GRUMMAN AMERICAN
FOR TRAINING USE ONLY – SECTION 7
MODEL GA‐7/COUGAR
AIRPLANE & SYSTEMS DESCRIPTIONS
7‐30
Issued: April 10, 1978
INSTRUMENT PRESSURE SYSTEM (Figure 7‐13)
An instrument pressure system is used on the GA‐7/Cougar to provide pressure for operation of the gyro
instruments. The pressure system consists of two inlet air filters, two engine driven dry air pumps, two regulators,
a pressure manifold, an inline filter, directional gyro, horizon gyro, differential pressure gauge with source
indicator, and necessary tubing and fittings. The two pumps are interconnected at the manifold to form a single
system. If either pump fails, a valve automatically closes in the manifold and the remaining pump continues to
operate all gyro instruments.
The two source indicators in the pressure gauge are red “Bull’s Eye” type indicators which retract out of sight in
the gauge face when the pumps are operating normally. The normal operating system pressure should be
between 4.3 to 6.1 PSI at engine normal operating speed. Should an air pump malfunction occur, the “Bull’s Eye”
for that pump will appear in the dial face.
Figure 7‐13. Pressure System Schematic.
PITOT‐STATIC SYSTEM
The pitot‐static system supplies ram air pressure to the airspeed indicator and static pressure to the airspeed
indicator, vertical speed indicator and altimeter. The system is composed of a pitot tube mounted on the lower
surface of the nose section, two external static ports, one on each side of the aft fuselage, and the associated
plumbing necessary to connect the instruments to the pressure sources. An alternate internal static pressure
system is provided to supply an alternate static source to the pilot’s instruments should the external static
pressure source malfunction. The control for the alternate static air is located adjacent to pilot’s air vent on the
instrument panel.
The airplane is equipped with a pitot heat system. The system consists of a heating element in the pitot tube, a
pitot heat switch located on the lower left side of the instrument panel, a 14‐ampere circuit breaker on the lower
right side of the instrument panel and associated wiring. When the pitot heat is turned on, the heating element in
the pitot tube is heated to maintain proper operation in possible icing conditions.