They improve safety by allowing the pilot to fly the aircraft in level flight, and make turns, without a reference outside the aircraft such as the horizon. It is adjustable for local barometric pressure which must be set correctly to obtain accurate altitude readings. As the aircraft ascends, the capsules expand and the static pressure drops, causing the altimeter to indicate a aircraft basic science pdf free download altitude.
The opposite effect occurs when descending. With the advancement in aviation and increased altitude ceiling, the altimeter dial had to be altered for use both at higher and lower altitudes. Hence when the needles were indicating lower altitudes i. 360-degree operation of the pointers was delineated by the appearance of a small window with oblique lines warning the pilot that he or she is nearer to the ground.
This modification was introduced in the early sixties after the recurrence of air accidents caused by the confusion in the pilot’s mind. At higher altitudes, the window will disappear. The compass shows the aircraft’s heading relative to magnetic north. Deviation, caused by the electrical wiring in the aircraft, which requires a Compass Correction Card. Additionally, the compass is subject to Dip Errors. 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.
Instrument panel equipped for “cloud flying”. The ADI is an Attitude Indicator with computer-driven steering bars, a task reliever during instrument flight. The CDI shows an aircraft’s lateral position in relation to a selected radial track. It is used for orientation, tracking to or from a station, and course interception. An RMI is remotely coupled to a gyrocompass so that it automatically rotates the azimuth card to represent aircraft heading.
Most US aircraft built since the 1940s have flight instruments arranged 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. Of the old basic six instruments, the turn and bank indicator is now obsolete. The instrument was included, but it was of little use in the first generation of jet airliners.
It was removed from many aircraft prior to glass cockpits becoming available. But the other five flight instruments, sometimes known as “the big five”, are still included in all cockpits. The way of displaying them has changed over time, though. In glass cockpits the flight instruments are shown on monitors. But the display is not shown by numbers, but as images of analog instruments.
The indicated airspeed, altimeter, and vertical speed indicator are displayed as columns with the indicated airspeed and altitude to the right of the horizon and the vertical speed to the left in the same pattern as in most older style “clock cockpits”. In good weather a pilot can fly by looking out the window. However, when flying in cloud or at night at least one gyroscopic instrument is necessary to orient the aircraft, being either an artificial horizon, turn and slip, or a gyro compass. The vertical speed indicator, or VSI, is more of “a good help” than absolutely essential. The gyrocompass can be used for navigation, but it is indeed a flight instrument as well.
It is needed to control the adjustment of the heading, to be the same as the heading of the landing runway. Indicated airspeed, or IAS, is the second most important instrument and indicates the airspeed very accurately in the range of 45 to 250 knots. At higher altitude a MACH-meter is used instead, to prevent the aircraft from overspeed. TAS, exists on some aircraft.
The altimeter displays the altitude in feet, but must be corrected to local air pressure at the landing airport. The altimeter may be adjusted to show an altitude of zero feet on the runway, but far more common is to adjust the altimeter to show the actual altitude when the aircraft has landed. In the latter case pilots must keep the runway elevation in mind. This instrument is however not among the “big five”, but must still be considered as a flight instrument. Instrument Flying Handbook, 2001, FAA-H-8083-15, US Dept.