12.40 Gyroscopic Instruments

12.40.2 Outline the basic principle of operation of the vacuum system.

• An engine-driven vacuum pump creates a low-pressure (suction) system
• This causes air to be drawn through the system
• Air flows through filters → instruments → pump → overboard

Operation:

• The airflow spins air-driven gyros in instruments such as:
  • Attitude indicator
  • Direction indicator
• A regulator maintains the correct vacuum level

Summary:
The vacuum system works by creating suction that draws air through instruments, spinning gyros to provide reliable instrument operation.

12.40.4 State the likely effects of reduced or nil suction in the vacuum system.

• Gyroscopic instruments slow down or stop
• Attitude indicator becomes unreliable or topples
• Direction indicator (heading indicator) becomes inaccurate and drifts
• Indications may become erratic or sluggish
• Possible complete failure of vacuum-driven instruments

Summary:
Reduced or nil suction leads to loss of reliable gyro instrument indications, increasing the risk of loss of attitude and heading reference.

12.40.6 Describe the gyroscopic properties of:

(a) rigidity;

Rigidity (or rigidity in space) is the tendency of a spinning gyroscope to maintain its orientation in space.