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Flight Instruments

The outside air temperature (OAT) gauge is a simple and effective device mounted so that the sensing element is exposed to the outside air. The sensing element consists of a bimetallic-type thermometer in which two dissimilar materials are welded together in a single strip and twisted into a helix. One end is anchored into protective tube and the other end is affixed to the pointer, which reads against the calibration on a circular face. OAT gauges are calibrated in degrees °C, °F, or both. An accurate air temperature provides the pilot with useful information about temperature lapse rate with altitude change.  [Figure 7-38]

Outside air temperature (OAT) gauge

Figure 7-38. Outside air temperature (OAT) gauge.

51DPcJTcMwL._SX381_BO1,204,203,200_Learn more about all of your flight instruments with the Instrument Flying Handbook. This is the FAA’s primary pilot resource for instrument flight rules (IFR) covering everything pertinent to operating an aircraft in instrument meteorological conditions (IMC) or without reference to outside visuals, relying solely on the information gleaned from the cockpit.


Compass Systems (Part Three) The Vertical Card Magnetic Compass

The floating magnet type of compass not only has all the errors just described, but also lends itself to confused reading. It is easy to begin a turn in the wrong direction because its card appears backward. East is on what the pilot would expect to be the west side. The vertical card magnetic compass […]

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Compass Systems (Part Two) Magnetic Compass Induced Errors

The magnetic compass is the simplest instrument in the panel, but it is subject to a number of errors that must be considered. Variation The Earth rotates about its geographic axis; maps and charts are drawn using meridians of longitude that pass through the geographic poles. Directions measured from the geographic poles are called true […]

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Compass Systems (Part One) The Magnetic Compass

One of the oldest and simplest instruments for indicating direction is the magnetic compass. It is also one of the basic instruments required by Title 14 of the Code of Federal Regulations (14 CFR) part 91 for both VFR and IFR flight. A magnet is a piece of material, usually a metal containing iron, which […]

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Heading Indicators (Part Four) Remote Indicating Compass

Remote indicating compasses were developed to compensate for the errors and limitations of the older type of heading indicators. The two panel-mounted components of a typical system are the pictorial navigation indicator and the slaving control and compensator unit. [Figure 7-29] The pictorial navigation indicator is commonly referred to as an HSI. The slaving control […]

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Heading Indicators (Part Three) The Flux Gate Compass System

As mentioned in a previous post, the lines of flux in the Earth’s magnetic field have two basic characteristics: a magnet aligns with them, and an electrical current is induced, or generated, in any wire crossed by them. The flux gate compass that drives slaved gyros uses the characteristic of current induction. The flux valve […]

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Heading Indicators (Part Two) Attitude and Heading Reference System (AHRS)

Electronic flight displays have replaced free-spinning gyros with solid-state laser systems that are capable of flight at any attitude without tumbling. This capability is the result of the development of the Attitude and Heading Reference System (AHRS). The AHRS sends attitude information to the PFD in order to generate the pitch and bank information of […]

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Heading Indicators (Part One)

The heading indicator is fundamentally a mechanical instrument designed to facilitate the use of the magnetic compass. Errors in the magnetic compass are numerous, making straight flight and precision turns to headings difficult to accomplish, particularly in turbulent air. A heading indicator, however, is not affected by the forces that make the magnetic compass difficult […]

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Attitude Indicator

The attitude indicator, with its miniature aircraft and horizon bar, displays a picture of the attitude of the aircraft. The relationship of the miniature aircraft to the horizon bar is the same as the relationship of the real aircraft to the actual horizon. The instrument gives an instantaneous indication of even the smallest changes in […]

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