-
3 signals which tell that the ground spoilers are commanded. Two of them must be present to permit the automatic braking.
-
a signal which gives the pedal position,
-
a signal which tells that the pressure in the Green system is low,
-
a signal which gives the longitudinal deceleration of the aircraft ADIRs.
-no tachometer failure.
-GROUND/FLIGHT information.
The auto brake logic supplies:
-
the command for the energization of the selector valve,
-
the braking command to the four servovalves,
-
the information below to the lighted pushbutton switches:
the system is armed or the deceleration rate that you get
-to the ECAM system: the deceleration rate that you select or the AUTOBRK disarm signal or the AUTO BRK FAULT signal if arming is not possible.
(3) Operation
(a) LOW mode
1 This mode is used at landing.
_
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Auto Brake Control Modes
Figure 044
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2_ The selector valve is energized by the extension command of
the ground spoilers.
3_ Braking is applied when the ground-spoilers extension signals
are present (speed of the main gear wheel > 80 kts).
The braking has a delay of 4 seconds (type1) or 2 seconds
(type 2). It is then progressively applied.
4_ The pressure supplied by the 4 servovalves gradually
increases, t = 3 s approx.
The programmed deceleration is reached progressively.
5_ The control circuit sends identical commands to the 4
servovalves.
6_ The BSCU uses the deceleration from the ADIRs and limits or
increases the braking order to make it reach the selected
deceleration rate.
(b) MED mode
1 This mode is used at landing.
_
2 The selector valve is energized by the extension command of
_ the ground spoilers.
3 Braking is applied when the ground-spoilers extension signals
_ are present (speed of the main gear wheel > 80 kts). The braking has two phases:
-
phase 1: the MED limited deceleration is progressively applied without delay until the A/C attitude is less than 1 degree or T= 5 seconds. The pressure supplied by the 4 servovalves gradually increases, The programmed deceleration (2 m/square second) is reached progressively.
-
phase 2: when the A/C attitude is less than 1 degree or T= 5 seconds, the MED deceleration is then progressively applied. The pressure supplied by the 4 servovalves gradually increases, The programmed deceleration (3 m/square second) is reached progressively.
4 The control circuit sends identical commands to the 4
_ servovalves.
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5_ The BSCU uses the deceleration from the ADIRs and limits or
increases the braking order to make it reach the selected
deceleration rate.
(c) MAX mode
1 This mode is selected before take-off in case of rejected
_ take-off (at least 2 out 3 spoilers must be out).
2 The command for the ground spoiler extension controls:
_
-
the energization of the selector valve,
-
the immediate delivery of a maximum pressure to the four brakes (with antiskid protection).
3 The programmed deceleration rate is such as the full pressure
_ is applied on the four brakes. A small differential braking is not permitted. The auto brake system is disengaged:
-when you put the landing-gear control lever in the UP position
- or when you push again the mode-selection pushbutton switch already selected. There is no AUTO BRK indication on the ECAM.
The automatic braking is only re-initiated after the selection of a new deceleration rate. This occurs if the signal for the extension of the ground spoilers is still generated. The automatic braking is totally and immediately cut off as soon as a ground spoilers-retraction signal is applied (this signal possibly results from a go-around command). The automatic braking is re-initiated as soon as there is a new mode selection (LOW or MED mode).
(d) In the MAX mode, the load required at the pedal to cut off the automatic braking is greater than that in the LO or MED mode (half travel). Travel of the two brake pedals: 7.5 degrees in LOW and MED. Travel of the one brake pedal: 10 degreess in LOW and MED. The pilot can disengage the AUTO BRAKE MAX mode when he depresses just one pedal
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