Basic of Aircraft Instruments

Just before the dawn of World War II, the Royal Air Force designated six flight instruments that would be installed in every single RAF aircraft. These guidelines were adopted by commercial and civil aviation manufacturers alike and came to be known as the “six pack.” The six pack consists of six instruments providing the pilot with constantly updating information of speed, altitude, ascension/descension, attitude, heading, as well as turning/banking. The individual instruments are the airspeed indicator (ASI), altimeter, vertical speed indicator (VSI), attitude indicator, heading indicator, and turn coordinator.

The first six pack instrument of the six pack, the airspeed indicator, is a tool that uses the pressure differential in a static pitot tube to measure and display the aircraft’s speed. A needle on the gauge points to the current indicated air speed. Standardized color-coded markings denote different levels of air speed like normal, caution, and do-not-exceed. The attitude indicator, sometimes referred to as the artificial horizon, uses an internal gyroscope to represent the aircraft’s attitude relative to the horizon, helping the pilot maintain straight and level flight.

The altimeter uses barometric pressure obtained from the static port to display the aircraft’s altitude above sea level. Because barometric pressure can change drastically due to environmental factors, altimeters feature an adjustment knob to pinpoint the pressure in the local atmosphere. Like the attitude indicator, the turn coordinator also uses an internal gyroscope, however in this case the gyro is used to display the aircraft’s roll rate and rate of turn.

The heading indicator is used to show the current compass direction that the aircraft is moving in. Using a 360 degree compass, the heading indicator shows headings in increments of five degrees. An adjustment knob turns the internal heading indicator compass to align with the aircraft’s magnetic compass. The final component of the six pack is the vertical speed indicator. This is an instrument that measures the internal pressure differential and uses that information to provide a visual representation of the pace at which the aircraft is climbing or descending. A chambered diaphragm connected to the static port expands or contracts relative to changes in altitude, causing the dial to move and indicate the rate at which the aircraft is climbing or descending.

At Veritable Aviation, owned and operated by ASAP Semiconductor, we can help you find all the six pack instruments as well as a huge collection of unique parts for the aerospace, civil aviation, and defense industries. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, email us at sales@veritableaviation.com or call us at 1-503-374-0340.



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