Flight instruments
Flight instruments are the instruments in the cockpit of an aircraft that provide the pilot with information about the flight situation of that aircraft, such as height, speed and altitude. The flight instruments are of particular use in conditions of poor visibility, such as in clouds, when such information is not available from visual reference outside the aircraft.
The term is sometimes used loosely as a synonym for cockpit instruments as a whole, in which context it can include engine instrument, navigational and communication equipment.
Contents
* 1 Flight instruments
o 1.1 Altimeter
o 1.2 Attitude indicator
o 1.3 Airspeed indicator
o 1.4 Magnetic compass
o 1.5 Heading indicator
o 1.6 Turn indicator
o 1.7 Vertical speed indicator
o 1.8 Course deviation indicator
o 1.9 Radio Magnetic Indicator
* 2 Layout
o 2.1 T arrangement
o 2.2 Basic Six
* 3 See also
* 4 References
* 5 External links
Flight instruments
Most aircraft have these flight instruments:
Altimeter
3-Pointer Altimeter.svg
The altimeter shows the aircraft's altitude above sea-level by measuring the difference between the pressure in a stack of aneroid capsules inside the altimeter and the atmospheric pressure obtained through the static system. It is adjustable for local barometric pressure which must be set correctly to obtain accurate altitude readings. As the aircraft ascends, the capsules expand as the static pressure drops therefore causing the altimeter to indicate a higher altitude. The opposite occurs when descending.
Attitude indicator
Attitude indicator level flight.svg
The attitude indicator (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.
Schempp-Hirth Janus-C glider Instrument panel equipped for "cloud flying". The turn and bank indicator is top center. The heading indicator is replaced by a GPS-driven computer with wind and glide data, driving two electronic variometer displays to the right.
Airspeed indicator
Airspeed indicator.svg
The airspeed indicator shows the aircraft's speed (usually in knots ) relative to the surrounding air. It works by measuring the ram-air pressure in the aircraft's pitot tube. 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
Aero Magnetic Compass.jpg
The 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).
Heading indicator
Heading indicator.svg
The heading indicator (also known as the directional gyro, or DG; sometimes also called the gyrocompass, though usually not in aviation applications) displays the aircraft's heading with respect to geographical north. Principle of operation is a spinning gyroscope, and is therefore subject to drift errors (called precession) which must be periodically corrected by calibrating the instrument to the magnetic compass. In many advanced aircraft (including almost all jet aircraft), the heading indicator is replaced by a Horizontal Situation Indicator (HSI) which provides the same heading information, but also assists with navigation
Turn indicator
Turn indicator.png
The turn 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. The original turn and bank indicator was replaced in the late 1960s and early '70s by the newer turn coordinator, which is responsive to roll as well as rate of turn, the turn and bank is typically only seen in aircraft manufactured prior to that time, or in gliders manufactured in Europe.
Vertical speed indicator
Vertical speed indicator.PNG
The VSI (also sometimes called a variometer). 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.
Additional panel instruments that may not be found in smaller aircraft include:
Course deviation indicator
Vor indicator.png
The CDI is an avionics instrument used in aircraft navigation to determine an aircraft's lateral position in relation to a track, which can be provided by a VOR or an Instrument Landing System.
This instrument can also be integrated with the heading indicator in a horizontal situation indicator.
Radio Magnetic Indicator
Adf rmi.jpg
An RMI is generally coupled to an automatic direction finder (ADF), which provides bearing for a tuned Non-directional beacon (NDB). While simple ADF displays may have only one needle, a typical RMI has two, coupled to different ADF receivers, allowing for position fixing using one instrument.
Layout
Six basic instruments in a light twin-engine airplane arranged in a "basic-T". From top left: airspeed indicator, attitude indicator, altimeter, turn coordinator, heading indicator, and vertical speed indicator
Most aircraft are equipped with a standard set of flight instruments which give the pilot information about the aircraft's attitude, airspeed, and altitude.
T arrangement
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, altimeter 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 altimeter, 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.
Basic Six
In 1937 the Royal Air Force (RAF) chose a set of six essential flight instruments which would remain the standard panel used for flying in Instrument Meteorological Conditions (IMC) for the next 20 years. They were:
* airspeed indicator (knots)
* attitude indicator
* vertical speed indicator (rate of climb)
* altimeter
* directional gyro (compass)
* turn and bank indicator (aircraft attitude)
This panel arrangement was incorporated into every RAF aircraft, from the light Tiger Moth, to the heavy Avro Lancaster, and minimized the type-conversion difficulties associated with Blind Flying, since a pilot trained on one aircraft could quickly become accustomed to any other if the instruments were identical.
This Basic Six set, also known as a six pack[1], was also adopted by commercial aviation. After the Second World War the arrangement was changed to: (top row) airspeed, artificial horizon, altimeter, (bottom row) radio compass, direction indicator, vertical speed.
The basic flight instruments
Although the instrument panel of an airplane may confuse you at first, you'll soon be familiar with the dials and switches and the valuable information they provide. The basic flight instruments are as follows:
Magnetic compass -- Like the compass you have seen in a car or boat, it tells you the airplane's heading -- the direction it's flying. It requires no power source.
Airspeed indicator -- It shows the speed of the airplane through the air.
Attitude indicator -- This instrument is like the horizon you see looking out from the pilot's seat. It tells you whether the nose of the airplane is pointed above or below the horizon and whether the airplane is turning (banking) to the left or right (left wing down or right wing down).
Altimeter -- This instrument shows the airplane's altitude in feet above sea level.
Vertical speed indicator -- This instrument tells you how quickly you're climbing or descending in feet per minute. When you're in level flight, it reads "0".
Heading indicator (directional gyro) -- This instrument is another compass. It shows the direction that the airplane is flying. It's usually bigger and easier to read than the magnetic compass, but requires some source of power to work.
Turn coordinator -- When you're turning the airplane, this instrument shows the rate and the direction of the turn. In this way you can adjust to a slower or faster rate of turn.
After your first few flights, you'll be thoroughly familiar with these instruments and how they work together with the airplane's control surfaces.
http://en.wikipedia.org/wiki/Flight_instruments