, PDF pp. 1063–1064, 1153–1155]
The brake accumulator stores hydraulic energy for its specified function when continuous supply is unavailable. Its indicated condition and brake pressure are different measurements. A parking-brake handle position does not by itself establish effective restraint, particularly after a supply loss or depletion. Chocks and the actual servicing/ground arrangement remain part of the secure-aircraft state. Normal takeoff MAX selection must not be confused with a source illustration that happens to show MAX when discussing landing controls. Landing deceleration choice belongs to the actual landing plan. [23, PDF p. 991] [87, PDF p. 89] [21, Landing/rollout guidance and stopping-system monitoring]
Brake temperature represents accumulated thermal load and cooling history, not only the final pedal application. Repeated taxi braking, a heavy landing and the use of available reverse produce different energy histories. Fans, when fitted, change cooling but do not remove the need to respect the applicable temperature/takeoff limitations. The current Fenix register documents brake-fan and tyre-pressure-indication options; absence of an optional display does not establish a flat tyre or a failed fan. Keep thermal condition, tyre condition, hydraulic pressure and automatic deceleration status separate during an advanced failure review. [21, PDF pp. 107–116, 188–194] [70, Available Options: brake fans and TPIS]