How Do Airplane Gauges Work In An Aircraft

To monitor the aircraft you are flying, you need to rely upon six instruments. These provide you with all the information you need about your aircraft’s motion, both on the ground and in air. There’s no safety factor working without these instruments doing their job properly, but when they do, you can fly safely even without the ground or horizon in your sightline.

There six are traditional flight instruments. While there are modern versions of these instruments that are technologically superior and advanced than the traditional ones, these still remain in use as back-ups for the times when the primary systems fail.

These are collectively called the 6-pack in the airmen lingo. Usually, the instruments are stacked upon one another, providing the main source of cockpit flight information. Categorised into pilot-static (or simply, static) and gyroscopic instruments, without these in proper order, you might just head towards a grand nosedive.

•    Pitot-static tube: This one gives you information about air pressure and drives three of the instruments - altimeter, airspeed indicator and vertical speed indicator. It remains mounted upon the airplane’s nose. An alternative place for it is the leading edge of the wings. The tube senses the change in air pressure (ram pressure) when the plane moves upwards through the air layers.

The ram pressure also changes with the airplane’s speed. There are holes along the side of the tube, through which, another sensor measures the static (local atmospheric) pressure, which reduces as you go up in the air.

•    Gyroscope: The gyroscope makes the heading indicator, the attitude indicator and the turn coordinator function. This is a rapidly spinning wheel within an instrument, providing a fixed plane of reference. It remains mounted on a set of swivels – a.k.a gimbals (appliance that allows instruments like compasses to remain horizontal under topsy-turvy situations) - that allows it to rotate. Set it in motion and the wheel maintains its orientation, irrespective of the position of its mounting, which changes as an airplane rolls, yaws and pitches.

Now that you’ve come to know what connects to what, let’s have an elaborate view of individual instruments and what each one of them does.

•    Airspeed Indicator: Indicates true airspeed (in knots/mach; mach is the ratio of the speed of a moving body to the speed of sound) with colour codings, which is the airplane’s actual speed in relation to the air; with temperature/density effects corrected. It functions by comparing ram pressure (from the pilot-tube) to static air pressure from static ports. There’s a diaphragm housed inside the instrument’s casing, which measures the pressure differential and depicts it on the instrument. You get information about normal, flap-operating and caution ranges that way; also minimum/maximum and other V-speeds.

•    Altimeter: Used to detect an aircraft's vertical height above the mean sea level (MSL) by correcting outside air pressure. The ideal pressure setting (when within 18,000 feet) and the altimeter depict the corresponding altitude above MSL. It operates in a similar way that a basic barometer works. At its heart is a sealed aneroid capsule that compares its inner pressure to the expanding/contracting pressure around it when the airplane ascends or descends. The altitude is displayed with the aid of a linkage and a pointer.

•    Vertical Speed Indicator: It measures an aircraft's climb and descent in feet-per-minute (or fpm). In a level flight, the VSI needle points to '0'. It’s an expandable capsule that depicts the static pressure inside it by comparing it to the metered static pressure outside, which changes rapidly with the climbs and descents.

•    Attitude Indicator: Considered the most important instrument for pilots, it telsl you if an Aircraft Flight Instruments is on a climb, a descent; turning or moving straight at a certain level. It also tells you when you pitch altitude and also when you bank.

•    Heading Indicator: This is a basic, vacuum-driven or electrically powered navigational tool, providing directional information to pilots. It works the same way as a magnetic compass does but it doesn’t seek north by itself. Instead, it depicts an accurate heading when you align it to a magnetic compass.

•    Turn Coordinator: The simplest of the lot, it’s either electric or vacuum-driven and uses a miniature Airplane Gauges that dips its wings showing the rate at which the plane rolls or turns. The tick marks (calibrations) depict a standard turning rate, with a full 360o degree standard turn taking around 120 seconds.

Includes an inclinometer - a ball suspended in fluid and acting like a pendulum, in response to gravity and centrifugal/centripetal forces, depicting coordinated/uncoordinated turns, which makes the pilot counteract uncoordinated turns using the rudder.