BACKGROUND OF INVENTION:
Components used in Anti skid control unit were difficult to procure as they are of obsolete and this affected fleet serviceability. There was a need to develop an improved Anti Skid Control Unit which could meet the requirement and improved serviceability. The newly developed Anti Skid Control Unit thus met all the desired requirements to perfection.
OBJECTIVE OF INVENTION:
Main objective is to mitigate the obsolescence issue so that new improved unit could be substituted for the conventional unit. This development is to reduce the cost, increase the serviceability and to promote self reliance in aerospace industry.
DETAIL DESCRIPTION OF INVENTION:
The Primary function of the Antiskid control Unit is to provide Maximum Braking efficiency under all runway conditions. The DC generator coupled to the wheel drive monitors the speed of the wheels and gives a proportional Input voltage to the Control unit. The Control unit works to prevent skid by sensing the condition of each individual wheel /sets and modifying the brake Pressure being applied to the wheel.
The different Protection in the control unit is as follows
> Touchdown protection
> Antiskid protection
> Fail safe protection
TOUCHDOWN PROTECTION
Touchdown protection is provided to prevent the application or brake pressure prior to wheel spin up. During a landing, the wheels must be allowed to spin up to provide the anti-skid system a 'reference' velocity to which individual wheel speeds can be conpared.

Test - As per BS 3(5 100
Thermal shock Test -As per MIL STD 810 E
Fluid contamination Test - As per B53G100
Corrosion salt mist test - As per JSS 55555
Transit drop Test - As per MIL STD 810 E
Mechanical shock Test - As per MIL STD 810 E
Toppling Test - As per JSS 55555
Drip Test As per BS3G100
The unit has undergone flight trials successfully on aircraft complied with flight test instrumentation to analyze the dynamic performance of the unit.
In touchdown protection mode, the Control unit commands the onti-skid Hydraulic valves to dump all brake pressure.
ANTISKID PROTECTION
The function of the skid control protection is to monitor the i;peed of a wheel, and to supply a pressure release signal to the skid control valve to remove applied brake pressure when the wheel deceleration rate indicates an impending skid.
The wheel speed signal is fed to the skid control circuit. Q2 is conducting due to the bias voltage of R8 and R9, and removes the Bias voltage of Q4 thru Q2. Q5 and Q6 are OFF thus permitting the full application of brakes. If there is a rapid fall in speed then the Discharge of C2 will reduce the Q2 Bias voltage and Q4 conducts thus conducting Q5 and Q6 activating the solenoid valve to release the Brake pressure. When wheel regains the rotational speed Q2 conducts and switches off Q4,Q5 and Q6.
FAIL SAFE PROTECTION
The function of the failsafe circuit is to protect the braking capability of the aircraft by making the skid control system inoperative if a pressure release signal lasts longer than 2 seconds, or if a skid control valve has an open circuit when the aircraft s on ground. If either of this condition exists, the failsafe circuit will turn off the internal power to the skid control system.

POWER LATCH CIRCUIT
The Function of Power Latch circuit is to provide +28VDC and +15V DC power to the skid control and to remove the power during Failsafe. When Power switch S2 is ON then the relay is latched on by the current flow through R42, C6 to switch Q12. So Kl contacts closes and supplies +28VDC to skid control circuit and maintains conduction of Q12. If valve lasts longer than 2sec, or valve coil is open, the fail safe circuit will ground the junction of R^-3 and R44 through Q13. This removes bias of Q12 and de energizes Relay Kl. Power can be restored only by resetting the switch S2
TESTS CARRIED OUT:
This unit was subjected to EMI/EMC tests and qualification tests to meet the operational and environmental specifications.
EMI / EMC Test - As per MIL STD 461 C and 462 D
Random Vibration Test - As per MIL STD 810 E
Low Temperature Test - As per TNAM 6150
High Temperature Test - As per TNAM 6150
Humidity Test - As per MIL STD 810E
Altitude Test - As per JSS 55555
Mould Growth - As per JSS 55555
Life Test - 500 hrs of continuous operation at rated Volt-amperes
Bump Test - As per BS3& 100

CLAIMS;
We claim
1. The issue of obsolescence has been resolved over and for all by developing improved Anti Skid Control Unit.
2. As the Anti Skid Control Unit is indigenously developed, we claim that the serviceability of the Jaguar fleet has been enhanced.