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Flight Instruments

Turn Indicators

Flight Instruments

Aircraft use two types of turn indicators: turn-and-slip indicator and turn coordinator. Because of the way the gyro is mounted, the turn-and-slip indicator shows only the rate of turn in degrees per second. The turn coordinator is mounted at an angle, or canted, so it can initially show roll rate. When the roll stabilizes, it […]

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Gyroscopic Flight Instruments – Sources of Power

Flight Instruments

In some aircraft, all the gyros are vacuum, pressure, or electrically operated. In other aircraft, vacuum or pressure systems provide the power for the heading and attitude indicators, while the electrical system provides the power for the turn coordinator. Most aircraft have at least two sources of power to ensure at least one source of […]

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Gyroscopic Flight Instruments – Gyroscopic Precession

Flight Instruments

Precession is the tilting or turning of a gyro in response to a deflective force. The reaction to this force does not occur at the point at which it was applied; rather, it occurs at a point that is 90° later in the direction of rotation. This principle allows the gyro to determine a rate […]

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Gyroscopic Flight Instruments – Rigidity in Space

Flight Instruments

Rigidity in space refers to the principle that a gyroscope remains in a fixed position in the plane in which it is spinning. An example of rigidity in space is that of a bicycle wheel. As the bicycle wheels increase speed, they become more and more stable in their plane of rotation. This is why […]

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Gyroscopic Flight Instruments

Flight Instruments

Several flight instruments utilize the properties of a gyroscope for their operation. The most common instruments containing gyroscopes are the turn coordinator, heading indicator, and the attitude indicator. To understand how these instruments operate requires knowledge of the gyroscopic instrument power systems, gyroscopic principles, and the operating principles of each instrument. Gyroscopic Principles Any spinning […]

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Blocked Static System

Flight Instruments

If the static system becomes blocked but the pitot tube remains clear, the ASI continues to operate; however, it is inaccurate. The airspeed indicates lower than the actual airspeed when the aircraft is operated above the altitude where the static ports became blocked, because the trapped static pressure is higher than normal for that altitude. […]

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Blocked Pitot System

Flight Instruments

The pitot system can become blocked completely or only partially if the pitot tube drain hole remains open. If the pitot tube becomes blocked and its associated drain hole remains clear, ram air no longer is able to enter the pitot system. Air already in the system vents through the drain hole, and the remaining […]

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Airspeed Indicator (ASI) – Other Airspeed Limitations

Flight Instruments

Some important airspeed limitations are not marked on the face of the ASI, but are found on placards and in the AFM/POH. These airspeeds include: Design maneuvering speed (VA)—the maximum speed at which the structural design’s limit load can be imposed (either by gusts or full deflection of the control surfaces) without causing structural damage. […]

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Airspeed Indicator (ASI) Markings

Flight Instruments

Aircraft weighing 12,500 pounds or less, manufactured after 1945, and certificated by the FAA, are required to have an airspeed indicator (ASI) marked in accordance with a standard color-coded marking system. This system of color-coded markings enables a pilot to determine at a glance certain airspeed limitations that are important to the safe operation of […]

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