GRUMMAN AMERICAN
FOR TRAINING USE ONLY – SECTION 7
MODEL GA‐7/COUGAR
AIRPLANE & SYSTEMS DESCRIPTIONS
7‐24
Issued: April 10, 1978
HYDRAULIC SYSTEM (Figure 7‐11)
A hydraulic system is provided for retraction and extension of the landing gears. The system consists of a power
pack assembly, lines, landing gear actuators, hydraulic pressure switch, relief valve, and manually operated
selector valve. The normal operating pressure for the system is 1500 psi. Actuation of the system is initiated by a
selector valve control handle located on the lower, left center portion of the instrument panel, adjacent to the
gear indicator lights.
HYDRAULIC POWER PACK
The hydraulic power pack consists of a reservoir, a DC electric motor driven pump and pressure control and relief
valves. The power pack is a 12‐volt unit located in the left side of the nose section.
BRAKE SYSTEM
An independent hydraulically actuated brake system is provided for each main wheel. Hydraulic master cylinders
are connected to each rudder pedal. The master cylinders are connected to wheel cylinders through lines and
hose assemblies. The brakes are operated from the pilot’s rudder pedals. Brakes for the copilot’s side are
available as optional equipment. The brakes are operated by applying toe pressure to the top of the rudder
pedals. The parking brake system consists of a manually operated knob connected to a parking brake valve located
in the brake lines. When pressure is applied to the brake system and the parking brake handle is pulled, pressure
is locked on the wheel cylinders by the parking brake valve. Pressure at the wheel cylinders is released by pushing
the parking brake knob in.
The brake linings and brake disc should be inspected during the preflight inspection. If the linings are less than
1/10 inch (0.100) thickness or the disc is less than 11/32 inch (0.345) thickness, they should be replaced as soon as
possible.
NOTE
The parking brake should be left off and wheel chocks installed if the airplane is
to be left unattended. Changes in ambient temperature can cause the brakes
to release or to exert excessive pressures.
