-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.
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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 braking is inhibited but the system stays armed.
The automatic braking is re-initiated as soon as there is a
new mode selection (LOW or MED mode).
(c) 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 degrees. The pilot can disengage the AUTO BRAKE MAX mode when he depresses just one pedal
(4) Disengagement in the event of failure The system cannot be armed and is disengaged in the cases below:
-arming is impossible when there is a Green low pressure or A/SKID failure (servovalve, pressure transducer, tachometer) or electrical supply failure.
-disengagement when there is a loss of the arming conditions.
**ON A/C 106-149, 221-299,
D. Auto Brake
(1) Principle
(a) Operation
R (Ref. Fig. 066A) The automatic braking system has these functions:
-generation of the arming or disarming orders to the system,
-servoing of the aircraft deceleration to a programmed deceleration rate,
-braking control when the spoiler signals are present, depending
on the requested deceleration. When an autobrake mode (LO, MED or MAX) is selected, the BSCU sends a controlled pressure to the brakes until the deceleration measured by the IRUs matches the programmed deceleration. The anti skid system operates to avoid wheel lock-up. The auto brake system avantages are:
-get the optimum deceleration rate compatible with the length of the runway,
-decrease the pilot workload during landing,
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R Auto Brake Control Figure 066A
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-decrease the number of pilot actions in case of rejected take-off (one action on throttle instead of two actions: braking + throttle)
-improve passenger comfort. Before landing, the pilot sets the deceleration rate he thinks to be adapted to the runway. For this purpose, he uses the AUTO BRK LO and MED on the center instrument panel. The pilot can disengage the autobrake when he depresses the pedals or when he pushes again the AUTO BRK LO and MED. Before takeoff, the pilot select the MAX mode.
(b) Indicating
Each lighted pushbutton switch is divided into two parts:
-
the lower part (ON legend) comes on blue to show that the pushbutton switch has been selected and the system armed,
-
the upper part (DECEL legend) comes on green: when 80% of the corresponding deceleration rate has been reached, (LO and MED pushbutton switches) or when you have a deceleration rate higher than 0.27 g (MAX pushbutton switch).
(2) Auto brake logic The auto brake logic is located in the BSCU on the control and monitoring boards of the SYS 1 and SYS 2. The signals below are sent to the logic circuits of the auto brake:
-
3 signals that the AUTO BRK LO/MED and MAX on the center instrument panel supply: 2 deceleration rates, LOW = 1.7 m/square second and MED = 3 m/square second (2 m/square second in MED limited) , and a MAX = 10 m/square second (higher than the maximum possible deceleration of the aircraft)
-
3 signals which tell that the ground spoilers are extended. 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,
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