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SIX PACK OVERVIEW



The “Six Pack”, no its not the one that is chilling in your refrigerator.


The six main basic flight instruments of an aircraft allow the pilot to operate the aircraft at its maximum performance and in a safe manner. All pilots need to become familiar and understand the basic operations with the instruments, systems and the errors associated with those instruments, such as the pitot-static system and instruments associated, and the gyroscopic instruments along with the compass.


Pitot-Static Instruments & System

Pitot-Static flight instruments are a combination of static air pressure and dynamic pressure when the aircraft is in motion. When these two pressures are working together, they operate three flight instruments:

  • Altimeter

  • Airspeed Indicator (ASI)

  • Vertical Speed Indicator (VSI)


Pitot System:

The pitot tube measures dynamic pressure when the aircraft is in motion, it doesn’t matter if the aircraft is moving in still air at 70 knots or the aircraft is facing into a 70-knot wind.

The pitot tube is designed with a large hole in the front of it which allows total pressure or ram aim to enter the chamber. At the back end of the pitot tube is a small drain hole that allows any moisture to drain out.


There are different types of Pitot's:

  • Pitot tube (Found on Cessna aircraft)

  • Pitot mast (Found on Piper aircraft)


During the preflight inspection, pilots must visually check both of the holes in the pitot tube to ensure they are clear of foreign object debris (FOD) and bugs and are not blocked.

The only flight instrument that uses the pitot tube system is the airspeed indicator (ASI).

Static System:

The Static system and pitot system work together. If a static port becomes blocked while the aircraft is in a climb, the airspeed indicator will show a decrease in airspeed. A blocked static port will also affect the altimeter and vertical speed indicator (VSI).

During the preflight inspection, pilots must visually check the holes in the static port to ensure they are clear of foreign object debris (FOD) and bugs and are not blocked.

TIP: If either the pitot tube or static port appears to be blocked or something is lodged inside i.e., bug, never try to clear it yourself, have a certified mechanic check it.



Gyroscopic Instruments & Systems

Gyroscopic (Gyros) instruments are either operated by a vacuum system, pressure powered or from the aircraft electrical power. There are three instruments, they are:

  • Turn Coordinator

  • Attitude Indicator

  • Heading indicator

Sources of Power:

As mentioned previously Gyros instruments are either operated by a vacuum system, pressure or from the aircraft electrical power. Some aircraft are built with two sources of vacuum or pressure systems in case one fails.

The vacuum system is one source of that operates the gyros, it is a vane type engine driven pump mounted to the accessory’s case of the aircraft engine. The vacuum spins the gyro by drawing air against the rotor vane, which spins the rotor at a high speed. The vacuum air also operates the gyros for the attitude and heading indicators.


Instrument checks

A gauge is mounted to the aircraft instrument panel, which indicates the amount of pressure. It is important that the pilot monitor the vacuum or suction gauge during flight. Due to the attitude indicator and heading indictor may not be a reliable source to indicate low suction pressure.


The normal operating range is indicated on the gauge, which is between 4.5 and 5.5 inches of mercury.







References:


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