Power Brake Mode

CHAPTER FIVE

STUDENT GUIDE FOR T-1A AIRCRAFT SYSTEMS

Power Brake Mode

An accumulator charged with 900 + 50 psi of nitrogen located just aft of the left main landing

gear wheelwell stabilizes hydraulic pressure during fluctuations of the hydraulic system.

Anti-Skid Brake Mode

An anti-skid control system is installed on the aircraft to electronically monitor and control the

power brake system, providing maximum braking efficiency through the prevention of wheel

skidding. Upon landing with the anti-skid switch in the ON position and the system operating

normally, anti-skid braking is available when either the wheels spin up to greater than 37 knots

or if a squat switch senses weight on wheels for greater than approximately 2.5 seconds,

whichever occurs first.

Emergency Brake System

The brake assemblies on the main gear wheels are designed to operate on nitrogen pressure for

emergency braking should the hydraulic brake system malfunction. The nitrogen storage

cylinder provides sufficient pressure for at least 7-10 emergency brake applications and is

controlled by a hand-operated valve that directs equal nitrogen pressure to each brake assembly.

If nitrogen pressure has been used to close the main gear doors after an emergency gear

extension, enough pressure remains for approximately 7-9 brake applications.

Emergency Brake Handle

The emergency brake handle placarded EMER BRAKE, is located on the right side of the center

pedestal and is connected to the brake valve. A clip, safety wired to prevent accidental actuation

of the emergency brake system, secures the brake handle. When the handle is rotated down, a

mechanical linkage opens the selector valve. High-pressure nitrogen is emitted from the nitrogen

bottle (located in the nose compartment) directly into the shuttle valves in the main gear brake

assemblies.

Parking Brake Handle

The parking brake handle, placarded PARKING BRAKE PULL is located below the P

instrument panel, left of the control column. Pulling the handle out will set the parking brake

valves, trapping the applied brake pressure in the brake lines.

5-8 HYDRAULIC POWER SUPPLY & SYSTEMS