(b) Regulation (Ref. Fig. 063) The control speed of the speed servoing of each wheel (4 independent wheels) is calculated by decreasing the reference speed by the value of the slip ratio. (Ref. Fig. 064)
Vc (t) = 0.935 VRef (t)- 0.9 (in m/s)
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Generation of the Reference Speed - Principle R Figure 058
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Generation of the Reference Speed - Flow Chart
Figure 059
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Gamma n Calculation
Figure 060
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V GROUND Calculation
Figure 061
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Generation of the Reference Speed - Flight/Ground Logic
Figure 062
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Regulation Circuit
Figure 063
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Programmed Input Control Speed R Figure 064
1EFF : 001-049, 051-099, 101-149, 151-199, 1 32-42-00Page A28 1201-299, 301-399, 1Config-1 Aug 01/05 1 1 1CES 1 The regulator compares the control speed to the braked wheel speed to establish, if necessary, a brake release order so as to decrease wheel slip. The corrective networks and the static gain of the regulator of one wheel are adjusted to maintain a high level of stability and accuracy. The regulator cannot, therefore, anticipate on the braking orders of the pilot. Below a 10 m/s reference speed, the regulator action is inhibited by forcing the control speed value at 0 m/s (enabling wheel locking). The regulator supplies numerical values converted into current to supply the coil: - of the Normal servovalve I1 or I2, - of the Alternate servovalve I'1 or I'2.
The current control is not affected by the impedance of the
servovalve coil.
When sufficient brake release current is available, the voltage
at the terminals of resistor R is sent to the lower ECAM DU.
It supplies the brake-release indication, REL (Release)
symbolized by 5 green bars on the wheel concerned.
The regulation circuit of the Normal or Alternate servovalve
supplies the REL information.
A regulation-inhibition circuit eliminates all the
brake-release orders that could occur:
-during an automatic in-flight wheel braking when the gear
retracts, - or during application of the Parking brake (for 3 s only).
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(4) Indicating (Ref. Fig. 065) The A/SKID & NOSE WHEEL control switch is located on the center instrument panel. All the indications are transmitted to the crew through the ECAM:
-
On the lower display unit, the WHEEL page gives the Release information, the NORMAL/ALT braking mode and the selected deceleration,
-
On the upper display unit the related warnings are displayed.
**ON A/C 001-049, 051-099, 101-105, 151-199, 201-220, 301-399,
D. Auto Brake
(1) Principle
(a) Operation
R (Ref. Fig. 066) The automatic braking system has the two functions below:
-generation of the arming or disarming orders to the system,
-supply of a programmed speed to the braking controller. This speed is initiated from the impact by the aircraft speed and decreases according to the deceleration ratio selected by the crew.
This programmed speed is used as a reference speed for the anti skid controllers of the braked wheels. And this as long as it is higher than the aircraft speed. Each wheel is thus servoed to this speed. If the tire-runway adherence does not permit to get the selected deceleration:
-
the aircraft speed is then higher than the programmed one,
-
the anti skid operates to get the optimum deceleration. When the adherence permits again to get the selected deceleration:
-
the programmed speed is then higher than the aircraft speed,
-
the automatic braking limits again the deceleration
progressively to the selected value. The auto brake system does the actions below:
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