The Core of the Cockpit: The Six-Pack

Although advancements in aircraft technology are designed to create a more efficient and reliable flight experience, most aircraft still rely on six traditional instruments known as the “six-pack”. Like how the core of the human body is necessary for maintaining posture and balance, the “six-pack” is necessary for informing the pilot of vital information regarding the status of the aircraft.

These six instruments are classified into two separate categories based on their respective operating mechanisms: static instruments and gyroscopic instruments. And each classification has three instruments. Static instruments operate based on comparing the pressure of an enclosed capsule to fluctuating environmental pressure to indicate things like speed and altitude. Gyroscopic instruments are based on gyroscopes which indicate orientation and direction. Gyroscopic instruments can be found in vacuum or electric driven variations.

The static instruments include the altimeter, airspeed indicator, and vertical speed indicator (VSI). As the name suggests, the altimeter relays information on the altitude, or vertical distance of the aircraft. The altimeter works by comparing the static pressure of an enclosed capsule to the fluctuating pressure of the aircraft as it ascends or descends. This is then translated to a gauge display to indicate the vertical distance of the aircraft over the mean sea level. The airspeed indicator works in a similar fashion but differs by comparing ram air pressure to a constant air pressure in order to measure the speed of the aircraft. Temperature and density, which are components in measuring pressure, are both accounted for when measuring true airspeed— the actual speed of the aircraft. The VSI operates similarly to the previous two in order to measure the rate of ascent or descent of the aircraft, which is measured in feet per minute (fpm). However, the VSI differs from the other two in that it is more sensitive to changes in pressure, which makes it more sensitive to abrupt changes in pressure like in turbulence.

Gyroscopic instruments include heading indicators, attitude indicators, and turn coordinators. Turn coordinators indicate the rate of turn or roll of the aircraft, which is measured through a one-dimensional gyroscope which leans either to the left or right. Heading indicators inform pilots on what direction the aircraft is heading on a two-dimensional gyroscope. Rather than through typical cardinal directions, the heading indicator measures the direction of the aircraft on a 360-degree compass. Attitude indicators tell the pilot whether the aircraft is ascending, descending, turning, or maintaining a level altitude; they operate based on a three-dimensional gyroscope with a center that maintains a constant position while the outer rings of the gyroscope revolve around it to simulate a horizon and the aircraft’s direction. 
The names and different classifications of the various instruments are very reflective on the functions and operational methods of each instrument. Although advanced technology has replaced and automated the functions of these instruments, they act as a failsafe and because of this they are able to maintain their rightful place in the dashboard of an aircraft. 
At NSN Parts Hub, owned and operated by ASAP Semiconductor, we can help you find all the aircraft altimeters, airspeed indicators, or aircraft cockpit parts you need, new or obsolete. As a premier supplier of 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, 24/7x365. For a quick and competitive quote, email us at sales@nsnpartshub.com or call us at +1-269-264-4495


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