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

Attitude Indicator.

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.

The attitude indicator is reliable and the most realistic flight instrument on the instrument panel. Its indications are very close approximations of the actual attitude of the airplane.

The essential components of the indicator are:

1. "miniature wings", horizontal lines with a dot between them representing the actual wings and nose of the aircraft.

2. the center horizon bar separating the two halves of the display, with the top half usually blue in color to represent sky and the bottom half usually dark to represent earth.

3. degree marks representing the bank angle. They run along the rim of the dial. On a typical indicator, the first 3 marks on both sides of the center mark are 10 degrees apart. The next is 60 degrees and the mark in the middle of the dial is 90 degrees.

If the symbolic aircraft dot is above the horizon line (blue background) the aircraft is nose up. If the symbolic aircraft dot is below the horizon line (brown background) the aircraft is nose down. When the dot and wings are on the horizon line, the aircraft is in level flight.

The pitch angle is relative to the ground, which is not as helpful as knowing the angle of attack of the wing, a much more critical measure of performance. The pilot must infer the total performance by using other instruments such as the airspeed indicator, altimeter, vertical speed indicator, and power instruments, e.g. an engine tachometer.

Most Russian-built aircraft have a somewhat different design. The background display is colored as in a Western instrument, but moves up and down only to indicate pitch. A symbol representing the aircraft (which is fixed in a Western instrument) rolls left or right to indicate bank angle.

Airspeed Indicator

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.

The airspeed indicator is used by the pilot during all phases of flight, from take-off, climb, cruise, descent and landing in order to maintain airspeeds specific to the aircraft type and operating conditions as specified in the Operating Manual.

During instrument flight, the airspeed indicator is used in addition to the Artificial horizon as an instrument of reference for pitch control during climbs, descents and turns.

The airspeed indicator is also used in dead reckoning, where time, speed, and bearing are used for navigation in the absence of aids such as NDBs, VORs or GPS.

Kinds of Airspeed

There are three kinds of airspeed that the pilot should understand:

1. Indicated Airspeed

2. Calibrated Airspeed

3. True Airspeed

4. Groundspeed

Indicated Airspeed

Indicated airspeed (IAS) is the direct instrument reading obtained from the airspeed indicator, uncorrected for variations in atmospheric density, installation error, or instrument error.

Calibrated Airspeed

Calibrated airspeed (CAS) is indicated airspeed corrected for installation error and instrument error.

True Airspeed

The true airspeed indicator (TAS) is calibrated to indicate true airspeed under standard sea level conditions. Because air density decreases with an increase in altitude, the airplane has to be flown faster at higher altitudes to cause the same pressure difference between pitot impact pressure and static pressure.

A pilot can find true airspeed by two methods. The first method, which is more accurate, involves using a computer. In this method, the calibrated airspeed is corrected for temperature and pressure variation by using the airspeed correction scale on the computer.

A second method, which is a “rule of thumb,” can be used to compute the approximate true airspeed. This is done by adding to the indicated airspeed 2 percent of the indicated airspeed for each 1,000 feet of altitude.

Groundspeed (GS)

The actual speed of the airplane over the ground. It is true airspeed adjusted for wind. Groundspeed decreases with a headwind, and increases with a tailwind.

Дата добавления: 2015-11-04