Flight instruments

Most aircraft are equipped with a standard set of flight instruments which give the pilot information about the aircraft's attitude, airspeed, and altitude.

Most aircraft have these six basic flight instruments:

;" : Gives the aircraft's height (usually in feet or meters) above some reference level (usually sea-level) by measuring the local air pressure. It is adjustable for local barometric pressure (referenced to sea level) which must be set correctly to obtain accurate altitude readings.

;" (also known as an "artificial horizon") : Shows the aircraft's attitude relative to the horizon. From this the pilot can tell whether the wings are level and if the aircraft nose is pointing above or below the horizon. This is a primary instrument for instrument flight and is also useful in conditions of poor visibility. Pilots are trained to use other instruments in combination should this instrument or its power fail.

;. The indicated airspeed must be corrected for air density (which varies with altitude, temperature and humidity) in order to obtain the true airspeed, and for wind conditions in order to obtain the speed over the ground.

; "Magnetic compass" : Shows the aircraft's heading relative to magnetic north. While reliable in steady level flight it can give confusing indications when turning, climbing, descending, or accelerating due to the inclination of the earth's magnetic field. For this reason, the heading indicator is also used for aircraft operation. For purposes of navigation it may be necessary to correct the direction indicated (which points to a magnetic pole) in order to obtain direction of true north or south (which points to the earth's axis of rotation).

; (HSI) which provides the same heading information, but also assists with navigation.

;":The turn and bank indicator, also called the turn and slip indicator, displays direction of turn and rate of turn. Internally mounted inclinometer displays 'quality' of turn, i.e. whether the turn is correctly coordinated, as opposed to an uncoordinated turn, wherein the aircraft would be in either a slip or a skid. Replaced in the late sixties and early seventies by the newer turn coordinator, the turn and bank is typically only seen in aircraft manufactured prior to that time, or in Gliders manufactured in Europe.

:A turn coordinator displays rate and direction of roll while the aircraft is rolling; displays rate and direction of turn while the aircraft is not rolling. Internally mounted inclinometer also displays quality of turn. Replaced the older "turn and bank indicator".

;. Senses changing air pressure, and displays that information to the pilot as a rate of climb or descent in feet per minute, meters per second or knots.

Arrangement in instrument panel

Most aircraft built since about 1953 have four of the flight instruments located in a standardized pattern called the T arrangement. The attitude indicator is in the top center, airspeed to the left, altitude to the right and heading indicator under the attitude indicator. The other two, turn-coordinator and vertical-speed, are usually found under the airspeed and altitude, but are given more latitude in placement. The magnetic compass will be above the instrument panel, often on the windscreen centerpost. In newer aircraft with glass cockpit instruments the layout of the displays conform to the basic T arrangement.

ee also

*Glass cockpit
*Cockpit
*Basic Six

External links

* [http://www.faa.gov/library/manuals/aviation/instrument_flying_handbook/ "Instrument Flying Handbook" (FAA-H-8083-15A)] 2007
* [http://www.daileyint.com/flying/flywar13.htm The Gyro Horizon Enables Instrument Flying] A history of how aircraft instrumentation was developed with an emphasis on the gyro horizon. (c) 2007