Hydraulic Package

STUDENT GUIDE FOR T-1A AIRCRAFT SYSTEMS

CHAPTER FIVE

504. HYDRAULIC PACKAGE

An air-over-oil type hydraulic reservoir uses filtered regulated engine bleed air to maintain

hydraulic pressure and prevent foaming of the hydraulic fluid in the reservoir. Each hydraulic

reservoir has a capacity of 1.1 gallons and air pressure is regulated to 15 psi.

The hydraulic system normally stabilizes at 1500 psi as indicated on the HYD PRESS indicator.

If the pressure exceeds 1500 psi, a relief valve opens at approximately 1650 psi, relieving the

overpressure condition. If the relief valve fails to relieve the overpressure condition, opening the

bypass valve returns the hydraulic fluid to the reservoir. Failure of the relief valve to relieve

pressure at 1650 psi is indicated by the flight deck HYD PRESS indicator display approaching

1850 psi.

505. HYDRAULIC SYSTEM CONTROLS AND INDICATORS

Hydraulic Pressure Bypass Switch

The switch is placarded HYD PRESS NORM - REL and is located adjacent to the HYD PRESS

indicator on the lower part of the P's instrument panel. When the guard is raised and the switch

is placed in the REL position, the bypass valve opens directing the hydraulic fluid back to the

reservoir.

Hydraulic Valve Position Switchlights

The switchlights are used to open or close, and indicate the position of the respective hydraulic

and fuel shutoff valves. Normally the top white half, placarded OPEN is illuminated. When the

guard is raised and the switch is pressed, the hydraulic and/or fuel shutoff valves will close and

the lower amber half, placarded CLOSE, will illuminate.

Hydraulic Pressure Indicator

The hydraulic pressure indicator placarded HYD PRESS (located on the lower portion of the P's

instrument panel) indicates hydraulic fluid pressure in psi.

Hydraulic Pressure Annunciators

These annunciators illuminate when system pressure falls below 750 psi.

Hydraulic Fluid Level Annunciator

This annunciator illuminates when the fluid level in the reservoir falls below 0.6 gallon.

506. HYDRAULIC SYSTEM LIMITATIONS

Refer to Instrument Markings, Section V, T.O. 1T-1A-1, for specific hydraulic system limits.

HYDRAULIC POWER SUPPLY & SYSTEMS

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